1
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Pliushcheuskaya P, Kesh S, Kaufmann E, Wucherpfennig S, Schwede F, Künze G, Nache V. Similar Binding Modes of cGMP Analogues Limit Selectivity in Modulating Retinal CNG Channels via the Cyclic Nucleotide-Binding Domain. ACS Chem Neurosci 2024; 15:1652-1668. [PMID: 38579109 PMCID: PMC11027099 DOI: 10.1021/acschemneuro.3c00665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 02/28/2024] [Accepted: 03/19/2024] [Indexed: 04/07/2024] Open
Abstract
In treating retinitis pigmentosa, a genetic disorder causing progressive vision loss, selective inhibition of rod cyclic nucleotide-gated (CNG) channels holds promise. Blocking the increased Ca2+-influx in rod photoreceptors through CNG channels can potentially delay disease progression and improve the quality of life for patients. To find inhibitors for rod CNG channels, we investigated the impact of 16 cGMP analogues on both rod and cone CNG channels using the patch-clamp technique. Although modifications at the C8 position of the guanine ring did not change the ligand efficacy, modifications at the N1 and N2 positions rendered cGMP largely ineffective in activating retinal CNG channels. Notably, PET-cGMP displayed selective potential, favoring rod over cone, whereas Rp-cGMPS showed greater efficiency in activating cone over rod CNG channels. Ligand docking and molecular dynamics simulations on cyclic nucleotide-binding domains showed comparable binding energies and binding modes for cGMP and its analogues in both rod and cone CNG channels (CNGA1 vs CNGA3 subunits). Computational experiments on CNGB1a vs CNGB3 subunits showed similar binding modes albeit with fewer amino acid interactions with cGMP due to an inactivated conformation of their C-helix. In addition, no clear correlation could be observed between the computational scores and the CNG channel efficacy values, suggesting additional factors beyond binding strength determining ligand selectivity and potency. This study highlights the importance of looking beyond the cyclic nucleotide-binding domain and toward the gating mechanism when searching for selective modulators. Future efforts in developing selective modulators for CNG channels should prioritize targeting alternative channel domains.
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Affiliation(s)
- Palina Pliushcheuskaya
- Institute
for Drug Discovery, Medical Faculty, University
of Leipzig, Leipzig 04103, Germany
| | - Sandeep Kesh
- Institute
of Physiology II, University Hospital Jena, Friedrich Schiller University
Jena, Jena 07743, Germany
| | - Emma Kaufmann
- Institute
of Physiology II, University Hospital Jena, Friedrich Schiller University
Jena, Jena 07743, Germany
| | - Sophie Wucherpfennig
- Institute
of Physiology II, University Hospital Jena, Friedrich Schiller University
Jena, Jena 07743, Germany
| | - Frank Schwede
- BIOLOG
Life Science Institute GmbH & Co KG, Bremen 28199, Germany
| | - Georg Künze
- Institute
for Drug Discovery, Medical Faculty, University
of Leipzig, Leipzig 04103, Germany
- Interdisciplinary
Center for Bioinformatics, University of
Leipzig, Leipzig 04107, Germany
- Center
for Scalable Data Analytics and Artificial Intelligence, University of Leipzig, Leipzig 04105, Germany
| | - Vasilica Nache
- Institute
of Physiology II, University Hospital Jena, Friedrich Schiller University
Jena, Jena 07743, Germany
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2
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Schmauder R, Eick T, Schulz E, Sammler G, Voigt E, Mayer G, Ginter H, Ditze G, Benndorf K. Fast functional mapping of ligand-gated ion channels. Commun Biol 2023; 6:1003. [PMID: 37783870 PMCID: PMC10545696 DOI: 10.1038/s42003-023-05340-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 09/11/2023] [Indexed: 10/04/2023] Open
Abstract
Ligand-gated ion channels are formed by three to five subunits that control the opening of the pore in a cooperative fashion. We developed a microfluidic chip-based technique for studying ion currents and fluorescence signals in either excised membrane patches or whole cells to measure activation and deactivation kinetics of the channels as well as ligand binding and unbinding when using confocal patch-clamp fluorometry. We show how this approach produces in a few seconds either unidirectional concentration-activation relationships at or near equilibrium and, moreover, respective time courses of activation and deactivation for a large number of freely designed steps of the ligand concentration. The short measuring period strongly minimizes the contribution of disturbing superimposing effects such as run-down phenomena and desensitization effects. To validate gating mechanisms, complex kinetic schemes are quantified without the requirement to have data at equilibrium. The new method has potential for functionally analyzing any ligand-gated ion channel and, beyond, also for other receptors.
