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Hellsberg E, Boytsov D, Chen Q, Niello M, Freissmuth M, Rudnick G, Zhang YW, Sandtner W, Forrest LR. Identification of the potassium-binding site in serotonin transporter. Proc Natl Acad Sci U S A 2024; 121:e2319384121. [PMID: 38652746 DOI: 10.1073/pnas.2319384121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Accepted: 03/11/2024] [Indexed: 04/25/2024] Open
Abstract
Clearance of serotonin (5-hydroxytryptamine, 5-HT) from the synaptic cleft after neuronal signaling is mediated by serotonin transporter (SERT), which couples this process to the movement of a Na+ ion down its chemical gradient. After release of 5-HT and Na+ into the cytoplasm, the transporter faces a rate-limiting challenge of resetting its conformation to be primed again for 5-HT and Na+ binding. Early studies of vesicles containing native SERT revealed that K+ gradients can provide an additional driving force, via K+ antiport. Moreover, under appropriate conditions, a H+ ion can replace K+. Intracellular K+ accelerates the resetting step. Structural studies of SERT have identified two binding sites for Na+ ions, but the K+ site remains enigmatic. Here, we show that K+ antiport can drive substrate accumulation into vesicles containing SERT extracted from a heterologous expression system, allowing us to study the residues responsible for K+ binding. To identify candidate binding residues, we examine many cation binding configurations using molecular dynamics simulations, predicting that K+ binds to the so-called Na2 site. Site-directed mutagenesis of residues in this site can eliminate the ability of both K+ and H+ to drive 5-HT accumulation into vesicles and, in patch clamp recordings, prevent the acceleration of turnover rates and the formation of a channel-like state by K+ or H+. In conclusion, the Na2 site plays a pivotal role in orchestrating the sequential binding of Na+ and then K+ (or H+) ions to facilitate 5-HT uptake in SERT.
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Affiliation(s)
- Eva Hellsberg
- Computational Structural Biology Section, National Institutes of Neurological Disorders and Stroke, NIH, Bethesda, MD 20892
| | - Danila Boytsov
- Center of Physiology and Pharmacology, Department of Pharmacology, Medical University of Vienna, Vienna 1090, Austria
| | - Qingyang Chen
- School of Life Sciences, Higher Education Mega Center, Guangzhou University, Guangzhou 510006, China
| | - Marco Niello
- Center of Physiology and Pharmacology, Department of Pharmacology, Medical University of Vienna, Vienna 1090, Austria
| | - Michael Freissmuth
- Center of Physiology and Pharmacology, Department of Pharmacology, Medical University of Vienna, Vienna 1090, Austria
| | - Gary Rudnick
- Department of Pharmacology, Yale University, New Haven, CT 06510
| | - Yuan-Wei Zhang
- School of Life Sciences, Higher Education Mega Center, Guangzhou University, Guangzhou 510006, China
| | - Walter Sandtner
- Center of Physiology and Pharmacology, Department of Pharmacology, Medical University of Vienna, Vienna 1090, Austria
| | - Lucy R Forrest
- Computational Structural Biology Section, National Institutes of Neurological Disorders and Stroke, NIH, Bethesda, MD 20892
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2
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Ün D, Kovalchuk V, El-Kasaby A, Kasture A, Koban F, Kudlacek O, Freissmuth M, Sucic S. Breaking the rules of SLC6 transporters: Export of the human creatine transporter-1 from the endoplasmic reticulum is supported by its N-terminus. J Neurochem 2024. [PMID: 38419374 DOI: 10.1111/jnc.16088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 02/13/2024] [Accepted: 02/15/2024] [Indexed: 03/02/2024]
Abstract
Mutations in the human creatine transporter 1 (CRT1/SLC6A8) cause the creatine transporter deficiency syndrome, which is characterized by intellectual disability, epilepsy, autism, and developmental delay. The vast majority of mutations cause protein misfolding and hence reduce cell surface expression. Hence, it is important to understand the molecular machinery supporting folding and export of CRT1 from the endoplasmic reticulum (ER). All other SLC6 members thus far investigated rely on a C-terminal motif for binding the COPII-component SEC24 to drive their ER export; their N-termini are dispensable. Here, we show that, in contrast, in CRT1 the C-terminal ER-export motif is cryptic and it is the N-terminus, which supports ER export. This conclusion is based on the following observations: (i) siRNA-induced depletion of individual SEC24 isoforms revealed that CRT1 relied on SEC24C for ER export. However, mutations of the C-terminal canonical ER-export motif of CRT1 did not impair its cell surface delivery. (ii) Nevertheless, the C-terminal motif of CRT1 was operational in a chimeric protein comprising the serotonin transporter (SERT/SLC6A4) and the C-terminus of CRT1. (iii) Tagging of the N-terminus-but not the C-terminus-with yellow fluorescent protein (YFP) resulted in ER retention. (iv) Serial truncations of the N-terminus showed that removal of ≥51 residues of CRT1 impaired surface delivery, because the truncated CRT1 were confined to the ER. (v) Mutation of P51 to alanine also reduced cell surface delivery of CRT1 and relieved its dependence on SEC24C. Thus, the ER-export motif in the N-terminus of CRT1 overrides the canonical C-terminal motif.
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Affiliation(s)
- Didem Ün
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Vasylyna Kovalchuk
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Ali El-Kasaby
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Ameya Kasture
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria
| | - Florian Koban
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Oliver Kudlacek
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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3
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Clarke A, Farr CV, El‐Kasaby A, Szöllősi D, Freissmuth M, Sucic S, Stockner T. Probing binding and occlusion of substrate in the human creatine transporter-1 by computation and mutagenesis. Protein Sci 2024; 33:e4842. [PMID: 38032325 PMCID: PMC10751730 DOI: 10.1002/pro.4842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 11/16/2023] [Accepted: 11/18/2023] [Indexed: 12/01/2023]
Abstract
In chordates, energy buffering is achieved in part through phosphocreatine, which requires cellular uptake of creatine by the membrane-embedded creatine transporter (CRT1/SLC6A8). Mutations in human slc6a8 lead to creatine transporter deficiency syndrome, for which there is only limited treatment. Here, we used a combined homology modeling, molecular dynamics, and experimental approach to generate a structural model of CRT1. Our observations support the following conclusions: contrary to previous proposals, C144, a key residue in the substrate binding site, is not present in a charged state. Similarly, the side chain D458 must be present in a protonated form to maintain the structural integrity of CRT1. Finally, we identified that the interaction chain Y148-creatine-Na+ is essential to the process of occlusion, which occurs via a "hold-and-pull" mechanism. The model should be useful to study the impact of disease-associated point mutations on the folding of CRT1 and identify approaches which correct folding-deficient mutants.
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Affiliation(s)
- Amy Clarke
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and PharmacologyMedical University of ViennaViennaAustria
| | - Clemens V. Farr
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and PharmacologyMedical University of ViennaViennaAustria
| | - Ali El‐Kasaby
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and PharmacologyMedical University of ViennaViennaAustria
| | - Daniel Szöllősi
- Department of Theoretical and Computational BiophysicsMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and PharmacologyMedical University of ViennaViennaAustria
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and PharmacologyMedical University of ViennaViennaAustria
| | - Thomas Stockner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and PharmacologyMedical University of ViennaViennaAustria
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4
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Koban F, Freissmuth M. The cell cycle protein MAD2 facilitates endocytosis of the serotonin transporter in the neuronal soma. EMBO Rep 2023; 24:e53408. [PMID: 37530743 PMCID: PMC10561363 DOI: 10.15252/embr.202153408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 06/23/2023] [Accepted: 07/14/2023] [Indexed: 08/03/2023] Open
Abstract
Monoamine transporters retrieve serotonin (SERT), dopamine (DAT), and norepinephrine (NET) from the synaptic cleft. Transporter internalization contributes to the regulation of their surface expression. Clathrin-mediated endocytosis of plasma membrane proteins requires adaptor protein-2 (AP2), which recruits cargo to the nascent clathrin cage. However, the intracellular portions of monoamine transporters are devoid of a conventional AP2-binding site. Here, we identify a MAD2 (mitotic arrest deficient-2) interaction motif in the C-terminus of SERT, which binds the closed conformation of MAD2 and allows for the recruitment of two additional mitotic spindle assembly checkpoint (SAC) proteins, BubR1 and p31comet , and of AP2. We visualize MAD2, BubR1, and p31comet in dorsal raphe neurons, and depletion of MAD2 in primary serotonergic rat neurons decreases SERT endocytosis in the soma. Our findings do not only provide mechanistic insights into transporter internalization but also allow for rationalizing why SAC proteins are present in post-mitotic neurons.
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Affiliation(s)
- Florian Koban
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and PharmacologyMedical University of ViennaViennaAustria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and PharmacologyMedical University of ViennaViennaAustria
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5
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Boytsov D, Schicker K, Hellsberg E, Freissmuth M, Sandtner W. Allosteric modulators of solute carrier function: a theoretical framework. Front Physiol 2023; 14:1166450. [PMID: 37250134 PMCID: PMC10210158 DOI: 10.3389/fphys.2023.1166450] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 04/24/2023] [Indexed: 05/31/2023] Open
Abstract
Large-scale drug screening is currently the basis for the identification of new chemical entities. This is a rather laborious approach, because a large number of compounds must be tested to cover the chemical space in an unbiased fashion. However, the structures of targetable proteins have become increasingly available. Thus, a new era has arguably been ushered in with the advent of methods, which allow for structure-based docking campaigns (i.e., virtual screens). Solute carriers (SLCs) are among the most promising drug targets. This claim is substantiated by the fact that a large fraction of the 400 solute carrier genes is associated with human diseases. The ability to dock large ligand libraries into selected structures of solute carriers has set the stage for rational drug design. In the present study, we show that these structure-based approaches can be refined by taking into account how solute carriers operate. We specifically address the feasibility of targeting solute carriers with allosteric modulators, because their actions differ fundamentally from those of ligands, which bind to the substrate binding site. For the pertinent analysis we used transition state theory in conjunction with the linear free energy relationship (LFER). These provide the theoretical framework to understand how allosteric modulators affect solute carrier function.
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Affiliation(s)
- D. Boytsov
- Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - K. Schicker
- Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - E. Hellsberg
- Computational Structural Biology Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, MD, United States
| | - M. Freissmuth
- Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - W. Sandtner
- Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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6
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Freissmuth M. Regulated Rapid Round Trips: Endocytotic Cycling of the Dopamine Transporter Shapes Motor Learning. J Biol Chem 2023; 299:104618. [PMID: 36935007 PMCID: PMC10124912 DOI: 10.1016/j.jbc.2023.104618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/15/2023] [Indexed: 03/19/2023] Open
Abstract
The level of dopamine transporters (DATs) in the neuronal plasma membrane shapes learning and motor coordination in mice. Mechanisms underlying the regulated internalization of DAT and its return to the cell surface have been intensively studied in heterologous cells and in neuronal cell bodies. However, whether this cycling also happens in synaptic boutons, or axon terminals, thought to be the major functional site for DAT expression, was an open question that Kearney and colleagues recently addressed in the JBC. They showed that DAT cycling in the presynaptic specialization of dopaminergic neurons is subject to control by a cell-autonomous loop comprising dopamine autoreceptors and metabotropic glutamate receptors. These results should inform future studies in neural development and motor learning.
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Affiliation(s)
- Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Austria.
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7
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Bhat S, El-Kasaby A, Kasture A, Boytsov D, Reichelt JB, Hummel T, Sucic S, Pifl C, Freissmuth M, Sandtner W. A mechanism of uncompetitive inhibition of the serotonin transporter. eLife 2023; 12:e82641. [PMID: 36648438 PMCID: PMC9883013 DOI: 10.7554/elife.82641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Accepted: 01/17/2023] [Indexed: 01/18/2023] Open
Abstract
The serotonin transporter (SERT/SLC6A4) is arguably the most extensively studied solute carrier (SLC). During its eponymous action - that is, the retrieval of serotonin from the extracellular space - SERT undergoes a conformational cycle. Typical inhibitors (antidepressant drugs and cocaine), partial and full substrates (amphetamines and their derivatives), and atypical inhibitors (ibogaine analogues) bind preferentially to different states in this cycle. This results in competitive or non-competitive transport inhibition. Here, we explored the action of N-formyl-1,3-bis (3,4-methylenedioxyphenyl)-prop-2-yl-amine (ECSI#6) on SERT: inhibition of serotonin uptake by ECSI#6 was enhanced with increasing serotonin concentration. Conversely, the KM for serotonin was lowered by augmenting ECSI#6. ECSI#6 bound with low affinity to the outward-facing state of SERT but with increased affinity to a potassium-bound state. Electrophysiological recordings showed that ECSI#6 preferentially interacted with the inward-facing state. Kinetic modeling recapitulated the experimental data and verified that uncompetitive inhibition arose from preferential binding of ECSI#6 to the K+-bound, inward-facing conformation of SERT. This binding mode predicted a pharmacochaperoning action of ECSI#6, which was confirmed by examining its effect on the folding-deficient mutant SERT-PG601,602AA: preincubation of HEK293 cells with ECSI#6 restored export of SERT-PG601,602AA from the endoplasmic reticulum and substrate transport. Similarly, in transgenic flies, the administration of ECSI#6 promoted the delivery of SERT-PG601,602AA to the presynaptic specialization of serotonergic neurons. To the best of our knowledge, ECSI#6 is the first example of an uncompetitive SLC inhibitor. Pharmacochaperones endowed with the binding mode of ECSI#6 are attractive, because they can rescue misfolded transporters at concentrations, which cause modest transport inhibition.
