1
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Sarkar P, Chattopadhyay A. Interplay of Cholesterol and Actin in Neurotransmitter GPCR Signaling: Insights from Chronic Cholesterol Depletion Using Statin. ACS Chem Neurosci 2023; 14:3855-3868. [PMID: 37804226 DOI: 10.1021/acschemneuro.3c00472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/09/2023] Open
Abstract
Serotonin1A receptors are important neurotransmitter receptors in the G protein-coupled receptor (GPCR) family and modulate a variety of neurological, behavioral, and cognitive functions. We recently showed that chronic cholesterol depletion by statins, potent inhibitors of HMG-CoA reductase (the rate-limiting enzyme in cholesterol biosynthesis), leads to polymerization of the actin cytoskeleton that alters lateral diffusion of serotonin1A receptors. However, cellular signaling by the serotonin1A receptor under chronic cholesterol depletion remains unexplored. In this work, we explored signaling by the serotonin1A receptor under statin-treated condition. We show that cAMP signaling by the receptor is reduced upon lovastatin treatment due to reduction in cholesterol as well as polymerization of the actin cytoskeleton. To the best of our knowledge, these results constitute the first report describing the effect of chronic cholesterol depletion on the signaling of a G protein-coupled neuronal receptor. An important message arising from these results is that it is prudent to include the contribution of actin polymerization while analyzing changes in membrane protein function due to chronic cholesterol depletion by statins. Notably, our results show that whereas actin polymerization acts as a negative regulator of cAMP signaling, cholesterol could act as a positive modulator. These results assume significance in view of reports highlighting symptoms of anxiety and depression in humans upon statin administration and the role of serotonin1A receptors in anxiety and depression. Overall, these results reveal a novel role of actin polymerization induced by chronic cholesterol depletion in modulating GPCR signaling, which could act as a potential therapeutic target.
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Affiliation(s)
- Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Amitabha Chattopadhyay
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
- Academy of Scientific and Innovative Research, Ghaziabad 201 002, India
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2
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Kumar A, Sarkar P, Chattopadhyay A. Metabolic depletion of sphingolipids inhibits agonist-induced endocytosis of the serotonin 1A receptor. Traffic 2023; 24:95-107. [PMID: 36533718 DOI: 10.1111/tra.12879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 10/11/2022] [Accepted: 10/18/2022] [Indexed: 12/23/2022]
Abstract
G protein-coupled receptors (GPCRs) are vital cellular signaling machinery and currently represent ~40% drug targets. Endocytosis of GPCRs is an important process that allows stringent spatiotemporal control over receptor population on the cell surface. Although the role of proteins in GPCR endocytosis is well addressed, the contribution of membrane lipids in this process is rather unexplored. Sphingolipids are essential functional lipids in higher eukaryotes and are implicated in several neurological functions. To understand the role of sphingolipids in GPCR endocytosis, we subjected cells expressing human serotonin1A receptors (an important neurotransmitter GPCR involved in cognitive and behavioral functions) to metabolic sphingolipid depletion using fumonisin B1 , an inhibitor of sphingolipid biosynthetic pathway. Our results, using flow cytometric analysis and confocal microscopic imaging, show that sphingolipid depletion inhibits agonist-induced endocytosis of the serotonin1A receptor in a concentration-dependent manner, which was restored when sphingolipid levels were replenished. We further show that there was no change in the internalization of transferrin, a marker for clathrin-mediated endocytosis, under sphingolipid-depleted condition, highlighting the specific requirement of sphingolipids for endocytosis of serotonin1A receptors. Our results reveal the regulatory role of sphingolipids in GPCR endocytosis and highlight the importance of neurotransmitter receptor trafficking in health and disease.
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Affiliation(s)
- Abhishek Kumar
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.,Amity Institute of Biotechnology, Amity University Haryana, Gurugram, India
| | - Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India
| | - Amitabha Chattopadhyay
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.,Academy of Scientific and Innovative Research, Ghaziabad, India
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3
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Chattopadhyay A, Sharma A. Smith-Lemli-Opitz syndrome: A pathophysiological manifestation of the Bloch hypothesis. Front Mol Biosci 2023; 10:1120373. [PMID: 36714259 PMCID: PMC9878332 DOI: 10.3389/fmolb.2023.1120373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 01/02/2023] [Indexed: 01/15/2023] Open
Abstract
The biosynthesis of cholesterol, an essential component of higher eukaryotic membranes, was worked out by Konrad Bloch (and Feodor Lynen) in the 1960s and they received the Nobel Prize around that time in recognition of their pioneering contributions. An elegant consequence of this was a hypothesis proposed by Konrad Bloch (the Bloch hypothesis) which suggests that each subsequent intermediate in the cholesterol biosynthesis pathway is superior in supporting membrane function in higher eukaryotes relative to its precursor. In this review, we discuss an autosomal recessive metabolic disorder, known as Smith-Lemli-Opitz syndrome (SLOS), associated with a defect in the Kandutsch-Russell pathway of cholesterol biosynthesis that results in accumulation of the immediate precursor of cholesterol in its biosynthetic pathway (7-dehydrocholesterol) and an altered cholesterol to total sterol ratio. Patients suffering from SLOS have several developmental, behavioral and cognitive abnormalities for which no drug is available yet. We characterize SLOS as a manifestation of the Bloch hypothesis and review its molecular etiology and current treatment. We further discuss defective Hedgehog signaling in SLOS and focus on the role of the serotonin1A receptor, a representative neurotransmitter receptor belonging to the GPCR family, in SLOS. Notably, ligand binding activity and cellular signaling of serotonin1A receptors are impaired in SLOS-like condition. Importantly, cellular localization and intracellular trafficking of the serotonin1A receptor (which constitute an important determinant of a GPCR cellular function) are compromised in SLOS. We highlight some of the recent developments and emerging concepts in SLOS pathobiology and suggest that novel therapies based on trafficking defects of target receptors could provide new insight into treatment of SLOS.
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Affiliation(s)
- Amitabha Chattopadhyay
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India,Academy of Scientific and Innovative Research, Ghaziabad, India,*Correspondence: Amitabha Chattopadhyay,
| | - Ashwani Sharma
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India,Academy of Scientific and Innovative Research, Ghaziabad, India
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4
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Mohole M, Sengupta D, Chattopadhyay A. Synergistic and Competitive Lipid Interactions in the Serotonin 1A Receptor Microenvironment. ACS Chem Neurosci 2022; 13:3403-3415. [PMID: 36351047 DOI: 10.1021/acschemneuro.2c00422] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The interaction of lipids with G-protein-coupled receptors (GPCRs) has been shown to modulate and dictate several aspects of GPCR organization and function. Diverse lipid interaction sites have been identified from structural biology, bioinformatics, and molecular dynamics studies. For example, multiple cholesterol interaction sites have been identified in the serotonin1A receptor, along with distinct and overlapping sphingolipid interaction sites. How these lipids interact with each other and what is the resultant effect on the receptor is still not clear. In this work, we have analyzed lipid-lipid crosstalk at the receptor of the serotonin1A receptor embedded in a membrane bilayer that mimics the neuronal membrane composition by long coarse-grain simulations. Using a set of similarity coefficients, we classified lipids that bind at the receptor together as synergistic cobinding, and those that bind individually as competitive. Our results show that certain lipids interact with the serotonin1A receptor in synergy with each other. Not surprisingly, the ganglioside GM1 and cholesterol show a synergistic cobinding, along with the relatively uncommon GM1-phosphatidylethanolamine (PE) and cholesterol-PE synergy. In contrast, certain lipid pairs such as cholesterol and sphingomyelin appear to be in competition at several sites, despite their coexistence in lipid nanodomains. In addition, we observed intralipid competition between two lipid tails, with the receptor exhibiting increased interactions with the unsaturated lipid tails. We believe our work represents an important step in understanding the diversity of GPCR-lipid interactions and exploring synergistic cobinding and competition in natural membranes.
