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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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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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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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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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Dutta A, Sarkar P, Shrivastava S, Chattopadhyay A. Effect of Hypoxia on the Function of the Human Serotonin 1A Receptor. ACS Chem Neurosci 2022; 13:1456-1466. [PMID: 35467841 DOI: 10.1021/acschemneuro.2c00181] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Cellular hypoxia causes numerous pathophysiological conditions associated with the disruption of oxygen homeostasis. Under oxygen-deficient conditions, cells adapt by controlling the cellular functions to facilitate the judicious use of available oxygen, such as cessation of cell growth and proliferation. In higher eukaryotes, the process of cholesterol biosynthesis is intimately coupled to the availability of oxygen, where the synthesis of one molecule of cholesterol requires 11 molecules of O2. Cholesterol is an essential component of higher eukaryotic membranes and is crucial for the physiological functions of several membrane proteins and receptors. The serotonin1A receptor, an important neurotransmitter G protein-coupled receptor associated with cognition and memory, has previously been shown to depend on cholesterol for its signaling and function. In this work, in order to explore the interdependence of oxygen levels, cholesterol biosynthesis, and the function of the serotonin1A receptor, we developed a cellular hypoxia model to explore the function of the human serotonin1A receptor heterologously expressed in Chinese hamster ovary cells. We observed cell cycle arrest at G1/S phase and the accumulation of lanosterol in cell membranes under hypoxic conditions, thereby validating our cellular model. Interestingly, we observed a significant reduction in ligand binding and disruption of downstream cAMP signaling of the serotonin1A receptor under hypoxic conditions. To the best of our knowledge, our results represent the first report linking the function of the serotonin1A receptor with hypoxia. From a broader perspective, these results contribute to our overall understanding of the molecular basis underlying neurological conditions often associated with hypoxia-induced brain dysfunction.
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Affiliation(s)
- Aritri Dutta
- 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
| | - Sandeep Shrivastava
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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Cholesterol-dependent endocytosis of GPCRs: implications in pathophysiology and therapeutics. Biophys Rev 2021; 13:1007-1017. [DOI: 10.1007/s12551-021-00878-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 10/26/2021] [Indexed: 10/19/2022] Open
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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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Sarkar P, Chattopadhyay A. Cholesterol footprint in high-resolution structures of serotonin receptors: Where are we now and what does it mean? Chem Phys Lipids 2021; 239:105120. [PMID: 34332970 DOI: 10.1016/j.chemphyslip.2021.105120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 07/24/2021] [Accepted: 07/24/2021] [Indexed: 10/20/2022]
Abstract
An emerging feature of several high-resolution GPCR structures is the presence of closely bound cholesterol molecules. In this Perspective, we share the excitement of the recent advancements in GPCR structural biology. We further highlight our laboratory's journey in comprehensively elucidating functional sensitivity of GPCRs (using the serotonin1A receptor as a representative neurotransmitter GPCR) to membrane cholesterol and validation using a variety of assays and molecular dynamics simulations. Although high-resolution structures of many GPCRs have been reported in the last few years, the structure of the serotoin1A receptor proved to be elusive for a long time. Very recently the cryo-EM structure of the serotoin1A receptor displaying 10 bound cholesterol molecules has been reported. We conclude by providing a critical analysis of caveats involved in GPCR structure determination.
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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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Kumar GA, Sarkar P, Stepniewski TM, Jafurulla M, Singh SP, Selent J, Chattopadhyay A. A molecular sensor for cholesterol in the human serotonin 1A receptor. SCIENCE ADVANCES 2021; 7:7/30/eabh2922. [PMID: 34301606 PMCID: PMC8302130 DOI: 10.1126/sciadv.abh2922] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 06/09/2021] [Indexed: 05/10/2023]
Abstract
The function of several G protein-coupled receptors (GPCRs) exhibits cholesterol sensitivity. Cholesterol sensitivity of GPCRs could be attributed to specific sequence and structural features, such as the cholesterol recognition/interaction amino acid consensus (CRAC) motif, that facilitate their cholesterol-receptor interaction. In this work, we explored the molecular basis of cholesterol sensitivity exhibited by the serotonin1A receptor, the most studied GPCR in the context of cholesterol sensitivity, by generating mutants of key residues in CRAC motifs in transmembrane helix 2 (TM2) and TM5 of the receptor. Our results show that a lysine residue (K101) in one of the CRAC motifs is crucial for sensing altered membrane cholesterol levels. Insights from all-atom molecular dynamics simulations showed that cholesterol-sensitive functional states of the serotonin1A receptor are associated with reduced conformational dynamics of extracellular loops of the receptor. These results constitute one of the first reports on the molecular mechanism underlying cholesterol sensitivity of GPCRs.
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Affiliation(s)
- G Aditya Kumar
- 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
| | - Tomasz Maciej Stepniewski
- Research Programme on Biomedical Informatics (GRIB), Department of Experimental and Health Sciences of Pompeu Fabra University (UPF)-Hospital del Mar Medical Research Institute (IMIM), 08003 Barcelona, Spain
- Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
| | - Md Jafurulla
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Shishu Pal Singh
- National Centre for Biological Sciences, UAS-GKVK Campus, Bellary Road, Bengaluru 560 065, India
| | - Jana Selent
- Research Programme on Biomedical Informatics (GRIB), Department of Experimental and Health Sciences of Pompeu Fabra University (UPF)-Hospital del Mar Medical Research Institute (IMIM), 08003 Barcelona, Spain.
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Pucadyil T, Kulkarni K, Sengupta D. Molecular Interplay at the Membrane and Impact on Cellular Physiology. J Membr Biol 2021; 254:239-242. [PMID: 34041579 PMCID: PMC8153518 DOI: 10.1007/s00232-021-00183-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/04/2021] [Indexed: 11/30/2022]
Affiliation(s)
| | - Kiran Kulkarni
- CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune, 411 008, India.
| | - Durba Sengupta
- CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune, 411 008, India.
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