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Affiliation(s)
- Ralf Schmauder
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, 07743, Jena, Germany.
| | - Thomas Eick
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, 07743, Jena, Germany
| | - Eckhard Schulz
- Hochschule Schmalkalden, Fakultät Elektrotechnik, Blechhammer, 98574, Schmalkalden, Germany
| | - Günther Sammler
- Zentrale Forschungswerkstätten, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, 07743, Jena, Germany
| | - Elmar Voigt
- Leibniz Institut für Photonische Technologien e.V., Albert-Einstein-Straße 9, 07745, Jena, Germany
| | - Günter Mayer
- Leibniz Institut für Photonische Technologien e.V., Albert-Einstein-Straße 9, 07745, Jena, Germany
| | - Holger Ginter
- Zentrale Forschungswerkstätten, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, 07743, Jena, Germany
| | - Günter Ditze
- Zentrale Forschungswerkstätten, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, 07743, Jena, Germany
| | - Klaus Benndorf
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, 07743, Jena, Germany.
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3
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Rasmussen M, Tolone A, Paquet-Durand F, Welinder C, Schwede F, Ekström P. The photoreceptor protective cGMP-analog Rp-8-Br-PET-cGMPS interacts with cGMP-interactors PKGI, PDE1, PDE6, and PKAI in the degenerating mouse retina. J Comp Neurol 2023; 531:935-951. [PMID: 36989379 DOI: 10.1002/cne.25475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 07/12/2022] [Accepted: 03/06/2023] [Indexed: 03/31/2023]
Abstract
The inherited eye disease retinitis pigmentosa (RP) causes the loss of photoreceptors by a still unknown cell death mechanism. During this degeneration, cyclic guanosine-3',5'-monophosphate (cGMP) levels become elevated, leading to over-activation of the cGMP-binding protein cGMP-dependent protein kinase (PKG). cGMP analogs selectively modified to have inhibitory actions on PKG have aided in impeding photoreceptor death, and one such cGMP analog is Rp-8-Br-PET-cGMPS. However, cGMP analogs have previously been shown to interact with numerous targets, so to better understand the therapeutic action of Rp-8-Br-PET-cGMPS, it is necessary to elucidate its target-selectivity and hence what potential cellular mechanism(s) it may affect within the photoreceptors. Here, we, therefore, applied affinity chromatography together with mass spectrometry to isolate and identify Rp-8-Br-PET-cGMPS interactors from retinas derived from three different murine RP models (i.e., rd1, rd2, and rd10 mice). Our findings revealed that Rp-8-Br-PET-cGMPS bound seven known cGMP-binding proteins, including PKG1β, PDE1β, PDE1c, PDE6α, and PKA1α. Furthermore, an additional 28 proteins were found to be associated with Rp-8-Br-PET-cGMPS. This latter group included MAPK1/3, which is known to connect with cGMP/PKG in other systems. However, in organotypic retinal cultures, Rp-8-Br-PET-cGMPS had no effect on photoreceptor MAPK1/3 expression or activity. To summarize, Rp-8-Br-PET-cGMPS is more target specific compared to regular cGMP.
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Affiliation(s)
- Michel Rasmussen
- Faculty of Medicine, Department of Clinical Sciences Lund, Lund University, Ophthalmology, Lund, Sweden
| | - Arianna Tolone
- Insitute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | | | - Charlotte Welinder
- Faculty of Medicine, Department of Clinical Sciences Lund, Mass Spectrometry, Lund University, Lund, Sweden
| | - Frank Schwede
- BIOLOG Life Science Institute GmbH & Co. KG, Bremen, Germany
| | - Per Ekström
- Faculty of Medicine, Department of Clinical Sciences Lund, Lund University, Ophthalmology, Lund, Sweden
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4
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cGMP Analogues with Opposing Actions on CNG Channels Selectively Modulate Rod or Cone Photoreceptor Function. Pharmaceutics 2022; 14:pharmaceutics14102102. [PMID: 36297537 PMCID: PMC9612005 DOI: 10.3390/pharmaceutics14102102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 09/23/2022] [Accepted: 09/28/2022] [Indexed: 11/09/2022] Open
Abstract
The vertebrate retina harbors rod and cone photoreceptors. Human vision critically depends on cone photoreceptor function. In the phototransduction cascade, cGMP activates distinct rod and cone isoforms of the cyclic nucleotide-gated (CNG) channel. Excessive cGMP levels initiate a pathophysiological rollercoaster, which starts with CNG channel over-activation, typically in rod photoreceptors. This triggers cell death of rods first, and then cones, and is the root cause of many blinding retinal diseases, including Retinitis pigmentosa. While targeting of CNG channels has been proposed for therapeutic purposes, thus far, it has not been possible to inhibit rod CNG channels without compromising cone function. Here, we present a novel strategy, based on cGMP analogues with opposing actions on CNG channels, which enables the selective modulation of either rod or cone photoreceptor activity. The combined treatment with the weak rod-selective CNG-channel inhibitor (Rp-8-Br-PET-cGMPS) and the cone-selective CNG-channel activator (8-pCPT-cGMP) essentially normalized rod CNG-channel function while preserving cone functionality at physiological and pathological cGMP levels. Hence, combinations of cGMP analogues with desired properties may elegantly address the isoform-specificity problem in future pharmacological therapies. Moreover, this strategy may allow for improvements in visual performance in certain light environments.