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Affiliation(s)
- Shreyas Bhat
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of ViennaViennaAustria
| | - Ali El-Kasaby
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of ViennaViennaAustria
| | - Ameya Kasture
- Department of Neurobiology, University of ViennaViennaAustria
| | - Danila Boytsov
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of ViennaViennaAustria
| | - Julian B Reichelt
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of ViennaViennaAustria
| | - Thomas Hummel
- Department of Neurobiology, University of ViennaViennaAustria
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of ViennaViennaAustria
| | - Christian Pifl
- Center for Brain Research, Medical University of ViennaViennaAustria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of ViennaViennaAustria
| | - Walter Sandtner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of ViennaViennaAustria
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8
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Arias HR, De Deurwaerdère P, El-Kasaby A, Di Giovanni G, Eom S, Lee JH, Freissmuth M, Chagraoui A. (+)-Catharanthine and (-)-18-methoxycoronaridine induce antidepressant-like activity in mice by differently recruiting serotonergic and norepinephrinergic neurotransmission. Eur J Pharmacol 2023; 939:175454. [PMID: 36549498 DOI: 10.1016/j.ejphar.2022.175454] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 11/29/2022] [Accepted: 12/12/2022] [Indexed: 12/23/2022]
Abstract
The antidepressant-like activity of (+)-catharanthine and (-)-18-methoxycoronaridine [(-)-18-MC] was studied in male and female mice using forced swim (FST) and tail suspension tests (TST). The underlying molecular mechanism was assessed by electrophysiological, radioligand, and functional experiments. The FST results showed that acute administration (40 mg/kg) of (+)-catharanthine or (-)-18-MC induces similar antidepressant-like activity in male and female mice at 1 h and 24 h, whereas the TST results showed a lower effect for (-)-18-MC at 24 h. Repeated treatment at lower dose (20 mg/kg) augmented the efficacy of both congeners. The FST results showed that (-)-18-MC reduces immobility and increases swimming times without changing climbing behavior, whereas (+)-catharanthine reduces immobility time, increases swimming times more markedly, and increases climbing behavior. To investigate the contribution of the serotonin and norepinephrine transporters in the antidepressant effects of (+)-catharanthine and (-)-18-MC, we conducted in vitro radioligand and functional studies. Results obtained demonstrated that (+)-catharanthine inhibits norepinephrine transporter with higher potency/affinity than that for (-)-18-MC, whereas both congeners inhibit serotonin transporter with similar potency/affinity. Moreover, whereas no congener activated/inhibited/potentiated the function of serotonin receptor 3A or serotonin receptor 3AB, both increased serotonin receptor 3A receptor desensitization. Depletion of serotonin decreased the antidepressant-like activity of both congeners, whereas norepinephrine depletion only decreased (+)-catharanthine's activity. Our study shows that coronaridine congeners induce antidepressant-like activity in a dose- and time-dependent, and sex-independent, manner. The antidepressant-like property of both compounds involves serotonin transporter inhibition, without directly activating/inhibiting serotonin receptors 3, while (+)-catharanthine also mobilizes norepinephrinergic neurotransmission.
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Affiliation(s)
- Hugo R Arias
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, OK, USA
| | - Philippe De Deurwaerdère
- Centre National de la Recherche Scientifique, Institut des Neurosciences Intégratives et Cognitives d'Aquitaine, UMR, 5287, Bordeaux, France
| | - Ali El-Kasaby
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Giuseppe Di Giovanni
- Laboratory of Neurophysiology, Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta, Neuroscience Division, School of Biosciences, Cardiff University, Cardiff, United Kingdom
| | - Sanung Eom
- Department of Biotechnology, Chonnam National University, Gwangju, South Korea
| | - Junho H Lee
- Department of Biotechnology, Chonnam National University, Gwangju, South Korea
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Abdeslam Chagraoui
- Department of Medical Biochemistry, Rouen University Hospital, CHU de Rouen, France; Différenciation et Communication Neuroendocrine, Endocrine et Germinale Laboratory, Institute for Research and Innovation in Biomedicine of Normandy (IRIB), University of Rouen, INSERM 1239, 76000, Rouen, France.
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9
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Irrgeher J, Berger T, Tchaikovsky A, Tschegg C, Gouya G, Lechner P, Retzmann A, Opper C, Firbas C, Freissmuth M, Peschel-Credner K, Anderle K, Meisslitzer C, Wolzt M, Prohaska T. Enriched stable 204Pb as tracer at ultra-low levels in clinical investigations. Anal Bioanal Chem 2023; 415:255-268. [PMID: 36136113 PMCID: PMC9823027 DOI: 10.1007/s00216-022-04311-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Revised: 08/23/2022] [Accepted: 08/29/2022] [Indexed: 01/11/2023]
Abstract
The potential of enriched Pb (204Pb) was assessed to monitor pathways of trace levels of Pb in the pg range within the human body via isotope pattern variation in situations where natural lead cannot be used as a tracer due to regulatory limitations. Isotope ratio measurements were accomplished by means of (multi-collector) inductively coupled plasma mass spectrometry including a comparison of single and multi-collector ICP-MS for low-level 204Pb assessment. Isotopic pattern results from a blend of a large quantity of the element with a natural isotopic composition and an enriched stable isotope at orders of magnitude lower levels pose a nontrivial analytical problem. Isotope pattern deconvolution was successfully applied as mathematical tool based on multiple linear regressions. The method allowed for deconvolving the isotope pattern from measured isotope ratios without knowing the quantities of different isotope sources incorporated and mixed into the sample at levels of < 1 pg 204Pb/g blood. The objective of this manuscript is to evaluate and summarize the analytical aspects for Pb isotope pattern deconvolution based on the results of a clinical trial, where a 204Pb-enriched isotope tracer was applied to investigate the bioavailability of orally applied Pb along with purified clinoptilolite tuff as potential supplement. This unique approach allows to reduce tracer amounts to harmless levels to human health, which are in accordance with the legal regulative to study enrichment levels of < 0.01% in human blood.
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Affiliation(s)
- Johanna Irrgeher
- Department of General, Analytical and Physical Chemistry, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben, Austria
| | - Thomas Berger
- Glock Health Science and Research GmbH, Hausfeldstraße 17, 2232 Deutsch-Wagram, Austria
| | | | - Cornelius Tschegg
- Glock Health Science and Research GmbH, Hausfeldstraße 17, 2232 Deutsch-Wagram, Austria
| | - Ghazaleh Gouya
- Gouya Insights, Elisabethstrasse 22/12, 1010 Vienna, Austria
| | - Peter Lechner
- LGS-INSIGHTS GmbH, Elisabethstrasse 22/12, 1010 Vienna, Austria
| | - Anika Retzmann
- Department of General, Analytical and Physical Chemistry, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben, Austria
| | - Christine Opper
- Department of General, Analytical and Physical Chemistry, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben, Austria ,TB Unterfrauner GmbH, Umseerstraße 39, 3040 Neulengbach, Austria
| | - Christa Firbas
- Department of Clinical Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Währingerstrasse 13a, Vienna, Austria
| | | | - Karolina Anderle
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Währingerstrasse 13a, Vienna, Austria
| | - Claudia Meisslitzer
- Glock Health Science and Research GmbH, Hausfeldstraße 17, 2232 Deutsch-Wagram, Austria
| | - Michael Wolzt
- Department of Clinical Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Thomas Prohaska
- Department of General, Analytical and Physical Chemistry, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben, Austria
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10
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Angenoorth TJF, Maier J, Stankovic S, Bhat S, Sucic S, Freissmuth M, Sitte HH, Yang JW. Rescue of Misfolded Organic Cation Transporter 3 Variants. Cells 2022; 12:39. [PMID: 36611832 PMCID: PMC9818475 DOI: 10.3390/cells12010039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 12/13/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022] Open
Abstract
Organic cation transporters (OCTs) are membrane proteins that take up monoamines, cationic drugs and xenobiotics. We previously reported novel missense mutations of organic cation transporter 3 (OCT3, SLC22A3), some with drastically impacted transport capabilities compared to wildtype. For some variants, this was due to ER retention and subsequent degradation of the misfolded transporter. For other transporter families, it was previously shown that treatment of misfolded variants with pharmacological and chemical chaperones could restore transport function to a certain degree. To investigate two potentially ER-bound, misfolded variants (D340G and R348W), we employed confocal and biochemical analyses. In addition, radiotracer uptake assays were conducted to assess whether pre-treatment with chaperones could restore transporter function. We show that pre-treatment of cells with the chemical chaperone 4-PBA (4-phenyl butyric acid) leads to increased membrane expression of misfolded variants and is associated with increased transport capacity of D340G (8-fold) and R348W (1.5 times) compared to untreated variants. We herein present proof of principle that folding-deficient SLC22 transporter variants, in particular those of OCT3, are amenable to rescue by chaperones. These findings need to be extended to other SLC22 members with corroborated disease associations.
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Affiliation(s)
- Thomas J. F. Angenoorth
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Währingerstraße 13A, 1090 Vienna, Austria
| | - Julian Maier
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Währingerstraße 13A, 1090 Vienna, Austria
| | - Stevan Stankovic
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Währingerstraße 13A, 1090 Vienna, Austria
| | - Shreyas Bhat
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Währingerstraße 13A, 1090 Vienna, Austria
- Department of Physics, Université de Montréal, 1375 Avenue Thérèse-Lavoie-Roux, Montréal, QC H3T 1J4, Canada
- Department of Pharmacology and Physiology, Université de Montréal, 2960 Chemin de la Tour, Montréal, QC H3T 1J4, Canada
| | - Sonja Sucic
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Währingerstraße 13A, 1090 Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Währingerstraße 13A, 1090 Vienna, Austria
| | - Harald H. Sitte
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Währingerstraße 13A, 1090 Vienna, Austria
| | - Jae-Won Yang
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Währingerstraße 13A, 1090 Vienna, Austria
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11
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Anderle K, Wolzt M, Moser G, Keip B, Peter J, Meisslitzer C, Gouya G, Freissmuth M, Tschegg C. Safety and efficacy of purified clinoptilolite-tuff treatment in patients with irritable bowel syndrome with diarrhea: Randomized controlled trial. World J Gastroenterol 2022; 28:6573-6588. [PMID: 36569277 PMCID: PMC9782844 DOI: 10.3748/wjg.v28.i46.6573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 09/09/2022] [Accepted: 11/16/2022] [Indexed: 12/08/2022] Open
Abstract
BACKGROUND Irritable bowel syndrome (IBS) is a highly prevalent gastrointestinal disorder with poor response to treatment. IBS with predominant diarrhea (IBS-D) is accompanied by abdominal pain as well as high stool frequency and urgency. Purified clinoptilolite-tuff (PCT), which is approved by the Food and Drug Administration for use as a dietary supplement with the brand name G-PUR®, has previously shown therapeutic potential in other indications based on its physical adsorption capacity.
AIM To assess whether symptoms of IBS-D can be ameliorated by oral treatment with PCT.
METHODS In this randomized, placebo-controlled, double-blind pilot study, 30 patients with IBS-D diagnosis based on Rome IV criteria were enrolled. Following a 4-wk run-in phase, 14 patients were randomized to receive a 12-wk treatment with G-PUR® (2 g three times daily), and 16 patients received placebo. The relief from IBS-D symptoms as measured by the proportion of responders according to the Subject’s Global Assessment (SGA) of Relief was assessed as the primary outcome. For the secondary outcomes, validated IBS-D associated symptom questionnaires, exploratory biomarkers and microbiome data were collected.
RESULTS The proportions of SGA of Relief responders after 12 wk were comparable in both groups, namely 21% in the G-PUR® group and 25% in the placebo group. After 4 wk of treatment, 36% of patients in the G-PUR® group vs 0% in the placebo group reported complete or considerable relief. An improvement in daily abdominal pain was noted in 94% vs 83% (P = 0.0353), and the median number of days with diarrhea per week decreased by 2.4 d vs 0.3 d in the G-PUR® and placebo groups, respectively. Positive trends were observed for 50% of responders in the Bristol Stool Form Scale. Positive trends were also noted for combined abdominal pain and stool consistency response and the Perceived Stress Questionnaire score. Only 64% in the G-PUR® group compared to 86% in the placebo group required rescue medication intake during the study. Stool microbiome studies showed a minor increase in diversity in the G-PUR® group but not in the placebo group. No PCT-related serious adverse events were reported.
CONCLUSION In this randomized, double-blind, placebo-controlled study, the PCT product, G-PUR®, demonstrated safety and clinical benefit towards some symptoms of IBS-D, representing a promising novel treatment option for these patients.
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Affiliation(s)
- Karolina Anderle
- Department of Clinical Pharmacology, Medical University of Vienna, Vienna 1090, Austria
| | - Michael Wolzt
- Department of Clinical Pharmacology, Medical University of Vienna, Vienna 1090, Austria
| | - Gabriele Moser
- Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Medical University of Vienna, Vienna 1090, Austria
| | - Bettina Keip
- Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Medical University of Vienna, Vienna 1090, Austria
| | - Johannes Peter
- Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Medical University of Vienna, Vienna 1090, Austria
| | - Claudia Meisslitzer
- Glock Health, Science and Research GmbH, Deutsch-Wagram 2232, Lower Austria, Austria
| | | | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna 1090, Austria
| | - Cornelius Tschegg
- Glock Health, Science and Research GmbH, Deutsch-Wagram 2232, Lower Austria, Austria
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12
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Farr CV, El-Kasaby A, Erdem FA, Sucic S, Freissmuth M, Sandtner W. Cooperative Binding of Substrate and Ions Drives Forward Cycling of the Human Creatine Transporter-1. Front Physiol 2022; 13:919439. [PMID: 35837012 PMCID: PMC9273935 DOI: 10.3389/fphys.2022.919439] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 06/09/2022] [Indexed: 11/25/2022] Open
Abstract
Creatine serves as an ATP buffer and is thus an integral component of cellular energy metabolism. Most cells maintain their creatine levels via uptake by the creatine transporter (CRT-1, SLC6A8). The activity of CRT-1, therefore, is a major determinant of cytosolic creatine concentrations. We determined the kinetics of CRT-1 in real time by relying on electrophysiological recordings of transport-associated currents. Our analysis revealed that CRT-1 harvested the concentration gradient of NaCl and the membrane potential but not the potassium gradient to achieve a very high concentrative power. We investigated the mechanistic basis for the ability of CRT-1 to maintain the forward cycling mode in spite of high intracellular concentrations of creatine: this is achieved by cooperative binding of substrate and co-substrate ions, which, under physiological ion conditions, results in a very pronounced (i.e. about 500-fold) drop in the affinity of creatine to the inward-facing state of CRT-1. Kinetic estimates were integrated into a mathematical model of the transport cycle of CRT-1, which faithfully reproduced all experimental data. We interrogated the kinetic model to examine the most plausible mechanistic basis of cooperativity: based on this systematic exploration, we conclude that destabilization of binary rather than ternary complexes is necessary for CRT-1 to maintain the observed cytosolic creatine concentrations. Our model also provides a plausible explanation why neurons, heart and skeletal muscle cells must express a creatine releasing transporter to achieve rapid equilibration of the intracellular creatine pool.
