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Abstract
The first step in vision is the absorption of photons by the photopigments in cone and rod photoreceptors. After initial amplification within the phototransduction cascade the signal is translated into an electrical signal by the action of cyclic nucleotide-gated (CNG) channels. CNG channels are ligand-gated ion channels that are activated by the binding of cyclic guanosine monophosphate (cGMP) or cyclic adenosine monophosphate (cAMP). Retinal CNG channels transduce changes in intracellular concentrations of cGMP into changes of the membrane potential and the Ca2+ concentration. Structurally, the CNG channels belong to the superfamily of pore-loop cation channels and share a common gross structure with hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and voltage-gated potassium channels (KCN). In this review, we provide an overview on the molecular properties of CNG channels and describe their physiological role in the phototransduction pathways. We also discuss insights into the pathophysiological role of CNG channel proteins that have emerged from the analysis of CNG channel-deficient animal models and human CNG channelopathies. Finally, we summarize recent gene therapy activities and provide an outlook for future clinical application.
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Affiliation(s)
- Stylianos Michalakis
- Center for Integrated Protein Science Munich (CIPSM), Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr, 5-13, 81377 Munich, Germany.
| | - Elvir Becirovic
- Center for Integrated Protein Science Munich (CIPSM), Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr, 5-13, 81377 Munich, Germany.
| | - Martin Biel
- Center for Integrated Protein Science Munich (CIPSM), Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr, 5-13, 81377 Munich, Germany.
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202
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Täger J, Kohl S, Birch DG, Wheaton DKH, Wissinger B, Reuter P. An early nonsense mutation facilitates the expression of a short isoform of CNGA3 by alternative translation initiation. Exp Eye Res 2018; 171:48-53. [PMID: 29499183 DOI: 10.1016/j.exer.2018.02.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 02/26/2018] [Accepted: 02/26/2018] [Indexed: 11/24/2022]
Abstract
The cyclic nucleotide-gated (CNG) channel - composed of CNGA3 and CNGB3 subunits - mediates the influx of cations in cone photoreceptors after light stimulation and thus is a key element in cone phototransduction. Mutations in CNGA3 and CNGB3 are associated with achromatopsia, a rare autosomal recessive retinal disorder. Here, we demonstrate that the presence of an early nonsense mutation in CNGA3 induces the usage of a downstream alternative translation initiation site giving rise to a short CNGA3 isoform. The expression of this short isoform was verified by Western blot analysis and DAB staining of HEK293 cells and cone photoreceptor-like 661W cells expressing CNGA3-GST fusion constructs. Functionality of the short isoform was confirmed by a cellular calcium influx assay. Furthermore, patients carrying an early nonsense mutation were analyzed for residual cone photoreceptor function in order to identify a potential role of the short isoform to modify the clinical outcome in achromatopsia patients. Yet the results suggest that the short isoform is not able to compensate for the loss of the long isoform leaving the biological role of this variant unclear.
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Affiliation(s)
- Joachim Täger
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany; Graduate School of Cellular and Molecular Neuroscience, University of Tübingen, Tübingen, Germany
| | - Susanne Kohl
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | | | | | - Bernd Wissinger
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany.
| | - Peggy Reuter
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany.
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203
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Ben Khemis I, Mechi N, Ben Lamine A. Stereochemical study of mouse muscone receptor MOR215-1 and vibrational theory based on statistical physics formalism. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2018; 136:54-60. [PMID: 29438653 DOI: 10.1016/j.pbiomolbio.2018.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 02/02/2018] [Accepted: 02/09/2018] [Indexed: 11/29/2022]
Abstract
In the biosensor system, olfactory receptor sites could be activated by odorant molecules and then the biological interactions are converted into electrical signals by a signal transduction cascade that leads the toopening of ion channels, generating a current that leads into the cilia and depolarizes the membrane. The aim of this paper is to present a new investigation that allows determining the olfactory band using a monolayer adsorption with identical sites modeling which may also describe the static and the dynamic sensitivities through the expression of the olfactory response. Moreover, knowing the size of receptor site in olfactory sensory neurons provides valuable information about the relationship between molecular structure and biological activity. The determination of microreceptors and mesoreceptors is mostly carried out via physical adsorption and the radius is calculated using the Kelvin equation. The mean values of radius obtained from the maximum of the receptor size distributions peaks are 4 nm for ℓ-muscone and 6 nm for d-muscone.
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Affiliation(s)
- Ismahene Ben Khemis
- Laboratory of Quantum Physics UR 11 ES 54, Faculty of Sciences of Monastir, Environnement Street, 5019, Monastir, Tunisia.
| | - Nesrine Mechi
- Laboratory of Quantum Physics UR 11 ES 54, Faculty of Sciences of Monastir, Environnement Street, 5019, Monastir, Tunisia
| | - Abdelmottaleb Ben Lamine
- Laboratory of Quantum Physics UR 11 ES 54, Faculty of Sciences of Monastir, Environnement Street, 5019, Monastir, Tunisia.
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204
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Zhang Y, Wang Y, Wang XH, Zhou WJ, Jin LP, Li MQ. Crosstalk between human endometrial stromal cells and decidual NK cells promotes decidualization in vitro by upregulating IL‑25. Mol Med Rep 2018; 17:2869-2878. [PMID: 29257317 PMCID: PMC5783502 DOI: 10.3892/mmr.2017.8267] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 10/10/2017] [Indexed: 11/24/2022] Open
Abstract
Embryo implantation is essential for a successful pregnancy, and leads to the decidualization of endometrial stromal cells (ESCs) in the secretory phase of the menstrual cycle. It has previously been demonstrated that decidual stromal cells (DSCs) co‑express interleukin (IL)‑25/IL‑17RB and that IL‑25 further promotes the proliferation of DSCs via activating c‑Jun n‑terminal kinase and protein kinase B signals, therefore the present study primarily focused on the role of IL‑25 in the process of decidualization in vitro. It was demonstrated that the expression of IL‑25/IL‑17RB in ESCs was decreased compared with DSCs. In addition, following decidualization, the expression levels of IL‑25/IL‑17RB in ESCs were significantly elevated. Recombinant human (rh) IL‑25 promoted the decidualization of ESCs in the presence of 8‑bromoadenosine 3',5'‑cyclic monophosphate sodium salt and 6α‑methyl17α‑acetoxyprogesterone, which was partially inhibited by anti‑human IL‑25 neutralizing antibody (anti‑IL‑25) or anti‑IL‑17RB. In addition, decidual natural killer (dNK) cells not only secreted IL‑25, however also further accelerated the decidualization in vitro. Therefore, these findings indicated that ESCs differentiate into DSCs in the presence of ovarian hormones, resulting in the upregulation of IL‑25/IL‑17RB expression in ESCs. Furthermore, IL‑25 secreted by ESCs and dNK cells further facilitates the decidualization of ESCs, which may form a positive feedback mechanism at the maternal‑fetal interface and thus contribute to the establishment and maintenance of normal pregnancy.
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Affiliation(s)
- Yuan Zhang
- Laboratory for Reproductive Immunology, Hospital of Obstetrics and Gynecology, Fudan University, Shanghai Medical College, Shanghai 200011, P.R. China
| | - Ying Wang
- Department of Obstetrics and Gynecology, Qilu Hospital of Shandong University, Jinan, Shandong 250012, P.R. China
| | - Xiao-Hui Wang
- Clinical and Translational Research Center, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai 201204, P.R. China
| | - Wen-Jie Zhou
- Laboratory for Reproductive Immunology, Hospital of Obstetrics and Gynecology, Fudan University, Shanghai Medical College, Shanghai 200011, P.R. China
| | - Li-Ping Jin
- Laboratory for Reproductive Immunology, Hospital of Obstetrics and Gynecology, Fudan University, Shanghai Medical College, Shanghai 200011, P.R. China
- Clinical and Translational Research Center, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai 201204, P.R. China
| | - Ming-Qing Li
- Laboratory for Reproductive Immunology, Hospital of Obstetrics and Gynecology, Fudan University, Shanghai Medical College, Shanghai 200011, P.R. China
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205
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Uchihashi T, Scheuring S. Applications of high-speed atomic force microscopy to real-time visualization of dynamic biomolecular processes. Biochim Biophys Acta Gen Subj 2018; 1862:229-240. [DOI: 10.1016/j.bbagen.2017.07.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 07/13/2017] [Indexed: 12/12/2022]
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206
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Kushida Y, Arai Y, Shimono K, Nagai T. Biomimetic Chemical Sensing by Fluorescence Signals Using a Virus-like Particle-Based Platform. ACS Sens 2018; 3:87-92. [PMID: 29256249 DOI: 10.1021/acssensors.7b00537] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The chemical receptors present in living organisms are promising tools for developing biomimetic chemical sensors. However, these receptors require lipid membranes for functioning under physiological conditions, which prevents their utilization in the production of cell-free in vitro chemical sensing systems. Here, we report the development of a cell-free biomimetic sensing platform using virus-like particles (VLPs) with intact ligand-gated Ca2+ channels and genetically encoded Ca2+ indicator (GECI). We observed that targeting GECI to the plasma membrane was essential for efficient loading GECI in the VLPs. Although the physiological Ca2+ concentration [Ca2+] maintained in the cells was low (∼10 nM), the concentration in the VLPs was high. This prevented the detection of the increase in [Ca2+] caused by binding of the ligand to the receptor. To address this problem, we employed Lyn-R-CEPIA1, which had low affinity for Ca2+, and a membrane targeting sequence. Thus, we succeeded in monitoring the activation of cyclic nucleotide-gated channels (CNG) on the VLPs by measuring the increase in fluorescence of Lyn-R-CEPIA1. Our VLP-based sensing system can act as a fundamental platform for all kinds of ligand-gated channels.
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Affiliation(s)
- Yuki Kushida
- Department
of Biotechnology, Graduate School of Engineering, Osaka University, 2-1
Yamadaoka, Suita 565-0871, Japan
- Advanced
Research Division, Panasonic Corporation, 3-4 Hikaridai,
Seika, Soraku, Kyoto 619-0237, Japan
| | - Yoshiyuki Arai
- Department
of Biotechnology, Graduate School of Engineering, Osaka University, 2-1
Yamadaoka, Suita 565-0871, Japan
- Department
of Biomolecular Science and Engineering, The Institute of Scientific
and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki 567-0047, Japan
| | - Ken Shimono
- Advanced
Research Division, Panasonic Corporation, 3-4 Hikaridai,
Seika, Soraku, Kyoto 619-0237, Japan
| | - Takeharu Nagai
- Department
of Biotechnology, Graduate School of Engineering, Osaka University, 2-1
Yamadaoka, Suita 565-0871, Japan
- Department
of Biomolecular Science and Engineering, The Institute of Scientific
and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki 567-0047, Japan
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207
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Fu S, Ping P, Wang F, Luo L. Synthesis, secretion, function, metabolism and application of natriuretic peptides in heart failure. J Biol Eng 2018; 12:2. [PMID: 29344085 PMCID: PMC5766980 DOI: 10.1186/s13036-017-0093-0] [Citation(s) in RCA: 99] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 12/21/2017] [Indexed: 12/11/2022] Open
Abstract
As a family of hormones with pleiotropic effects, natriuretic peptide (NP) system includes atrial NP (ANP), B-type NP (BNP), C-type NP (CNP), dendroaspis NP and urodilatin, with NP receptor-A (guanylate cyclase-A), NP receptor-B (guanylate cyclase-B) and NP receptor-C (clearance receptor). These peptides are genetically distinct, but structurally and functionally related for regulating circulatory homeostasis in vertebrates. In humans, ANP and BNP are encoded by NP precursor A (NPPA) and NPPB genes on chromosome 1, whereas CNP is encoded by NPPC on chromosome 2. NPs are synthesized and secreted through certain mechanisms by cardiomyocytes, fibroblasts, endotheliocytes, immune cells (neutrophils, T-cells and macrophages) and immature cells (embryonic stem cells, muscle satellite cells and cardiac precursor cells). They are mainly produced by cardiovascular, brain and renal tissues in response to wall stretch and other causes. NPs provide natriuresis, diuresis, vasodilation, antiproliferation, antihypertrophy, antifibrosis and other cardiometabolic protection. NPs represent body's own antihypertensive system, and provide compensatory protection to counterbalance vasoconstrictor-mitogenic-sodium retaining hormones, released by renin-angiotensin-aldosterone system (RAAS) and sympathetic nervous system (SNS). NPs play central roles in regulation of heart failure (HF), and are inactivated through not only NP receptor-C, but also neutral endopeptidase (NEP), dipeptidyl peptidase-4 and insulin degrading enzyme. Both BNP and N-terminal proBNP are useful biomarkers to not only make the diagnosis and assess the severity of HF, but also guide the therapy and predict the prognosis in patients with HF. Current NP-augmenting strategies include the synthesis of NPs or agonists to increase NP bioactivity and inhibition of NEP to reduce NP breakdown. Nesiritide has been established as an available therapy, and angiotensin receptor blocker NEP inhibitor (ARNI, LCZ696) has obtained extremely encouraging results with decreased morbidity and mortality. Novel pharmacological approaches based on NPs may promote a therapeutic shift from suppressing the RAAS and SNS to re-balancing neuroendocrine dysregulation in patients with HF. The current review discussed the synthesis, secretion, function and metabolism of NPs, and their diagnostic, therapeutic and prognostic values in HF.