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5
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Schirmeyer J, Eick T, Schulz E, Hummert S, Sattler C, Schmauder R, Benndorf K. Subunit promotion energies for channel opening in heterotetrameric olfactory CNG channels. PLoS Comput Biol 2022; 18:e1010376. [PMID: 35998156 PMCID: PMC9512249 DOI: 10.1371/journal.pcbi.1010376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 09/26/2022] [Accepted: 07/11/2022] [Indexed: 11/18/2022] Open
Abstract
Cyclic nucleotide-gated (CNG) ion channels of olfactory sensory neurons contain three types of homologue subunits, two CNGA2 subunits, one CNGA4 subunit and one CNGB1b subunit. Each subunit carries an intracellular cyclic nucleotide binding domain (CNBD) whose occupation by up to four cyclic nucleotides evokes channel activation. Thereby, the subunits interact in a cooperative fashion. Here we studied 16 concatamers with systematically disabled, but still functional, binding sites and quantified channel activation by systems of intimately coupled state models transferred to 4D hypercubes, thereby exploiting a weak voltage dependence of the channels. We provide the complete landscape of free energies for the complex activation process of heterotetrameric channels, including 32 binding steps, in both the closed and open channel, as well as 16 closed-open isomerizations. The binding steps are specific for the subunits and show pronounced positive cooperativity for the binding of the second and the third ligand. The energetics of the closed-open isomerizations were disassembled to elementary subunit promotion energies for channel opening, ΔΔGfpn, adding to the free energy of the closed-open isomerization of the empty channel, E0. The ΔΔGfpn values are specific for the four subunits and presumably invariant for the specific patterns of liganding. In conclusion, subunit cooperativity is confined to the CNBD whereas the subunit promotion energies for channel opening are independent. Olfactory sensory neurons (OSNs) in the nose transmit the information of odor molecules to electrical signals that are conducted to central parts of the brain. Olfactory cyclic nucleotide-gated (CNG) ion channels, located in the cell membrane of the OSNs, are relevant proteins in this process. These olfactory CNG channels are formed by three types of homologue subunits and each of these subunits contains a cyclic nucleotide binding domain (CNBD). A channel is activated by the binding of up to four cyclic nucleotides. The process of channel activation is only poorly understood. Herein we analyzed this activation process in great detail by concatenating these four subunits, disabling the CNBDs by mutations and performing extended computational fit analyses providing all 32 constants for the different binding steps at different degrees of liganding and, in addition, elementary subunit promotion energies for channel opening for all subunits. Our data suggest that subunit cooperativity is confined to the action of the CNBD.
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Affiliation(s)
- Jana Schirmeyer
- Institute of Physiology II, Jena University Hospital, Friedrich Schiller University Jena, Jena, Germany
| | - Thomas Eick
- Institute of Physiology II, Jena University Hospital, Friedrich Schiller University Jena, Jena, Germany
| | - Eckhard Schulz
- Schmalkalden University of Applied Sciences, Faculty of Electrical Engineering, Blechhammer, Schmalkalden, Germany
| | - Sabine Hummert
- Institute of Physiology II, Jena University Hospital, Friedrich Schiller University Jena, Jena, Germany
- Schmalkalden University of Applied Sciences, Faculty of Electrical Engineering, Blechhammer, Schmalkalden, Germany
| | - Christian Sattler
- Institute of Physiology II, Jena University Hospital, Friedrich Schiller University Jena, Jena, Germany
| | - Ralf Schmauder
- Institute of Physiology II, Jena University Hospital, Friedrich Schiller University Jena, Jena, Germany
| | - Klaus Benndorf
- Institute of Physiology II, Jena University Hospital, Friedrich Schiller University Jena, Jena, Germany
- * E-mail:
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6
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Sattler C, Benndorf K. Enlightening activation gating in P2X receptors. Purinergic Signal 2022; 18:177-191. [PMID: 35188598 PMCID: PMC9123132 DOI: 10.1007/s11302-022-09850-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 02/04/2022] [Indexed: 12/20/2022] Open
Abstract
P2X receptors are trimeric nonselective cation channels gated by ATP. They assemble from seven distinct subunit isoforms as either homo- or heteromeric complexes and contain three extracellularly located binding sites for ATP. P2X receptors are expressed in nearly all tissues and are there involved in physiological processes like synaptic transmission, pain, and inflammation. Thus, they are a challenging pharmacological target. The determination of crystal and cryo-EM structures of several isoforms in the last decade in closed, open, and desensitized states has provided a firm basis for interpreting the huge amount of functional and biochemical data. Electrophysiological characterization in conjugation with optical approaches has generated significant insights into structure–function relationships of P2X receptors. This review focuses on novel optical and related approaches to better understand the conformational changes underlying the activation of these receptors.