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Affiliation(s)
- Madhura Mohole
- CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune411 008, India.,Academy of Scientific and Innovative Research, Ghaziabad201 002, India
| | - Durba Sengupta
- CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune411 008, India.,Academy of Scientific and Innovative Research, Ghaziabad201 002, India
| | - Amitabha Chattopadhyay
- Academy of Scientific and Innovative Research, Ghaziabad201 002, India.,CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad500 007, India
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5
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Sarkar P, Bhat A, Chattopadhyay A. Lysine 101 in the CRAC Motif in Transmembrane Helix 2 Confers Cholesterol-Induced Thermal Stability to the Serotonin 1A Receptor. J Membr Biol 2022; 255:739-746. [PMID: 35986776 DOI: 10.1007/s00232-022-00262-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 08/05/2022] [Indexed: 12/24/2022]
Abstract
G protein-coupled receptors (GPCRs) constitute the largest class of membrane proteins that transduce signals across the plasma membrane and orchestrate a multitude of physiological processes within cells. The serotonin1A receptor is a crucial neurotransmitter receptor in the GPCR family involved in a multitude of neurological, behavioral and cognitive functions. We have previously shown, using a combination of experimental and simulation approaches, that membrane cholesterol acts as a key regulator of organization, dynamics, signaling and endocytosis of the serotonin1A receptor. In addition, we showed that membrane cholesterol stabilizes the serotonin1A receptor against thermal deactivation. In the present work, we explored the molecular basis of cholesterol-induced thermal stability of the serotonin1A receptor. For this, we explored the possible role of the K101 residue in a cholesterol recognition/interaction amino acid consensus (CRAC) motif in transmembrane helix 2 in conferring the thermal stability of the serotonin1A receptor. Our results show that a mutation in the K101 residue leads to loss in thermal stability of the serotonin1A receptor imparted by cholesterol, independent of membrane cholesterol content. We envision that our results could have potential implications in structural biological advancements of GPCRs and design of thermally stabilized receptors for drug development.
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Affiliation(s)
- Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500 007, India
| | - Akrati Bhat
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500 007, India
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6
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Shrivastava S, Sarkar P, Preira P, Salomé L, Chattopadhyay A. Cholesterol-Dependent Dynamics of the Serotonin 1A Receptor Utilizing Single Particle Tracking: Analysis of Diffusion Modes. J Phys Chem B 2022; 126:6682-6690. [PMID: 35973070 DOI: 10.1021/acs.jpcb.2c03941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
G protein-coupled receptors (GPCRs) are signaling hubs in cell membranes that regulate a wide range of physiological processes and are popular drug targets. Serotonin1A receptors are important members of the GPCR family and are implicated in neuropsychiatric disorders. Cholesterol is a key constituent of higher eukaryotic membranes and is believed to contribute to the segregated distribution of membrane constituents into domains. To explore the role of cholesterol in lateral dynamics of GPCRs, we utilized single particle tracking (SPT) to monitor diffusion of serotonin1A receptors under acute and chronic cholesterol-depleted conditions. Our results show that the short-term diffusion coefficient of the receptor decreases upon cholesterol depletion, irrespective of the method of cholesterol depletion. Analysis of SPT trajectories revealed that relative populations of receptors undergoing various modes of diffusion change upon cholesterol depletion. Notably, in cholesterol-depleted cells, we observed an increase in the confined population of the receptor accompanied by a reduction in diffusion coefficient for chronic cholesterol depletion. These results are supported by our recent work and present observations that show polymerization of G-actin in response to chronic cholesterol depletion. Taken together, our results bring out the interdependence of cholesterol and actin cytoskeleton in regulating diffusion of GPCRs in membranes.
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Affiliation(s)
- Sandeep Shrivastava
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Pascal Preira
- Institut de Pharmacologie et de Biologie Structurale, CNRS, Université de Toulouse (UPS), 31 077 Toulouse, France
| | - Laurence Salomé
- Institut de Pharmacologie et de Biologie Structurale, CNRS, Université de Toulouse (UPS), 31 077 Toulouse, France
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7
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Pal S, Chattopadhyay A. Hydration Dynamics in Biological Membranes: Emerging Applications of Terahertz Spectroscopy. J Phys Chem Lett 2021; 12:9697-9709. [PMID: 34590862 DOI: 10.1021/acs.jpclett.1c02576] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Water drives the spontaneous self-assembly of lipids and proteins into quasi two-dimensional biological membranes that act as catalytic scaffolds for numerous processes central to life. However, the functional relevance of hydration in membrane biology is only beginning to be addressed, predominantly because of challenges associated with direct measurements of hydration microstructure and dynamics in a biological milieu. Our recent work on the novel interplay of membrane electrostatics and crowding in shaping membrane hydration dynamics utilizing terahertz (THz) spectroscopy represents an important step in this context. In this Perspective, we provide a glimpse into the ever-broadening functional landscape of hydration dynamics in biological membranes in the backdrop of the unique physical chemistry of water molecules. We further highlight the immense (and largely untapped) potential of the THz toolbox in addressing contemporary problems in membrane biology, while emphasizing the adaptability of the analytical framework reported recently by us to such studies.
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Affiliation(s)
- Sreetama Pal
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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8
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Sharma A, Kumar GA, Chattopadhyay A. Late endosomal/lysosomal accumulation of a neurotransmitter receptor in a cellular model of Smith-Lemli-Opitz syndrome. Traffic 2021; 22:332-344. [PMID: 34418249 DOI: 10.1111/tra.12811] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Revised: 08/16/2021] [Accepted: 08/18/2021] [Indexed: 12/17/2022]
Abstract
Smith-Lemli-Opitz syndrome (SLOS) is a congenital and developmental malformation syndrome associated with defective cholesterol biosynthesis. It is characterized by accumulation of 7-dehydrocholesterol (the immediate biosynthetic precursor of cholesterol in the Kandutsch-Russell pathway) and an altered cholesterol to total sterol ratio. Because SLOS is associated with neurological malfunction, exploring the function and trafficking of neuronal receptors and their interaction with membrane lipids under these conditions assume significance. In this work, we generated a cellular model of SLOS in HEK-293 cells stably expressing the human serotonin1A receptor (an important neurotransmitter G-protein coupled receptor) using AY 9944, an inhibitor for the enzyme 3β-hydroxy-steroid-∆7 -reductase (7-DHCR). Using a quantitative flow cytometry based assay, we show that the plasma membrane population of serotonin1A receptors was considerably reduced under these conditions without any change in total cellular expression of the receptor. Interestingly, the receptors were trafficked to sterol-enriched LysoTracker positive compartments, which accumulated under these conditions. To the best of our knowledge, our results constitute one of the first reports demonstrating intracellular accumulation and misregulated traffic of a neurotransmitter GPCR in SLOS-like conditions. We believe these results assume relevance in our overall understanding of the molecular basis underlying the functional relevance of neurotransmitter receptors in SLOS.
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Affiliation(s)
- Ashwani Sharma
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.,Academy of Scientific and Innovative Research, Ghaziabad, India
| | - G Aditya Kumar
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India
| | - Amitabha Chattopadhyay
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.,Academy of Scientific and Innovative Research, Ghaziabad, India
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9
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Kumar A, Sarkar P, Chattopadhyay A. Metabolic Depletion of Sphingolipids Reduces Cell Surface Population of the Human Serotonin 1A Receptor due to Impaired Trafficking. ACS Chem Neurosci 2021; 12:1189-1196. [PMID: 33760584 DOI: 10.1021/acschemneuro.1c00017] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Sphingolipids and their metabolites are increasingly implicated in the pathogenesis of many metabolic and neurological diseases. It has been postulated that sphingolipids coalesce with cholesterol to form laterally segregated lipid domains that are involved in protein sorting and trafficking. In this work, we have explored the effect of metabolic depletion of sphingolipids on cell surface expression of the human serotonin1A receptor, a neurotransmitter G protein-coupled receptor. We used fumonisin B1 (FB1), a fungal mycotoxin, to inhibit sphingolipid biosynthesis in HEK-293 cells stably expressing the human serotonin1A receptor. Our results obtained using flow cytometric analysis and confocal microscopic imaging show that the cell surface population of the serotonin1A receptor is reduced under sphingolipid-depleted condition. Western blot analysis confirmed that there was no significant difference in total cellular level of the serotonin1A receptor upon depletion of sphingolipids. Interestingly, the effect of FB1 on serotonin1A receptor population was reversed upon replenishment with sphingolipids. These results indicate that sphingolipid depletion does not alter total cellular receptor levels, but impairs serotonin1A receptor trafficking to the cellular plasma membrane. These results could provide mechanistic insights into the role of sphingolipids in modulation of neurotransmitter receptor signaling and trafficking in health and disease.
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Affiliation(s)
- Abhishek Kumar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
- Amity Institute of Biotechnology, Amity University Haryana, Amity Education Valley, Gurugram 122 413, India
| | - Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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10
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Sarkar P, Chattopadhyay A. Insights into cellular signaling from membrane dynamics. Arch Biochem Biophys 2021; 701:108794. [PMID: 33571482 DOI: 10.1016/j.abb.2021.108794] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 01/20/2021] [Accepted: 02/03/2021] [Indexed: 12/16/2022]
Abstract
Biological membranes allow morphological compartmentalization of cells and represent complex micro-heterogeneous fluids exhibiting a range of dynamics. The plasma membrane occupies a central place in cellular signaling which allows the cell to perform a variety of functions. In this review, we analyze cellular signaling in a dynamic biophysical framework guided by the "mobile receptor hypothesis". We describe a variety of examples from literature in which lateral diffusion of signaling membrane proteins acts as an important determinant in the efficiency of signaling. A major focus in our review is on membrane-embedded G protein-coupled receptors (GPCRs) which act as cellular signaling hubs for diverse cellular functions. Taken together, we describe a dynamics-based signaling paradigm with chosen examples from literature to elucidate how such a paradigm helps us understand signaling by GPCRs, maintenance of cellular polarity in yeast and infection by pathogens. We envision that with further technological advancement, it would be possible to explore cellular signaling more holistically as cells undergo development, differentiation and aging, thereby providing us a robust window into the dynamics of the cellular interior and its functional correlates.