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Affiliation(s)
- Shihui Fu
- Department of Geriatric Cardiology, Chinese People’s Liberation Army General Hospital, Beijing, 100853 China
- Department of Cardiology and Hainan Branch, Chinese People’s Liberation Army, General Hospital, Beijing, China
| | - Ping Ping
- Department of Pharmaceutical Care, Chinese People’s, Liberation Army General Hospital, Beijing, China
| | - Fengqi Wang
- Department of Cardiology and Hainan Branch, Chinese People’s Liberation Army, General Hospital, Beijing, China
| | - Leiming Luo
- Department of Geriatric Cardiology, Chinese People’s Liberation Army General Hospital, Beijing, 100853 China
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208
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Mazzolini M, Arcangeletti M, Marchesi A, Napolitano LMR, Grosa D, Maity S, Anselmi C, Torre V. The gating mechanism in cyclic nucleotide-gated ion channels. Sci Rep 2018; 8:45. [PMID: 29311674 PMCID: PMC5758780 DOI: 10.1038/s41598-017-18499-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 12/04/2017] [Indexed: 11/09/2022] Open
Abstract
Cyclic nucleotide-gated (CNG) channels mediate transduction in several sensory neurons. These channels use the free energy of CNs' binding to open the pore, a process referred to as gating. CNG channels belong to the superfamily of voltage-gated channels, where the motion of the α-helix S6 controls gating in most of its members. To date, only the open, cGMP-bound, structure of a CNG channel has been determined at atomic resolution, which is inadequate to determine the molecular events underlying gating. By using electrophysiology, site-directed mutagenesis, chemical modification, and Single Molecule Force Spectroscopy, we demonstrate that opening of CNGA1 channels is initiated by the formation of salt bridges between residues in the C-linker and S5 helix. These events trigger conformational changes of the α-helix S5, transmitted to the P-helix and leading to channel opening. Therefore, the superfamily of voltage-gated channels shares a similar molecular architecture but has evolved divergent gating mechanisms.
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Affiliation(s)
- Monica Mazzolini
- International School for Advanced Studies, Trieste, 34136, Italy.
| | | | - Arin Marchesi
- INSERM U1006, Aix-Marseille Université, Parc Scientifique et Technologique de Luminy, Marseille, 13009, France
| | - Luisa M R Napolitano
- International School for Advanced Studies, Trieste, 34136, Italy
- Structural Biology Laboratory, Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Trieste, 34149, Italy
| | - Debora Grosa
- International School for Advanced Studies, Trieste, 34136, Italy
| | - Sourav Maity
- International School for Advanced Studies, Trieste, 34136, Italy
| | - Claudio Anselmi
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Vincent Torre
- International School for Advanced Studies, Trieste, 34136, Italy.
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209
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Hirji N, Aboshiha J, Georgiou M, Bainbridge J, Michaelides M. Achromatopsia: clinical features, molecular genetics, animal models and therapeutic options. Ophthalmic Genet 2018; 39:149-157. [PMID: 29303385 DOI: 10.1080/13816810.2017.1418389] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Achromatopsia is an autosomal recessive condition, characterised by reduced visual acuity, impaired colour vision, photophobia and nystagmus. The symptoms can be profoundly disabling, and there is no cure currently available. However, the recent development of gene-based interventions may lead to improved outcomes in the future. This article aims to provide a comprehensive review of the clinical features of the condition, its genetic basis and the underlying pathogenesis. We also explore the insights derived from animal models, including the implications for gene supplementation approaches. Finally, we discuss current human gene therapy trials.
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Affiliation(s)
- Nashila Hirji
- a UCL Institute of Ophthalmology, University College London , London , UK.,b Moorfields Eye Hospital , London , UK
| | - Jonathan Aboshiha
- a UCL Institute of Ophthalmology, University College London , London , UK.,b Moorfields Eye Hospital , London , UK
| | - Michalis Georgiou
- a UCL Institute of Ophthalmology, University College London , London , UK.,b Moorfields Eye Hospital , London , UK
| | - James Bainbridge
- a UCL Institute of Ophthalmology, University College London , London , UK.,b Moorfields Eye Hospital , London , UK
| | - Michel Michaelides
- a UCL Institute of Ophthalmology, University College London , London , UK.,b Moorfields Eye Hospital , London , UK
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210
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Demidchik V, Tyutereva EV, Voitsekhovskaja OV. The role of ion disequilibrium in induction of root cell death and autophagy by environmental stresses. FUNCTIONAL PLANT BIOLOGY : FPB 2018; 45:28-46. [PMID: 32291019 DOI: 10.1071/fp16380] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 12/09/2016] [Indexed: 05/26/2023]
Abstract
Environmental stresses such as salinity, drought, oxidants, heavy metals, hypoxia, extreme temperatures and others can induce autophagy and necrosis-type programmed cell death (PCD) in plant roots. These reactions are accompanied by the generation of reactive oxygen species (ROS) and ion disequilibrium, which is induced by electrolyte/K+ leakage through ROS-activated ion channels, such as the outwardly-rectifying K+ channel GORK and non-selective cation channels. Here, we discuss mechanisms of the stress-induced ion disequilibrium and relate it with ROS generation and onset of morphological, biochemical and genetic symptoms of autophagy and PCD in roots. Based on our own data and that in the literature, we propose a hypothesis on the induction of autophagy and PCD in roots by loss of cytosolic K+. To support this, we present data showing that in conditions of salt stress-induced autophagy, gork1-1 plants lacking root K+ efflux channel have fewer autophagosomes compared with the wild type. Overall, literature analyses and presented data strongly suggest that stress-induced root autophagy and PCD are controlled by the level of cytosolic potassium and ROS.
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Affiliation(s)
- Vadim Demidchik
- Laboratory of Plant Ecological Physiology, Komarov Botanical Institute, Russian Academy of Sciences, ul. Professora Popova 2, 197376St Petersburg, Russia
| | - Elena V Tyutereva
- Laboratory of Plant Ecological Physiology, Komarov Botanical Institute, Russian Academy of Sciences, ul. Professora Popova 2, 197376St Petersburg, Russia
| | - Olga V Voitsekhovskaja
- Laboratory of Plant Ecological Physiology, Komarov Botanical Institute, Russian Academy of Sciences, ul. Professora Popova 2, 197376St Petersburg, Russia
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211
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Schmidpeter PAM, Nimigean CM. Fluorescence Titrations to Determine the Binding Affinity of Cyclic Nucleotides to SthK Ion Channels. Bio Protoc 2018; 8:e3041. [PMID: 30417032 DOI: 10.21769/bioprotoc.3041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
The cyclic-nucleotide modulated ion channel family includes cyclic nucleotide-gated (CNG) and hyperpolarization-activated and cyclic nucleotide-modulated (HCN) channels, which play essential roles in visual and olfactory signaling and the heart pacemaking activity. Functionally, these channels have been extensively characterized by electrophysiological techniques from protein heterologously expressed in Xenopus oocytes and mammalian cells. On the other hand, expression and purification of these proteins for biophysical and structural analyses in vitro is problematic and expensive and, accordingly, only limited information on the purified channels is available in the literature. Here we describe a protocol for binding studies of fluorescently labeled cyclic nucleotides to a homologue of eukaryotic CNG channels. Furthermore, we describe how to directly probe binding of unlabeled cyclic nucleotides in a competition assay. The use of fluorescence as a sensitive probe for ligand binding reduces the amount of protein needed and enables fast and easy measurements using standard laboratory equipment.
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Affiliation(s)
| | - Crina M Nimigean
- Weill Cornell Medicine, Department of Anesthesiology, New York, NY, USA
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212
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Musheshe N, Schmidt M, Zaccolo M. cAMP: From Long-Range Second Messenger to Nanodomain Signalling. Trends Pharmacol Sci 2017; 39:209-222. [PMID: 29289379 DOI: 10.1016/j.tips.2017.11.006] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 11/14/2017] [Accepted: 11/17/2017] [Indexed: 12/21/2022]
Abstract
How cAMP generates hormone-specific effects has been debated for many decades. Fluorescence resonance energy transfer (FRET)-based sensors for cAMP allow real-time imaging of the second messenger in intact cells with high spatiotemporal resolution. This technology has made it possible to directly demonstrate that cAMP signals are compartmentalised. The details of such signal compartmentalisation are still being uncovered, and recent findings reveal a previously unsuspected submicroscopic heterogeneity of intracellular cAMP. A model is emerging where specificity depends on compartmentalisation and where the physiologically relevant signals are those that occur within confined nanodomains, rather than bulk changes in cytosolic cAMP. These findings subvert the classical notion of cAMP signalling and provide a new framework for the development of targeted therapeutic approaches.
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Affiliation(s)
- Nshunge Musheshe
- Department of Molecular Pharmacology, University of Groningen, The Netherlands; Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Martina Schmidt
- Department of Molecular Pharmacology, University of Groningen, The Netherlands; Groningen Research Institute for Asthma and COPD, GRIAC, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
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213
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James ZM, Zagotta WN. Structural insights into the mechanisms of CNBD channel function. J Gen Physiol 2017; 150:225-244. [PMID: 29233886 PMCID: PMC5806680 DOI: 10.1085/jgp.201711898] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 11/28/2017] [Indexed: 12/28/2022] Open
Abstract
James and Zagotta discuss how recent cryoEM structures inform our understanding of cyclic nucleotide–binding domain channels. Cyclic nucleotide-binding domain (CNBD) channels are a family of ion channels in the voltage-gated K+ channel superfamily that play crucial roles in many physiological processes. CNBD channels are structurally similar but functionally very diverse. This family includes three subfamilies: (1) the cyclic nucleotide-gated (CNG) channels, which are cation-nonselective, voltage-independent, and cyclic nucleotide-gated; (2) the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which are weakly K+ selective, hyperpolarization-activated, and cyclic nucleotide-gated; and (3) the ether-à-go-go-type (KCNH) channels, which are strongly K+ selective, depolarization-activated, and cyclic nucleotide-independent. Recently, several high-resolution structures have been reported for intact CNBD channels, providing a structural framework to better understand their diverse function. In this review, we compare and contrast the recent structures and discuss how they inform our understanding of ion selectivity, voltage-dependent gating, and cyclic nucleotide–dependent gating within this channel family.
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Affiliation(s)
- Zachary M James
- Department of Physiology and Biophysics, University of Washington, Seattle, WA
| | - William N Zagotta
- Department of Physiology and Biophysics, University of Washington, Seattle, WA
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214
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Sartiani L, Mannaioni G, Masi A, Novella Romanelli M, Cerbai E. The Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels: from Biophysics to Pharmacology of a Unique Family of Ion Channels. Pharmacol Rev 2017; 69:354-395. [PMID: 28878030 DOI: 10.1124/pr.117.014035] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 07/07/2017] [Indexed: 12/22/2022] Open
Abstract
Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels are important members of the voltage-gated pore loop channels family. They show unique features: they open at hyperpolarizing potential, carry a mixed Na/K current, and are regulated by cyclic nucleotides. Four different isoforms have been cloned (HCN1-4) that can assemble to form homo- or heterotetramers, characterized by different biophysical properties. These proteins are widely distributed throughout the body and involved in different physiologic processes, the most important being the generation of spontaneous electrical activity in the heart and the regulation of synaptic transmission in the brain. Their role in heart rate, neuronal pacemaking, dendritic integration, learning and memory, and visual and pain perceptions has been extensively studied; these channels have been found also in some peripheral tissues, where their functions still need to be fully elucidated. Genetic defects and altered expression of HCN channels are linked to several pathologies, which makes these proteins attractive targets for translational research; at the moment only one drug (ivabradine), which specifically blocks the hyperpolarization-activated current, is clinically available. This review discusses current knowledge about HCN channels, starting from their biophysical properties, origin, and developmental features, to (patho)physiologic role in different tissues and pharmacological modulation, ending with their present and future relevance as drug targets.