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Affiliation(s)
| | | | | | | | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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13
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Schicker K, Farr CV, Boytsov D, Freissmuth M, Sandtner W. Optimizing the Substrate Uptake Rate of Solute Carriers. Front Physiol 2022; 13:817886. [PMID: 35185619 PMCID: PMC8850955 DOI: 10.3389/fphys.2022.817886] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 01/10/2022] [Indexed: 11/16/2022] Open
Abstract
The diversity in solute carriers arose from evolutionary pressure. Here, we surmised that the adaptive search for optimizing the rate of substrate translocation was also shaped by the ambient extracellular and intracellular concentrations of substrate and co-substrate(s). We explored possible solutions by employing kinetic models, which were based on analytical expressions of the substrate uptake rate, that is, as a function of the microscopic rate constants used to parameterize the transport cycle. We obtained the defining terms for five reaction schemes with identical transport stoichiometry (i.e., Na+: substrate = 2:1). We then utilized an optimization algorithm to find the set of numeric values for the microscopic rate constants, which provided the largest value for the substrate uptake rate: The same optimized rate was achieved by different sets of numerical values for the microscopic rate constants. An in-depth analysis of these sets provided the following insights: (i) In the presence of a low extracellular substrate concentration, a transporter can only cycle at a high rate, if it has low values for both, the Michaelis-Menten constant (KM) for substrate and the maximal substrate uptake rate (Vmax). (ii) The opposite is true for a transporter operating at high extracellular substrate concentrations. (iii) Random order of substrate and co-substrate binding is superior to sequential order, if a transporter is to maintain a high rate of substrate uptake in the presence of accumulating intracellular substrate. Our kinetic models provide a framework to understand how and why the transport cycles of closely related transporters differ.
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Affiliation(s)
| | | | | | | | - Walter Sandtner
- Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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14
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Deinsberger J, Marquart E, Nizet S, Meisslitzer C, Tschegg C, Uspenska K, Gouya G, Niederdöckl J, Freissmuth M, Wolzt M, Weber B. Topically administered purified clinoptilolite-tuff for the treatment of cutaneous wounds: a prospective, randomized phase I clinical trial. Wound Repair Regen 2022; 30:198-209. [PMID: 35043507 PMCID: PMC9306511 DOI: 10.1111/wrr.12991] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 11/17/2021] [Accepted: 01/01/2022] [Indexed: 12/20/2022]
Abstract
In an ageing society, chronic ulcers pose an increasingly relevant healthcare issue associated with significant morbidity and an increasing financial burden. Hence, there is an unmet medical need for novel, cost‐effective therapies that improve healing of chronic cutaneous wounds. This prospective, randomised, open‐label, phase I trial investigated the safety and tolerability of topically administered purified clinoptilolite‐tuff (PCT), mainly consisting of the naturally occurring zeolite‐mineral clinoptilolite, in artificial wounds in healthy male volunteers compared to the standard of care (SoC). We found that topically administered PCT was safe for therapeutic application in acute wounds in healthy male volunteers. No significant differences in wound healing or wound conditions were observed compared to SoC‐treated wounds. However, we found a significantly higher proportion of CD68‐positive cells and a significantly lower proportion of α‐smooth muscle actin‐positive cells in PCT‐treated wounds. Scanning electron microscopy revealed PCT particles in the restored dermis in some cases. However, these did not impede wound healing or clinical symptoms. Hence, purified PCT could represent an attractive, cost‐effective wound treatment promoting the process of healing.
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Affiliation(s)
- Julia Deinsberger
- Department of Dermatology, Vienna General Hospital, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Elias Marquart
- Department of Dermatology, Vienna General Hospital, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Stephane Nizet
- Glock Health, Science and Research GmbH, Hausfeldstraße 17, 2232, Deutsch-Wagram, Austria
| | - Claudia Meisslitzer
- Glock Health, Science and Research GmbH, Hausfeldstraße 17, 2232, Deutsch-Wagram, Austria
| | - Cornelius Tschegg
- Glock Health, Science and Research GmbH, Hausfeldstraße 17, 2232, Deutsch-Wagram, Austria
| | | | - Ghazaleh Gouya
- Gouya-Insights, Elisabethstraße 22/12, 1010, Vienna, Austria
| | - Jan Niederdöckl
- Department of Clinical Pharmacology, Vienna General Hospital, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Michael Freissmuth
- Center for Physiology and Pharmacology, Institute of Pharmacology, Gaston H. Glock Laboratories for Exploratory Drug Research, Medical University of Vienna, Waehringer Straße 13a, 1090, Vienna, Austria
| | - Michael Wolzt
- Department of Clinical Pharmacology, Vienna General Hospital, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Benedikt Weber
- Department of Dermatology, Vienna General Hospital, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
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15
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Ponleitner M, Szöllösi D, El-Kasaby A, Koban F, Freissmuth M, Stockner T. Thermal unfolding of the human serotonin transporter: differential effect by stabilizing and destabilizing mutations and cholesterol on thermodynamic and kinetic stability. Mol Pharmacol 2021; 101:95-105. [PMID: 34866045 DOI: 10.1124/molpharm.121.000413] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 11/21/2021] [Indexed: 11/22/2022] Open
Abstract
Folding-deficient mutants of SLC6 (solute carrier 6) family members have been linked to human diseases. The serotonin transporter (SERT/SLC6A4) is an important drug target in the treatment of depression, anxiety and obsessive-compulsive disorders and - with structural information in several conformational states - one of the best understood transporters. Here, we surmised that thermal unfolding offered a glimpse on the folding energy landscape of SLC6 transporters. We carried out molecular dynamic (MD) simulations to understand the mechanistic basis for enhanced and reduced stability, respectively, of the thermostabilized variant SERT-Y110A/I291A/T439S, which had previously been used for crystallization of human SERT in the outward-facing state, and of the folding-deficient SERT-P601A/G602A. We also examined the hydrophobic mismatch caused by the absence of cholesterol to explore the contribution of cholesterol to protein stability. When compared to wild type SERT, the thermodynamic and kinetic stability of SERT-Y110A/I291A/T439S was enhanced. In the other instances, changes in these two components were not correlated: the mutations in SERT-P601A/G602A led to a drop in thermodynamic but an increase in kinetic stability. The divergence was even more pronounced after cholesterol depletion, which reduced thermodynamic stability but increased the kinetic stability of wild type SERT to a level comparable to that of SERT-Y110A/I291A/T439S. We conclude that the low cholesterol content of the endoplasmic reticulum facilitates progression of the folding trajectory by reducing the energy difference between folding intermediates and the native state. Significance Statement Point mutations in solute carrier 6 (SLC6) family members cause folding diseases. The serotonin transporter (SERT/SLC6A4) is a target for antidepressants and the best understood SLC6. We carried out molecular dynamics simulations and examined thermal unfolding of wild type and mutant SERT variants to understand their folding energy landscape. In the folding-deficient SERT-P012A/G602A, changes in kinetic and thermodynamic stability were not correlated. Similarly, cholesterol depletion lowered thermodynamic but enhanced kinetic stability. Our observations allow for rationalizing the action of pharmacochaperones.
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Affiliation(s)
| | | | - Ali El-Kasaby
- Institute of Pharmacology, Medical University of Vienna, Austria
| | | | - Michael Freissmuth
- Institute of Pharmacology, Centre of Physiology and Pharmacology, Medical University of Vienna, Austria
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16
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Muratspahić E, Retzl B, Duerrauer L, Freissmuth M, Becker CFW, Gruber CW. Genome Mining-Based Discovery of Blenny Fish-Derived Peptides Targeting the Mouse κ-Opioid Receptor. Front Pharmacol 2021; 12:773029. [PMID: 34744752 PMCID: PMC8569185 DOI: 10.3389/fphar.2021.773029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 10/01/2021] [Indexed: 11/13/2022] Open
Abstract
Over the past years, peptides have attracted increasing interest for G protein-coupled receptor (GPCR) drug discovery and development. Peptides occupy a unique chemical space that is not easily accessible for small molecules and antibodies and provide advantages over these ligand classes such as lower toxicity and higher selectivity. The κ-opioid receptor (KOR) is a prototypic GPCR and an appealing therapeutic target for the development of safer and more effective analgesics. Recently, peptides have emerged as analgesic drug candidates with improved side effect profiles. We have previously identified plant-derived peptides, which activate KOR. Based on this precedent, here we relied on publicly available databases to discover novel KOR peptide ligands by genome mining. Using human preprodynorphin as a query, we identified blenny fish-derived peptides, referred to as blenniorphins, capable of binding to and activating KOR with nanomolar affinity and potency, respectively. Additionally, the blenniorphins altered β-arrestin-2 recruitment at the KOR. Our study demonstrates the utility of genome mining to identify peptide GPCR ligands with intriguing pharmacological properties and unveils the potential of blenny fishes as a source for novel KOR ligands.
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Affiliation(s)
- Edin Muratspahić
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Bernhard Retzl
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Leopold Duerrauer
- Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Michael Freissmuth
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria.,Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Christian F W Becker
- Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Christian W Gruber
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
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17
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Kossmeier M, Themanns M, Hatapoglu L, Kogler B, Keuerleber S, Lichtenecker J, Sauermann R, Bucsics A, Freissmuth M, Zebedin-Brandl E. Assessing the Accuracy of Sales Forecasts Submitted by Pharmaceutical Companies Applying for Reimbursement in Austria. Front Pharmacol 2021; 12:726758. [PMID: 34483937 PMCID: PMC8414520 DOI: 10.3389/fphar.2021.726758] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 07/30/2021] [Indexed: 11/18/2022] Open
Abstract
Objectives: Reimbursement decisions on new medicines require an assessment of their value. In Austria, when applying for reimbursement of new medicines, pharmaceutical companies are also obliged to submit forecasts of future sales. We systematically examined the accuracy of these pharmaceutical sales forecasts and hence the usefulness of these forecasts for reimbursement evaluations. Methods: We retrospectively analyzed reimbursement applications of 102 new drugs submitted between 2005 and 2014, which were accepted for reimbursement outside of hospitals, and for which actual reimbursed sales were available for at least 3 years. The main outcome variable was the accuracy ratio, defined as the ratio of forecasted sales submitted by pharmaceutical companies when applying for reimbursement to actual sales from reimbursement data. Results: The median accuracy ratio [95% confidence interval] was 1.33 [1.03; 1.74, range 0.15–37.5], corresponding to a median overestimation of actual sales by 33%. Forecasts of actual sales for 55.9% of all examined products either overestimated actual sales by more than 100% or underestimated them by more than 50%. The accuracy of sales forecasts did not show systematic change over the analyzed decade nor was it discernibly influenced by reimbursement status (restricted or unrestricted), the degree of therapeutic benefit, or the therapeutic area of the pharmaceutical product. Sales forecasts of drugs with a higher degree of innovation and those within a dynamic market tended to be slightly more accurate. Conclusions: The majority of sales forecasts provided by applicants for reimbursement evaluations in Austria were highly inaccurate and were on average too optimistic. This is in line with published results for other jurisdictions and highlights the need for caution when using such forecasts for reimbursement procedures.
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Affiliation(s)
| | | | | | | | | | | | | | - Anna Bucsics
- MoCA (Mechanism of Coordinated Access to Orphan Medicinal Products), Brussels, Belgium
| | - Michael Freissmuth
- Institute of Pharmacology, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Eva Zebedin-Brandl
- Institute of Pharmacology, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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18
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Muratspahić E, Tomašević N, Nasrollahi-Shirazi S, Gattringer J, Emser FS, Freissmuth M, Gruber CW. Plant-Derived Cyclotides Modulate κ-Opioid Receptor Signaling. J Nat Prod 2021; 84:2238-2248. [PMID: 34308635 PMCID: PMC8406418 DOI: 10.1021/acs.jnatprod.1c00301] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Cyclotides are plant-derived disulfide-rich peptides comprising a cyclic cystine knot, which confers remarkable stability against thermal, proteolytic, and chemical degradation. They represent an emerging class of G protein-coupled receptor (GPCR) ligands. In this study, utilizing a screening approach of plant extracts and pharmacological analysis we identified cyclotides from Carapichea ipecacuanha to be ligands of the κ-opioid receptor (KOR), an attractive target for developing analgesics with reduced side effects and therapeutics for multiple sclerosis (MS). This prompted us to verify whether [T20K]kalata B1, a cyclotide in clinical development for the treatment of MS, is able to modulate KOR signaling. T20K bound to and fully activated KOR in the low μM range. We then explored the ability of T20K to allosterically modulate KOR. Co-incubation of T20K with KOR ligands resulted in positive allosteric modulation in functional cAMP assays by altering either the efficacy of dynorphin A1-13 or the potency and efficacy of U50,488 (a selective KOR agonist), respectively. In addition, T20K increased the basal response upon cotreatment with U50,488. In the bioluminescence resonance energy transfer assay T20K negatively modulated the efficacy of U50,488. This study identifies cyclotides capable of modulating KOR and highlights the potential of plant-derived peptides as an opportunity to develop cyclotide-based KOR modulators.