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Affiliation(s)
- Christian Sattler
- Institut Für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, 07740, Jena, Germany.
| | - Klaus Benndorf
- Institut Für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, 07740, Jena, Germany.
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7
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Das S, Popp V, Power M, Groeneveld K, Yan J, Melle C, Rogerson L, Achury M, Schwede F, Strasser T, Euler T, Paquet-Durand F, Nache V. Redefining the role of Ca 2+-permeable channels in photoreceptor degeneration using diltiazem. Cell Death Dis 2022; 13:47. [PMID: 35013127 PMCID: PMC8748460 DOI: 10.1038/s41419-021-04482-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 10/07/2021] [Accepted: 11/23/2021] [Indexed: 12/18/2022]
Abstract
Hereditary degeneration of photoreceptors has been linked to over-activation of Ca2+-permeable channels, excessive Ca2+-influx, and downstream activation of Ca2+-dependent calpain-type proteases. Unfortunately, after more than 20 years of pertinent research, unequivocal evidence proving significant and reproducible photoreceptor protection with Ca2+-channel blockers is still lacking. Here, we show that both D- and L-cis enantiomers of the anti-hypertensive drug diltiazem were very effective at blocking photoreceptor Ca2+-influx, most probably by blocking the pore of Ca2+-permeable channels. Yet, unexpectedly, this block neither reduced the activity of calpain-type proteases, nor did it result in photoreceptor protection. Remarkably, application of the L-cis enantiomer of diltiazem even led to a strong increase in photoreceptor cell death. These findings shed doubt on the previously proposed links between Ca2+ and retinal degeneration and are highly relevant for future therapy development as they may serve to refocus research efforts towards alternative, Ca2+-independent degenerative mechanisms.
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Affiliation(s)
- Soumyaparna Das
- Institute for Ophthalmic Research, University of Tübingen, 72076, Tübingen, Germany
| | - Valerie Popp
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University Jena, 07743, Jena, Germany
| | - Michael Power
- Institute for Ophthalmic Research, University of Tübingen, 72076, Tübingen, Germany.,Werner Reichardt Centre for Integrative Neuroscience (CIN), University of Tübingen, 72076, Tübingen, Germany
| | - Kathrin Groeneveld
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University Jena, 07743, Jena, Germany.,Biomolecular Photonics Group, University Hospital Jena, Friedrich Schiller University Jena, 07743, Jena, Germany
| | - Jie Yan
- Institute for Ophthalmic Research, University of Tübingen, 72076, Tübingen, Germany
| | - Christian Melle
- Biomolecular Photonics Group, University Hospital Jena, Friedrich Schiller University Jena, 07743, Jena, Germany
| | - Luke Rogerson
- Werner Reichardt Centre for Integrative Neuroscience (CIN), University of Tübingen, 72076, Tübingen, Germany
| | - Marlly Achury
- Institute for Ophthalmic Research, University of Tübingen, 72076, Tübingen, Germany
| | - Frank Schwede
- BIOLOG Life Science Institute GmbH & Co KG, 28199, Bremen, Germany
| | - Torsten Strasser
- Institute for Ophthalmic Research, University of Tübingen, 72076, Tübingen, Germany
| | - Thomas Euler
- Institute for Ophthalmic Research, University of Tübingen, 72076, Tübingen, Germany.,Werner Reichardt Centre for Integrative Neuroscience (CIN), University of Tübingen, 72076, Tübingen, Germany
| | | | - Vasilica Nache
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University Jena, 07743, Jena, Germany.