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Affiliation(s)
- Laura Sartiani
- Department of Neurosciences, Psychology, Drug Research, and Child Health, University of Florence, Firenze, Italy
| | - Guido Mannaioni
- Department of Neurosciences, Psychology, Drug Research, and Child Health, University of Florence, Firenze, Italy
| | - Alessio Masi
- Department of Neurosciences, Psychology, Drug Research, and Child Health, University of Florence, Firenze, Italy
| | - Maria Novella Romanelli
- Department of Neurosciences, Psychology, Drug Research, and Child Health, University of Florence, Firenze, Italy
| | - Elisabetta Cerbai
- Department of Neurosciences, Psychology, Drug Research, and Child Health, University of Florence, Firenze, Italy
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215
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Campbell SL, van Groen T, Kadish I, Smoot LHM, Bolger GB. Altered phosphorylation, electrophysiology, and behavior on attenuation of PDE4B action in hippocampus. BMC Neurosci 2017; 18:77. [PMID: 29197324 PMCID: PMC5712142 DOI: 10.1186/s12868-017-0396-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2016] [Accepted: 11/28/2017] [Indexed: 01/19/2023] Open
Abstract
Background PDE4 cyclic nucleotide phosphodiesterases regulate 3′, 5′ cAMP abundance in the CNS and thereby regulate PKA activity and phosphorylation of CREB, which has been implicated in learning and memory, depression and other functions. The PDE4 isoform PDE4B1 also interacts with the DISC1 protein, implicated in neural development and behavioral disorders. The cellular functions of PDE4B1 have been investigated extensively, but its function(s) in the intact organism remained unexplored. Results To specifically disrupt PDE4B1, we developed mice that express a PDE4B1-D564A transgene in the hippocampus and forebrain. The transgenic mice showed enhanced phosphorylation of CREB and ERK1/2 in hippocampus. Hippocampal neurogenesis was increased in the transgenic mice. Hippocampal electrophysiological studies showed increased baseline synaptic transmission and enhanced LTP in male transgenic mice. Behaviorally, male transgenic mice showed increased activity in prolonged open field testing, but neither male nor female transgenic mice showed detectable anxiety-like behavior or antidepressant effects in the elevated plus-maze, tail-suspension or forced-swim tests. Neither sex showed any significant differences in associative fear conditioning or showed any demonstrable abnormalities in pre-pulse inhibition. Conclusions These data support the use of an isoform-selective approach to the study of PDE4B1 function in the CNS and suggest a probable role of PDE4B1 in synaptic plasticity and behavior. They also provide additional rationale and a refined approach to the development of small-molecule PDE4B1-selective inhibitors, which have potential functions in disorders of cognition, memory, mood and affect.
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Affiliation(s)
- Susan L Campbell
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.,Center for Glial Biology in Health, Disease, and Cancer, Virginia Tech Carilion Research Institute, 2 Riverside Circle, Roanoke, VA, 24016, USA
| | - Thomas van Groen
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Inga Kadish
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Lisa High Mitchell Smoot
- Department of Medicine, University of Alabama at Birmingham, NP 2501, 1720 2nd Ave S, Birmingham, AL, 35294-3300, USA
| | - Graeme B Bolger
- Department of Pharmacology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA. .,Department of Medicine, University of Alabama at Birmingham, NP 2501, 1720 2nd Ave S, Birmingham, AL, 35294-3300, USA. .,Center for Glial Biology in Health, Disease, and Cancer, Virginia Tech Carilion Research Institute, 2 Riverside Circle, Roanoke, VA, 24016, USA.
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216
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Morshedian A, Fain GL. The evolution of rod photoreceptors. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0074. [PMID: 28193819 DOI: 10.1098/rstb.2016.0074] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/02/2016] [Indexed: 12/29/2022] Open
Abstract
Photoreceptors in animals are generally of two kinds: the ciliary or c-type and the rhabdomeric or r-type. Although ciliary photoreceptors are found in many phyla, vertebrates seem to be unique in having two distinct kinds which together span the entire range of vision, from single photons to bright light. We ask why the principal photoreceptors of vertebrates are ciliary and not rhabdomeric, and how rods evolved from less sensitive cone-like photoreceptors to produce our duplex retina. We suggest that the principal advantage of vertebrate ciliary receptors is that they use less ATP than rhabdomeric photoreceptors. This difference may have provided sufficient selection pressure for the development of a completely ciliary eye. Although many of the details of rod evolution are still uncertain, present evidence indicates that (i) rods evolved very early before the split between the jawed and jawless vertebrates, (ii) outer-segment discs make no contribution to rod sensitivity but may have evolved to increase the efficiency of protein renewal, and (iii) evolution of the rod was incremental and multifaceted, produced by the formation of several novel protein isoforms and by changes in protein expression, with no one alteration having more than a few-fold effect on transduction activation or inactivation.This article is part of the themed issue 'Vision in dim light'.
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Affiliation(s)
- Ala Morshedian
- Department of Integrative Biology and Physiology, University of California Los Angeles, Los Angeles, CA 90095-7239, USA
| | - Gordon L Fain
- Department of Integrative Biology and Physiology, University of California Los Angeles, Los Angeles, CA 90095-7239, USA .,Department of Ophthalmology and Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, CA 90095-7000, USA
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217
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Liu C, Xie C, Grant K, Su Z, Gao W, Liu Q, Zhou L. Patch-clamp fluorometry-based channel counting to determine HCN channel conductance. J Gen Physiol 2017; 148:65-76. [PMID: 27353446 PMCID: PMC4924933 DOI: 10.1085/jgp.201511559] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 05/23/2016] [Indexed: 11/20/2022] Open
Abstract
Counting ion channels on cell membranes is of fundamental importance for the study of channel biophysics. Channel counting has thus far been tackled by classical approaches, such as radioactive labeling of ion channels with blockers, gating current measurements, and nonstationary noise analysis. Here, we develop a counting method based on patch-clamp fluorometry (PCF), which enables simultaneous electrical and optical recordings, and apply it to EGFP-tagged, hyperpolarization-activated and cyclic nucleotide-regulated (HCN) channels. We use a well-characterized and homologous cyclic nucleotide-gated (CNG) channel to establish the relationship between macroscopic fluorescence intensity and the total number of channels. Subsequently, based on our estimate of the total number of HCN channels, we determine the single-channel conductance of HCN1 and HCN2 to be 0.46 and 1.71 pS, respectively. Such a small conductance would present a technical challenge for traditional electrophysiology. This PCF-based technique provides an alternative method for counting particles on cell membranes, which could be applied to biophysical studies of other membrane proteins.
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Affiliation(s)
- Chang Liu
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298 School of Medicine, Nankai University, Tianjin 300071, China
| | - Changan Xie
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298
| | - Khade Grant
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298
| | - Zhuocheng Su
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298
| | - Weihua Gao
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298
| | - Qinglian Liu
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298
| | - Lei Zhou
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298
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218
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Cao X, Wu Z, Xiong S, Cao L, Sethi G, Bian JS. The role of hydrogen sulfide in cyclic nucleotide signaling. Biochem Pharmacol 2017; 149:20-28. [PMID: 29158149 DOI: 10.1016/j.bcp.2017.11.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 11/16/2017] [Indexed: 01/07/2023]
Abstract
Hydrogen sulfide (H2S) is recognized as an endogenous gaseous transmitter alongside nitric oxide (NO) and carbon monoxide (CO). By integrating into multiple signaling pathways, H2S elicits biological functions in various mammalian systems. Among these pathways, cyclic nucleotide signaling has gradually gained attention in the past decade. Based on current evidence, it seems that H2S may differentially affect the activity of resting adenylyl cyclases (ACs) and activated ACs, therefore playing a dual role in the regulation of cyclic adenosine monophosphate (cAMP) mediated signaling. However, how H2S achieves the differential regulation on ACs remains unknown at molecular level. In the context of cyclic guanosine monophosphate (cGMP) regulation, H2S augments its downstream signaling at least through three different mechanisms: (1) H2S potentiates the response of soluble guanylyl cyclases (sGCs) to NO; (2) H2S inhibits activity of phosphodiesterases (PDEs); and (3) H2S enhances the production of NO. By regulating cyclic nucleotide signaling, H2S possesses therapeutic potentials particularly for hypertension and cardiac injury which have also been discussed in the current review. Nevertheless, a detailed portrayal of H2S mediated interaction with target proteins is still required for a better understanding of the role of this important gaseous mediator in regulating cyclic nucleotide signaling.
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Affiliation(s)
- Xu Cao
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117600, Singapore
| | - Zhiyuan Wu
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117600, Singapore; Life Science Institute, National University of Singapore, Singapore
| | - Siping Xiong
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117600, Singapore
| | - Lei Cao
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117600, Singapore
| | - Gautam Sethi
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117600, Singapore
| | - Jin-Song Bian
- Life Science Institute, National University of Singapore, Singapore.
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219
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Petersen-Jones SM, Occelli LM, Winkler PA, Lee W, Sparrow JR, Tsukikawa M, Boye SL, Chiodo V, Capasso JE, Becirovic E, Schön C, Seeliger MW, Levin AV, Michalakis S, Hauswirth WW, Tsang SH. Patients and animal models of CNGβ1-deficient retinitis pigmentosa support gene augmentation approach. J Clin Invest 2017; 128:190-206. [PMID: 29202463 PMCID: PMC5749539 DOI: 10.1172/jci95161] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 10/10/2017] [Indexed: 01/07/2023] Open
Abstract
Retinitis pigmentosa (RP) is a major cause of blindness that affects 1.5 million people worldwide. Mutations in cyclic nucleotide-gated channel β 1 (CNGB1) cause approximately 4% of autosomal recessive RP. Gene augmentation therapy shows promise for treating inherited retinal degenerations; however, relevant animal models and biomarkers of progression in patients with RP are needed to assess therapeutic outcomes. Here, we evaluated RP patients with CNGB1 mutations for potential biomarkers of progression and compared human phenotypes with those of mouse and dog models of the disease. Additionally, we used gene augmentation therapy in a CNGβ1-deficient dog model to evaluate potential translation to patients. CNGB1-deficient RP patients and mouse and dog models had a similar phenotype characterized by early loss of rod function and slow rod photoreceptor loss with a secondary decline in cone function. Advanced imaging showed promise for evaluating RP progression in human patients, and gene augmentation using adeno-associated virus vectors robustly sustained the rescue of rod function and preserved retinal structure in the dog model. Together, our results reveal an early loss of rod function in CNGB1-deficient patients and a wide window for therapeutic intervention. Moreover, the identification of potential biomarkers of outcome measures, availability of relevant animal models, and robust functional rescue from gene augmentation therapy support future work to move CNGB1-RP therapies toward clinical trials.