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Affiliation(s)
- Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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11
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Kumar GA, Chattopadhyay A. Membrane cholesterol regulates endocytosis and trafficking of the serotonin 1A receptor: Insights from acute cholesterol depletion. Biochim Biophys Acta Mol Cell Biol Lipids 2021; 1866:158882. [PMID: 33429076 DOI: 10.1016/j.bbalip.2021.158882] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 12/24/2020] [Accepted: 01/06/2021] [Indexed: 12/12/2022]
Abstract
Endocytosis and intracellular trafficking constitute important regulatory features associated with G protein-coupled receptor (GPCR) function. GPCR endocytosis involves several remodeling events at the plasma membrane orchestrated by a concerted interplay of a large number of proteins and membrane lipids. Although considerable literature exists on the protein framework underlying GPCR endocytosis, the role of membrane lipids in this process remains largely unexplored. In order to explore the role of membrane cholesterol (an essential and important lipid in higher eukaryotes) in GPCR endocytosis, we monitored the effect of acute cholesterol depletion using methyl-β-cyclodextrin (MβCD) on endocytosis and intracellular trafficking of the serotonin1A receptor, an important neurotransmitter GPCR. Our results show that the serotonin1A receptor exhibits agonist-induced clathrin-mediated endocytosis with a concentration-dependent inhibition in internalization with increasing concentrations of MβCD, which was restored upon cholesterol replenishment. Interestingly, subsequent to internalization under these conditions, serotonin1A receptors were re-routed toward lysosomal degradation, instead of endosomal recycling observed under normal conditions, thereby implicating membrane cholesterol in modulation of intracellular trafficking of the receptor. This raises the possibility of a novel cholesterol-dependent role of intracellular sorting proteins in GPCR trafficking. These results differ from our previous observations on the endocytosis of the serotonin1A receptor upon statin-induced chronic cholesterol depletion, in terms of endocytic pathway. We conclude that analysis of complex cellular trafficking events such as GPCR endocytosis under acute and chronic cholesterol depletion conditions should be carried out with caution due to fundamental differences underlying these processes.
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Affiliation(s)
- G Aditya Kumar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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12
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Rao BD, Sarkar P, Chattopadhyay A. Effect of tertiary amine local anesthetics on G protein-coupled receptor lateral diffusion and actin cytoskeletal reorganization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183547. [PMID: 33417968 DOI: 10.1016/j.bbamem.2020.183547] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 12/09/2020] [Accepted: 12/16/2020] [Indexed: 10/22/2022]
Abstract
Although widely used clinically, the mechanism underlying the action of local anesthetics remains elusive. Direct interaction of anesthetics with membrane proteins and modulation of membrane physical properties by anesthetics are plausible mechanisms proposed, although a combination of these two mechanisms cannot be ruled out. In this context, the role of G protein-coupled receptors (GPCRs) in local anesthetic action is a relatively new area of research. We show here that representative tertiary amine local anesthetics induce a reduction in two-dimensional diffusion coefficient of the serotonin1A receptor, an important neurotransmitter GPCR. The corresponding change in mobile fraction is varied, with tetracaine exhibiting the maximum reduction in mobile fraction, whereas the change in mobile fraction for other local anesthetics was not appreciable. These results are supported by quantitation of cellular F-actin, using a confocal microscopic approach previously developed by us, which showed that a pronounced increase in F-actin level was induced by tetracaine. These results provide a novel perspective on the action of local anesthetics in terms of GPCR lateral diffusion and actin cytoskeleton reorganization.
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Affiliation(s)
- Bhagyashree D Rao
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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13
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Rao BD, Sarkar P, Chattopadhyay A. Selectivity in agonist and antagonist binding to Serotonin 1A receptors via G-protein coupling. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183265. [PMID: 32156647 DOI: 10.1016/j.bbamem.2020.183265] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 03/04/2020] [Accepted: 03/05/2020] [Indexed: 12/16/2022]
Abstract
G protein-coupled receptors (GPCRs) constitute the largest superfamily of membrane proteins in higher eukaryotes, and facilitate information transfer from the extracellular environment to the cellular interior upon activation by ligands. Their role in diverse signaling processes makes them an attractive choice as drug targets. GPCRs are coupled to heterotrimeric G-proteins which represent an important interface through which signal transduction occurs across the plasma membrane upon activation by ligands. To obtain further insight into the molecular details of interaction of G-proteins with GPCRs, in this work, we explored the selectivity of binding of specific agonists and antagonists to the serotonin1A receptor under conditions of progressive G-protein inactivation. The serotonin1A receptor is an important neurotransmitter receptor belonging to the GPCR family and is a popular drug target. By use of a number of agents to inactivate G-proteins, we show here that the serotonin1A receptor displays differential discrimination between agonist and antagonist binding. Our results show a reduction in binding sites of the receptor upon treatment with G-protein inactivating agents. In addition, G-protein coupling efficiency was enhanced when G-proteins were inactivated using urea and alkaline pH. We envision that our results could be useful in achieving multiple signaling states of the receptor by fine tuning the conditions of G-protein inactivation and in structural biology of GPCRs bound to specific ligands.
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Affiliation(s)
- Bhagyashree D Rao
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India; CSIR-Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007, India; Academy of Scientific and Innovative Research, Ghaziabad 201 002, India
| | - Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Amitabha Chattopadhyay
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India; Academy of Scientific and Innovative Research, Ghaziabad 201 002, India.
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14
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Kumar GA, Chattopadhyay A. Statin-Induced Chronic Cholesterol Depletion Switches GPCR Endocytosis and Trafficking: Insights from the Serotonin 1A Receptor. ACS Chem Neurosci 2020; 11:453-465. [PMID: 31880914 DOI: 10.1021/acschemneuro.9b00659] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Endocytosis is a key regulatory mechanism adopted by G protein-coupled receptors (GPCRs) to modulate downstream signaling responses within a stringent spatiotemporal regime. Although the role of membrane lipids has been extensively studied in the context of the function, organization, and dynamics of GPCRs, their role in receptor endocytosis remains largely unexplored. Cholesterol, the predominant sterol in higher eukaryotes, plays a crucial role in maintaining the structure and organization of cell membranes and is involved in essential cellular processes in health and disease. The serotonin1A receptor is a representative GPCR involved in neuronal development and in neuropsychiatric disorders such as anxiety and depression. We recently combined quantitative flow cytometric and confocal microscopic approaches to demonstrate that the serotonin1A receptor undergoes clathrin-mediated endocytosis upon agonist stimulation and subsequently traffics along the endosomal recycling pathway. In this work, we show that statin-induced chronic cholesterol depletion switches the endocytic pathway of the serotonin1A receptor from clathrin- to caveolin-mediated endocytosis. Interestingly, under these conditions, a significant proportion of endocytosed receptors is rerouted toward lysosomal degradation. To the best of our knowledge, these results constitute one of the first comprehensive reports on the role of membrane cholesterol in GPCR endocytosis and trafficking. These results are significant in our overall understanding of the modulatory effects of membrane lipids on GPCR endocytosis and trafficking and could provide novel insight in developing therapeutic interventions against neuropsychiatric disorders such as depression.
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Affiliation(s)
- G. Aditya Kumar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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15
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Shrivastava S, Sarkar P, Preira P, Salomé L, Chattopadhyay A. Role of Actin Cytoskeleton in Dynamics and Function of the Serotonin 1A Receptor. Biophys J 2019; 118:944-956. [PMID: 31606121 DOI: 10.1016/j.bpj.2019.08.034] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 08/13/2019] [Accepted: 08/29/2019] [Indexed: 12/19/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are important membrane proteins in higher eukaryotes that carry out a vast array of cellular signaling and act as major drug targets. The serotonin1A receptor is a prototypical member of the GPCR family and is implicated in neuropsychiatric disorders such as anxiety and depression, besides serving as an important drug target. With an overall goal of exploring the functional consequence of altered receptor dynamics, in this work, we probed the role of the actin cytoskeleton in the dynamics, ligand binding, and signaling of the serotonin1A receptor. We monitored receptor dynamics utilizing single particle tracking, which provides information on relative distribution of receptors in various diffusion modes in addition to diffusion coefficient. We show here that the short-term diffusion coefficient of the receptor increases upon actin destabilization by cytochalasin D. In addition, analysis of individual trajectories shows that there are changes in relative populations of receptors undergoing various types of diffusion upon actin destabilization. The release of dynamic constraint was evident by an increase in the radius of confinement of the receptor upon actin destabilization. The functional implication of such actin destabilization was manifested as an increase in specific agonist binding and downstream signaling, monitored by measuring reduction in cellular cAMP levels. These results bring out the interdependence of GPCR dynamics with cellular signaling.