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Affiliation(s)
- Edin Muratspahić
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
| | - Nataša Tomašević
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
| | - Shahrooz Nasrollahi-Shirazi
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
- Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
| | - Jasmin Gattringer
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
| | - Fabiola Susanna Emser
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
| | - Michael Freissmuth
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
- Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
| | - Christian W Gruber
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
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19
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Bhat S, Niello M, Schicker K, Pifl C, Sitte HH, Freissmuth M, Sandtner W. Handling of intracellular K + determines voltage dependence of plasmalemmal monoamine transporter function. eLife 2021; 10:67996. [PMID: 34061030 PMCID: PMC8192120 DOI: 10.7554/elife.67996] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 05/30/2021] [Indexed: 12/16/2022] Open
Abstract
The concentrative power of the transporters for dopamine (DAT), norepinephrine (NET), and serotonin (SERT) is thought to be fueled by the transmembrane Na+ gradient, but it is conceivable that they can also tap other energy sources, for example, membrane voltage and/or the transmembrane K+ gradient. We have addressed this by recording uptake of endogenous substrates or the fluorescent substrate APP+(4-(4-dimethylamino)phenyl-1-methylpyridinium) under voltage control in cells expressing DAT, NET, or SERT. We have shown that DAT and NET differ from SERT in intracellular handling of K+. In DAT and NET, substrate uptake was voltage-dependent due to the transient nature of intracellular K+ binding, which precluded K+ antiport. SERT, however, antiports K+ and achieves voltage-independent transport. Thus, there is a trade-off between maintaining constant uptake and harvesting membrane potential for concentrative power, which we conclude to occur due to subtle differences in the kinetics of co-substrate ion binding in closely related transporters.
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Affiliation(s)
- Shreyas Bhat
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Marco Niello
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Klaus Schicker
- Division of Neurophysiology and Neuropharmacology, Centre for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Christian Pifl
- Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Harald H Sitte
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Walter Sandtner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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20
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Ranftler C, Nagl D, Sparer A, Röhrich A, Freissmuth M, El-Kasaby A, Nasrollahi Shirazi S, Koban F, Tschegg C, Nizet S. Binding and neutralization of C. difficile toxins A and B by purified clinoptilolite-tuff. PLoS One 2021; 16:e0252211. [PMID: 34043688 PMCID: PMC8158989 DOI: 10.1371/journal.pone.0252211] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 05/11/2021] [Indexed: 12/31/2022] Open
Abstract
Clostridioides difficile (C. difficile) infection is a major public health problem worldwide. The current treatment of C. difficile-associated diarrhea relies on the use of antibacterial agents. However, recurrences are frequent. The main virulence factors of C. difficile are two secreted cytotoxic proteins toxin A and toxin B. Alternative research exploring toxin binding by resins found a reduced rate of recurrence by administration of tolevamer. Hence, binding of exotoxins may be useful in preventing a relapse provided that the adsorbent is innocuous. Here, we examined the toxin binding capacity of G-PUR®, a purified version of natural clinoptilolite-tuff. Our observations showed that the purified clinoptilolite-tuff adsorbed clinically relevant amounts of C. difficile toxins A and B in vitro and neutralized their action in a Caco-2 intestinal model. This conclusion is based on four independent sets of findings: G-PUR® abrogated toxin-induced (i) RAC1 glucosylation, (ii) redistribution of occludin, (iii) rarefaction of the brush border as visualized by scanning electron microscopy and (iv) breakdown of the epithelial barrier recorded by transepithelial electrical resistance monitoring. Finally, we confirmed that the epithelial monolayer tolerated G-PUR® over a wide range of particle densities. Our findings justify the further exploration of purified clinoptilolite-tuff as a safe agent in the treatment and/or prevention of C. difficile-associated diarrhea.
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Affiliation(s)
- Carmen Ranftler
- GLOCK Health, Science and Research G.m.b.H., Deutsch-Wagram, Austria
| | - Dietmar Nagl
- GLOCK Health, Science and Research G.m.b.H., Deutsch-Wagram, Austria
| | - Andreas Sparer
- GLOCK Health, Science and Research G.m.b.H., Deutsch-Wagram, Austria
| | - Andreas Röhrich
- GLOCK Health, Science and Research G.m.b.H., Deutsch-Wagram, Austria
| | - Michael Freissmuth
- Institute of Pharmacology & Gaston H. Glock Research Laboratories for Explorative Drug Development, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Ali El-Kasaby
- Institute of Pharmacology & Gaston H. Glock Research Laboratories for Explorative Drug Development, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Shahrooz Nasrollahi Shirazi
- Institute of Pharmacology & Gaston H. Glock Research Laboratories for Explorative Drug Development, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Florian Koban
- Institute of Pharmacology & Gaston H. Glock Research Laboratories for Explorative Drug Development, Centre of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Cornelius Tschegg
- GLOCK Health, Science and Research G.m.b.H., Deutsch-Wagram, Austria
| | - Stephane Nizet
- GLOCK Health, Science and Research G.m.b.H., Deutsch-Wagram, Austria
- * E-mail:
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21
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Ng J, Barral S, De La Fuente Barrigon C, Lignani G, Erdem FA, Wallings R, Privolizzi R, Rossignoli G, Alrashidi H, Heasman S, Meyer E, Ngoh A, Pope S, Karda R, Perocheau D, Baruteau J, Suff N, Antinao Diaz J, Schorge S, Vowles J, Marshall LR, Cowley SA, Sucic S, Freissmuth M, Counsell JR, Wade-Martins R, Heales SJR, Rahim AA, Bencze M, Waddington SN, Kurian MA. Gene therapy restores dopamine transporter expression and ameliorates pathology in iPSC and mouse models of infantile parkinsonism. Sci Transl Med 2021; 13:eaaw1564. [PMID: 34011628 PMCID: PMC7612279 DOI: 10.1126/scitranslmed.aaw1564] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 08/20/2020] [Accepted: 02/20/2021] [Indexed: 12/11/2022]
Abstract
Most inherited neurodegenerative disorders are incurable, and often only palliative treatment is available. Precision medicine has great potential to address this unmet clinical need. We explored this paradigm in dopamine transporter deficiency syndrome (DTDS), caused by biallelic loss-of-function mutations in SLC6A3, encoding the dopamine transporter (DAT). Patients present with early infantile hyperkinesia, severe progressive childhood parkinsonism, and raised cerebrospinal fluid dopamine metabolites. The absence of effective treatments and relentless disease course frequently leads to death in childhood. Using patient-derived induced pluripotent stem cells (iPSCs), we generated a midbrain dopaminergic (mDA) neuron model of DTDS that exhibited marked impairment of DAT activity, apoptotic neurodegeneration associated with TNFα-mediated inflammation, and dopamine toxicity. Partial restoration of DAT activity by the pharmacochaperone pifithrin-μ was mutation-specific. In contrast, lentiviral gene transfer of wild-type human SLC6A3 complementary DNA restored DAT activity and prevented neurodegeneration in all patient-derived mDA lines. To progress toward clinical translation, we used the knockout mouse model of DTDS that recapitulates human disease, exhibiting parkinsonism features, including tremor, bradykinesia, and premature death. Neonatal intracerebroventricular injection of human SLC6A3 using an adeno-associated virus (AAV) vector provided neuronal expression of human DAT, which ameliorated motor phenotype, life span, and neuronal survival in the substantia nigra and striatum, although off-target neurotoxic effects were seen at higher dosage. These were avoided with stereotactic delivery of AAV2.SLC6A3 gene therapy targeted to the midbrain of adult knockout mice, which rescued both motor phenotype and neurodegeneration, suggesting that targeted AAV gene therapy might be effective for patients with DTDS.
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Affiliation(s)
- Joanne Ng
- Gene Transfer Technology Group, EGA-Institute for Women's Health, University College London, London, WC1E 6HX, UK
- Developmental Neurosciences, Zayed Centre for Research into Rare Disease in Children, GOS-Institute of Child Health, University College London, London, WC1N 1DZ, UK
| | - Serena Barral
- Developmental Neurosciences, Zayed Centre for Research into Rare Disease in Children, GOS-Institute of Child Health, University College London, London, WC1N 1DZ, UK.
| | | | - Gabriele Lignani
- Clinical and Experimental Epilepsy, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Fatma A Erdem
- Developmental Neurosciences, Zayed Centre for Research into Rare Disease in Children, GOS-Institute of Child Health, University College London, London, WC1N 1DZ, UK
- Institute of Pharmacology and Gaston H. Glock Laboratories for Exploratory Drug Research, Centre of Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
| | - Rebecca Wallings
- Oxford Parkinson's Disease Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3PT, UK
| | - Riccardo Privolizzi
- Gene Transfer Technology Group, EGA-Institute for Women's Health, University College London, London, WC1E 6HX, UK
- Developmental Neurosciences, Zayed Centre for Research into Rare Disease in Children, GOS-Institute of Child Health, University College London, London, WC1N 1DZ, UK
| | - Giada Rossignoli
- Developmental Neurosciences, Zayed Centre for Research into Rare Disease in Children, GOS-Institute of Child Health, University College London, London, WC1N 1DZ, UK
| | - Haya Alrashidi
- Genetics and Genomic Medicine, GOS-Institute of Child Health, University College London, London, WC1N 1EH, UK
| | - Sonja Heasman
- Developmental Neurosciences, Zayed Centre for Research into Rare Disease in Children, GOS-Institute of Child Health, University College London, London, WC1N 1DZ, UK
| | - Esther Meyer
- Developmental Neurosciences, Zayed Centre for Research into Rare Disease in Children, GOS-Institute of Child Health, University College London, London, WC1N 1DZ, UK
| | - Adeline Ngoh
- Developmental Neurosciences, Zayed Centre for Research into Rare Disease in Children, GOS-Institute of Child Health, University College London, London, WC1N 1DZ, UK
| | - Simon Pope
- Neurometabolic Unit, National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG, UK
| | - Rajvinder Karda
- Gene Transfer Technology Group, EGA-Institute for Women's Health, University College London, London, WC1E 6HX, UK
| | - Dany Perocheau
- Gene Transfer Technology Group, EGA-Institute for Women's Health, University College London, London, WC1E 6HX, UK
| | - Julien Baruteau
- Gene Transfer Technology Group, EGA-Institute for Women's Health, University College London, London, WC1E 6HX, UK
- Genetics and Genomic Medicine, GOS-Institute of Child Health, University College London, London, WC1N 1EH, UK
| | - Natalie Suff
- Gene Transfer Technology Group, EGA-Institute for Women's Health, University College London, London, WC1E 6HX, UK
- Department of Women and Children's Health, King's College London, London, WC2R 2LS, UK
| | - Juan Antinao Diaz
- Gene Transfer Technology Group, EGA-Institute for Women's Health, University College London, London, WC1E 6HX, UK
| | - Stephanie Schorge
- Clinical and Experimental Epilepsy, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
- Pharmacology, School of Pharmacy, University College London, London, WC1N 1AX, UK
| | - Jane Vowles
- James Martin Stem Cell Facility, Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, UK
| | - Lucy R Marshall
- Infection, Immunity, Inflammation, GOS-Institute of Child Health, University College London, London, WC1N 1EH, UK
| | - Sally A Cowley
- James Martin Stem Cell Facility, Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, UK
| | - Sonja Sucic
- Institute of Pharmacology and Gaston H. Glock Laboratories for Exploratory Drug Research, Centre of Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and Gaston H. Glock Laboratories for Exploratory Drug Research, Centre of Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
| | - John R Counsell
- Developmental Neurosciences, GOS-Institute of Child Health, University College London, London, WC1N 1EH, UK
| | - Richard Wade-Martins
- Oxford Parkinson's Disease Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3PT, UK
| | - Simon J R Heales
- Genetics and Genomic Medicine, GOS-Institute of Child Health, University College London, London, WC1N 1EH, UK
- Neurometabolic Unit, National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG, UK
| | - Ahad A Rahim
- Pharmacology, School of Pharmacy, University College London, London, WC1N 1AX, UK
| | - Maximilien Bencze
- Developmental Neurosciences, GOS-Institute of Child Health, University College London, London, WC1N 1EH, UK
- University Paris Est Creteil, INSERM, IMRB, 94000 Creteil, France
| | - Simon N Waddington
- Gene Transfer Technology Group, EGA-Institute for Women's Health, University College London, London, WC1E 6HX, UK.
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Faculty of Health Sciences, University of the Witwatersrand, 2193 Johannesburg, South Africa
| | - Manju A Kurian
- Developmental Neurosciences, Zayed Centre for Research into Rare Disease in Children, GOS-Institute of Child Health, University College London, London, WC1N 1DZ, UK
- Department of Neurology, Great Ormond Street Hospital for Children, London, WC1N 3JH, UK
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22
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Saha K, Yang JW, Hofmaier T, Venkatesan S, Steinkellner T, Kudlacek O, Sucic S, Freissmuth M, Sitte HH. Constitutive Endocytosis of the Neuronal Glutamate Transporter Excitatory Amino Acid Transporter-3 Requires ARFGAP1. Front Physiol 2021; 12:671034. [PMID: 34040545 PMCID: PMC8141794 DOI: 10.3389/fphys.2021.671034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 04/13/2021] [Indexed: 12/12/2022] Open
Abstract
The eukaryotic endocytic pathway regulates protein levels available at the plasma membrane by recycling them into specific endosomal compartments. ARFGAP1 is a component of the coat protein I (COPI) complex but it also plays a role in promoting adapter protein-2 (AP-2) mediated endocytosis. The excitatory amino acid transporter-3 (EAAT3) mediates the reuptake of glutamate from the synaptic cleft to achieve rapid termination of synaptic transmission at glutamatergic synapses. In this study, we identified two interacting proteins of EAAT3 by mass spectrometry (MS) ARFGAP1 and ARF6. We explored the role of ARFGAP1 and ARF6 in the endocytosis of EAAT3. Our data revealed that ARFGAP1 plays a role in the recycling of EAAT3, by utilizing its GTPase activating protein (GAP) activity and ARF6 acting as the substrate. ARFGAP1 promotes cargo sorting of EAAT3 via a single phenylalanine residue (F508) located at the C-terminus of the transporter. ARFGAP1-promoted AP-2 dependent endocytosis is abolished upon neutralizing F508. We utilized a heterologous expression system to identify an additional motif in the C-terminus of EAAT3 that regulates its endocytosis. Impairment in endocytosis did not affect somatodendritic targeting in cultured hippocampal neurons. Our findings support a model where endocytosis of EAAT3 is a multifactorial event regulated by ARFGAP1, occurring via the C-terminus of the transporter, and is the first study to examine the role of ARFGAP1 in the endocytosis of a transport protein.