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Affiliation(s)
- Simon M Petersen-Jones
- Department of Small Animal Clinical Sciences, Michigan State University, East Lansing, Michigan, USA
| | - Laurence M Occelli
- Department of Small Animal Clinical Sciences, Michigan State University, East Lansing, Michigan, USA
| | - Paige A Winkler
- Department of Small Animal Clinical Sciences, Michigan State University, East Lansing, Michigan, USA
| | - Winston Lee
- Department of Ophthalmology Pathology & Cell Biology, College of Physicians and Surgeons, Columbia University, New York, New York, USA
| | - Janet R Sparrow
- Department of Ophthalmology Pathology & Cell Biology, College of Physicians and Surgeons, Columbia University, New York, New York, USA
| | - Mai Tsukikawa
- Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Sanford L Boye
- Department of Ophthalmology, University of Florida, Gainesville, Florida, USA
| | - Vince Chiodo
- Department of Ophthalmology, University of Florida, Gainesville, Florida, USA
| | - Jenina E Capasso
- Ocular Genetics, Wills Eye Hospital (WEH), Philadelphia, Pennsylvania, USA
| | - Elvir Becirovic
- Center for Integrated Protein Science Munich (CIPSM), Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Christian Schön
- Center for Integrated Protein Science Munich (CIPSM), Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Mathias W Seeliger
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Alex V Levin
- Thomas Jefferson University, Philadelphia, Pennsylvania, USA.,Ocular Genetics, Wills Eye Hospital (WEH), Philadelphia, Pennsylvania, USA
| | - Stylianos Michalakis
- Center for Integrated Protein Science Munich (CIPSM), Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - William W Hauswirth
- Department of Ophthalmology, University of Florida, Gainesville, Florida, USA
| | - Stephen H Tsang
- Department of Ophthalmology Pathology & Cell Biology, College of Physicians and Surgeons, Columbia University, New York, New York, USA.,Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, New York, USA.,Jonas Children's Vision Care and Bernard & Shirlee Brown Glaucoma Laboratory, Department of Ophthalmology, Columbia University Medical Center (CUMC), Edward S. Harkness Eye Institute, New York, New York, USA
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220
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Sancho M, Bradley E, Garcia-Pascual A, Triguero D, Thornbury KD, Hollywood MA, Sergeant GP. Involvement of cyclic nucleotide-gated channels in spontaneous activity generated in isolated interstitial cells of Cajal from the rabbit urethra. Eur J Pharmacol 2017; 814:216-225. [DOI: 10.1016/j.ejphar.2017.08.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 08/15/2017] [Accepted: 08/15/2017] [Indexed: 11/16/2022]
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221
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Lorenz R, Bertinetti D, Herberg FW. cAMP-Dependent Protein Kinase and cGMP-Dependent Protein Kinase as Cyclic Nucleotide Effectors. Handb Exp Pharmacol 2017; 238:105-122. [PMID: 27885524 DOI: 10.1007/164_2015_36] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The cAMP-dependent protein kinase (PKA) and the cGMP-dependent protein kinase (PKG) are homologous enzymes with different binding and activation specificities for cyclic nucleotides. Both enzymes harbor conserved cyclic nucleotide-binding (CNB) domains. Differences in amino acid composition of these CNB domains mediate cyclic nucleotide selectivity in PKA and PKG, respectively. Recently, the presence of the noncanonical cyclic nucleotides cCMP and cUMP in eukaryotic cells has been proven, while the existence of cellular cIMP and cXMP remains unclear. It was shown that the main effectors of cyclic nucleotide signaling, PKA and PKG, can be activated by each of these noncanonical cyclic nucleotides. With unique effector proteins still missing, such cross-activation effects might have physiological relevance. Therefore, we approach PKA and PKG as cyclic nucleotide effectors in this chapter. The focus of this chapter is the general cyclic nucleotide-binding properties of both kinases as well as the selectivity for cAMP or cGMP, respectively. Furthermore, we discuss the binding affinities and activation potencies of noncanonical cyclic nucleotides.
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Affiliation(s)
- Robin Lorenz
- Department of Biochemistry, University of Kassel, Heinrich-Plett-Str. 40, 34132, Kassel, Germany
| | - Daniela Bertinetti
- Department of Biochemistry, University of Kassel, Heinrich-Plett-Str. 40, 34132, Kassel, Germany
| | - Friedrich W Herberg
- Department of Biochemistry, University of Kassel, Heinrich-Plett-Str. 40, 34132, Kassel, Germany.
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222
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Tanwar M, Khera L, Haokip N, Kaul R, Naorem A, Kateriya S. Modulation of cyclic nucleotide-mediated cellular signaling and gene expression using photoactivated adenylyl cyclase as an optogenetic tool. Sci Rep 2017; 7:12048. [PMID: 28935957 PMCID: PMC5608697 DOI: 10.1038/s41598-017-12162-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 09/01/2017] [Indexed: 11/09/2022] Open
Abstract
Cyclic nucleotide signaling pathway plays a significant role in various biological processes such as cell growth, transcription, inflammation, in microbial pathogenesis, etc. Modulation of cyclic nucleotide levels by optogenetic tools has overcome certain limitations of studying transduction cascade by pharmacological agents and has allowed several ways to modulate biological processes in a spatiotemporal manner. Here, we have shown the optogenetic modulation of the cyclooxygenase 2 (Cox-2) gene expression and their downstream effector molecule (PGE2) in HEK-293T cells and the development process of Dictyostelium discoideum via modulating the cyclic nucleotide (cAMP) signaling pathway utilizing photoactivated adenylyl cyclases (PACs) as an optogenetic tool. Light-induced activation of PACs in HEK-293T cells increases the cAMP level that leads to activation of cAMP response element-binding protein (CREB) transcription factor and further upregulates downstream Cox-2 gene expression and their downstream effector molecule prostaglandin E2. In D. discoideum, the light-regulated increase in cAMP level affects the starvation-induced developmental process. These PACs could modulate the cAMP levels in a light-dependent manner and have a potential to control gene expression and their downstream effector molecules with varying magnitude. It would enable one to utilize PAC as a tool to decipher cyclic nucleotide mediated signaling pathway regulations and their mechanism.
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Affiliation(s)
- Meenakshi Tanwar
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India
| | - Lohit Khera
- Department of Microbiology, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India
| | - Nemneineng Haokip
- Department of Genetics, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India
| | - Rajeev Kaul
- Department of Microbiology, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India
| | - Aruna Naorem
- Department of Genetics, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India
| | - Suneel Kateriya
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India. .,School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India.
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223
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Niebert S, van Belle GJ, Vogelgesang S, Manzke T, Niebert M. The Serotonin Receptor Subtype 5b Specifically Interacts with Serotonin Receptor Subtype 1A. Front Mol Neurosci 2017; 10:299. [PMID: 28983239 PMCID: PMC5613149 DOI: 10.3389/fnmol.2017.00299] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 09/06/2017] [Indexed: 11/13/2022] Open
Abstract
Previously, we described the dysregulation of serotonin (5-HT) receptor subtype 5b (5-ht5b) in a mouse model of Rett syndrome (RTT). 5-ht5b has not been extensively studied, so we set out to characterize it in more detail. Unlike common cell surface receptors, 5-ht5b displays no membrane expression, while receptor clusters are located in endosomes. This unusual subcellular localization is at least in part controlled by glycosylation of the N-terminus, with 5-ht5b possessing fewer glycosylation sites than related receptors. We analyzed whether the localization to endosomes has any functional relevance and found that 5-ht5b receptors can specifically interact with 5-HT1A receptors and retain them in endosomal compartments. This interaction reduces 5-HT1A surface expression and is mediated by interactions between the fourth and fifth trans-membrane domain (TMD). This possibly represents a mechanism by which 5-ht5b receptors regulate the activity of other 5-HT receptor.
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Affiliation(s)
- Sabine Niebert
- Department of Maxillofacial Surgery, University Medical CenterGöttingen, Germany
| | - Gijsbert J van Belle
- Institute of Cardiovascular Physiology, University Medical CenterGöttingen, Germany
| | - Steffen Vogelgesang
- Institute of Neuro- and Sensory Physiology, University Medical CenterGöttingen, Germany.,Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University Medical CenterGöttingen, Germany
| | - Till Manzke
- Institute of Neuro- and Sensory Physiology, University Medical CenterGöttingen, Germany.,Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University Medical CenterGöttingen, Germany
| | - Marcus Niebert
- Institute of Neuro- and Sensory Physiology, University Medical CenterGöttingen, Germany.,Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University Medical CenterGöttingen, Germany
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224
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Maity S, Ilieva N, Laio A, Torre V, Mazzolini M. New views on phototransduction from atomic force microscopy and single molecule force spectroscopy on native rods. Sci Rep 2017; 7:12000. [PMID: 28931892 PMCID: PMC5607320 DOI: 10.1038/s41598-017-11912-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 08/25/2017] [Indexed: 12/11/2022] Open
Abstract
By combining atomic force microscopy (AFM) imaging and single-molecule force spectroscopy (SMFS), we analyzed membrane proteins of the rod outer segments (OS). With this combined approach we were able to study the membrane proteins in their natural environment. In the plasma membrane we identified native cyclic nucleotide-gated (CNG) channels which are organized in single file strings. We also identified rhodopsin located both in the discs and in the plasma membrane. SMFS reveals strikingly different mechanical properties of rhodopsin unfolding in the two environments. Molecular dynamic simulations suggest that this difference is likely to be related to the higher hydrophobicity of the plasma membrane, due to the higher cholesterol concentration. This increases rhodopsin mechanical stability lowering the rate of transition towards its active form, hindering, in this manner, phototransduction.
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Affiliation(s)
- Sourav Maity
- International School for Advanced Studies (SISSA-ISAS) via Bonomea 265, 34136, Trieste, Italy
| | - Nina Ilieva
- International School for Advanced Studies (SISSA-ISAS) via Bonomea 265, 34136, Trieste, Italy
| | - Alessandro Laio
- International School for Advanced Studies (SISSA-ISAS) via Bonomea 265, 34136, Trieste, Italy
| | - Vincent Torre
- International School for Advanced Studies (SISSA-ISAS) via Bonomea 265, 34136, Trieste, Italy.
| | - Monica Mazzolini
- International School for Advanced Studies (SISSA-ISAS) via Bonomea 265, 34136, Trieste, Italy.
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225
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Abstract
Soluble guanylyl cyclase (sGC) is the principal enzyme in mediating the biological actions of nitric oxide. On activation, sGC converts guanosine triphosphate to guanosine 3',5'-cyclic monophosphate (cGMP), which mediates diverse physiological processes including vasodilation, platelet aggregation, and myocardial functions predominantly by acting on cGMP-dependent protein kinases. Cyclic GMP has long been considered as the sole second messenger for sGC action. However, emerging evidence suggests that, in addition to cGMP, other nucleoside 3',5'-cyclic monophosphates (cNMPs) are synthesized by sGC in response to nitric oxide stimulation, and some of these nucleoside 3',5'-cyclic monophosphates are involved in various physiological activities. For example, inosine 3',5'-cyclic monophosphate synthesized by sGC may play a critical role in hypoxic augmentation of vasoconstriction. The involvement of cytidine 3',5'-cyclic monophosphate and uridine 3',5'-cyclic monophosphate in certain cardiovascular activities is also implicated.
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226
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Barreto Ortiz S, Hori D, Nomura Y, Yun X, Jiang H, Yong H, Chen J, Paek S, Pandey D, Sikka G, Bhatta A, Gillard A, Steppan J, Kim JH, Adachi H, Barodka VM, Romer L, An SS, Shimoda LA, Santhanam L, Berkowitz DE. Opsin 3 and 4 mediate light-induced pulmonary vasorelaxation that is potentiated by G protein-coupled receptor kinase 2 inhibition. Am J Physiol Lung Cell Mol Physiol 2017; 314:L93-L106. [PMID: 28882814 DOI: 10.1152/ajplung.00091.2017] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We recently demonstrated that blue light induces vasorelaxation in the systemic mouse circulation, a phenomenon mediated by the nonvisual G protein-coupled receptor melanopsin (Opsin 4; Opn4). Here we tested the hypothesis that nonvisual opsins mediate photorelaxation in the pulmonary circulation. We discovered Opsin 3 (Opn3), Opn4, and G protein-coupled receptor kinase 2 (GRK2) in rat pulmonary arteries (PAs) and in pulmonary arterial smooth muscle cells (PASMCs), where the opsins interact directly with GRK2, as demonstrated with a proximity ligation assay. Light elicited an intensity-dependent relaxation of PAs preconstricted with phenylephrine (PE), with a maximum response between 400 and 460 nm (blue light). Wavelength-specific photorelaxation was attenuated in PAs from Opn4-/- mice and further reduced following shRNA-mediated knockdown of Opn3. Inhibition of GRK2 amplified the response and prevented physiological desensitization to repeated light exposure. Blue light also prevented PE-induced constriction in isolated PAs, decreased basal tone, ablated PE-induced single-cell contraction of PASMCs, and reversed PE-induced depolarization in PASMCs when GRK2 was inhibited. The photorelaxation response was modulated by soluble guanylyl cyclase but not by protein kinase G or nitric oxide. Most importantly, blue light induced significant vasorelaxation of PAs from rats with chronic pulmonary hypertension and effectively lowered pulmonary arterial pressure in isolated intact perfused rat lungs subjected to acute hypoxia. These findings show that functional Opn3 and Opn4 in PAs represent an endogenous "optogenetic system" that mediates photorelaxation in the pulmonary vasculature. Phototherapy in conjunction with GRK2 inhibition could therefore provide an alternative treatment strategy for pulmonary vasoconstrictive disorders.