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Affiliation(s)
| | - Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India
| | - Pascal Preira
- Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Laurence Salomé
- Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, UPS, Toulouse, France.
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16
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Meher G, Sinha S, Pattnaik GP, Ghosh Dastidar S, Chakraborty H. Cholesterol Modulates Membrane Properties and the Interaction of gp41 Fusion Peptide To Promote Membrane Fusion. J Phys Chem B 2019; 123:7113-7122. [PMID: 31345037 DOI: 10.1021/acs.jpcb.9b04577] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An envelope glycoprotein, gp41, is crucial for the entry of human immunodeficiency virus (HIV) into the host cell. The 20-23 N-terminal amino acid sequence of gp41 plays an important role in promoting fusion between viral and host cells. Interestingly, the structure and function of the fusion peptide are extremely sensitive to the characteristics of the lipid environment. In this present work, we have extensively utilized steady-state and time-resolved fluorescence spectroscopy in tandem with molecular dynamics simulation to elucidate peptide binding and peptide-induced perturbation to the membrane. We have used two depth-dependent fluorescence probes, 1,6-diphenyl-1,3,5-hexatriene (DPH) and its trimethylammonium derivative (TMA-DPH), to monitor the effect of peptide binding along the bilayer normal and have reconciled the experimental observation with the insights from the simulated molecular events. We have further monitored the effect of membrane cholesterol on peptide-induced membrane perturbation. The molecular dynamics simulation data show that the peptide alters the membrane properties in the vicinity of the peptide and it penetrates to a larger extent into the bilayer when the membrane contains cholesterol. Our results clearly elucidate that cholesterol alters the membrane physical properties in favor of membrane fusion and interaction pattern of the fusion peptide with the membrane in a concentration-dependent fashion. The role of cholesterol is specifically important as the host eukaryotic cells contain a decent amount of cholesterol that might be critical for the entry of HIV into the host cells.
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Affiliation(s)
- Geetanjali Meher
- School of Chemistry , Sambalpur University , Jyoti Vihar, Burla , Odisha 768 019 , India
| | - Souvik Sinha
- Division of Bioinformatics , Bose Institute , P-1/12 C.I.T. Scheme VII M , Kolkata 700054 , India
| | - Gourab Prasad Pattnaik
- School of Chemistry , Sambalpur University , Jyoti Vihar, Burla , Odisha 768 019 , India
| | - Shubhra Ghosh Dastidar
- Division of Bioinformatics , Bose Institute , P-1/12 C.I.T. Scheme VII M , Kolkata 700054 , India
| | - Hirak Chakraborty
- School of Chemistry , Sambalpur University , Jyoti Vihar, Burla , Odisha 768 019 , India
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17
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Bahari Z, Meftahi GH. Spinal α 2 -adrenoceptors and neuropathic pain modulation; therapeutic target. Br J Pharmacol 2019; 176:2366-2381. [PMID: 30657594 DOI: 10.1111/bph.14580] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 11/23/2018] [Accepted: 12/04/2018] [Indexed: 12/22/2022] Open
Abstract
Neuropathic pain can arise from disease or damage to the nervous system. The most common symptoms of neuropathic pain include spontaneous pain, allodynia, and hyperalgesia. There is still limited knowledge about the factors that initiate and maintain neuropathic pain. However, ample evidence has proved the antinociceptive role of spinal α-adrenoceptors following nerve injury. It is well-documented that noradrenergic descending pathways from supraspinal loci exert an inhibitory influence on the spinal cord nociceptive neurons, mostly through the activation of spinal α2 -adrenoceptors. This, in turn, suppresses transmission of pain input and the hyperexcitability of spinal dorsal horn neurons. There is considerable evidence demonstrating that spinal application of α2 -adrenoceptor agonists leads to analgesic effects in animal models of neuropathic pain. Today, despite the recent rapid development of neuroscience and drug discovery, effective drugs with clear basic mechanisms have remained a mystery. Here, we give an overview of the cellular mechanisms through which brainstem adrenergic descending inhibitory processing can alter spinal pain transmission to the higher centres, and how these pathways change in neuropathic pain conditions focusing on the role of spinal α2 -adrenoceptors in the spinal dorsal horn. We then suggest that α2 -adrenoceptor agonist may be useful to treat neuropathic pain. LINKED ARTICLES: This article is part of a themed section on Adrenoceptors-New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc.
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Affiliation(s)
- Zahra Bahari
- Neuroscience Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran.,Department of Physiology and Medical Physics, Faculty of Medicine, Baqiyatallah University of Medical Sciences, Tehran, Iran
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18
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Fatakia SN, Sarkar P, Chattopadhyay A. A collage of cholesterol interaction motifs in the serotonin 1A receptor: An evolutionary implication for differential cholesterol interaction. Chem Phys Lipids 2019; 221:184-192. [PMID: 30822391 DOI: 10.1016/j.chemphyslip.2019.02.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 02/25/2019] [Accepted: 02/25/2019] [Indexed: 12/22/2022]
Abstract
The serotonin1A receptor is a representative member of the G protein-coupled receptor (GPCR) superfamily and acts as an important drug target. In our previous work, we comprehensively demonstrated that membrane cholesterol is necessary in the organization, dynamics and function of the serotonin1A receptor. In this context, analysis of high-resolution GPCR crystal structures in general and in silico studies of the serotonin1A receptor in particular, have suggested the presence of cholesterol interaction sites (hotspots) in various regions of the receptor. In this work, we have identified an evolutionarily conserved collage of four categories of cholesterol interaction motifs associated with transmembrane helix V and the adjacent intracellular loop 3 fragment of the vertebrate serotonin1A receptor. This collage of motifs represents a total of twenty diverse context-dependent cholesterol interaction configurations. We envision that the gamut of cholesterol interaction sites, characterized by sequence plasticity in cholesterol interaction, could be relevant in receptor-cholesterol interaction in membranes of varying cholesterol content and organization, as found in diverse cell types. We conclude that an evolutionarily conserved mechanism of GPCR-cholesterol interaction allows the serotonin1A receptor to adapt to diverse membrane cholesterol levels during natural evolution.
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Affiliation(s)
- Sarosh N Fatakia
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.
| | - Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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19
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Sarkar P, Chattopadhyay A. Exploring membrane organization at varying spatiotemporal resolutions utilizing fluorescence-based approaches: implications in membrane biology. Phys Chem Chem Phys 2019; 21:11554-11563. [DOI: 10.1039/c9cp02087j] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Representative experimental approaches based on dynamic fluorescence microscopy to analyze organization and dynamics of membrane lipids and proteins.
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Affiliation(s)
- Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology
- Hyderabad 500 007
- India
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20
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A Critical Analysis of Molecular Mechanisms Underlying Membrane Cholesterol Sensitivity of GPCRs. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1115:21-52. [PMID: 30649754 DOI: 10.1007/978-3-030-04278-3_2] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
G protein-coupled receptors (GPCRs) are the largest and a diverse family of proteins involved in signal transduction across biological membranes. GPCRs mediate a wide range of physiological processes and have emerged as major targets for the development of novel drug candidates in all clinical areas. Since GPCRs are integral membrane proteins, regulation of their organization, dynamics, and function by membrane lipids, in particular membrane cholesterol, has emerged as an exciting area of research. Cholesterol sensitivity of GPCRs could be due to direct interaction of cholesterol with the receptor (specific effect). Alternately, GPCR function could be influenced by the effect of cholesterol on membrane physical properties (general effect). In this review, we critically analyze the specific and general mechanisms of the modulation of GPCR function by membrane cholesterol, taking examples from representative GPCRs. While evidence for both the proposed mechanisms exists, there appears to be no clear-cut distinction between these two mechanisms, and a combination of these mechanisms cannot be ruled out in many cases. We conclude that classifying the mechanism underlying cholesterol sensitivity of GPCR function merely into these two mutually exclusive classes could be somewhat arbitrary. A more holistic approach could be suitable for analyzing GPCR-cholesterol interaction.