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8
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Thermodynamic profile of mutual subunit control in a heteromeric receptor. Proc Natl Acad Sci U S A 2021; 118:2100469118. [PMID: 34301910 PMCID: PMC8325370 DOI: 10.1073/pnas.2100469118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cyclic nucleotide-gated (CNG) ion channels of olfactory neurons are tetrameric membrane receptors that are composed of two A2 subunits, one A4 subunit, and one B1b subunit. Each subunit carries a cyclic nucleotide-binding domain in the carboxyl terminus, and the channels are activated by the binding of cyclic nucleotides. The mechanism of cooperative channel activation is still elusive. Using a complete set of engineered concatenated olfactory CNG channels, with all combinations of disabled binding sites and fit analyses with systems of allosteric models, the thermodynamics of microscopic cooperativity for ligand binding was subunit- and state-specifically quantified. We show, for the closed channel, that preoccupation of each of the single subunits increases the affinity of each other subunit with a Gibbs free energy (ΔΔG) of ∼-3.5 to ∼-5.5 kJ ⋅ mol-1, depending on the subunit type, with the only exception that a preoccupied opposite A2 subunit has no effect on the other A2 subunit. Preoccupation of two neighbor subunits of a given subunit causes the maximum affinity increase with ΔΔG of ∼-9.6 to ∼-9.9 kJ ⋅ mol-1 Surprisingly, triple preoccupation leads to fewer negative ΔΔG values for a given subunit as compared to double preoccupation. Channel opening increases the affinity of all subunits. The equilibrium constants of closed-open isomerizations systematically increase with progressive liganding. This work demonstrates, on the example of the heterotetrameric olfactory CNG channel, a strategy to derive detailed insights into the specific mutual control of the individual subunits in a multisubunit membrane receptor.
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9
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Abbas F, Vinberg F. Transduction and Adaptation Mechanisms in the Cilium or Microvilli of Photoreceptors and Olfactory Receptors From Insects to Humans. Front Cell Neurosci 2021; 15:662453. [PMID: 33867944 PMCID: PMC8046925 DOI: 10.3389/fncel.2021.662453] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 03/02/2021] [Indexed: 12/11/2022] Open
Abstract
Sensing changes in the environment is crucial for survival. Animals from invertebrates to vertebrates use both visual and olfactory stimuli to direct survival behaviors including identification of food sources, finding mates, and predator avoidance. In primary sensory neurons there are signal transduction mechanisms that convert chemical or light signals into an electrical response through ligand binding or photoactivation of a receptor, that can be propagated to the olfactory and visual centers of the brain to create a perception of the odor and visual landscapes surrounding us. The fundamental principles of olfactory and phototransduction pathways within vertebrates are somewhat analogous. Signal transduction in both systems takes place in the ciliary sub-compartments of the sensory cells and relies upon the activation of G protein-coupled receptors (GPCRs) to close cyclic nucleotide-gated (CNG) cation channels in photoreceptors to produce a hyperpolarization of the cell, or in olfactory sensory neurons open CNG channels to produce a depolarization. However, while invertebrate phototransduction also involves GPCRs, invertebrate photoreceptors can be either ciliary and/or microvillar with hyperpolarizing and depolarizing responses to light, respectively. Moreover, olfactory transduction in invertebrates may be a mixture of metabotropic G protein and ionotropic signaling pathways. This review will highlight differences of the visual and olfactory transduction mechanisms between vertebrates and invertebrates, focusing on the implications to the gain of the transduction processes, and how they are modulated to allow detection of small changes in odor concentration and light intensity over a wide range of background stimulus levels.
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Affiliation(s)
- Fatima Abbas
- Vinberg Lab, Department of Ophthalmology and Visual Science, John A. Moran Center, University of Utah, Salt Lake City, UT, United States
| | - Frans Vinberg
- Vinberg Lab, Department of Ophthalmology and Visual Science, John A. Moran Center, University of Utah, Salt Lake City, UT, United States
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Boccaccio A, Menini A, Pifferi S. The cyclic AMP signaling pathway in the rodent main olfactory system. Cell Tissue Res 2021; 383:429-443. [PMID: 33447881 DOI: 10.1007/s00441-020-03391-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 12/10/2020] [Indexed: 01/15/2023]
Abstract
Odor perception begins with the detection of odorant molecules by the main olfactory epithelium located in the nasal cavity. Odorant molecules bind to and activate a large family of G-protein-coupled odorant receptors and trigger a cAMP-mediated transduction cascade that converts the chemical stimulus into an electrical signal transmitted to the brain. Morever, odorant receptors and cAMP signaling plays a relevant role in olfactory sensory neuron development and axonal targeting to the olfactory bulb. This review will first explore the physiological response of olfactory sensory neurons to odorants and then analyze the different components of cAMP signaling and their different roles in odorant detection and olfactory sensory neuron development.