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Affiliation(s)
- Kusumika Saha
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria.,Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Descartes, Paris, France
| | - Jae-Won Yang
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Tina Hofmaier
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - SanthoshKannan Venkatesan
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Thomas Steinkellner
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Oliver Kudlacek
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Harald H Sitte
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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23
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Bhat S, Guthrie DA, Kasture A, El-Kasaby A, Cao J, Bonifazi A, Ku T, Giancola JB, Hummel T, Freissmuth M, Newman AH. Tropane-Based Ibogaine Analog Rescues Folding-Deficient Serotonin and Dopamine Transporters. ACS Pharmacol Transl Sci 2021; 4:503-516. [PMID: 33860180 PMCID: PMC8033614 DOI: 10.1021/acsptsci.0c00102] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Indexed: 02/05/2023]
Abstract
![]()
Missense
mutations that give rise to protein misfolding are rare,
but collectively, defective protein folding diseases are consequential.
Folding deficiencies are amenable to pharmacological correction (pharmacochaperoning),
but the underlying mechanisms remain enigmatic. Ibogaine and its active
metabolite noribogaine correct folding defects in the dopamine transporter
(DAT), but they rescue only a very limited number of folding-deficient
DAT mutant proteins, which give rise to infantile Parkinsonism and
dystonia. Herein, a series of analogs was generated by reconfiguring
the complex ibogaine ring system and exploring the structural requirements
for binding to wild-type transporters, as well as for rescuing two
equivalent synthetic folding-deficient mutants, SERT-PG601,602AA and DAT-PG584,585AA. The most active tropane-based
analog (9b) was also an effective pharmacochaperone in vivo in Drosophila harboring the DAT-PG584,585AA mutation and rescued 6 out of 13 disease-associated
human DAT mutant proteins in vitro. Hence, a novel
lead pharmacochaperone has been identified that demonstrates medication
development potential for patients harboring DAT mutations.
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Affiliation(s)
- Shreyas Bhat
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Waehringerstrasse 13a, Vienna 1090, Austria
| | - Daryl A Guthrie
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, Maryland 21224, United States
| | - Ameya Kasture
- Department of Neurobiology, University of Vienna, Vienna 1090, Austria
| | - Ali El-Kasaby
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Waehringerstrasse 13a, Vienna 1090, Austria
| | - Jianjing Cao
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, Maryland 21224, United States
| | - Alessandro Bonifazi
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, Maryland 21224, United States
| | - Therese Ku
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, Maryland 21224, United States
| | - JoLynn B Giancola
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, Maryland 21224, United States
| | - Thomas Hummel
- Department of Neurobiology, University of Vienna, Vienna 1090, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Waehringerstrasse 13a, Vienna 1090, Austria
| | - Amy Hauck Newman
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, Maryland 21224, United States
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24
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Schicker K, Bhat S, Farr C, Burtscher V, Horner A, Freissmuth M, Sandtner W. Descriptors of Secondary Active Transporter Function and How They Relate to Partial Reactions in the Transport Cycle. Membranes (Basel) 2021; 11:178. [PMID: 33802510 PMCID: PMC8001282 DOI: 10.3390/membranes11030178] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 02/25/2021] [Accepted: 02/27/2021] [Indexed: 12/19/2022]
Abstract
Plasmalemmal solute carriers (SLCs) gauge and control solute abundance across cellular membranes. By virtue of this action, they play an important role in numerous physiological processes. Mutations in genes encoding the SLCs alter amino acid sequence that often leads to impaired protein function and onset of monogenic disorders. To understand how these altered proteins cause disease, it is necessary to undertake relevant functional assays. These experiments reveal descriptors of SLC function such as the maximal transport velocity (Vmax), the Michaelis constant for solute uptake (KM), potencies for inhibition of transporter function (IC50/EC50), and many more. In several instances, the mutated versions of different SLC transporters differ from their wild-type counterparts in the value of these descriptors. While determination of these experimental parameters can provide conjecture as to how the mutation gives rise to disease, they seldom provide any definitive insights on how a variant differ from the wild-type transporter in its operation. This is because the experimental determination of association between values of the descriptors and several partial reactions a transporter undergoes is casual, but not causal, at best. In the present study, we employ kinetic models that allow us to derive explicit mathematical terms and provide experimental descriptors as a function of the rate constants used to parameterize the kinetic model of the transport cycle. We show that it is possible to utilize these mathematical expressions to deduce, from experimental outcomes, how the mutation has impinged on partial reactions in the transport cycle.
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Affiliation(s)
- Klaus Schicker
- Center for Physiology and Pharmacology, Division of Neurophysiology and Neuropharmacology, Medical University of Vienna, 1090 Vienna, Austria;
| | - Shreyas Bhat
- Center of Physiology and Pharmacology, Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, 1090 Vienna, Austria; (S.B.); (C.F.); (V.B.); (M.F.)
| | - Clemens Farr
- Center of Physiology and Pharmacology, Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, 1090 Vienna, Austria; (S.B.); (C.F.); (V.B.); (M.F.)
| | - Verena Burtscher
- Center of Physiology and Pharmacology, Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, 1090 Vienna, Austria; (S.B.); (C.F.); (V.B.); (M.F.)
| | - Andreas Horner
- Institute of Biophysics, Johannes Kepler University Linz, 4040 Linz, Austria;
| | - Michael Freissmuth
- Center of Physiology and Pharmacology, Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, 1090 Vienna, Austria; (S.B.); (C.F.); (V.B.); (M.F.)
| | - Walter Sandtner
- Center of Physiology and Pharmacology, Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, 1090 Vienna, Austria; (S.B.); (C.F.); (V.B.); (M.F.)
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25
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Bhat S, El-Kasaby A, Freissmuth M, Sucic S. Functional and Biochemical Consequences of Disease Variants in Neurotransmitter Transporters: A Special Emphasis on Folding and Trafficking Deficits. Pharmacol Ther 2020; 222:107785. [PMID: 33310157 PMCID: PMC7612411 DOI: 10.1016/j.pharmthera.2020.107785] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 12/02/2020] [Indexed: 01/30/2023]
Abstract
Neurotransmitters, such as γ-aminobutyric acid, glutamate, acetyl choline, glycine and the monoamines, facilitate the crosstalk within the central nervous system. The designated neurotransmitter transporters (NTTs) both release and take up neurotransmitters to and from the synaptic cleft. NTT dysfunction can lead to severe pathophysiological consequences, e.g. epilepsy, intellectual disability, or Parkinson’s disease. Genetic point mutations in NTTs have recently been associated with the onset of various neurological disorders. Some of these mutations trigger folding defects in the NTT proteins. Correct folding is a prerequisite for the export of NTTs from the endoplasmic reticulum (ER) and the subsequent trafficking to their pertinent site of action, typically at the plasma membrane. Recent studies have uncovered some of the key features in the molecular machinery responsible for transporter protein folding, e.g., the role of heat shock proteins in fine-tuning the ER quality control mechanisms in cells. The therapeutic significance of understanding these events is apparent from the rising number of reports, which directly link different pathological conditions to NTT misfolding. For instance, folding-deficient variants of the human transporters for dopamine or GABA lead to infantile parkinsonism/dystonia and epilepsy, respectively. From a therapeutic point of view, some folding-deficient NTTs are amenable to functional rescue by small molecules, known as chemical and pharmacological chaperones.
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Affiliation(s)
- Shreyas Bhat
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Ali El-Kasaby
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
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26
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Farr CV, El-Kasaby A, Freissmuth M, Sucic S. The Creatine Transporter Unfolded: A Knotty Premise in the Cerebral Creatine Deficiency Syndrome. Front Synaptic Neurosci 2020; 12:588954. [PMID: 33192443 PMCID: PMC7644880 DOI: 10.3389/fnsyn.2020.588954] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 09/18/2020] [Indexed: 12/16/2022] Open
Abstract
Creatine provides cells with high-energy phosphates for the rapid reconstitution of hydrolyzed adenosine triphosphate. The eponymous creatine transporter (CRT1/SLC6A8) belongs to a family of solute carrier 6 (SLC6) proteins. The key role of CRT1 is to translocate creatine across tissue barriers and into target cells, such as neurons and myocytes. Individuals harboring mutations in the coding sequence of the human CRT1 gene develop creatine transporter deficiency (CTD), one of the pivotal underlying causes of cerebral creatine deficiency syndrome. CTD encompasses an array of clinical manifestations, including severe intellectual disability, epilepsy, autism, development delay, and motor dysfunction. CTD is characterized by the absence of cerebral creatine, which implies an indispensable role for CRT1 in supplying the brain cells with creatine. CTD-associated variants dramatically reduce or abolish creatine transport activity by CRT1. Many of these are point mutations that are known to trigger folding defects, leading to the retention of encoded CRT1 proteins in the endoplasmic reticulum and precluding their delivery to the cell surface. Misfolding of several related SLC6 transporters also gives rise to detrimental pathologic conditions in people; e.g., mutations in the dopamine transporter induce infantile parkinsonism/dystonia, while mutations in the GABA transporter 1 cause treatment-resistant epilepsy. In some cases, folding defects are amenable to rescue by small molecules, known as pharmacological and chemical chaperones, which restore the cell surface expression and transport activity of the previously non-functional proteins. Insights from the recent molecular, animal and human case studies of CTD add toward our understanding of this complex disorder and reveal the wide-ranging effects elicited upon CRT1 dysfunction. This grants novel therapeutic prospects for the treatment of patients afflicted with CTD, e.g., modifying the creatine molecule to facilitate CRT1-independent entry into brain cells, or correcting folding-deficient and loss-of-function CTD variants using pharmacochaperones and/or allosteric modulators. The latter justifies a search for additional compounds with a capacity to correct mutation-specific defects.
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Affiliation(s)
| | | | | | - Sonja Sucic
- Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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27
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Nasrollahi-Shirazi S, Szöllösi D, Yang Q, Muratspahic E, El-Kasaby A, Sucic S, Stockner T, Nanoff C, Freissmuth M. Functional Impact of the G279S Substitution in the Adenosine A 1-Receptor (A 1R-G279S 7.44), a Mutation Associated with Parkinson's Disease. Mol Pharmacol 2020; 98:250-266. [PMID: 32817461 DOI: 10.1124/molpharm.120.000003] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 06/17/2020] [Indexed: 12/21/2022] Open
Abstract
In medium-size, spiny striatal neurons of the direct pathway, dopamine D1- and adenosine A1-receptors are coexpressed and are mutually antagonistic. Recently, a mutation in the gene encoding the A1-receptor (A1R), A1R-G279S7.44, was identified in an Iranian family: two affected offspring suffered from early-onset l-DOPA-responsive Parkinson's disease. The link between the mutation and the phenotype is unclear. Here, we explored the functional consequence of the G279S substitution on the activity of the A1-receptor after heterologous expression in HEK293 cells. The mutation did not affect surface expression and ligand binding but changed the susceptibility to heat denaturation: the thermodynamic stability of A1R-G279S7.44 was enhanced by about 2 and 8 K when compared with wild-type A1-receptor and A1R-Y288A7.53 (a folding-deficient variant used as a reference), respectively. In contrast, the kinetic stability was reduced, indicating a lower energy barrier for conformational transitions in A1R-G279S7.44 (73 ± 23 kJ/mol) than in wild-type A1R (135 ± 4 kJ/mol) or in A1R-Y288A7.53 (184 ± 24 kJ/mol). Consistent with this lower energy barrier, A1R-G279S7.44 was more effective in promoting guanine nucleotide exchange than wild-type A1R. We detected similar levels of complexes formed between D1-receptors and wild-type A1R or A1R-G279S7.44 by coimmunoprecipitation and bioluminescence resonance energy transfer. However, lower concentrations of agonist were required for half-maximum inhibition of dopamine-induced cAMP accumulation in cells coexpressing D1-receptor and A1R-G279S7.44 than in those coexpressing wild-type A1R. These observations predict enhanced inhibition of dopaminergic signaling by A1R-G279S7.44 in vivo, consistent with a pathogenic role in Parkinson's disease. SIGNIFICANCE STATEMENT: Parkinson's disease is caused by a loss of dopaminergic input from the substantia nigra to the caudate nucleus and the putamen. Activation of the adenosine A1-receptor antagonizes responses elicited by dopamine D1-receptor. We show that this activity is more pronounced in a mutant version of the A1-receptor (A1R-G279S7.44), which was identified in individuals suffering from early-onset Parkinson's disease.