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21
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Li S, Sun C, Rong P, Zhai X, Zhang J, Baker M, Wang S. Auricular vagus nerve stimulation enhances central serotonergic function and inhibits diabetic neuropathy development in Zucker fatty rats. Mol Pain 2018; 14:1744806918787368. [PMID: 29921169 PMCID: PMC6055102 DOI: 10.1177/1744806918787368] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Painful neuropathy is a frequent comorbidity in diabetes. Zucker diabetic fatty (fa/fa) rats develop type 2 diabetes spontaneously with aging and show nociceptive hypersensitivity at the age of 13 weeks. In preclinical and clinical studies, the treatment of diabetic neuropathy is challenging, but complementary medicine such as transcutaneous auricular vagus nerve stimulation (taVNS) appears beneficial to the relief of neuropathic pain. However, the mechanism behind the effectiveness of taVNS remains unclear. In this study, we show that daily 30-min taVNS (2/15 Hz, 2 mA) for consecutive 27 days effectively inhibited the development of nociceptive hypersensitivity in Zucker diabetic fatty rats as detected by thermal hyperalgesia and mechanical allodynia in hindpaw. We also demonstrated that this beneficial effect in nociceptive behavior is related to an elevated serotonin (5-HT) plasma concentration and an upregulated expression of 5-HT receptor type 1A (5-HT1AR) in hypothalamus. We conclude that daily 30-min taVNS sessions lessen diabetic neuropathy development by enhancing serotonergic function in genetically diabetes prone individuals. Perspective This article presents taVNS as a new approach to inhibit the development of diabetic neuropathy in genetically prone individuals. This approach could potentially help clinicians who seek to avoid the complication of neuropathic pain in diabetic patient or to relieve the pain if there was one.
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Affiliation(s)
- Shaoyuan Li
- 1 Department of Anatomy, Xinxiang Medical University, Xinxiang, Henan, China.,2 Department of Physiology, Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Chunli Sun
- 1 Department of Anatomy, Xinxiang Medical University, Xinxiang, Henan, China
| | - Peijing Rong
- 2 Department of Physiology, Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Xu Zhai
- 2 Department of Physiology, Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Jinling Zhang
- 2 Department of Physiology, Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Max Baker
- 3 Department of Anesthesia, University of Iowa, Iowa City, IA, USA
| | - Shuxing Wang
- 1 Department of Anatomy, Xinxiang Medical University, Xinxiang, Henan, China.,3 Department of Anesthesia, University of Iowa, Iowa City, IA, USA
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22
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Sengupta D, Prasanna X, Mohole M, Chattopadhyay A. Exploring GPCR–Lipid Interactions by Molecular Dynamics Simulations: Excitements, Challenges, and the Way Forward. J Phys Chem B 2018; 122:5727-5737. [DOI: 10.1021/acs.jpcb.8b01657] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Durba Sengupta
- CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008, India
- Academy of Scientific and Innovative Research, Sector 19, Kamla Nehru Nagar, Ghaziabad 201 002, India
| | - Xavier Prasanna
- CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008, India
| | - Madhura Mohole
- CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008, India
- Academy of Scientific and Innovative Research, Sector 19, Kamla Nehru Nagar, Ghaziabad 201 002, India
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23
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Mohole M, Prasanna X, Sengupta D, Chattopadhyay A. Molecular Signatures of Cholesterol Interaction with Serotonin Receptors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1112:151-160. [DOI: 10.1007/978-981-13-3065-0_11] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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24
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Shrivastava S, Jafurulla M, Tiwari S, Chattopadhyay A. Identification of Sphingolipid-binding Motif in G Protein-coupled Receptors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1112:141-149. [DOI: 10.1007/978-981-13-3065-0_10] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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25
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Di Cesare Mannelli L, Ghelardini C, Micheli L, Del Bello F, Giannella M, Piergentili A, Pigini M, Quaglia W. Synergic stimulation of serotonin 5-HT1A receptor and α2-adrenoceptors for neuropathic pain relief: Preclinical effects of 2-substituted imidazoline derivatives. Eur J Pharmacol 2017. [DOI: 10.1016/j.ejphar.2017.06.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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26
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Membrane cholesterol oxidation in live cells enhances the function of serotonin 1A receptors. Chem Phys Lipids 2017; 203:71-77. [DOI: 10.1016/j.chemphyslip.2017.01.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Revised: 01/15/2017] [Accepted: 01/15/2017] [Indexed: 12/14/2022]
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27
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Jafurulla M, Chattopadhyay A. Structural Stringency of Cholesterol for Membrane Protein Function Utilizing Stereoisomers as Novel Tools: A Review. Methods Mol Biol 2017; 1583:21-39. [PMID: 28205164 DOI: 10.1007/978-1-4939-6875-6_3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Cholesterol is an important lipid in the context of membrane protein function. The function of a number of membrane proteins, including G protein-coupled receptors (GPCRs) and ion channels, has been shown to be dependent on membrane cholesterol. However, the molecular mechanism underlying such regulation is still being explored. In some cases, specific interaction between cholesterol and the protein has been implicated. In other cases, the effect of cholesterol on the membrane properties has been attributed for the regulation of protein function. In this article, we have provided an overview of experimental approaches that are useful for determining the degree of structural stringency of cholesterol for membrane protein function. In the process, we have highlighted the role of immediate precursors in cholesterol biosynthetic pathway in the function of membrane proteins. Special emphasis has been given to the application of stereoisomers of cholesterol in deciphering the structural stringency required for regulation of membrane protein function. A comprehensive examination of these processes would help in understanding the molecular basis of cholesterol regulation of membrane proteins in subtle details.
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Affiliation(s)
- Md Jafurulla
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500 007, India
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28
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Jafurulla M, Bandari S, Pucadyil TJ, Chattopadhyay A. Sphingolipids modulate the function of human serotonin 1A receptors: Insights from sphingolipid-deficient cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:598-604. [PMID: 27984018 DOI: 10.1016/j.bbamem.2016.10.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 10/16/2016] [Accepted: 10/25/2016] [Indexed: 11/18/2022]
Abstract
Sphingolipids are essential components of eukaryotic cell membranes and are known to modulate a variety of cellular functions. It is becoming increasingly clear that membrane lipids play a crucial role in modulating the function of integral membrane proteins such as G protein-coupled receptors (GPCRs). In this work, we utilized LY-B cells, that are sphingolipid-auxotrophic mutants defective in sphingolipid biosynthesis, to monitor the role of cellular sphingolipids in the function of an important neurotransmitter receptor, the serotonin1A receptor. Serotonin1A receptors belong to the family of GPCRs and are implicated in behavior, development and cognition. Our results show that specific ligand binding and G-protein coupling of the serotonin1A receptor exhibit significant enhancement under sphingolipid-depleted conditions, which reversed to control levels upon replenishment of cellular sphingolipids. In view of the reported role of sphingolipids in neuronal metabolism and pathogenesis of several neuropsychiatric disorders, exploring the role of serotonin1A receptors under conditions of defective sphingolipid metabolism assumes relevance, and could contribute to our overall understanding of such neuropsychiatric disorders. This article is part of a Special Issue entitled: Lipid order/lipid defects and lipid-control of protein activity edited by Dirk Schneider.