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Affiliation(s)
- Anna Boccaccio
- Institute of Biophysics, National Research Council (CNR), Genova, Italy.
| | - Anna Menini
- Neurobiology Group, SISSA, Scuola Internazionale Superiore di Studi Avanzati, Trieste, Italy
| | - Simone Pifferi
- Neurobiology Group, SISSA, Scuola Internazionale Superiore di Studi Avanzati, Trieste, Italy.,Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona, Italy
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11
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Rasmussen M, Welinder C, Schwede F, Ekström P. The cGMP system in normal and degenerating mouse neuroretina: New proteins with cGMP interaction potential identified by a proteomics approach. J Neurochem 2020; 157:2173-2186. [PMID: 33230839 PMCID: PMC8359485 DOI: 10.1111/jnc.15251] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 11/19/2020] [Accepted: 11/20/2020] [Indexed: 12/17/2022]
Abstract
The hereditary disease Retinitis pigmentosa results in severe vision loss due to photoreceptor degeneration by unclear mechanisms. In several disease models, the second messenger cGMP accumulates in the degenerating photoreceptors, where it may over‐activate specific cGMP‐interacting proteins, like cGMP‐dependent protein kinase. Moreover, interventions that counteract the activity of these proteins lead to reduced photoreceptor cell death. Yet there is little or no information whether other than such regular cGMP‐interactors are present in the retina, which we, therefore, investigated in wild‐type and retinal degeneration (rd1, rd10, and rd2) mouse models. An affinity chromatography based proteomics approach that utilized immobilized cGMP analogs was applied to enrich and select for regular and potentially new cGMP‐interacting proteins as identified by mass spectrometry. This approach revealed 12 regular and 10 potentially new retinal cGMP‐interacting proteins (e.g., EPAC2 and CaMKIIα). Several of the latter were found to be expressed in the photoreceptors and to have proximity to cGMP and may thus be of interest when defining prospective therapeutic targets or biomarkers for retinal degeneration.
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Affiliation(s)
- Michel Rasmussen
- Faculty of Medicine, Department of Clinical Sciences Lund, Lund University, Ophthalmology, Lund, Sweden
| | - Charlotte Welinder
- Faculty of Medicine, Department of Clinical Sciences Lund, Oncology, Lund University, Lund, Sweden
| | - Frank Schwede
- BIOLOG Life Science Institute GmbH & Co. KG, Bremen, Germany
| | - Per Ekström
- Faculty of Medicine, Department of Clinical Sciences Lund, Lund University, Ophthalmology, Lund, Sweden
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12
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Otte M, Schweinitz A, Lelle M, Thon S, Enke U, Yüksel S, Schmauder R, Bonus M, Gohlke H, Benndorf K. Novel Fluorescent Cyclic Nucleotide Derivatives to Study CNG and HCN Channel Function. Biophys J 2019; 116:2411-2422. [PMID: 31130235 DOI: 10.1016/j.bpj.2019.05.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 04/19/2019] [Accepted: 05/01/2019] [Indexed: 12/29/2022] Open
Abstract
A highly specific molecular interaction of diffusible ligands with their receptors belongs to the key processes in cellular signaling. Because an appropriate method to monitor the unitary binding events is still missing, most of our present knowledge is based on ensemble signals recorded from a big number of receptors, such as ion currents or fluorescence changes of suitably labeled receptors, and reasoning from these data to the ligand binding. To study the binding process itself, appropriately tagged ligands are required that fully activate the receptors and report the binding at the same time. Herein, we tailored a series of 18 novel fluorescent cyclic nucleotide derivatives by attaching 6 different dyes via different alkyl linkers to the 8-position of the purine ring of cGMP or cAMP. The biological activity was determined in inside-out macropatches containing either homotetrameric (CNGA2), heterotetrameric (CNGA2:CNGA4:CNGB1b), or hyperpolarization-activated cyclic nucleotide-modulated (HCN2) channels. All these novel fluorescent ligands are efficient to activate the channels, and the potency of most of them significantly exceeded that of the natural cyclic nucleotides cGMP or cAMP. Moreover, some of them showed an enhanced brightness when bound to the channels. The best of our derivatives bear great potential to systematically analyze the activation mechanism in CNG and HCN channels, at both the level of ensemble and single-molecule analyses.
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Affiliation(s)
- Maik Otte
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Andrea Schweinitz
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Marco Lelle
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Susanne Thon
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Uta Enke
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Sezin Yüksel
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Ralf Schmauder
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Michele Bonus
- Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Holger Gohlke
- Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany; John von Neumann Institute for Computing, Jülich Supercomputing Centre & Institute for Complex Systems Structural Biochemistry, Forschungszentrum Jülich, GmbH, Jülich, Germany
| | - Klaus Benndorf
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany.