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Affiliation(s)
- Shahrooz Nasrollahi-Shirazi
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Daniel Szöllösi
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Qiong Yang
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Edin Muratspahic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Ali El-Kasaby
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Thomas Stockner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Christian Nanoff
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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Zhu R, Sandtner W, Ahiable JEA, Newman AH, Freissmuth M, Sitte HH, Hinterdorfer P. Allosterically Linked Binding Sites in Serotonin Transporter Revealed by Single Molecule Force Spectroscopy. Front Mol Biosci 2020; 7:99. [PMID: 32656227 PMCID: PMC7325972 DOI: 10.3389/fmolb.2020.00099] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 05/01/2020] [Indexed: 01/24/2023] Open
Abstract
Crystal structures and experiments relying on the tools of molecular pharmacology reported conflicting results on ligand binding sites in neurotransmitter/sodium symporters (NSS). We explored the number and functionality of ligand binding sites of NSS in a physiological setting by designing novel tools for atomic force microscopy (AFM). These allow for directly measuring the interaction forces between the serotonin transporter (SERT) and the antidepressant S-citalopram (S-CIT) on the single molecule level: the AFM cantilever tips were functionalized with S-CIT via a flexible polyethylene glycol (PEG) linker. The tip chemistry was validated by specific force measurements and recognition imaging on CHO cells. Two distinct populations of characteristic binding strengths of S-CIT binding to SERT were revealed in Na+-containing buffer. In contrast, in Li+-containing buffer, SERT showed only low force interactions. Conversely, the vestibular mutant SERT-G402H merely displayed the high force population. These observations provide physical evidence for the existence of two binding sites in SERT. The dissociation rate constant of both binding sites was extracted by varying the dynamics of the force-probing experiments. Competition experiments revealed that the two sites are allosterically coupled and exert reciprocal modulation.
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Affiliation(s)
- Rong Zhu
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Walter Sandtner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Joan E A Ahiable
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Amy Hauck Newman
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, United States
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Harald H Sitte
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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Esendir E, Burtscher V, Sandtner W, Freissmuth M. Interrogating the Role of Extracellular Loops 2 and 4 (EL2 and EL4) of the Serotonin Transporter with Antibody Fragments. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.03940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Eray Esendir
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology Medical University of Vienna Austria
| | - Verena Burtscher
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology Medical University of Vienna Austria
| | - Walter Sandtner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology Medical University of Vienna Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology Medical University of Vienna Austria
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Cukaci C, Freissmuth M, Mann C, Marti J, Sperl V. Against all odds-the persistent popularity of homeopathy. Wien Klin Wochenschr 2020; 132:232-242. [PMID: 32152694 PMCID: PMC7253376 DOI: 10.1007/s00508-020-01624-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Accepted: 02/26/2020] [Indexed: 12/03/2022]
Abstract
The use of homeopathy is remarkably popular. Popularity, however, is not an arbiter in a scientific discourse. In fact, the assumptions underlying homeopathy violate fundamental laws of nature. Homeopathy does not have any explanatory power and fails other criteria established for a scientific approach. Two large-scale efforts have recently documented that in spite of a plethora of clinical trials there is no evidence that homeopathic remedies have any therapeutic effect, which goes beyond that of a placebo. Relaxed regulations and lack of scientific literacy and of health education allow for continuous thriving of homeopathy. While the tide may be changing on the regulatory side, health education of the general public is presumably more important to support informed decision making by patients. Otherwise, the responsible patient, who is posited to decide on the medical choices, remains a convenient legal fiction.
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Affiliation(s)
- Cemre Cukaci
- Association of Medical Students, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology, Centre of Physiology and Pharmacology, Medical University of Vienna, Währinger Str. 13a, 1090, Vienna, Austria.
| | - Christopher Mann
- Association of Medical Students, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria
| | - Joshua Marti
- Association of Medical Students, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria
| | - Veronika Sperl
- Association of Medical Students, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria
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31
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Zhu R, Gobl J, Holy M, Kudlacek O, Sandtner W, Stockner T, Gruber HJ, Freissmuth M, Hauck Newman A, Sitte HH, Hinterdorfer P. Two Distinct Ligand Binding Sites in Monoamine Transporters Monitored by Nanopharmacological Force Sensing. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.3337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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32
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Burtscher V, Hasenhuetl PS, Hotka M, Freissmuth M, Sandtner W. Deciphering the Nature of M1R Transient Currents. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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33
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Zebedin-Brandl E, Themanns M, Kazemi Z, Nasrollahi-Shirazi S, Mussbacher M, Heyes E, Meissl K, Prchal-Murphy M, Strohmaier W, Krumpl G, Freissmuth M. Regimen-dependent synergism and antagonism of treprostinil and vildagliptin in hematopoietic cell transplantation. J Mol Med (Berl) 2019; 98:233-243. [PMID: 31872285 PMCID: PMC7007891 DOI: 10.1007/s00109-019-01869-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 11/12/2019] [Accepted: 12/10/2019] [Indexed: 02/07/2023]
Abstract
The cell dose in umbilical cord blood units is a major determinant for the outcome of hematopoietic cell transplantation. Prostaglandin analogs and dipeptidylpeptidase-4 (DPP4/CD26)-inhibitors enhance the ability of hematopoietic stem cells (HSCs) to reconstitute hematopoiesis. Here we explored the synergism between treprostinil, a stable prostaglandin agonist, and the DPP4/CD26-inhibitor vildagliptin. The combination of treprostinil and forskolin caused a modest but statistically significant increase in the surface levels of DPP4/CD26 on hematopoietic stem and progenitor cells (HSPCs) derived from murine bone and human cord blood. Their migration towards stromal cell-derived factor-1 (SDF-1/CXCL12) was enhanced, if they were pretreated with treprostinil and forskolin, and further augmented by vildagliptin. Administration of vildagliptin rescued 25% of lethally irradiated recipient mice injected with a limiting number of untreated HSPCs, but 90 to 100% of recipients injected with HSPCs preincubated with treprostinil and forskolin. The efficacy of vildagliptin surpassed that of treprostinil (60% rescue). Surprisingly, concomitant administration of vildagliptin and treprostinil resulted in poor survival of recipients indicating mutual antagonism, which was recapitulated when homing of and colony formation by HSPCs were assessed. These observations of regimen-dependent synergism and antagonism of treprostinil and vildagliptin are of translational relevance for the design of clinical trials. KEY MESSAGES: Pretreatment with treprostinil increases surface levels of DPP4/CD26 in HSPCs. Vildagliptin enhances in vitro migration of pretreated HSPCs. Vildagliptin enhances in vivo homing and engraftment of pretreated HSPCs. Unexpected mutual antagonism in vivo by concomitant administration of vildagliptin and treprostinil.
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Affiliation(s)
- Eva Zebedin-Brandl
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, 1090, Vienna, Austria
| | - Madeleine Themanns
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, 1090, Vienna, Austria
| | - Zahra Kazemi
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, 1090, Vienna, Austria
| | - Shahrooz Nasrollahi-Shirazi
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, 1090, Vienna, Austria
| | - Marion Mussbacher
- Institute of Vascular Biology, Centre of Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Elizabeth Heyes
- Institute for Medical Biochemistry, University of Veterinary Medicine, 1210, Vienna, Austria
| | - Katrin Meissl
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine, 1210, Vienna, Austria
| | - Michaela Prchal-Murphy
- Institute of Pharmacology and Toxicology, Department of Biomedical Sciences, University of Veterinary Medicine, 1210, Vienna, Austria
| | | | - Guenther Krumpl
- MRN Medical Research GmbH, Postgasse 11, 1010, Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, 1090, Vienna, Austria.
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34
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Altenbrunner-Martinek B, Witek M, Koppatz K, Freissmuth M, Kraft A, Sutter C, Torres S, Gelfert C, Wittek T. Effect of rain on absorption after transdermal application of flunixin in calves. J Vet Pharmacol Ther 2019; 43:87-90. [PMID: 31833566 PMCID: PMC7003742 DOI: 10.1111/jvp.12829] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 11/04/2019] [Accepted: 11/19/2019] [Indexed: 11/27/2022]
Abstract
Flunixin is a nonsteroidal anti‐inflammatory drug (NSAID) that has anti‐inflammatory, anti‐pyretic, and analgesic effects. Recently, a novel transdermal formulation was developed (Finadyne® Transdermal, MSD Animal Health) and is now the first NSAID registered to be administered as a pour‐on product in cattle. According to the manufacturer's instructions, the pour‐on product should be applied only to dry skin and exposure to rain should be avoided for at least 6 hr after application. The objective of the study was to evaluate the effect of simulated exposure to light or heavy rain on flunixin absorption and bioavailability within the first 4 hr after administration. Therefore, an isocratic HPLC method was developed to quantify flunixin concentrations in bovine serum by UV detection. Light rain decreased flunixin absorption only when rain started immediately after flunixin administration, while light rain starting more than 30 min after administration of flunixin had no effect on absorption. Absorption and bioavailability of flunixin was impacted under simulated heavy rain conditions, when exposure to rain occurred within one hour after the application of the pour‐on formulation, but not later.
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Affiliation(s)
| | - Martin Witek
- Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University Vienna, Vienna, Austria
| | - Karl Koppatz
- Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University Vienna, Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University Vienna, Vienna, Austria
| | - Alinta Kraft
- Clinic for Ruminants, University for Veterinary Medicine Vienna, Vienna, Austria
| | - Charlene Sutter
- Clinic for Ruminants, University for Veterinary Medicine Vienna, Vienna, Austria
| | | | | | - Thomas Wittek
- Clinic for Ruminants, University for Veterinary Medicine Vienna, Vienna, Austria
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35
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Geetha N, Mihaly J, Stockenhuber A, Blasi F, Uhrin P, Binder BR, Freissmuth M, Breuss JM. Withdrawal: Signal integration and coincidence detection in the mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) cascade: Concomitant activation of receptor tyrosine kinases and of LRP-1 leads to sustained ERK phosphorylation via down-regulation of dual specificity phosphatases (DUSP1 and -6). J Biol Chem 2019; 294:13201. [DOI: 10.1074/jbc.w119.010444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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36
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Erdem FA, Ilic M, Koppensteiner P, Gołacki J, Lubec G, Freissmuth M, Sandtner W. A comparison of the transport kinetics of glycine transporter 1 and glycine transporter 2. J Gen Physiol 2019; 151:1035-1050. [PMID: 31270129 PMCID: PMC6683666 DOI: 10.1085/jgp.201912318] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 04/16/2019] [Accepted: 06/17/2019] [Indexed: 12/20/2022] Open
Abstract
Erdem et al. compare the kinetics of the SLC6 family glycine transporters GlyT1 and GlyT2. Though the two transporters are rate-limited by distinct reaction steps, they both display high transport capacity, with the kinetics of GlyT1 sufficient to supply extracellular glycine to the NMDA receptor. Transporters of the solute carrier 6 (SLC6) family translocate their cognate substrate together with Na+ and Cl−. Detailed kinetic models exist for the transporters of GABA (GAT1/SLC6A1) and the monoamines dopamine (DAT/SLC6A3) and serotonin (SERT/SLC6A4). Here, we posited that the transport cycle of individual SLC6 transporters reflects the physiological requirements they operate under. We tested this hypothesis by analyzing the transport cycle of glycine transporter 1 (GlyT1/SLC6A9) and glycine transporter 2 (GlyT2/SLC6A5). GlyT2 is the only SLC6 family member known to translocate glycine, Na+, and Cl− in a 1:3:1 stoichiometry. We analyzed partial reactions in real time by electrophysiological recordings. Contrary to monoamine transporters, both GlyTs were found to have a high transport capacity driven by rapid return of the empty transporter after release of Cl− on the intracellular side. Rapid cycling of both GlyTs was further supported by highly cooperative binding of cosubstrate ions and substrate such that their forward transport mode was maintained even under conditions of elevated intracellular Na+ or Cl−. The most important differences in the transport cycle of GlyT1 and GlyT2 arose from the kinetics of charge movement and the resulting voltage-dependent rate-limiting reactions: the kinetics of GlyT1 were governed by transition of the substrate-bound transporter from outward- to inward-facing conformations, whereas the kinetics of GlyT2 were governed by Na+ binding (or a related conformational change). Kinetic modeling showed that the kinetics of GlyT1 are ideally suited for supplying the extracellular glycine levels required for NMDA receptor activation.
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Affiliation(s)
- Fatma Asli Erdem
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Marija Ilic
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | | | - Jakub Gołacki
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Gert Lubec
- Neuroproteomics, Paracelsus Private Medical University, Salzburg, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Walter Sandtner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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Niello M, Cintulova D, Hellsberg E, Jäntsch K, Holy M, Ayatollahi LH, Cozzi NV, Freissmuth M, Sandtner W, Ecker GF, Mihovilovic MD, Sitte HH. para-Trifluoromethyl-methcathinone is an allosteric modulator of the serotonin transporter. Neuropharmacology 2019; 161:107615. [PMID: 31028773 DOI: 10.1016/j.neuropharm.2019.04.021] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 04/17/2019] [Accepted: 04/19/2019] [Indexed: 11/15/2022]
Abstract
The transporters for dopamine (DAT) and serotonin (SERT) are important targets in the treatment of psychiatric disorders including major depression, anxiety and attention-deficit hyperactivity disorder. Drugs acting at these transporters can act as inhibitors or as releasers. In addition, it has been recently appreciated that some compounds are less efficacious releasers than amphetamine. Thus, they are classified as partial releasers. Compounds can act on both SERT and DAT or display exquisite selectivity for either SERT or DAT, but the structural basis for selectivity is poorly understood. The trifluoromethyl-substitution of methcathinone in the para-position has been shown to dramatically shift the selectivity of methcathinone (MCAT) towards SERT. Here, we examined MCAT, para-trifluoromethyl-methcathinone (pCF3MCAT) and other analogues to understand (i) the determinants of selectivity and (ii) the effects of the para-CF3-substitution of MCAT on the transport cycle. We systematically tested different para-substituted MCATs by biochemical, computational and electrophysiological approaches: addition of the pCF3group, but not of other substituents with larger van der Waal's volume, lipophilicity or polarity, converted the DAT-selective MCAT into a SERT-selective partial releaser. Electrophysiological and superfusion experiments, together with kinetic modelling, showed that pCF3MCAT, but not MCAT, trapped a fraction of SERTs in an inactive state by occupying the S2-site. These findings define a new mechanism of action for partial releasers, which is distinct from the other two known binding modes underlying partial release. Our observations highlight the fact that the substrate permeation pathway of monoamine transporters supports multiple binding modes, which can be exploited for drug design. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
- Marco Niello
- Institute of Pharmacology, Medical University, Vienna, Austria
| | | | - Eva Hellsberg
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria
| | - Kathrin Jäntsch
- Institute of Pharmacology, Medical University, Vienna, Austria
| | - Marion Holy
- Institute of Pharmacology, Medical University, Vienna, Austria
| | | | - Nicholas V Cozzi
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, Madison, USA
| | | | - Walter Sandtner
- Institute of Pharmacology, Medical University, Vienna, Austria
| | - Gerhard F Ecker
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria
| | | | - Harald H Sitte
- Institute of Pharmacology, Medical University, Vienna, Austria.