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Affiliation(s)
- Md Jafurulla
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Suman Bandari
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Thomas J Pucadyil
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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29
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Del Bello F, Cilia A, Carrieri A, Fasano DC, Ghelardini C, Di Cesare Mannelli L, Micheli L, Santini C, Diamanti E, Giannella M, Giorgioni G, Mammoli V, Paoletti CD, Petrelli R, Piergentili A, Quaglia W, Pigini M. The Versatile 2-Substituted Imidazoline Nucleus as a Structural Motif of Ligands Directed to the Serotonin 5-HT1A
Receptor. ChemMedChem 2016; 11:2287-2298. [DOI: 10.1002/cmdc.201600383] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 08/30/2016] [Indexed: 11/12/2022]
Affiliation(s)
- Fabio Del Bello
- School of Pharmacy; Medicinal Chemistry Unit; University of Camerino; Via S. Agostino 1 62032 Camerino Italy
| | - Antonio Cilia
- Recordati S.p.A.; Drug Discovery; via Civitali 1 20148 Milano (Italy)
| | - Antonio Carrieri
- Department of Pharmacy-Drug Science; University of Bari “Aldo Moro”; Via E. Orabona 4 70125 Bari Italy
| | - Domenico Claudio Fasano
- Department of Pharmacy-Drug Science; University of Bari “Aldo Moro”; Via E. Orabona 4 70125 Bari Italy
| | - Carla Ghelardini
- Department of Neuroscience, Psychology, Drug Research and; Child Health - Neurofarba - Pharmacology and Toxicology Section; University of Florence; Viale Pieraccini 6 50039 Firenze Italy
| | - Lorenzo Di Cesare Mannelli
- Department of Neuroscience, Psychology, Drug Research and; Child Health - Neurofarba - Pharmacology and Toxicology Section; University of Florence; Viale Pieraccini 6 50039 Firenze Italy
| | - Laura Micheli
- Department of Neuroscience, Psychology, Drug Research and; Child Health - Neurofarba - Pharmacology and Toxicology Section; University of Florence; Viale Pieraccini 6 50039 Firenze Italy
| | - Carlo Santini
- School of Science and Technology; University of Camerino; Via S. Agostino 1 62032 Camerino Italy
| | - Eleonora Diamanti
- School of Pharmacy; Medicinal Chemistry Unit; University of Camerino; Via S. Agostino 1 62032 Camerino Italy
| | - Mario Giannella
- School of Pharmacy; Medicinal Chemistry Unit; University of Camerino; Via S. Agostino 1 62032 Camerino Italy
| | - Gianfabio Giorgioni
- School of Pharmacy; Medicinal Chemistry Unit; University of Camerino; Via S. Agostino 1 62032 Camerino Italy
| | - Valerio Mammoli
- School of Pharmacy; Medicinal Chemistry Unit; University of Camerino; Via S. Agostino 1 62032 Camerino Italy
| | - Corinne Dalila Paoletti
- School of Pharmacy; Medicinal Chemistry Unit; University of Camerino; Via S. Agostino 1 62032 Camerino Italy
| | - Riccardo Petrelli
- School of Pharmacy; Medicinal Chemistry Unit; University of Camerino; Via S. Agostino 1 62032 Camerino Italy
| | - Alessandro Piergentili
- School of Pharmacy; Medicinal Chemistry Unit; University of Camerino; Via S. Agostino 1 62032 Camerino Italy
| | - Wilma Quaglia
- School of Pharmacy; Medicinal Chemistry Unit; University of Camerino; Via S. Agostino 1 62032 Camerino Italy
| | - Maria Pigini
- School of Pharmacy; Medicinal Chemistry Unit; University of Camerino; Via S. Agostino 1 62032 Camerino Italy
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30
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Patra SM, Chakraborty S, Shahane G, Prasanna X, Sengupta D, Maiti PK, Chattopadhyay A. Differential dynamics of the serotonin1A receptor in membrane bilayers of varying cholesterol content revealed by all atom molecular dynamics simulation. Mol Membr Biol 2016; 32:127-37. [PMID: 26508556 DOI: 10.3109/09687688.2015.1096971] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The serotonin1A receptor belongs to the superfamily of G protein-coupled receptors (GPCRs) and is a potential drug target in neuropsychiatric disorders. The receptor has been shown to require membrane cholesterol for its organization, dynamics and function. Although recent work suggests a close interaction of cholesterol with the receptor, the structural integrity of the serotonin1A receptor in the presence of cholesterol has not been explored. In this work, we have carried out all atom molecular dynamics simulations, totaling to 3 μs, to analyze the effect of cholesterol on the structure and dynamics of the serotonin1A receptor. Our results show that the presence of physiologically relevant concentration of membrane cholesterol alters conformational dynamics of the serotonin1A receptor and, on an average lowers conformational fluctuations. Our results show that, in general, transmembrane helix VII is most affected by the absence of membrane cholesterol. These results are in overall agreement with experimental data showing enhancement of GPCR stability in the presence of membrane cholesterol. Our results constitute a molecular level understanding of GPCR-cholesterol interaction, and represent an important step in our overall understanding of GPCR function in health and disease.
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Affiliation(s)
- Swarna M Patra
- a Center for Condensed Matter Theory, Department of Physics, Indian Institute of Science , Bangalore , India .,b Department of Chemistry , RV College of Engineering , Bangalore , India
| | - Sudip Chakraborty
- a Center for Condensed Matter Theory, Department of Physics, Indian Institute of Science , Bangalore , India
| | - Ganesh Shahane
- c CSIR-National Chemical Laboratory , Pune , India , and
| | | | - Durba Sengupta
- c CSIR-National Chemical Laboratory , Pune , India , and
| | - Prabal K Maiti
- a Center for Condensed Matter Theory, Department of Physics, Indian Institute of Science , Bangalore , India
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31
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Ubaldi M, Del Bello F, Domi E, Pigini M, Nasuti C. Investigation of allyphenyline efficacy in the treatment of alcohol withdrawal symptoms. Eur J Pharmacol 2015; 760:122-8. [PMID: 25895641 DOI: 10.1016/j.ejphar.2015.04.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Revised: 03/31/2015] [Accepted: 04/02/2015] [Indexed: 10/23/2022]
Abstract
We have recently demonstrated that allyphenyline, behaving as α2C-adrenoceptor/serotonin 5-HT1A receptor agonist and α2A-adrenoceptor antagonist, in mice enhanced morphine analgesia, attenuated morphine withdrawal symptoms, showed significant antidepressant-like activity and was devoid of sedative side effects. Opioid and alcohol withdrawal shares several common neurobiological and molecular mechanisms. Therefore, in this study we expanded our analysis of the pharmacological properties of allyphenyline by investigating its ability to prevent the expression of somatic withdrawal signs, anxiety-like behavior and hyperlocomotion associated with chronic ethanol intoxication. Rats were subjected to induction of ethanol dependence via repeated daily intragastric ethanol (20%) administration for 4 consecutive days. Twelve hours after the last alcohol administration, somatic alcohol withdrawal signs were scored. Results revealed a significant expression of physical withdrawal signs that were not affected by intraperitoneal (i.p.) administration of allyphenyline at the doses of 0.05, 0.275 and 0.5 mg/kg. In contrast, allyphenyline (0.05 and 0.275 mg/kg i.p.) significantly reduced hyperanxiety-like behavior observed 6 days after alcohol intoxication as measured using the defensive burying test. Allyphenyline also reduced open field hyperlocomotor activity associated with alcohol withdrawal. Notably, the anxiolytic effect of the compound, as well as the already reported antidepressant action, was observed at very low doses, suggesting the involvement of its α2C-adrenoceptor/serotonin 5-HT1A receptor agonism. Therefore, the present investigation suggests that allyphenyline might represent an interesting pharmacological tool to investigate the potential of compounds exhibiting α2C-adrenoceptor/serotonin 5-HT1A receptor agonism and α2A-adrenoceptor antagonism in the treatment of hyperanxiety and hyperlocomotion occurring during alcohol withdrawal in dependent subjects.
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Affiliation(s)
- Massimo Ubaldi
- School of Pharmacy, Pharmacology Unit, University of Camerino, via Madonna delle Carceri, 62032 Camerino, Italy.
| | - Fabio Del Bello
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino, via S. Agostino 1, 62032 Camerino, Italy.
| | - Esi Domi
- School of Pharmacy, Pharmacology Unit, University of Camerino, via Madonna delle Carceri, 62032 Camerino, Italy
| | - Maria Pigini
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino, via S. Agostino 1, 62032 Camerino, Italy
| | - Cinzia Nasuti
- School of Pharmacy, Pharmacology Unit, University of Camerino, via Madonna delle Carceri, 62032 Camerino, Italy
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Chakraborty H, Chattopadhyay A. Excitements and challenges in GPCR oligomerization: molecular insight from FRET. ACS Chem Neurosci 2015; 6:199-206. [PMID: 25363209 DOI: 10.1021/cn500231d] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are the largest family of proteins involved in signal transduction across cell membranes, and they represent major drug targets in all clinical areas. Oligomerization of GPCRs and its implications in drug discovery constitute an exciting area in contemporary biology. In this Review, we have highlighted the application of fluorescence resonance energy transfer (FRET) in exploring GPCR oligomerization, with special emphasis on possible pitfalls and experimental complications involved. Based on FRET photophysics, we discuss some of the possible complications, and recommend that FRET results in complex cellular environments should be interpreted with caution. Although both hetero- and homo-FRET are used in measurements of GPCR oligomerization, we suggest that homo-FRET enjoys certain advantages over hetero-FRET. Given the seminal role of GPCRs as current drug targets, we envision that methodological progress in studying GPCR oligomerization would result in better therapeutic strategies.