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Lelle M, Otte M, Thon S, Bertinetti D, Herberg FW, Benndorf K. Chemical synthesis and biological activity of novel brominated 7-deazaadenosine-3',5'-cyclic monophosphate derivatives. Bioorg Med Chem 2019; 27:1704-1713. [PMID: 30879860 DOI: 10.1016/j.bmc.2019.03.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 03/09/2019] [Accepted: 03/11/2019] [Indexed: 11/19/2022]
Abstract
Synthetic derivatives of cyclic adenosine monophosphate, such as halogenated or other more hydrophobic analogs, are widely used compounds, to investigate diverse signal transduction pathways of eukaryotic cells. This inspired us to develop cyclic nucleotides, which exhibit chemical structures composed of brominated 7-deazaadenines and the phosphorylated ribosugar. The synthesized 8-bromo- and 7-bromo-7-deazaadenosine-3',5'-cyclic monophosphates rank among the most potent activators of cyclic nucleotide-regulated ion channels as well as cAMP-dependent protein kinase. Moreover, these substances bind tightly to exchange proteins directly activated by cAMP.
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Affiliation(s)
- Marco Lelle
- Institute of Physiology II, University Hospital Jena, Kollegiengasse 9, 07743 Jena, Germany
| | - Maik Otte
- Institute of Physiology II, University Hospital Jena, Kollegiengasse 9, 07743 Jena, Germany
| | - Susanne Thon
- Institute of Physiology II, University Hospital Jena, Kollegiengasse 9, 07743 Jena, Germany
| | - Daniela Bertinetti
- Department of Biochemistry, University of Kassel, Heinrich-Plett-Straße 40, 34132 Kassel, Germany
| | - Friedrich W Herberg
- Department of Biochemistry, University of Kassel, Heinrich-Plett-Straße 40, 34132 Kassel, Germany
| | - Klaus Benndorf
- Institute of Physiology II, University Hospital Jena, Kollegiengasse 9, 07743 Jena, Germany.
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14
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Hydrophobic alkyl chains substituted to the 8-position of cyclic nucleotides enhance activation of CNG and HCN channels by an intricate enthalpy - entropy compensation. Sci Rep 2018; 8:14960. [PMID: 30297855 PMCID: PMC6175941 DOI: 10.1038/s41598-018-33050-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 09/19/2018] [Indexed: 01/01/2023] Open
Abstract
Cyclic nucleotide-gated (CNG) and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are tetrameric non-specific cation channels in the plasma membrane that are activated by either cAMP or cGMP binding to specific binding domains incorporated in each subunit. Typical apparent affinities of these channels for these cyclic nucleotides range from several hundred nanomolar to tens of micromolar. Here we synthesized and characterized novel cAMP and cGMP derivatives by substituting either hydrophobic alkyl chains or similar-sized more hydrophilic heteroalkyl chains to the 8-position of the purine ring with the aim to obtain full agonists of higher potency. The compounds were tested in homotetrameric CNGA2, heterotetrameric CNGA2:CNGA4:CNGB1b and homotetrameric HCN2 channels. We show that nearly all compounds are full agonists and that longer alkyl chains systematically increase the apparent affinity, at the best more than 30 times. The effects are stronger in CNG than HCN2 channels which, however, are constitutively more sensitive to cAMP. Kinetic analyses reveal that the off-rate is significantly slowed by the hydrophobic alkyl chains. Molecular dynamics simulations and free energy calculations suggest that an intricate enthalpy - entropy compensation underlies the higher apparent affinity of the derivatives with the longer alkyl chains, which is shown to result from a reduced loss of configurational entropy upon binding.
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15
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Kowal J, Biyani N, Chami M, Scherer S, Rzepiela AJ, Baumgartner P, Upadhyay V, Nimigean CM, Stahlberg H. High-Resolution Cryoelectron Microscopy Structure of the Cyclic Nucleotide-Modulated Potassium Channel MloK1 in a Lipid Bilayer. Structure 2017; 26:20-27.e3. [PMID: 29249605 DOI: 10.1016/j.str.2017.11.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2017] [Revised: 09/16/2017] [Accepted: 11/15/2017] [Indexed: 01/26/2023]
Abstract
Eukaryotic cyclic nucleotide-modulated channels perform their diverse physiological roles by opening and closing their pores to ions in response to cyclic nucleotide binding. We here present a structural model for the cyclic nucleotide-modulated potassium channel homolog from Mesorhizobium loti, MloK1, determined from 2D crystals in the presence of lipids. Even though crystals diffract electrons to only ∼10 Å, using cryoelectron microscopy (cryo-EM) and recently developed computational methods, we have determined a 3D map of full-length MloK1 in the presence of cyclic AMP (cAMP) at ∼4.5 Å isotropic 3D resolution. The structure provides a clear picture of the arrangement of the cyclic nucleotide-binding domains with respect to both the pore and the putative voltage sensor domains when cAMP is bound, and reveals a potential gating mechanism in the context of the lipid-embedded channel.