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Muratspahić E, Freissmuth M, Gruber CW. Nature-Derived Peptides: A Growing Niche for GPCR Ligand Discovery. Trends Pharmacol Sci 2019; 40:309-326. [PMID: 30955896 DOI: 10.1016/j.tips.2019.03.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 02/26/2019] [Accepted: 03/06/2019] [Indexed: 12/11/2022]
Abstract
G protein-coupled receptors (GPCRs) represent important drug targets, as they regulate pivotal physiological processes and they have proved to be readily druggable. Natural products have been and continue to be amongst the most valuable sources for drug discovery and development. Here, we surveyed small molecules and (poly-)peptides derived from plants, animals, fungi, and bacteria, which modulate GPCR signaling. Among naturally occurring compounds, peptides from plants, cone-snails, snakes, spiders, scorpions, fungi, and bacteria are of particular interest as lead compounds for the development of GPCR ligands, since they cover a chemical space, which differs from that of synthetic small molecules. Peptides, however, face challenges, some of which can be overcome by studying plant-derived compounds. We argue here that the opportunities outweigh the challenges.
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Affiliation(s)
- Edin Muratspahić
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Austria; Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center for Physiology and Pharmacology, Medical University of Vienna, Austria
| | - Christian W Gruber
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Austria.
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Sucic S, El‐Kasaby A, Freissmuth M. 4‐Phenylbutyrate rescues folding‐deficient creatine transporter‐1 variants linked to the creatine transporter deficiency syndrome. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.780.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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40
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Kasture AS, Bartel D, Steinkellner T, Sucic S, Hummel T, Freissmuth M. Distinct contribution of axonal and somatodendritic serotonin transporters in drosophila olfaction. Neuropharmacology 2019; 161:107564. [PMID: 30851308 DOI: 10.1016/j.neuropharm.2019.03.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 02/11/2019] [Accepted: 03/03/2019] [Indexed: 01/07/2023]
Abstract
The serotonin transporter (SERT) regulates serotonergic neurotransmission by retrieving released serotonin and replenishing vesicular stores. SERT is not only delivered to axons but it is also present on the neuronal soma and on dendrites. It has not been possible to restrict the distribution of SERT without affecting transporter function. Hence, the physiological role of somatodendritic SERT remains enigmatic. The SERT C-terminus harbors a conserved RI-motif, which recruits SEC24C, a cargo receptor in the coatomer protein-II coat. Failure to engage SEC24C precludes axonal enrichment of SERT. Here we introduced a point mutation into the RI-motif of human SERT causing confinement of the resulting - otherwise fully functional - hSERT-R607A on the somatodendritic membrane of primary rat dorsal raphe neurons. Transgenic expression of the corresponding Drosophila mutant dSERT-R599A led to its enrichment in the somatodendritic compartment of serotonergic neurons in the fly brain. We explored the possible physiological role of somatodendritic SERT by comparing flies harboring wild type SERT and dSERT-R599A in a behavioral paradigm for serotonin-modulated odor perception. When globally re-expressed in serotonergic neurons, wild type SERT but not dSERT-R599A restored ethanol preference. In contrast, dSERT-R599A restored ethanol preference after targeted expression in contralaterally projecting, serotonin-immunoreactive deuterocerebral (CSD) interneurons, while expression of wild type SERT caused ethanol aversion. We conclude that, in CSD neurons, (i) somatodendritic SERT supports ethanol attraction, (ii) axonal SERT specifies ethanol aversion, (iii) the effect of axonal SERT can override that of somatodendritic SERT. These observations demonstrate a distinct biological role of somatodendritic and axonal serotonin transport. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
- Ameya Sanjay Kasture
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria; Department of Neurobiology, University of Vienna, A-1090 Vienna, Austria
| | - Daniela Bartel
- Department of Neurobiology, University of Vienna, A-1090 Vienna, Austria
| | - Thomas Steinkellner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Thomas Hummel
- Department of Neurobiology, University of Vienna, A-1090 Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
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Hasenhuetl PS, Bhat S, Freissmuth M, Sandtner W. Functional Selectivity and Partial Efficacy at the Monoamine Transporters: A Unified Model of Allosteric Modulation and Amphetamine-Induced Substrate Release. Mol Pharmacol 2018; 95:303-312. [PMID: 30567955 DOI: 10.1124/mol.118.114793] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 12/13/2018] [Indexed: 12/13/2022] Open
Abstract
All clinically approved drugs targeting the plasmalemmal transporters for dopamine, norepinephrine, and serotonin act either as competitive uptake inhibitors or as amphetamine-like releasers. Monoamine transporter (MAT) ligands that allosterically affect MAT-mediated substrate uptake, release, or both were recently discovered. Their modes of action have not yet been explained in a unified framework. Here, we go beyond competitive inhibitors and classic amphetamines and introduce concepts for partial efficacy at and allosteric modulation of MATs. After we elaborate on a kinetic account for amphetamine action, we provide an explanation for partial release (i.e., the observation that some amphetamines are less efficacious than others in inducing monoamine efflux). We then elucidate mechanisms of allosteric inhibition and stimulation of MATs, which can be functionally selective for either substrate uptake or amphetamine-induced release. These concepts are integrated into a parsimonious kinetic framework, which relies exclusively on physiologic transport modes (without any deviation from an alternating access mechanism). The model posits cooperative substrate and Na+ binding and functional selectivity by conformational selection (i.e., preference of the allosteric modulators for the substrate-loaded or substrate-free states of the transporter). Thus, current knowledge about the kinetics of monoamine transport is sufficiently detailed to provide a quantitative description of the releasing action of amphetamines, of substrate uptake, and of selective modulation thereof by allosteric modulators.
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Affiliation(s)
- Peter S Hasenhuetl
- Institute of Pharmacology, Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Shreyas Bhat
- Institute of Pharmacology, Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology, Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Walter Sandtner
- Institute of Pharmacology, Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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Kovalchuk V, Samluk Ł, Juraszek B, Jurkiewicz-Trząska D, Sucic S, Freissmuth M, Nałęcz KA. Trafficking of the amino acid transporter B 0,+ (SLC6A14) to the plasma membrane involves an exclusive interaction with SEC24C for its exit from the endoplasmic reticulum. Biochim Biophys Acta Mol Cell Res 2018; 1866:252-263. [PMID: 30445147 PMCID: PMC6314439 DOI: 10.1016/j.bbamcr.2018.11.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 11/02/2018] [Accepted: 11/12/2018] [Indexed: 12/16/2022]
Abstract
A plasma membrane amino acid transporter B0,+ (ATB0,+), encoded by the SLC6A14 gene, is specific for neutral and basic amino acids. It is up-regulated in several types of malignant cancers. Neurotransmitter transporters of the SLC6 family interact with specific SEC24 proteins of the COPII complex along their pathway from the endoplasmic reticulum (ER) to Golgi. This study focused on the possible role of SEC24 proteins in ATB0,+ trafficking. Rat ATB0,+ was expressed in HEK293 cells, its localization and trafficking were examined by Western blot, deglycosylation, immunofluorescence (co-localization with ER and trans-Golgi markers) and biotinylation. The expression of ATB0,+ at the plasma membrane was decreased by dominant negative mutants of SAR1, a GTPase, whose activity triggers the formation of the COPII complex. ATB0,+ co-precipitated with SEC24C (but not with the remaining isoforms A, B and D). This interaction was confirmed by immunocytochemistry and the proximity ligation assay. Co-localization of SEC24C with endogenous ATB0,+ was also observed in MCF-7 breast cancer cells. Contrary to the endogenous transporter, part of the overexpressed ATB0,+ is directed to proteolysis, a process significantly reversed by a proteasome inhibitor bortezomib. Co-transfection with a SEC24C dominant negative mutant attenuated ATB0,+ expression at the plasma membrane, due to proteolytic degradation. These results support a hypothesis that lysine at position +2 downstream of the ER export "RI" motif on the cargo protein is crucial for SEC24C binding and for further trafficking to the Golgi. Moreover, there is an equilibrium between ER export and degradation mechanisms in case of overexpressed transporter.
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Affiliation(s)
- Vasylyna Kovalchuk
- Laboratory of Transport through Biomembranes, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland
| | - Łukasz Samluk
- Laboratory of Transport through Biomembranes, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland
| | - Barbara Juraszek
- Laboratory of Transport through Biomembranes, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland
| | - Dominika Jurkiewicz-Trząska
- Laboratory of Transport through Biomembranes, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Katarzyna A Nałęcz
- Laboratory of Transport through Biomembranes, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland.
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Burtscher V, Hotka M, Li Y, Freissmuth M, Sandtner W. A label-free approach to detect ligand binding to cell surface proteins in real time. eLife 2018; 7:e34944. [PMID: 29697048 PMCID: PMC5991833 DOI: 10.7554/elife.34944] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 04/25/2018] [Indexed: 01/01/2023] Open
Abstract
Electrophysiological recordings allow for monitoring the operation of proteins with high temporal resolution down to the single molecule level. This technique has been exploited to track either ion flow arising from channel opening or the synchronized movement of charged residues and/or ions within the membrane electric field. Here, we describe a novel type of current by using the serotonin transporter (SERT) as a model. We examined transient currents elicited on rapid application of specific SERT inhibitors. Our analysis shows that these currents originate from ligand binding and not from a long-range conformational change. The Gouy-Chapman model predicts that adsorption of charged ligands to surface proteins must produce displacement currents and related apparent changes in membrane capacitance. Here we verified these predictions with SERT. Our observations demonstrate that ligand binding to a protein can be monitored in real time and in a label-free manner by recording the membrane capacitance.
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Affiliation(s)
- Verena Burtscher
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug DevelopmentCenter of Physiology and Pharmacology, Medical University of ViennaViennaAustria
| | - Matej Hotka
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug DevelopmentCenter of Physiology and Pharmacology, Medical University of ViennaViennaAustria
| | - Yang Li
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug DevelopmentCenter of Physiology and Pharmacology, Medical University of ViennaViennaAustria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug DevelopmentCenter of Physiology and Pharmacology, Medical University of ViennaViennaAustria
| | - Walter Sandtner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug DevelopmentCenter of Physiology and Pharmacology, Medical University of ViennaViennaAustria
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Hasenhuetl PS, Bhat S, Mayer FP, Sitte HH, Freissmuth M, Sandtner W. A kinetic account for amphetamine-induced monoamine release. J Gen Physiol 2018; 150:431-451. [PMID: 29439119 PMCID: PMC5839721 DOI: 10.1085/jgp.201711915] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 01/18/2018] [Indexed: 01/14/2023] Open
Abstract
This study on serotonin transporters shows that amphetamine-induced monoamine release requires cooperative substrate and cosubstrate binding. A kinetic model is presented that can account qualitatively and quantitatively for the releasing action of amphetamines. The plasmalemmal monoamine transporters for dopamine, norepinephrine, and serotonin (SERT) are targets for amphetamines. In vivo, amphetamines elicit most, if not all, of their actions by triggering monoamine efflux. This is thought to be accomplished by an amphetamine-induced switch from the forward-transport to the substrate-exchange mode. The mechanism underlying this switch has remained elusive; available kinetic models posit that substrates and cosubstrate Na+ ions bind either in a random or in a sequential order. Neither can account for all reported experimental observations. We used electrophysiological recordings to interrogate crucial conformational transitions associated with the binding of five different substrates (serotonin, para-chloroamphetamine, and the high-affinity naphthyl-propan-amines PAL-287, PAL-1045, and PAL-1046) to human SERT expressed in HEK293 cells; specifically, we determined the relaxation kinetics of SERT from a substrate-loaded to a substrate-free state at various intracellular and extracellular Na+ concentrations. These rates and their dependence on intracellular and extracellular Na+ concentrations differed considerably between substrates. We also examined the effect of K+ on substrate affinity and found that K+ enhanced substrate dissociation. A kinetic model was developed, which allowed for random, but cooperative, binding of substrate and Na+ (or K+). The synthetic data generated by this model recapitulated the experimental observations. More importantly, the cooperative binding model accounted for the releasing action of amphetamines without any digression from alternating access. To the best of our knowledge, this model is the first to provide a mechanistic framework for amphetamine-induced monoamine release and to account for the findings that some substrates are less efficacious than others in promoting the substrate-exchange mode.