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Affiliation(s)
- Hirak Chakraborty
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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Chattopadhyay A, Rao BD, Jafurulla M. Solubilization of G Protein-Coupled Receptors. Methods Enzymol 2015; 557:117-34. [DOI: 10.1016/bs.mie.2015.01.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Chattopadhyay A, Jafurulla M. Novel insights in membrane biology utilizing fluorescence recovery after photobleaching. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 842:27-40. [PMID: 25408335 DOI: 10.1007/978-3-319-11280-0_3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Abstract
G protein-coupled receptors (GPCRs) are the largest class of molecules involved in signal transduction across cell membranes and represent major targets in the development of novel drug candidates in all clinical areas. Although there have been some recent leads, structural information on GPCRs is relatively rare due to the difficulty associated with crystallization. A specific reason for this is the intrinsic flexibility displayed by GPCRs, which is necessary for their functional diversity. Since GPCRs are integral membrane proteins, interaction of membrane lipids with them constitutes an important area of research in GPCR biology. In particular, membrane cholesterol has been reported to have a modulatory role in the function of a number of GPCRs. The role of membrane cholesterol in GPCR function is discussed with specific example of the serotonin1A receptor. Recent results show that GPCRs are characterized with structural motifs that preferentially associate with cholesterol. An emerging and important concept is oligomerization of GPCRs and its role in GPCR function and signaling. The role of membrane cholesterol in GPCR oligomerization is highlighted. Future research in GPCR biology would offer novel insight in basic biology and provide new avenues for drug discovery.
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Fiorino F, Severino B, Magli E, Ciano A, Caliendo G, Santagada V, Frecentese F, Perissutti E. 5-HT(1A) receptor: an old target as a new attractive tool in drug discovery from central nervous system to cancer. J Med Chem 2013; 57:4407-26. [PMID: 24295064 DOI: 10.1021/jm400533t] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The serotonin receptor subtype 5-HT(1A) was one of the first serotonin receptor subtypes pharmacologically characterized. This receptor subtype has long been object of intense research and is implicated in the pathogenesis and treatment of anxiety and depressive disorders. In recent years, new chemical entities targeting the 5-HT(1A) receptor (alone or in combination with other molecular targets) have been proposed for novel therapeutic uses in neuroprotection, cognitive impairment, Parkinson's disease, pain treatment, malignant carcinoid syndrome, and prostate cancer. This Perspective compares existing data on expression and signaling activity of the 5-HT(1A) receptor to a ligand with an intrinsic agonist or antagonist profile. Our purpose is also to make a complete overview, useful for underlining the features needed to select a specific pharmacological profile rather than another one. This aspect could be really interesting to consider and justify the 5-HT(1A) receptor as a new attractive target for drug discovery.
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Affiliation(s)
- Ferdinando Fiorino
- Dipartimento di Farmacia, Università degli Studi di Napoli "Federico II" , Via D. Montesano, 49, 80131, Napoli, Italy
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Jafurulla M, Rao BD, Sreedevi S, Ruysschaert JM, Covey DF, Chattopadhyay A. Stereospecific requirement of cholesterol in the function of the serotonin1A receptor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:158-63. [PMID: 24008092 DOI: 10.1016/j.bbamem.2013.08.015] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 08/16/2013] [Accepted: 08/23/2013] [Indexed: 01/04/2023]
Abstract
The serotonin1A receptor is an important member of the G protein-coupled receptor (GPCR) family. It is involved in the generation and modulation of a variety of cognitive and behavioral functions and serves as a drug target. Previous work from our laboratory has established the sensitivity of the function of the serotonin1A receptor to membrane cholesterol. Solubilization of the hippocampal serotonin1A receptor utilizing the zwitterionic detergent CHAPS is accompanied by loss of cholesterol and results in reduction in specific ligand binding. Replenishment of cholesterol to solubilized membranes restores specific ligand binding to the receptor. We utilized this strategy of sterol replenishment of solubilized membranes to explore the stereospecific stringency of cholesterol for receptor function. We used two stereoisomers of cholesterol, ent-cholesterol (enantiomer of cholesterol) and epi-cholesterol (a diastereomer of cholesterol), for this purpose. Importantly, we show here that while ent-cholesterol could replace cholesterol in supporting receptor function, epi-cholesterol could not. These results imply that the requirement of membrane cholesterol for the serotonin1A receptor function is diastereospecific, yet not enantiospecific. Our results extend and help define specificity of the interaction of membrane cholesterol with the serotonin1A receptor, and represent the first report utilizing ent-cholesterol to examine stereospecificity of GPCR-cholesterol interaction.
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Affiliation(s)
- Md Jafurulla
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India
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Membrane cholesterol stabilizes the human serotonin1A receptor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2936-42. [DOI: 10.1016/j.bbamem.2012.07.032] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2012] [Revised: 07/20/2012] [Accepted: 07/23/2012] [Indexed: 12/17/2022]
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Singh P, Haldar S, Chattopadhyay A. Differential effect of sterols on dipole potential in hippocampal membranes: implications for receptor function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012. [PMID: 23201544 DOI: 10.1016/j.bbamem.2012.11.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Dipole potential is the potential difference within the membrane bilayer, which originates due to the nonrandom arrangement of lipid dipoles and water molecules at the membrane interface. In this work, we have explored the possible correlation between functional modulation of a G protein-coupled receptor (the serotonin(1A) receptor) and membrane dipole potential, under conditions of altered membrane sterol composition. We have previously shown that the ligand binding activity of the hippocampal serotonin(1A) receptor is reduced upon cholesterol depletion and could be restored upon replenishment with cholesterol. Interestingly, when the replenishment was carried out with an immediate biosynthetic precursor of cholesterol (7-DHC), differing with cholesterol merely in a double bond, the ligand binding activity of the receptor was not restored. In order to understand the mechanistic framework of receptor-cholesterol interaction, we carried out dipole potential measurements of hippocampal membranes under these conditions, by the dual wavelength ratiometric approach using an electrochromic probe (di-8-ANEPPS). We show here that dipole potential of hippocampal membranes is reduced upon progressive depletion of cholesterol and is restored upon replenishment with cholesterol, but not with 7-DHC. Our results show that the recovery of ligand binding activity of the serotonin(1A) receptor upon replenishment with cholesterol (but not with 7-DHC) could be related to the differential ability of these closely related sterols to modulate membrane dipole potential. We conclude that subtle changes in membrane dipole potential could be crucial in understanding the complex interplay between membrane lipids and proteins in the cellular milieu.
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Affiliation(s)
- Pushpendra Singh
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Hyderabad, India
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Sengupta D, Chattopadhyay A. Identification of Cholesterol Binding Sites in the Serotonin1A Receptor. J Phys Chem B 2012; 116:12991-6. [DOI: 10.1021/jp309888u] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Durba Sengupta
- National Chemical
Laboratory, Council of Scientific and Industrial Research, Dr. Homi Bhabha Road, Pune 411 008, India
| | - Amitabha Chattopadhyay
- Centre for Cellular
and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007,
India
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Role of glycosphingolipids in the function of human serotonin1A
receptors. J Neurochem 2012; 123:716-24. [DOI: 10.1111/jnc.12008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2012] [Revised: 09/02/2012] [Accepted: 09/04/2012] [Indexed: 11/26/2022]
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Sahu SK, Saxena R, Chattopadhyay A. Cholesterol depletion modulates detergent resistant fraction of human serotonin(1A) receptors. Mol Membr Biol 2012; 29:290-8. [PMID: 22594670 DOI: 10.3109/09687688.2012.688147] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Insolubility of membrane components in non-ionic detergents such as Triton X-100 at low temperature is a widely used biochemical criterion to identify, isolate and characterize membrane domains. In this work, we monitored the detergent insolubility of the serotonin(1A) receptor in CHO cell membranes and its modulation by membrane cholesterol. The serotonin(1A) receptor is an important member of the G-protein coupled receptor family. It is implicated in the generation and modulation of various cognitive, behavioral and developmental functions and serves as a drug target. Our results show that a significant fraction (∼28%) of the serotonin(1A) receptor resides in detergent-resistant membranes (DRMs). Interestingly, the fraction of the serotonin(1A) receptor in DRMs exhibits a reduction upon membrane cholesterol depletion. In addition, we show that contents of DRM markers such as flotillin-1, caveolin-1 and GM₁ are altered in DRMs upon cholesterol depletion. These results assume significance since the function of the serotonin(1A) receptor has previously been shown to be affected by membrane lipids, specifically cholesterol. Our results are relevant in the context of membrane organization of the serotonin(1A) receptor in particular, and G-protein coupled receptors in general.