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Affiliation(s)
- Julia Kowal
- Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, WRO-1058, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Nikhil Biyani
- Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, WRO-1058, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Mohamed Chami
- Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, WRO-1058, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Sebastian Scherer
- Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, WRO-1058, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Andrzej J Rzepiela
- SIB, Biozentrum, University of Basel, Klingelbergstrasse, 4056 Basel, Switzerland
| | - Paul Baumgartner
- Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, WRO-1058, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Vikrant Upadhyay
- Weill Cornell Medical College, Department of Anesthesiology, Box 124, 525 East 68th Street, Room A-1050, New York, NY 10065, USA
| | - Crina M Nimigean
- Weill Cornell Medical College, Department of Anesthesiology, Box 124, 525 East 68th Street, Room A-1050, New York, NY 10065, USA.
| | - Henning Stahlberg
- Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, WRO-1058, Mattenstrasse 26, 4058 Basel, Switzerland.
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Abstract
Isolated congenital anosmia (ICA) is a rare condition that is associated with life-long inability to smell. Here we report a genetic characterization of a large Iranian family segregating ICA. Whole exome sequencing in five affected family members and five healthy members revealed a stop gain mutation in CNGA2 (OMIM 300338) (chrX:150,911,102; CNGA2. c.577C > T; p.Arg193*). The mutation segregates in an X-linked pattern, as all the affected family members are hemizygotes, whereas healthy family members are either heterozygote or homozygote for the reference allele. cnga2 knockout mice are congenitally anosmic and have abnormal olfactory system physiology, additionally Karstensen et al. recently reported two anosmic brothers sharing a CNGA2 truncating variant. Our study in concert with these findings provides strong support for role of CNGA2 gene with pathogenicity of ICA in humans. Together, these results indicate that mutations in key olfactory signaling pathway genes are responsible for human disease.
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Springer MS, Gatesy J. Inactivation of the olfactory marker protein (OMP) gene in river dolphins and other odontocete cetaceans. Mol Phylogenet Evol 2017; 109:375-387. [PMID: 28193458 DOI: 10.1016/j.ympev.2017.01.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 01/25/2017] [Accepted: 01/29/2017] [Indexed: 11/18/2022]
Abstract
Various toothed whales (Odontoceti) are unique among mammals in lacking olfactory bulbs as adults and are thought to be anosmic (lacking the olfactory sense). At the molecular level, toothed whales have high percentages of pseudogenic olfactory receptor genes, but species that have been investigated to date retain an intact copy of the olfactory marker protein gene (OMP), which is highly expressed in olfactory receptor neurons and may regulate the temporal resolution of olfactory responses. One hypothesis for the retention of intact OMP in diverse odontocete lineages is that this gene is pleiotropic with additional functions that are unrelated to olfaction. Recent expression studies provide some support for this hypothesis. Here, we report OMP sequences for representatives of all extant cetacean families and provide the first molecular evidence for inactivation of this gene in vertebrates. Specifically, OMP exhibits independent inactivating mutations in six different odontocete lineages: four river dolphin genera (Platanista, Lipotes, Pontoporia, Inia), sperm whale (Physeter), and harbor porpoise (Phocoena). These results suggest that the only essential role of OMP that is maintained by natural selection is in olfaction, although a non-olfactory role for OMP cannot be ruled out for lineages that retain an intact copy of this gene. Available genome sequences from cetaceans and close outgroups provide evidence of inactivating mutations in two additional genes (CNGA2, CNGA4), which imply further pseudogenization events in the olfactory cascade of odontocetes. Selection analyses demonstrate that evolutionary constraints on all three genes (OMP, CNGA2, CNGA4) have been greatly reduced in Odontoceti, but retain a signature of purifying selection on the stem Cetacea branch and in Mysticeti (baleen whales). This pattern is compatible with the 'echolocation-priority' hypothesis for the evolution of OMP, which posits that negative selection was maintained in the common ancestor of Cetacea and was not relaxed significantly until the evolution of echolocation in Odontoceti.
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Affiliation(s)
- Mark S Springer
- Department of Biology, University of California, Riverside, CA 92521, USA.
| | - John Gatesy
- Division of Vertebrate Zoology, American Museum of Natural History, New York, NY 10024, USA.
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