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Affiliation(s)
- Peter S Hasenhuetl
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Shreyas Bhat
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Felix P Mayer
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Harald H Sitte
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Walter Sandtner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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Nizet S, Muñoz E, Fiebich BL, Abuja PM, Kashofer K, Zatloukal K, Tangermann S, Kenner L, Tschegg C, Nagl D, Scheichl L, Meisslitzer-Ruppitsch C, Freissmuth M, Berger T. Clinoptilolite in Dextran Sulphate Sodium-Induced Murine Colitis: Efficacy and Safety of a Microparticulate Preparation. Inflamm Bowel Dis 2017; 24:54-66. [PMID: 29272495 PMCID: PMC6176897 DOI: 10.1093/ibd/izx042] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Indexed: 12/13/2022]
Abstract
Background Clinoptilolite is an aluminium silicate of natural origin; the microporous structure and the net negative charge of its crystal lattice allows for adsorption of ions, toxins, inflammatory mediators, and some microorganisms. We generated 2 preparations of purified clinoptilolite, which differed by about 10-fold in particle size, ie, a standard powder (GHC1) and a microparticulate fraction (GHC2) with a size of 3.6 µm and 0.39 µm (d50) respectively. These were examined for their ability to accelerate the recovery of mice from DSS (dextran sulphate sodium)-induced intestinal inflammation. Methods Efficacy of clinoptilolite preparations was investigated by administering DSS-treated mice twice daily with 30 mg GHC2 or GHC1 for 5 consecutive days, followed by 5 days of recovery without DSS. To explore the safety of the microparticulate preparation (GHC2), mice were subjected to 4 cycles of DSS-exposure. We specifically verified that clinoptilolite microparticles were not systemically bioavailable by examining the gut tissue and the liver for the accumulation of microparticles by transmission electron microscopy. Results Treatment of mice with GHC2 was superior to GHC1 and as effective as the reference compound 5-aminosalicylic acid in ameliorating the damage induced by the exposure to DSS. In addition, no clinoptilolite particle was observed in the intestinal epithelial layer, gut-associated lymph follicles, or in the liver. Conclusion Our observations confirm that a microparticulate preparation of clinoptilolite is safe and effective in a murine model of inflammatory bowel disease and supports the hypothesis that the adsorptive capacity of clinoptilolite is of potential therapeutic relevance.
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Affiliation(s)
- Stéphane Nizet
- GLOCK Health, Science and Research GmbH, Deutsch-Wagram, Austria
| | - Eduardo Muñoz
- Maimonides Biomedical Research Institute of Córdoba, Reina Sofía University Hospital, Department of Cell Biology, Physiology and Immunology, University of Córdoba, Córdoba, Spain
| | | | - Peter M Abuja
- Institute of Pathology, Medical University of Graz, Graz, Austria
| | - Karl Kashofer
- Institute of Pathology, Medical University of Graz, Graz, Austria
| | - Kurt Zatloukal
- Institute of Pathology, Medical University of Graz, Graz, Austria
| | - Simone Tangermann
- Department of Experimental and Laboratory Animal Pathology, Medical University of Vienna, Austria
| | - Lukas Kenner
- Department of Experimental and Laboratory Animal Pathology, Medical University of Vienna, Austria
- Ludwig Boltzmann Institute for Cancer Research (LBI-CR), Vienna, Austria
| | | | - Dietmar Nagl
- GLOCK Health, Science and Research GmbH, Deutsch-Wagram, Austria
| | - Laurenz Scheichl
- GLOCK Health, Science and Research GmbH, Deutsch-Wagram, Austria
| | | | - Michael Freissmuth
- Institute of Pharmacology & Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center for Physiology and Pharmacology, Medical University Vienna, Vienna, Austria
| | - Thomas Berger
- GLOCK Health, Science and Research GmbH, Deutsch-Wagram, Austria
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Asjad HMM, Nasrollahi-Shirazi S, Sucic S, Freissmuth M, Nanoff C. Relax, Cool Down and Scaffold: How to Restore Surface Expression of Folding-Deficient Mutant GPCRs and SLC6 Transporters. Int J Mol Sci 2017; 18:ijms18112416. [PMID: 29135937 PMCID: PMC5713384 DOI: 10.3390/ijms18112416] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2017] [Revised: 11/11/2017] [Accepted: 11/12/2017] [Indexed: 01/01/2023] Open
Abstract
Many diseases arise from mutations, which impair protein folding. The study of folding-deficient variants of G protein-coupled receptors and solute carrier 6 (SLC6) transporters has shed light on the folding trajectory, how it is monitored and how misfolding can be remedied. Reducing the temperature lowers the energy barrier between folding intermediates and thereby eliminates stalling along the folding trajectory. For obvious reasons, cooling down is not a therapeutic option. One approach to rescue misfolded variants is to use membrane-permeable orthosteric ligands. Antagonists of GPCRs are—in many instances—effective pharmacochaperones: they restore cell surface expression provided that they enter cells and bind to folding intermediates. Pharmacochaperoning of SLC6 transporters is less readily achieved because the ionic conditions in the endoplasmic reticulum (ER) are not conducive to binding of typical inhibitors. The second approach is to target the heat-shock protein (HSP) relay, which monitors the folding trajectory on the cytosolic side. Importantly, orthosteric ligands and HSP-inhibitors are not mutually exclusive. In fact, pharmacochaperones and HSP-inhibitors can act in an additive or synergistic manner. This was exemplified by rescuing disease-causing, folding-deficient variants of the human dopamine transporters with the HSP70 inhibitor pifithrin-μ and the pharmacochaperone noribogaine in Drosophila melanogaster.
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Affiliation(s)
- H M Mazhar Asjad
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
| | - Shahrooz Nasrollahi-Shirazi
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
| | - Christian Nanoff
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
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47
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Asjad HMM, Kasture A, El-Kasaby A, Sackel M, Hummel T, Freissmuth M, Sucic S. Pharmacochaperoning in a Drosophila model system rescues human dopamine transporter variants associated with infantile/juvenile parkinsonism. J Biol Chem 2017; 292:19250-19265. [PMID: 28972153 PMCID: PMC5702666 DOI: 10.1074/jbc.m117.797092] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 09/06/2017] [Indexed: 12/19/2022] Open
Abstract
Point mutations in the gene encoding the human dopamine transporter (hDAT, SLC6A3) cause a syndrome of infantile/juvenile dystonia and parkinsonism. To unravel the molecular mechanism underlying these disorders and investigate possible pharmacological therapies, here we examined 13 disease-causing DAT mutants that were retained in the endoplasmic reticulum when heterologously expressed in HEK293 cells. In three of these mutants, i.e. hDAT-V158F, hDAT-G327R, and hDAT-L368Q, the folding deficit was remedied with the pharmacochaperone noribogaine or the heat shock protein 70 (HSP70) inhibitor pifithrin-μ such that endoplasmic reticulum export of and radioligand binding and substrate uptake by these DAT mutants were restored. In Drosophila melanogaster, DAT deficiency results in reduced sleep. We therefore exploited the power of targeted transgene expression of mutant hDAT in Drosophila to explore whether these hDAT mutants could also be pharmacologically rescued in an intact organism. Noribogaine or pifithrin-μ treatment supported hDAT delivery to the presynaptic terminals of dopaminergic neurons and restored sleep to normal length in DAT-deficient (fumin) Drosophila lines expressing hDAT-V158F or hDAT-G327R. In contrast, expression of hDAT-L368Q in the Drosophila DAT mutant background caused developmental lethality, indicating a toxic action not remedied by pharmacochaperoning. Our observations identified those mutations most likely amenable to pharmacological rescue in the affected children. In addition, our findings also highlight the challenges of translating insights from pharmacochaperoning in cell culture to the clinical situation. Because of the evolutionary conservation in dopaminergic neurotransmission between Drosophila and people, pharmacochaperoning of DAT in D. melanogaster may allow us to bridge that gap.
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Affiliation(s)
- H M Mazhar Asjad
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Ameya Kasture
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Ali El-Kasaby
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Michael Sackel
- the Department of Neurobiology, University of Vienna, A-1090 Vienna, Austria
| | - Thomas Hummel
- the Department of Neurobiology, University of Vienna, A-1090 Vienna, Austria
| | - Michael Freissmuth
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Sonja Sucic
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
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48
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Kasture A, Stockner T, Freissmuth M, Sucic S. An unfolding story: Small molecules remedy misfolded monoamine transporters. Int J Biochem Cell Biol 2017; 92:1-5. [PMID: 28890376 DOI: 10.1016/j.biocel.2017.09.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 08/24/2017] [Accepted: 09/06/2017] [Indexed: 12/16/2022]
Abstract
The key role of monoamine transporters is to take up neurotransmitters from the synaptic cleft and rapidly terminate neurotransmission. Monoamine transporters begin their journey by folding in the endoplasmic reticulum. Upon achieving their natively-folded state, the oligomerized transporters engage the coat protein complex II machinery and exit the endoplasmic reticulum compartment in a concentrative fashion. The transporters are subsequently sorted in the endoplasmic reticulum-Golgi intermediate complex and the Golgi apparatus, prior to reaching their pivotal site of action at the plasma membrane. Stringent quality-control mechanisms ensure that only the correctly-folded protein cargo departs the endoplasmic reticulum. Genetic point mutations in the coding sequences of monoamine transporters can trigger severe physiologic deficiencies by inducing folding defects. Protein misfolding precludes the delivery of functional monoamine transporters to the cell surface. Chemical- and/or pharmacological-chaperone molecules, which facilitate folding, have proven effective in restoring the activity of several misfolded pathological variants of monoamine transporters.
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Affiliation(s)
- Ameya Kasture
- Institute of Pharmacology, Center of Physiology and Pharmacology and Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, Austria
| | - Thomas Stockner
- Institute of Pharmacology, Center of Physiology and Pharmacology and Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology, Center of Physiology and Pharmacology and Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology, Center of Physiology and Pharmacology and Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, Austria.
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Bhat S, Hasenhuetl PS, Kasture A, El-Kasaby A, Baumann MH, Blough BE, Sucic S, Sandtner W, Freissmuth M. Conformational state interactions provide clues to the pharmacochaperone potential of serotonin transporter partial substrates. J Biol Chem 2017; 292:16773-16786. [PMID: 28842491 PMCID: PMC5633137 DOI: 10.1074/jbc.m117.794081] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 07/25/2017] [Indexed: 12/15/2022] Open
Abstract
Point mutations in SLC6 transporters cause misfolding, which can be remedied by pharmacochaperones. The serotonin transporter (SERT/SLC6A4) has a rich pharmacology including inhibitors, releasers (amphetamines, which promote the exchange mode), and more recently, discovered partial substrates. We hypothesized that partial substrates trapped the transporter in one or several states of the transport cycle. This conformational trapping may also be conducive to folding. We selected naphthylpropane-2-amines of the phenethylamine library (PAL) including the partial substrate PAL1045 and its congeners PAL287 and PAL1046. We analyzed their impact on the transport cycle of SERT by biochemical approaches and by electrophysiological recordings; substrate-induced peak currents and steady-state currents monitored the translocation of substrate and co-substrate Na+ across the lipid bilayer and the transport cycle, respectively. These experiments showed that PAL1045 and its congeners bound with different affinities (ranging from nm to μm) to various conformational intermediates of SERT during the transport cycle. Consistent with the working hypothesis, PAL1045 was the most efficacious compound in restoring surface expression and transport activity to the folding-deficient mutant SERT-601PG602-AA. These experiments provide a proof-of-principle for a rational search for pharmacochaperones, which may be useful to restore function to clinically relevant folding-deficient transporter mutants.
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Affiliation(s)
- Shreyas Bhat
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Peter S Hasenhuetl
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Ameya Kasture
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Ali El-Kasaby
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Michael H Baumann
- the Translational Pharmacology Section, Intramural Research Program, National Institute on Drug Abuse, Baltimore, Maryland 21224, and
| | - Bruce E Blough
- Center for Drug Discovery, Research Triangle Institute, Research Triangle Park, North Carolina 27709-1294
| | - Sonja Sucic
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Walter Sandtner
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Michael Freissmuth
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria,
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Mayer FP, Luf A, Nagy C, Holy M, Schmid R, Freissmuth M, Sitte HH. Application of a Combined Approach to Identify New Psychoactive Street Drugs and Decipher Their Mechanisms at Monoamine Transporters. Curr Top Behav Neurosci 2017; 32:333-350. [PMID: 28025810 DOI: 10.1007/7854_2016_63] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Psychoactive compounds can cause acute and long-term health problems and lead to addiction. In addition to well-studied and legally controlled compounds like cocaine, new psychoactive substances (NPS) are appearing in street drug markets as replacement strategies and legal alternatives. NPS are effectively marketed as "designer drugs" or "research chemicals" without any knowledge of their underlying pharmacological mode of action and their potential toxicological effects and obviously devoid of any registration process. As of 2016, the knowledge of structure-activity relationships for most NPS is scarce, and predicting detailed pharmacological activity of newly emerging drugs is a challenging task. Therefore, it is important to combine different approaches and employ biological test systems that are superior to mere chemical analysis in recognizing novel and potentially harmful street drugs. In this chapter, we provide a detailed description of techniques to decipher the molecular mechanism of action of NPS that target the high-affinity transporters for dopamine, norepinephrine, and serotonin. In addition, this chapter provides insights into a combined approach to identify and characterize new psychoactive street drugs of unknown content in a collaboration with the Austrian prevention project "checkit!."
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Affiliation(s)
- Felix P Mayer
- Center of Physiology and Pharmacology, Institute of Pharmacology, Medical University Vienna, Waehringerstrasse 13a, A-1090, Vienna, Austria
| | - Anton Luf
- Clinical Department of Laboratory Medicine, Medical University of Vienna, Waehringer Guertel 10-20, 1090, Vienna, Austria
| | - Constanze Nagy
- checkit! - Suchthilfe Wien GmbH, Gumpendorfer Gürtel 8, 1060, Vienna, Austria
| | - Marion Holy
- Center of Physiology and Pharmacology, Institute of Pharmacology, Medical University Vienna, Waehringerstrasse 13a, A-1090, Vienna, Austria
| | - Rainer Schmid
- Clinical Department of Laboratory Medicine, Medical University of Vienna, Waehringer Guertel 10-20, 1090, Vienna, Austria
| | - Michael Freissmuth
- Center of Physiology and Pharmacology, Institute of Pharmacology, Medical University Vienna, Waehringerstrasse 13a, A-1090, Vienna, Austria
| | - Harald H Sitte
- Center of Physiology and Pharmacology, Institute of Pharmacology, Medical University Vienna, Waehringerstrasse 13a, A-1090, Vienna, Austria.
- Center for Addiction Research and Science - Medical University Vienna, Waehringerstrasse 13A, 1090, Vienna, Austria.
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