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Affiliation(s)
- Sebastian Barreto Ortiz
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland
| | - Daijiro Hori
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland.,Division of Cardiac Surgery, Johns Hopkins University , Baltimore, Maryland
| | - Yohei Nomura
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland.,Division of Cardiac Surgery, Johns Hopkins University , Baltimore, Maryland
| | - Xin Yun
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins Asthma and Allergy Center, Johns Hopkins University , Baltimore, Maryland
| | - Haiyang Jiang
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins Asthma and Allergy Center, Johns Hopkins University , Baltimore, Maryland
| | - Hwanmee Yong
- Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health , Baltimore, Maryland
| | - James Chen
- Department of Biomedical Engineering, Johns Hopkins University , Baltimore, Maryland
| | - Sam Paek
- Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health , Baltimore, Maryland
| | - Deepesh Pandey
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland
| | - Gautam Sikka
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland
| | - Anil Bhatta
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland
| | - Andrew Gillard
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland
| | - Jochen Steppan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland
| | - Jae Hyung Kim
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland
| | - Hideo Adachi
- Department of Cardiovascular Surgery, Saitama Medical Center, Jichi Medical University, Shimotsuke, Japan
| | - Viachaslau M Barodka
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland
| | - Lewis Romer
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland.,Department of Biomedical Engineering, Johns Hopkins University , Baltimore, Maryland.,Departments of Cell Biology, Pediatrics, and the Center for Cell Dynamics, Johns Hopkins University , Baltimore, Maryland
| | - Steven S An
- Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health , Baltimore, Maryland
| | - Larissa A Shimoda
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins Asthma and Allergy Center, Johns Hopkins University , Baltimore, Maryland
| | - Lakshmi Santhanam
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland.,Department of Biomedical Engineering, Johns Hopkins University , Baltimore, Maryland
| | - Dan E Berkowitz
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland.,Department of Biomedical Engineering, Johns Hopkins University , Baltimore, Maryland
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Birkholz TR, Beane WS. The planarian TRPA1 homolog mediates extraocular behavioral responses to near-ultraviolet light. J Exp Biol 2017; 220:2616-2625. [PMID: 28495872 PMCID: PMC5536891 DOI: 10.1242/jeb.152298] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 05/04/2017] [Indexed: 12/17/2022]
Abstract
Although light is most commonly thought of as a visual cue, many animals possess mechanisms to detect light outside of the eye for various functions, including predator avoidance, circadian rhythms, phototaxis and migration. Here we confirm that planarians (like Caenorhabditis elegans, leeches and Drosophila larvae) are capable of detecting and responding to light using extraocular photoreception. We found that, when either eyeless or decapitated worms were exposed to near-ultraviolet (near-UV) light, intense wild-type photophobic behaviors were still observed. Our data also revealed that behavioral responses to green wavelengths were mediated by ocular mechanisms, whereas near-UV responses were driven by extraocular mechanisms. As part of a candidate screen to uncover the genetic basis of extraocular photoreception in the planarian species Schmidtea mediterranea, we identified a potential role for a homolog of the transient receptor potential channel A1 (TRPA1) in mediating behavioral responses to extraocular light cues. RNA interference (RNAi) to Smed-TrpA resulted in worms that lacked extraocular photophobic responses to near-UV light, a mechanism previously only identified in Drosophila These data show that the planarian TRPA1 homolog is required for planarian extraocular-light avoidance and may represent a potential ancestral function of this gene. TRPA1 is an evolutionarily conserved detector of temperature and chemical irritants, including reactive oxygen species that are byproducts of UV-light exposure. Our results suggest that planarians possess extraocular photoreception and display an unconventional TRPA1-mediated photophobic response to near-UV light.
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Affiliation(s)
- Taylor R Birkholz
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Avenue, Kalamazoo, MI 49008, USA
| | - Wendy S Beane
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Avenue, Kalamazoo, MI 49008, USA
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228
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Xu Y, Yang J, Wang Y, Wang J, Yu Y, Long Y, Wang Y, Zhang H, Ren Y, Chen J, Wang Y, Zhang X, Guo X, Wu F, Zhu S, Lin Q, Jiang L, Wu C, Wang H, Wan J. OsCNGC13 promotes seed-setting rate by facilitating pollen tube growth in stylar tissues. PLoS Genet 2017; 13:e1006906. [PMID: 28708858 PMCID: PMC5533464 DOI: 10.1371/journal.pgen.1006906] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 07/28/2017] [Accepted: 07/05/2017] [Indexed: 11/29/2022] Open
Abstract
Seed-setting rate is a critical determinant of grain yield in rice (Oryza sativa L.). Rapid and healthy pollen tube growth in the style is required for high seed-setting rate. The molecular mechanisms governing this process remain largely unknown. In this study, we isolate a dominant low seed-setting rate rice mutant, sss1-D. Cellular examination results show that pollen tube growth is blocked in about half of the mutant styles. Molecular cloning and functional assays reveals that SSS1-D encodes OsCNGC13, a member of the cyclic nucleotide-gated channel family. OsCNGC13 is preferentially expressed in the pistils and its expression is dramatically reduced in the heterozygous plant, suggesting a haploinsufficiency nature for the dominant mutant phenotype. We show that OsCNGC13 is permeable to Ca2+. Consistent with this, accumulation of cytoplasmic calcium concentration ([Ca2+]cyt) is defective in the sss1-D mutant style after pollination. Further, the sss1-D mutant has altered extracellular matrix (ECM) components and delayed cell death in the style transmission tract (STT). Based on these results, we propose that OsCNGC13 acts as a novel maternal sporophytic factor required for stylar [Ca2+]cyt accumulation, ECM components modification and STT cell death, thus facilitating the penetration of pollen tube in the style for successful double fertilization and seed-setting in rice. Rice is not only the staple food for more than half of the world’s population, but also a model species for plant developmental and genetic studies. After pollination, rice pollen grains adhere and hydrate at the surface of stigmatic papilla cells. Then, the germinated pollen tubes invade the stigma and navigate through the style transmission tract to reach the micropyle of the embryo sac for fertilization. During this long and arduous process, pollen tube requires abundant communication with the surrounding sporophytic maternal tissues. However, how the growth of pollen tube is regulated by maternal tissue remains largely elusive. This work identifies a typical cyclic nucleotide-gated channel protein in rice, OsCNGC13, which can mediate Ca2+ inward current. Our results suggest that OsCNGC13 acts as a novel maternal sporophytic factor required for stylar [Ca2+]cyt accumulation, extracellular matrix components modification and style cell death, thus facilitating the penetration of pollen tube in the style for successful double fertilization and seed-setting in rice. These findings provide new insights into the molecular genetic control mechanisms of seed-setting rate/grain yield in rice and expand our knowledge on the cyclic nucleotide-gated channel proteins in plant sexual reproduction.
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Affiliation(s)
- Yang Xu
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, China
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Jie Yang
- Institute of Food Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, China
| | - Yihua Wang
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, China
| | - Jiachang Wang
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, China
| | - Yang Yu
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, China
| | - Yu Long
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, National Plant Gene Research Centre (Beijing), China Agricultural University, Beijing, China
| | - Yunlong Wang
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, China
| | - Huan Zhang
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, China
| | - Yulong Ren
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Jun Chen
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Ying Wang
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Xin Zhang
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Xiuping Guo
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Fuqing Wu
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Shanshan Zhu
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Qibing Lin
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Ling Jiang
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, China
| | - Chuanyin Wu
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Haiyang Wang
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Jianmin Wan
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, China
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
- * E-mail:
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229
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Mutations of PKA cyclic nucleotide-binding domains reveal novel aspects of cyclic nucleotide selectivity. Biochem J 2017; 474:2389-2403. [PMID: 28583991 DOI: 10.1042/bcj20160969] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 06/02/2017] [Accepted: 06/05/2017] [Indexed: 11/17/2022]
Abstract
Cyclic AMP and cyclic GMP are ubiquitous second messengers that regulate the activity of effector proteins in all forms of life. The main effector proteins, the 3',5'-cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) and the 3',5'-cyclic guanosine monophosphate (cGMP)-dependent protein kinase (PKG), are preferentially activated by cAMP and cGMP, respectively. However, the molecular basis of this cyclic nucleotide selectivity is still not fully understood. Analysis of isolated cyclic nucleotide-binding (CNB) domains of PKA regulatory subunit type Iα (RIα) reveals that the C-terminal CNB-B has a higher cAMP affinity and selectivity than the N-terminal CNB-A. Here, we show that introducing cGMP-specific residues using site-directed mutagenesis reduces the selectivity of CNB-B, while the combination of two mutations (G316R/A336T) results in a cGMP-selective binding domain. Furthermore, introducing the corresponding mutations (T192R/A212T) into the PKA RIα CNB-A turns this domain into a highly cGMP-selective domain, underlining the importance of these contacts for achieving cGMP specificity. Binding data with the generic purine nucleotide 3',5'-cyclic inosine monophosphate (cIMP) reveal that introduced arginine residues interact with the position 6 oxygen of the nucleobase. Co-crystal structures of an isolated CNB-B G316R/A336T double mutant with either cAMP or cGMP reveal that the introduced threonine and arginine residues maintain their conserved contacts as seen in PKG I CNB-B. These results improve our understanding of cyclic nucleotide binding and the molecular basis of cyclic nucleotide specificity.
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230
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Abstract
Fertilization is exceptionally complex and, depending on the species, happens in entirely different environments. External fertilizers in aquatic habitats, like marine invertebrates or fish, release their gametes into the seawater or freshwater, whereas sperm from most internal fertilizers like mammals cross the female genital tract to make their way to the egg. Various chemical and physical cues guide sperm to the egg. Quite generally, these cues enable signaling pathways that ultimately evoke a cellular Ca2+ response that modulates the waveform of the flagellar beat and, hence, the swimming path. To cope with the panoply of challenges to reach and fertilize the egg, sperm from different species have developed their own unique repertoire of signaling molecules and mechanisms. Here, we review the differences and commonalities for sperm sensory signaling in marine invertebrates (sea urchin), fish (zebrafish), and mammals (mouse, human).
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Affiliation(s)
- Dagmar Wachten
- Minerva Max Planck Research Group, Molecular Physiology, Center of Advanced European Studies and Research (caesar), 53175 Bonn, Germany
| | - Jan F Jikeli
- Minerva Max Planck Research Group, Molecular Physiology, Center of Advanced European Studies and Research (caesar), 53175 Bonn, Germany
| | - U Benjamin Kaupp
- Department Molecular Sensory Systems, Center of Advanced European Studies and Research (caesar), 53175 Bonn, Germany
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231
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Torres-Quesada O, Mayrhofer JE, Stefan E. The many faces of compartmentalized PKA signalosomes. Cell Signal 2017; 37:1-11. [PMID: 28528970 DOI: 10.1016/j.cellsig.2017.05.012] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 05/16/2017] [Accepted: 05/17/2017] [Indexed: 01/03/2023]
Abstract
Cellular signal transmission requires the dynamic formation of spatiotemporally controlled molecular interactions. At the cell surface information is received by receptor complexes and relayed through intracellular signaling platforms which organize the actions of functionally interacting signaling enzymes and substrates. The list of hormone or neurotransmitter pathways that utilize the ubiquitous cAMP-sensing protein kinase A (PKA) system is expansive. This requires that the specificity, duration, and intensity of PKA responses are spatially and temporally restricted. Hereby, scaffolding proteins take the center stage for ensuring proper signal transmission. They unite second messenger sensors, activators, effectors, and kinase substrates within cellular micro-domains to precisely control and route signal propagation. A-kinase anchoring proteins (AKAPs) organize such subcellular signalosomes by tethering the PKA holoenzyme to distinct cell compartments. AKAPs differ in their modular organization showing pathway specific arrangements of interaction motifs or domains. This enables the cell- and compartment- guided assembly of signalosomes with unique enzyme composition and function. The AKAP-mediated clustering of cAMP and other second messenger sensing and interacting signaling components along with functional successive enzymes facilitates the rapid and precise dissemination of incoming signals. This review article delineates examples for different means of PKA regulation and for snapshots of compartmentalized PKA signalosomes.