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Affiliation(s)
- Santosh Kumar Sahu
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Hyderabad, India
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Intracellular Loop 2 Peptides of the Human 5HT1a Receptor are Differential Activators of Gi. INTERNATIONAL JOURNAL OF PEPTIDES 2012; 2012:490734. [PMID: 22649462 PMCID: PMC3357532 DOI: 10.1155/2012/490734] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 02/10/2012] [Accepted: 02/24/2012] [Indexed: 11/17/2022]
Abstract
Peptide mimics of intracellular loop 2 (ic2) of the human 5HT1a receptor have been studied with respect to their ability to inhibit agonist binding via interference with receptor-G-protein coupling. These peptides give shallow concentration-effect relationships. Additionally, these peptides have been studied with respect to their ability to trigger the signal transduction system of this Gi-coupled receptor. Two signaling parameters have been quantified: concentration of intracellular cAMP and changes in incorporation into the G protein of a stable analog of GTP. In both cases, peptide mimics near midloop of ic2 actually show agonist activity with efficacy falling off toward both loop termini near TM 3 and TM 4. Previous results have suggested that the loop region near the TM3/ic2 interface is primarily responsible for receptor-G-protein coupling, while the current result emphasizes the mid-ic2 loop region's ability to activate the G protein following initial coupling. A limited number of peptides from the receptor's TM5/ic3 loop vicinity were also studied regarding agonist inhibition and G-protein activation. These peptides provide additional evidence that the human 5HT1a receptor, TM5/ic3 loop region, is involved in both coupling and activation actions. Overall, these results provide further information about potential pharmacological intervention and drug development with respect to the human 5HT1a receptor/G-protein system. Finally, the structural evidence generated here provides testable models pending crystallization and X-ray analysis of the receptor.
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Chattopadhyay A, Paila YD, Shrivastava S, Tiwari S, Singh P, Fantini J. Sphingolipid-Binding Domain in the Serotonin1A Receptor. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 749:279-93. [DOI: 10.1007/978-1-4614-3381-1_19] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Paila YD, Kombrabail M, Krishnamoorthy G, Chattopadhyay A. Oligomerization of the serotonin(1A) receptor in live cells: a time-resolved fluorescence anisotropy approach. J Phys Chem B 2011; 115:11439-47. [PMID: 21866959 DOI: 10.1021/jp201458h] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The serotonin(1A) receptor is a representative member of the G-protein coupled receptor (GPCR) superfamily and serves as an important target in the development of therapeutic agents for neuropsychiatric disorders. Oligomerization of GPCRs is an important contemporary issue since it is believed to be a crucial determinant for cellular signaling. In this work, we monitored the oligomerization status of the serotonin(1A) receptor tagged to enhanced yellow fluorescent protein (5-HT(1A)R-EYFP) in live cells utilizing time-resolved fluorescence anisotropy decay. We interpret the unresolved fast component of the observed anisotropy decay as fluorescence resonance energy transfer (FRET) between 5-HT(1A)R-EYFP molecules (homo-FRET). Homo-FRET enjoys certain advantages over hetero-FRET in the analysis of receptor oligomerization. Our results reveal the presence of constitutive oligomers of the serotonin(1A) receptor in live cells. We further show that the oligomerization status of the receptor is independent of ligand stimulation and sphingolipid depletion. Interestingly, acute (but not chronic) cholesterol depletion appears to enhance the oligomerization process. Importantly, our results are independent of receptor expression level, thereby ruling out complications arising due to high expression. These results have potential implications in future therapeutic strategies in pathophysiological conditions in which serotonin(1A) receptors are implicated.
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Affiliation(s)
- Yamuna Devi Paila
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India
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Singh P, Jafurulla M, Paila YD, Chattopadhyay A. Desmosterol replaces cholesterol for ligand binding function of the serotonin(1A) receptor in solubilized hippocampal membranes: support for nonannular binding sites for cholesterol? BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2428-34. [PMID: 21763272 DOI: 10.1016/j.bbamem.2011.06.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Revised: 06/25/2011] [Accepted: 06/27/2011] [Indexed: 01/07/2023]
Abstract
The serotonin(1A) receptor is an important member of the G-protein coupled receptor family, and is involved in the generation and modulation of a variety of cognitive and behavioral functions. Solubilization of the hippocampal serotonin(1A) receptor by CHAPS is accompanied by loss of cholesterol that results in a reduction in specific agonist binding activity. Replenishment of cholesterol to solubilized membranes restores membrane cholesterol content and significantly recovers specific agonist binding. In order to test the stringency of cholesterol requirement, we solubilized native hippocampal membranes followed by replenishment with desmosterol. Desmosterol is the immediate biosynthetic precursor of cholesterol in the Bloch pathway differing only in a double bond at the 24th position. Our results show that replenishment with desmosterol restores ligand binding of serotonin(1A) receptors. This is consistent with earlier results showing that desmosterol can replace cholesterol in a large number of cases. However, these results appear to be contradictory to our earlier findings, performed by sterol manipulation utilizing methyl-β-cyclodextrin, in which we observed that replacing cholesterol with desmosterol is unable to restore specific ligand binding of the hippocampal serotonin(1A) receptor. We discuss the possible molecular mechanism, in terms of nonannular lipid binding sites around the receptor, giving rise to these differences.
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47
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Metabolic depletion of sphingolipids enhances the mobility of the human serotonin1A receptor. Biochem Biophys Res Commun 2011; 411:180-4. [DOI: 10.1016/j.bbrc.2011.06.127] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 06/18/2011] [Indexed: 12/22/2022]
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Björk K, Svenningsson P. Modulation of monoamine receptors by adaptor proteins and lipid rafts: role in some effects of centrally acting drugs and therapeutic agents. Annu Rev Pharmacol Toxicol 2011; 51:211-42. [PMID: 20887195 DOI: 10.1146/annurev-pharmtox-010510-100520] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The monoamines and their cognate receptors are widespread in the central nervous system and are vital for normal brain function. Dysfunction in these systems underlies several psychiatric and neurological disease states, and consequently monoamines are targets of a host of pharmacotherapies. This review provides an overview on how monoamine receptors are regulated by adaptor proteins and lipid rafts with emphasis on interactions in nerve cells. Monoamine receptors have prominent intracellular loops that provide binding sites for adaptor proteins. Receptor function is further modulated by cholesterol and submembranous microdomains termed lipid rafts. These interactions determine several facets of G protein-coupled receptor (GPCR) function including trafficking, localization, and signaling. Possible roles of adaptor proteins and lipid rafts in disease states and in mediating actions of drugs and therapeutic agents are also discussed.
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Affiliation(s)
- Karl Björk
- Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
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49
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Paila YD, Tiwari S, Sengupta D, Chattopadhyay A. Molecular modeling of the human serotonin(1A) receptor: role of membrane cholesterol in ligand binding of the receptor. MOLECULAR BIOSYSTEMS 2010; 7:224-34. [PMID: 20967314 DOI: 10.1039/c0mb00148a] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Serotonin(1A) receptors are important neurotransmitter receptors and belong to the superfamily of G-protein coupled receptors (GPCRs). Although it is an important drug target, the crystal structure of the serotonin(1A) receptor has not been solved yet. Earlier homology models of the serotonin(1A) receptor were generated using rhodopsin as a template. We have used two recent crystal structures of the human β(2)-adrenergic receptor, one of which shows specific cholesterol binding site(s), as templates to model the human serotonin(1A) receptor. Since the sequence similarity between the serotonin(1A) receptor and β(2)-adrenergic receptor is considerably higher than the similarity between the serotonin(1A) receptor and rhodopsin, our model is more reliable. Based on these templates, we generated models of the serotonin(1A) receptor in the absence and presence of cholesterol. The receptor model appears more compact in the presence of cholesterol. We validated the stability of 'compactness' using coarse-grain MD simulation. Importantly, all ligands exhibit higher binding energies when docked to the receptor in the presence of cholesterol, thereby implying that membrane cholesterol facilitates ligand binding to the serotonin(1A) receptor. To the best of our knowledge, this is one of the first reports in which lipid-specific receptor conformations have been modeled by homology modeling.
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Affiliation(s)
- Yamuna Devi Paila
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India.
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50
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Lacivita E, Masotti AC, Jafurulla M, Saxena R, Rangaraj N, Chattopadhyay A, Colabufo NA, Berardi F, Perrone R, Leopoldo M. Identification of a red-emitting fluorescent ligand for in vitro visualization of human serotonin 5-HT(1A) receptors. Bioorg Med Chem Lett 2010; 20:6628-32. [PMID: 20888762 DOI: 10.1016/j.bmcl.2010.09.027] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Revised: 09/03/2010] [Accepted: 09/04/2010] [Indexed: 01/24/2023]
Abstract
The 5-HT(1A) receptor subtype is the most thoroughly studied serotonin receptor subtype. We report here the design, synthesis and characterization of two new fluorescent ligands for the 5-HT(1A) receptor. The new 1-arylpiperazine-based red-emitting fluorescent compound 6 displayed good binding affinity at the 5-HT(1A) receptor (K(i)=35 nM) and was able to label specifically the human 5-HT(1A) receptor stably expressed in CHO cells visualized using confocal laser scanning microscopy.
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Affiliation(s)
- Enza Lacivita
- Università degli Studi di Bari A. Moro, Dipartimento Farmaco-Chimico, via Orabona, 4, 70125 Bari, Italy
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