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Affiliation(s)
- Omar Torres-Quesada
- Institute of Biochemistry and Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Johanna E Mayrhofer
- Institute of Biochemistry and Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Eduard Stefan
- Institute of Biochemistry and Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria.
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232
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May-Simera H, Nagel-Wolfrum K, Wolfrum U. Cilia - The sensory antennae in the eye. Prog Retin Eye Res 2017; 60:144-180. [PMID: 28504201 DOI: 10.1016/j.preteyeres.2017.05.001] [Citation(s) in RCA: 96] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 05/04/2017] [Accepted: 05/08/2017] [Indexed: 12/21/2022]
Abstract
Cilia are hair-like projections found on almost all cells in the human body. Originally believed to function merely in motility, the function of solitary non-motile (primary) cilia was long overlooked. Recent research has demonstrated that primary cilia function as signalling hubs that sense environmental cues and are pivotal for organ development and function, tissue hoemoestasis, and maintenance of human health. Cilia share a common anatomy and their diverse functional features are achieved by evolutionarily conserved functional modules, organized into sub-compartments. Defects in these functional modules are responsible for a rapidly growing list of human diseases collectively termed ciliopathies. Ocular pathogenesis is common in virtually all classes of syndromic ciliopathies, and disruptions in cilia genes have been found to be causative in a growing number of non-syndromic retinal dystrophies. This review will address what is currently known about cilia contribution to visual function. We will focus on the molecular and cellular functions of ciliary proteins and their role in the photoreceptor sensory cilia and their visual phenotypes. We also highlight other ciliated cell types in tissues of the eye (e.g. lens, RPE and Müller glia cells) discussing their possible contribution to disease progression. Progress in basic research on the cilia function in the eye is paving the way for therapeutic options for retinal ciliopathies. In the final section we describe the latest advancements in gene therapy, read-through of non-sense mutations and stem cell therapy, all being adopted to treat cilia dysfunction in the retina.
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Affiliation(s)
- Helen May-Simera
- Institute of Molecular Physiology, Cilia Biology, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany
| | - Kerstin Nagel-Wolfrum
- Institute of Molecular Physiology, Molecular Cell Biology, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany
| | - Uwe Wolfrum
- Institute of Molecular Physiology, Molecular Cell Biology, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
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233
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Butler MR, Ma H, Yang F, Belcher J, Le YZ, Mikoshiba K, Biel M, Michalakis S, Iuso A, Križaj D, Ding XQ. Endoplasmic reticulum (ER) Ca 2+-channel activity contributes to ER stress and cone death in cyclic nucleotide-gated channel deficiency. J Biol Chem 2017; 292:11189-11205. [PMID: 28495882 DOI: 10.1074/jbc.m117.782326] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 05/01/2017] [Indexed: 02/05/2023] Open
Abstract
Endoplasmic reticulum (ER) stress and mislocalization of improperly folded proteins have been shown to contribute to photoreceptor death in models of inherited retinal degenerative diseases. In particular, mice with cone cyclic nucleotide-gated (CNG) channel deficiency, a model for achromatopsia, display both early-onset ER stress and opsin mistrafficking. By 2 weeks of age, these mice show elevated signaling from all three arms of the ER-stress pathway, and by 1 month, cone opsin is improperly distributed away from its normal outer segment location to other retinal layers. This work investigated the role of Ca2+-release channels in ER stress, protein mislocalization, and cone death in a mouse model of CNG-channel deficiency. We examined whether preservation of luminal Ca2+ stores through pharmacological and genetic suppression of ER Ca2+ efflux protects cones by attenuating ER stress. We demonstrated that the inhibition of ER Ca2+-efflux channels reduced all three arms of ER-stress signaling while improving opsin trafficking to cone outer segments and decreasing cone death by 20-35%. Cone-specific gene deletion of the inositol-1,4,5-trisphosphate receptor type I (IP3R1) also significantly increased cone density in the CNG-channel-deficient mice, suggesting that IP3R1 signaling contributes to Ca2+ homeostasis and cone survival. Consistent with the important contribution of organellar Ca2+ signaling in this achromatopsia mouse model, significant differences in dynamic intraorganellar Ca2+ levels were detected in CNG-channel-deficient cones. These results thus identify a novel molecular link between Ca2+ homeostasis and cone degeneration, thereby revealing novel therapeutic targets to preserve cones in inherited retinal degenerative diseases.
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Affiliation(s)
| | | | - Fan Yang
- From the Departments of Cell Biology
| | | | - Yun-Zheng Le
- From the Departments of Cell Biology.,Internal Medicine, and.,Ophthalmology and.,the Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Katsuhiko Mikoshiba
- the Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Hirosawa Wako-shi, Saitama 351-0198, Japan
| | - Martin Biel
- the Center for Integrated Protein Science Munich (CIPSM) and Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, 81377 Munich, Germany, and
| | - Stylianos Michalakis
- the Center for Integrated Protein Science Munich (CIPSM) and Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, 81377 Munich, Germany, and
| | - Anthony Iuso
- the John A. Moran Eye Center, University of Utah, Salt Lake City, Utah 84132
| | - David Križaj
- the John A. Moran Eye Center, University of Utah, Salt Lake City, Utah 84132
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234
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Pseudoscaffolds and anchoring proteins: the difference is in the details. Biochem Soc Trans 2017; 45:371-379. [PMID: 28408477 DOI: 10.1042/bst20160329] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 01/18/2017] [Accepted: 01/20/2017] [Indexed: 12/18/2022]
Abstract
Pseudokinases and pseudophosphatases possess the ability to bind substrates without catalyzing their modification, thereby providing a mechanism to recruit potential phosphotargets away from active enzymes. Since many of these pseudoenzymes possess other characteristics such as localization signals, separate catalytic sites, and protein-protein interaction domains, they have the capacity to influence signaling dynamics in local environments. In a similar manner, the targeting of signaling enzymes to subcellular locations by A-kinase-anchoring proteins (AKAPs) allows for precise and local control of second messenger signaling events. Here, we will discuss how pseudoenzymes form 'pseudoscaffolds' and compare and contrast this compartment-specific regulatory role with the signal organization properties of AKAPs. The mitochondria will be the focus of this review, as they are dynamic organelles that influence a broad range of cellular processes such as metabolism, ATP synthesis, and apoptosis.
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235
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Rose K, Walston ST, Chen J. Separation of photoreceptor cell compartments in mouse retina for protein analysis. Mol Neurodegener 2017; 12:28. [PMID: 28399904 PMCID: PMC5387348 DOI: 10.1186/s13024-017-0171-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 03/30/2017] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND Light exposure triggers movement of certain signaling proteins within the cellular compartments of the highly polarized rod photoreceptor cell. This redistribution of proteins between the inner and outer segment compartments affects the performance and physiology of the rod cell. In addition, newly synthesized phototransduction proteins traverse from the site of their synthesis in the inner segment, through the thin connecting cilium, to reach their destination in the outer segment. Processes that impede normal trafficking of these abundant proteins lead to cell death. The study of movement and unique localization of biomolecules within the different compartments of the rod cell would be greatly facilitated by techniques that reliably separate these compartments. Ideally, these methods can be applied to the mouse retina due to the widespread usage of transgenic mouse models in the investigation of basic visual processes and disease mechanisms that affect vision. Although the retina is organized in distinct layers, the small and highly curved mouse retina makes physical separation of retinal layers a challenge. We introduce two peeling methods that efficiently and reliably isolate the rod outer segment and other cell compartments for Western blots to examine protein movement across these compartments. METHODS The first separation method employs Whatman® filter paper to successively remove the rod outer segments from isolated, live mouse retinas. The second method utilizes ScotchTM tape to peel the rod outer segment layer and the rod inner segment layer from lyophilized mouse retinas. Both procedures can be completed within one hour. RESULTS We utilize these two protocols on dark-adapted and light-exposed retinas of C57BL/6 mice and subject the isolated tissue layers to Western blots to demonstrate their effectiveness in detecting light-induced translocation of transducin (GNAT1) and rod arrestin (ARR1). Furthermore, we provide evidence that RGS9 does not undergo light-induced translocation. CONCLUSIONS These results demonstrate the effectiveness of the two different peeling protocols for the separation of the layered compartments of the mouse retina and their utility for investigations of protein compositions within these compartments.
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Affiliation(s)
- Kasey Rose
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Steven T Walston
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, California, USA
| | - Jeannie Chen
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA. .,Department of Cell & Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
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236
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Abstract
Glaucoma is characterized by a slow and progressive degeneration of the optic nerve, including retinal ganglion cell (RGC) axons in the optic nerve head (ONH), leading to visual impairment. Despite its high prevalence, the biological basis of glaucoma pathogenesis still is not yet fully understood, and the factors contributing to its progression are currently not well characterized. Intraocular pressure (IOP) is the only modifiable risk factor, and reduction of IOP is the standard treatment for glaucoma. However, lowering IOP itself is not always effective for preserving visual function in patients with primary open-angle glaucoma. The second messenger cyclic adenosine 3′,5′-monophosphate (cAMP) regulates numerous biological processes in the central nervous system including the retina and the optic nerve. Although recent studies revealed that cAMP generated by adenylyl cyclases (ACs) is important in regulating aqueous humor dynamics in ocular tissues, such as the ciliary body and trabecular meshwork, as well as cell death and growth in the retina and optic nerve, the functional role and significance of cAMP in glaucoma remain to be elucidated. In this review, we will discuss the functional role of cAMP in aqueous humor dynamics and IOP regulation, and review the current medications, which are related to the cAMP signaling pathway, for glaucoma treatment. Also, we will further focus on cAMP signaling in RGC growth and regeneration by soluble AC as well as ONH astrocytes by transmembrane ACs to understand its potential role in the pathogenesis of glaucoma neurodegeneration
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Affiliation(s)
- Myoung Sup Shim
- Hamilton Glaucoma Center and Department of Ophthalmology, Shiley Eye Institute, University of California San Diego, La Jolla, CA 92037, USA
| | - Keun-Young Kim
- Center for Research on Biological Systems, National Center for Microscopy and Imaging Research and Department of Neuroscience, University of California San Diego, La Jolla 92093, CA 92093, USA
| | - Won-Kyu Ju
- Hamilton Glaucoma Center and Department of Ophthalmology, Shiley Eye Institute, University of California San Diego, La Jolla, CA 92037, USA
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237
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Torres-Quesada O, Röck R, Stefan E. Systematic Quantification of GPCR/cAMP-Controlled Protein Kinase A Interactions. Horm Metab Res 2017; 49:240-249. [PMID: 28427097 DOI: 10.1055/s-0042-110791] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The diffusible second messenger cyclic AMP (cAMP) originates from multiple G protein-coupled receptor (GPCR) cascades activating the intracellular key effector protein kinase A (PKA). Spatially and temporally restricted cAMP-fluxes are directly sensed by macromolecular PKA complexes. The consequences are alterations of molecular interactions, which lead to activation of compartmentalized PKA phosphotransferase activities, regulating a vast array of cellular functions. To decode cell-type and cell-compartment specific PKA functions, the spatio-temporal dynamics of small molecule:protein interactions, protein:protein interactions (PPIs), cAMP-mobilization, and phosphotransferase activities need to be determined directly in the appropriate cellular context. A collection of cell-based reporters has been developed to either visualize or quantitatively measure kinase activities or PKA complex formation/dissociation. In this review, we list a collection of unimolecular and bimolecular PKA biosensors, followed by the specification of the modular design of a Renilla luciferase based protein-fragment complementation assay (PCA) platform for measuring PKA network interactions. We discuss the application spectrum of the PCA reporter to identify, quantify, and dissect dynamic and transient PKA complexes downstream of specific GPCR activities. We specify the implementation of a PCA PKA platform to systematically quantify the concurrent involvement of receptor-cAMP signaling, post-translational modifications, and kinase subunit mutations/perturbations in PKA activation. The systematic quantification of transient PKA network interactions will contribute to a better understanding how GPCR-recognized input signals are streamlined through the compartmentalized and cAMP-interacting PKA signalosome.
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Affiliation(s)
- O Torres-Quesada
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - R Röck
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - E Stefan
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
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238
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Sivakumar A, Kumar S, Yathish HM, Mishra C, Modi RP, Chaudhary R, Khan S, Sivamani B, Ghosh SK, Sarkar M. Expression Profiling and Identification of Novel SNPs in CatSper2 Gene and Their Influence on Sperm Motility Parameters in Bovines. Anim Biotechnol 2017; 29:34-40. [DOI: 10.1080/10495398.2017.1294597] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- A. Sivakumar
- Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, India
| | - Subodh Kumar
- Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, India
| | - H. M. Yathish
- Department of Animal Genetics and Breeding, Veterinary College, Bidar, India
| | - Chinmoy Mishra
- Department of Animal Breeding and Genetics, OUAT, Bhubaneswar, India
| | - Rajendra Prasad Modi
- Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, India
| | - Rajni Chaudhary
- Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, India
| | - Subuhi Khan
- Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, India
| | - B. Sivamani
- Nutrition, Genetics and Biotechnology Division, Central Institute of Brackishwater Aquaculture, Chennai, India
| | - S. K. Ghosh
- Division of Animal Reproduction, Indian Veterinary Research Institute, Izatnagar, India
| | - Mihir Sarkar
- Division of Physiology & Climatology, Indian Veterinary Research Institute, Izatnagar, India
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Lamb TD, Hunt DM. Evolution of the vertebrate phototransduction cascade activation steps. Dev Biol 2017; 431:77-92. [PMID: 28347645 DOI: 10.1016/j.ydbio.2017.03.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 02/28/2017] [Accepted: 03/20/2017] [Indexed: 02/06/2023]
Abstract
We examine the molecular phylogeny of the proteins underlying the activation steps of vertebrate phototransduction, for both agnathan and jawed vertebrate taxa. We expand the number of taxa analysed and we update the alignment and tree building methodology from a previous analysis. For each of the four primary components (the G-protein transducin alpha subunit, GαT, the cyclic GMP phosphodiesterase, PDE6, and the alpha and beta subunits of the cGMP-gated ion channel, CNGC), the phylogenies appear consistent with expansion from an ancestral proto-vertebrate cascade during two rounds of whole-genome duplication followed by divergence of the agnathan and jawed vertebrate lineages. In each case, we consider possible scenarios for the underlying gene duplications and losses, and we apply relevant constraints to the tree construction. From tests of the topology of the resulting trees, we obtain a scenario for the expansion of each component during 2R that accurately fits the observations. Similar analysis of the visual opsins indicates that the only expansion to have occurred during 2R was the formation of Rh1 and Rh2. Finally, we propose a hypothetical scenario for the conversion of an ancestral chordate cascade into the proto-vertebrate phototransduction cascade, prior to whole-genome duplication. Together, our models provide a plausible account for the origin and expansion of the vertebrate phototransduction cascade.
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Affiliation(s)
- Trevor D Lamb
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, The Australian National University, ACT 2600, Australia.
| | - David M Hunt
- The Lions Eye Institute, The University of Western Australia, WA 6009, Australia; School of Biological Sciences, The University of Western Australia, WA 6009, Australia
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240
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Compartmentalized cGMP Responses of Olfactory Sensory Neurons in Caenorhabditis elegans. J Neurosci 2017; 37:3753-3763. [PMID: 28270568 DOI: 10.1523/jneurosci.2628-16.2017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 02/23/2017] [Accepted: 02/24/2017] [Indexed: 01/13/2023] Open
Abstract
Cyclic guanosine monophosphate (cGMP) plays a crucial role as a second messenger in the regulation of sensory signal transduction in many organisms. In AWC olfactory sensory neurons of Caenorhabditis elegans, cGMP also has essential and distinctive functions in olfactory sensation and adaptation. According to molecular genetic studies, when nematodes are exposed to odorants, a decrease in cGMP regulates cGMP-gated channels for olfactory sensation. Conversely, for olfactory adaptation, an increase in cGMP activates protein kinase G to modulate cellular physiological functions. Although these opposing cGMP responses in single neurons may occur at the same time, it is unclear how cGMP actually behaves in AWC sensory neurons. A hypothetical explanation for opposing cGMP responses is region-specific behaviors in AWC: for odor sensation, cGMP levels in cilia could decrease, whereas odor adaptation is mediated by increased cGMP levels in soma. Therefore, we visualized intracellular cGMP in AWC with a genetically encoded cGMP indicator, cGi500, and examined spatiotemporal cGMP responses in AWC neurons. The cGMP imaging showed that, after odor exposure, cGMP levels in AWC cilia decreased transiently, whereas levels in dendrites and soma gradually increased. These region-specific responses indicated that the cGMP responses in AWC neurons are explicitly compartmentalized. In addition, we performed Ca2+ imaging to examine the relationship between cGMP and Ca2+ These results suggested that AWC sensory neurons are in fact analogous to vertebrate photoreceptor neurons.SIGNIFICANCE STATEMENT Cyclic guanosine monophosphate (cGMP) plays crucial roles in the regulation of sensory signal transduction in many animals. In AWC olfactory sensory neurons of Caenorhabditis elegans, cGMP also has essential and distinctive functions involving olfactory sensation and adaptation. Here, we visualized intracellular cGMP in AWC neurons with a genetically encoded cGMP indicator and examined how these different functions could be regulated by the same second messenger in single neurons. cGMP imaging showed that, after odor application, cGMP levels in cilia decreased transiently, whereas levels in dendrites and soma gradually increased. These region-specific responses indicated that the responses in AWC neurons are explicitly compartmentalized. In addition, by combining cGMP and Ca2+ imaging, we observed that AWC neurons are analogous to vertebrate photoreceptor neurons.
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Salesse C. Physiologie du signal visuel rétinien : de la phototransduction jusqu’au cycle visuel. J Fr Ophtalmol 2017; 40:239-250. [DOI: 10.1016/j.jfo.2016.12.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 12/16/2016] [Indexed: 11/28/2022]
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242
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The peripheral olfactory system of vertebrates: molecular, structural and functional basics of the sense of smell. ACTA ACUST UNITED AC 2017. [DOI: 10.1007/s13295-011-0021-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Abstract
The sense of smell provides people and animals with an abundance of information about their environment, helping them to navigate, detect potential threats, control food intake, choose sexual partners and significantly influence intraspecies social behavior. The perception of odors begins with the binding of odor molecules to specialized olfactory receptor proteins, which nearly all belong to the superfamily of G protein-coupled receptors. Altogether, five different olfactory receptor gene families have been described to date, among them the largest gene family in the genome with over 1000 genes in rodents. The signal transduction cascade coupled to the receptors has already been well characterized for this family. Three different classes of receptor neurons-ciliated, microvillous and crypt receptor neurons-can be distinguished by their anatomical and molecular characteristics. Generally, an individual receptor neuron expresses only a single olfactory receptor gene, and olfactory receptor neurons that express the same receptor converge into a common target structure, a glomerulus, which generates a receptotopic map in the first olfactory brain region, the olfactory bulb. This review article provides a general overview of the peripheral detection of odorants on the one hand, while on the other it focuses on recent advances in the field, including new findings on the peripheral modulation of olfactory signals.
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243
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Einav T, Phillips R. Monod-Wyman-Changeux Analysis of Ligand-Gated Ion Channel Mutants. J Phys Chem B 2017; 121:3813-3824. [PMID: 28134524 DOI: 10.1021/acs.jpcb.6b12672] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We present a framework for computing the gating properties of ligand-gated ion channel mutants using the Monod-Wyman-Changeux (MWC) model of allostery. We derive simple analytic formulas for key functional properties such as the leakiness, dynamic range, half-maximal effective concentration ([EC50]), and effective Hill coefficient, and explore the full spectrum of phenotypes that are accessible through mutations. Specifically, we consider mutations in the channel pore of nicotinic acetylcholine receptor (nAChR) and the ligand binding domain of a cyclic nucleotide-gated (CNG) ion channel, demonstrating how each mutation can be characterized as only affecting a subset of the biophysical parameters. In addition, we show how the unifying perspective offered by the MWC model allows us, perhaps surprisingly, to collapse the plethora of dose-response data from different classes of ion channels into a universal family of curves.
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Affiliation(s)
- Tal Einav
- Department of Physics, California Institute of Technology , Pasadena, California 91125, United States
| | - Rob Phillips
- Department of Applied Physics and Division of Biology and Biological Engineering, California Institute of Technology , Pasadena, California 91125, United States
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244
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Bader A, Bintig W, Begandt D, Klett A, Siller IG, Gregor C, Schaarschmidt F, Weksler B, Romero I, Couraud PO, Hell SW, Ngezahayo A. Adenosine receptors regulate gap junction coupling of the human cerebral microvascular endothelial cells hCMEC/D3 by Ca 2+ influx through cyclic nucleotide-gated channels. J Physiol 2017; 595:2497-2517. [PMID: 28075020 DOI: 10.1113/jp273150] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 12/16/2016] [Indexed: 12/25/2022] Open
Abstract
KEY POINTS Gap junction channels are essential for the formation and regulation of physiological units in tissues by allowing the lateral cell-to-cell diffusion of ions, metabolites and second messengers. Stimulation of the adenosine receptor subtype A2B increases the gap junction coupling in the human blood-brain barrier endothelial cell line hCMEC/D3. Although the increased gap junction coupling is cAMP-dependent, neither the protein kinase A nor the exchange protein directly activated by cAMP were involved in this increase. We found that cAMP activates cyclic nucleotide-gated (CNG) channels and thereby induces a Ca2+ influx, which leads to the increase in gap junction coupling. The report identifies CNG channels as a possible physiological link between adenosine receptors and the regulation of gap junction channels in endothelial cells of the blood-brain barrier. ABSTRACT The human cerebral microvascular endothelial cell line hCMEC/D3 was used to characterize the physiological link between adenosine receptors and the gap junction coupling in endothelial cells of the blood-brain barrier. Expressed adenosine receptor subtypes and connexin (Cx) isoforms were identified by RT-PCR. Scrape loading/dye transfer was used to evaluate the impact of the A2A and A2B adenosine receptor subtype agonist 2-phenylaminoadenosine (2-PAA) on the gap junction coupling. We found that 2-PAA stimulated cAMP synthesis and enhanced gap junction coupling in a concentration-dependent manner. This enhancement was accompanied by an increase in gap junction plaques formed by Cx43. Inhibition of protein kinase A did not affect the 2-PAA-related enhancement of gap junction coupling. In contrast, the cyclic nucleotide-gated (CNG) channel inhibitor l-cis-diltiazem, as well as the chelation of intracellular Ca2+ with BAPTA, or the absence of external Ca2+ , suppressed the 2-PAA-related enhancement of gap junction coupling. Moreover, we observed a 2-PAA-dependent activation of CNG channels by a combination of electrophysiology and pharmacology. In conclusion, the stimulation of adenosine receptors in hCMEC/D3 cells induces a Ca2+ influx by opening CNG channels in a cAMP-dependent manner. Ca2+ in turn induces the formation of new gap junction plaques and a consecutive sustained enhancement of gap junction coupling. The report identifies CNG channels as a physiological link that integrates gap junction coupling into the adenosine receptor-dependent signalling of endothelial cells of the blood-brain barrier.
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Affiliation(s)
- Almke Bader
- Institute of Biophysics, Leibniz University Hannover, Hannover, Germany
| | - Willem Bintig
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Daniela Begandt
- Walter Brendel Centre of Experimental Medicine, Department of Cardiovascular Physiology and Pathophysiology, Biomedical Center, Ludwig-Maximilians-Universität München, Planegg-Martinsried, Germany
| | - Anne Klett
- Institute of Biophysics, Leibniz University Hannover, Hannover, Germany
| | - Ina G Siller
- Institute of Biophysics, Leibniz University Hannover, Hannover, Germany
| | - Carola Gregor
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | | | - Babette Weksler
- Weill Medical College of Cornell University, New York, NY, USA
| | - Ignacio Romero
- Department of Biological Sciences, The Open University, Walton Hall, Milton Keynes, UK
| | - Pierre-Olivier Couraud
- INSERM, U1016, Institut Cochin, Paris, France.,CNRS, UMR8104, Paris, France.,Université Paris Descartes, Paris, France
| | - Stefan W Hell
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Anaclet Ngezahayo
- Institute of Biophysics, Leibniz University Hannover, Hannover, Germany.,Center for Systems Neuroscience Hannover, University of Veterinary Medicine Hannover Foundation, Hannover, Germany
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245
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Li M, Zhou X, Wang S, Michailidis I, Gong Y, Su D, Li H, Li X, Yang J. Structure of a eukaryotic cyclic-nucleotide-gated channel. Nature 2017; 542:60-65. [PMID: 28099415 DOI: 10.1038/nature20819] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2016] [Accepted: 11/23/2016] [Indexed: 12/11/2022]
Abstract
Cyclic-nucleotide-gated channels are essential for vision and olfaction. They belong to the voltage-gated ion channel superfamily but their activities are controlled by intracellular cyclic nucleotides instead of transmembrane voltage. Here we report a 3.5-Å-resolution single-particle electron cryo-microscopy structure of a cyclic-nucleotide-gated channel from Caenorhabditis elegans in the cyclic guanosine monophosphate (cGMP)-bound open state. The channel has an unusual voltage-sensor-like domain, accounting for its deficient voltage dependence. A carboxy-terminal linker connecting S6 and the cyclic-nucleotide-binding domain interacts directly with both the voltage-sensor-like domain and the pore domain, forming a gating ring that couples conformational changes triggered by cyclic nucleotide binding to the gate. The selectivity filter is lined by the carboxylate side chains of a functionally important glutamate and three rings of backbone carbonyls. This structure provides a new framework for understanding mechanisms of ion permeation, gating and channelopathy of cyclic-nucleotide-gated channels and cyclic nucleotide modulation of related channels.
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Affiliation(s)
- Minghui Li
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Xiaoyuan Zhou
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Shu Wang
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences, Chinese Academy of Sciences, Kunming 650223, China.,Key Laboratory of Bioactive Peptides of Yunnan Province, Chinese Academy of Sciences, Kunming 650223, China.,Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming 650204, China
| | - Ioannis Michailidis
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Ye Gong
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences, Chinese Academy of Sciences, Kunming 650223, China.,Key Laboratory of Bioactive Peptides of Yunnan Province, Chinese Academy of Sciences, Kunming 650223, China.,Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China
| | - Deyuan Su
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences, Chinese Academy of Sciences, Kunming 650223, China.,Key Laboratory of Bioactive Peptides of Yunnan Province, Chinese Academy of Sciences, Kunming 650223, China.,Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming 650204, China
| | - Huan Li
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences, Chinese Academy of Sciences, Kunming 650223, China.,Key Laboratory of Bioactive Peptides of Yunnan Province, Chinese Academy of Sciences, Kunming 650223, China.,Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming 650204, China
| | - Xueming Li
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jian Yang
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA.,Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences, Chinese Academy of Sciences, Kunming 650223, China.,Key Laboratory of Bioactive Peptides of Yunnan Province, Chinese Academy of Sciences, Kunming 650223, China.,Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China
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246
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Bolger GB. The PDE4 cAMP-Specific Phosphodiesterases: Targets for Drugs with Antidepressant and Memory-Enhancing Action. ADVANCES IN NEUROBIOLOGY 2017; 17:63-102. [PMID: 28956330 DOI: 10.1007/978-3-319-58811-7_4] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The PDE4 cyclic nucleotide phosphodiesterases are essential regulators of cAMP abundance in the CNS through their ability to regulate PKA activity, the phosphorylation of CREB, and other important elements of signal transduction. In pre-clinical models and in early-stage clinical trials, PDE4 inhibitors have been shown to have antidepressant and memory-enhancing activity. However, the development of clinically-useful PDE4 inhibitors for CNS disorders has been limited by variable efficacy and significant side effects. Recent structural studies have greatly enhanced our understanding of the molecular configuration of PDE4 enzymes, especially the "long" PDE4 isoforms that are abundant in the CNS. The new structural data provide a rationale for the development of a new generation of PDE4 inhibitors that specifically act on long PDE4 isoforms. These next generation PDE4 inhibitors may also be capable of targeting the interactions of select long forms with their "partner" proteins, such as RACK1, β-arrestin, and DISC1. They would therefore have the ability to affect cAMP levels in specific cellular compartments and target localized cellular functions, such as synaptic plasticity. These new agents might also be able to target PDE4 populations in select regions of the CNS that are implicated in learning and memory, affect, and cognition. Potential therapeutic uses of these agents could include affective disorders, memory enhancement, and neurogenesis.
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Affiliation(s)
- Graeme B Bolger
- Departments of Medicine and Pharmacology, University of Alabama at Birmingham, 1720 2nd Avenue South, NP 2501, Birmingham, AL, 35294-3300, USA.
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247
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Maity S, Marchesi A, Torre V, Mazzolini M. Structural Heterogeneity of CNGA1 Channels Revealed by Electrophysiology and Single-Molecule Force Spectroscopy. ACS OMEGA 2016; 1:1205-1219. [PMID: 31457189 PMCID: PMC6640748 DOI: 10.1021/acsomega.6b00202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 10/14/2016] [Indexed: 06/10/2023]
Abstract
The determination at atomic resolution of the three-dimensional molecular structure of membrane proteins such as receptors and several ion channels has been a major breakthrough in structural biology. The molecular structure of several members of the superfamily of voltage-gated ionic channels such as K+ and Na+ is now available. However, despite several attempts, the molecular structure at atomic resolution of the full cyclic nucleotide-gated (CNG) ion channel, although a member of the same superfamily of voltage-gated ion channels, has not been obtained yet, neither by X-ray crystallography nor by electron cryomicroscopy (cryo-EM). It is possible that CNG channels have a high structural heterogeneity, making difficult crystallization and single-particle analysis. To address this issue, we have combined single-molecule force spectroscopy (SMFS) and electrophysiological experiments to characterize the structural heterogeneity of CNGA1 channels expressed in Xenopus laevis oocytes. The unfolding of the cytoplasmic domain had force peaks, occurring with a probability from 0.2 to 0.96. Force peaks during the unfolding of the transmembrane domain had a probability close to 1, but the distribution of the increase in contour length between two successive force peaks had multiple maxima differing by tens of nanometers. Concomitant electrophysiological experiments showed that the rundown in mutant channels S399C is highly variable and that the effect of thiol reagents when specific residues were mutated was consistent with a dynamic structural heterogeneity. These results show that CNGA1 channels have a wide spectrum of native conformations that are difficult to detect with X-ray crystallography and cryo-EM.
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248
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Han X, Shen L, Wang Q, Cen X, Wang J, Wu M, Li P, Zhao W, Zhang Y, Zhao G. Cyclic AMP Inhibits the Activity and Promotes the Acetylation of Acetyl-CoA Synthetase through Competitive Binding to the ATP/AMP Pocket. J Biol Chem 2016; 292:1374-1384. [PMID: 27974467 DOI: 10.1074/jbc.m116.753640] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 12/08/2016] [Indexed: 11/06/2022] Open
Abstract
The high-affinity biosynthetic pathway for converting acetate to acetyl-coenzyme A (acetyl-CoA) is catalyzed by the central metabolic enzyme acetyl-coenzyme A synthetase (Acs), which is finely regulated both at the transcriptional level via cyclic AMP (cAMP)-driven trans-activation and at the post-translational level via acetylation inhibition. In this study, we discovered that cAMP directly binds to Salmonella enterica Acs (SeAcs) and inhibits its activity in a substrate-competitive manner. In addition, cAMP binding increases SeAcs acetylation by simultaneously promoting Pat-dependent acetylation and inhibiting CobB-dependent deacetylation, resulting in enhanced SeAcs inhibition. A crystal structure study and site-directed mutagenesis analyses confirmed that cAMP binds to the ATP/AMP pocket of SeAcs, and restrains SeAcs in an open conformation. The cAMP contact residues are well conserved from prokaryotes to eukaryotes, suggesting a general regulatory mechanism of cAMP on Acs.
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Affiliation(s)
- Xiaobiao Han
- From the Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.,the University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liqiang Shen
- the Key Laboratory of Synthetic Biology, Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Qijun Wang
- the Department of Medical Microbiology and Parasitology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Xufeng Cen
- From the Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Jin Wang
- From the Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Meng Wu
- the Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Peng Li
- From the Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Wei Zhao
- From the Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China,
| | - Yu Zhang
- the Key Laboratory of Synthetic Biology, Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China,
| | - Guoping Zhao
- the Key Laboratory of Synthetic Biology, Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China, .,the State Key Lab of Genetic Engineering & Institutes of Biomedical Sciences, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai 200433, China.,the Shanghai-MOST Key Laboratory of Disease and Health Genomics, Chinese National Human Genome Center at Shanghai, Shanghai 201203, China.,the Department of Microbiology and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR, China, and
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249
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Zhang F, Zhang L, Qi Y, Xu H. Mitochondrial cAMP signaling. Cell Mol Life Sci 2016; 73:4577-4590. [PMID: 27233501 PMCID: PMC5097110 DOI: 10.1007/s00018-016-2282-2] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 04/25/2016] [Accepted: 05/20/2016] [Indexed: 12/19/2022]
Abstract
Cyclic adenosine 3, 5'-monophosphate (cAMP) is a ubiquitous second messenger regulating many biological processes, such as cell migration, differentiation, proliferation and apoptosis. cAMP signaling functions not only on the plasma membrane, but also in the nucleus and in organelles such as mitochondria. Mitochondrial cAMP signaling is an indispensable part of the cytoplasm-mitochondrion crosstalk that maintains mitochondrial homeostasis, regulates mitochondrial dynamics, and modulates cellular stress responses and other signaling pathways. Recently, the compartmentalization of mitochondrial cAMP signaling has attracted great attentions. This new input should be carefully taken into account when we interpret the findings of mitochondrial cAMP signaling. In this review, we summarize previous and recent progress in our understanding of mitochondrial cAMP signaling, including the components of the signaling cascade, and the function and regulation of this signaling pathway in different mitochondrial compartments.
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Affiliation(s)
- Fan Zhang
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Liping Zhang
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Yun Qi
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Hong Xu
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
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250
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Voß B, Seifert R, Kaupp UB, Grubmüller H. A Quantitative Model for cAMP Binding to the Binding Domain of MloK1. Biophys J 2016; 111:1668-1678. [PMID: 27760354 PMCID: PMC5073059 DOI: 10.1016/j.bpj.2016.09.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 09/03/2016] [Accepted: 09/12/2016] [Indexed: 01/03/2023] Open
Abstract
Ligand-protein binding processes are essential in biological systems. A well-studied system is the binding of cyclic adenosine monophosphate to the cyclic nucleotide binding domain of the bacterial potassium channel MloK1. Strikingly, the measured on-rate for cyclic adenosine monophosphate binding is two orders of magnitude slower than a simple Smoluchowski diffusion model would suggest. To resolve this discrepancy and to characterize the ligand-binding path in structural and energetic terms, we calculated 1100 ligand-binding molecular dynamics trajectories and tested two scenarios: In the first scenario, the ligand transiently binds to the protein surface and then diffuses along the surface into the binding site. In the second scenario, only ligands that reach the protein surface in the vicinity of the binding site proceed into the binding site. Here, a binding funnel, which increasingly confines the translational as well as the rotational degrees of freedom, determines the binding pathways and limits the on-rate. From the simulations, we identified five surface binding states and calculated the rates between these surface binding states, the binding site, and the bulk. We find that the transient binding of the ligands to the surface binding states does not affect the on-rate, such that this effect alone cannot explain the observed low on-rate. Rather, by quantifying the translational and rotational degrees of freedom and by calculating the binding committor, our simulations confirmed the existence of a binding funnel as the main bottleneck. Direct binding via the binding funnel dominates the binding kinetics, and only ∼10% of all ligands proceed via the surface into the binding site. The simulations further predict an on-rate between 15 and 40μs-1(mol/l)-1, which agrees with the measured on-rate.
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Affiliation(s)
- Béla Voß
- Department for Theoretical and Computational Biophysics, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
| | | | - U Benjamin Kaupp
- Department of Sensory Systems, Forschungszentrum Caesar, Bonn, Germany
| | - Helmut Grubmüller
- Department for Theoretical and Computational Biophysics, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
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