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Isu UH, Badiee SA, Polasa A, Tabari SH, Derakhshani-Molayousefi M, Moradi M. Cholesterol Dependence of the Conformational Changes in Metabotropic Glutamate Receptor 1. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.17.589854. [PMID: 38659864 PMCID: PMC11042357 DOI: 10.1101/2024.04.17.589854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Metabotropic glutamate receptors (mGluRs) are class C G protein-coupled receptors that function as obligate dimers in regulating neurotransmission and synaptic plasticity in the central nervous system. The mGluR1 subtype has been shown to be modulated by the membrane lipid environment, particularly cholesterol, though the molecular mechanisms remain elusive. In this study, we employed all-atom molecular dynamics simulations to investigate the effects of cholesterol on the conformational dynamics of the mGluR1 seven-transmembrane (7TM) domain in an inactive state model. Simulations were performed with three different cholesterol concentrations (0%, 10%, and 25%) in a palmitoyl-oleoyl phosphatidylcholine (POPC) lipid bilayer system. Our results demonstrate that cholesterol induces conformational changes in the mGluR1 dimer more significantly than in the individual protomers. Notably, cholesterol modulates the dynamics and conformations of the TM1 and TM2 helices at the dimer interface. Interestingly, an intermediate cholesterol concentration of 10% elicits more pronounced conformational changes compared to both cholesterol-depleted (0%) and cholesterol-enriched (25%) systems. Specific electrostatic interaction unique to the 10% cholesterol system further corroborate these conformational differences. Given the high sequence conservation of the 7TM domains across mGluR subtypes, the cholesterol-dependent effects observed in mGluR1 are likely applicable to other members of this receptor family. Our findings provide atomistic insights into how cholesterol modulates the conformational landscape of mGluRs, which could impact their function and signaling mechanisms.
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2
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Menon I, Sych T, Son Y, Morizumi T, Lee J, Ernst OP, Khelashvili G, Sezgin E, Levitz J, Menon AK. A cholesterol switch controls phospholipid scrambling by G protein-coupled receptors. J Biol Chem 2024; 300:105649. [PMID: 38237683 PMCID: PMC10874734 DOI: 10.1016/j.jbc.2024.105649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Revised: 01/04/2024] [Accepted: 01/07/2024] [Indexed: 01/30/2024] Open
Abstract
Class A G protein-coupled receptors (GPCRs), a superfamily of cell membrane signaling receptors, moonlight as constitutively active phospholipid scramblases. The plasma membrane of metazoan cells is replete with GPCRs yet has a strong resting trans-bilayer phospholipid asymmetry, with the signaling lipid phosphatidylserine confined to the cytoplasmic leaflet. To account for the persistence of this lipid asymmetry in the presence of GPCR scramblases, we hypothesized that GPCR-mediated lipid scrambling is regulated by cholesterol, a major constituent of the plasma membrane. We now present a technique whereby synthetic vesicles reconstituted with GPCRs can be supplemented with cholesterol to a level similar to that of the plasma membrane and show that the scramblase activity of two prototypical GPCRs, opsin and the β1-adrenergic receptor, is impaired upon cholesterol loading. Our data suggest that cholesterol acts as a switch, inhibiting scrambling above a receptor-specific threshold concentration to disable GPCR scramblases at the plasma membrane.
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Affiliation(s)
- Indu Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - Taras Sych
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Solna, Sweden
| | - Yeeun Son
- Graduate program in Biochemistry, Cell and Molecular Biology, Weill Cornell Graduate School, New York, New York, USA; Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Takefumi Morizumi
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Joon Lee
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - Oliver P Ernst
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - George Khelashvili
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, USA; Institute of Computational Biomedicine, Weill Cornell Medical College, New York, New York, USA
| | - Erdinc Sezgin
- Graduate program in Biochemistry, Cell and Molecular Biology, Weill Cornell Graduate School, New York, New York, USA
| | - Joshua Levitz
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - Anant K Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA.
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3
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Menon I, Sych T, Son Y, Morizumi T, Lee J, Ernst OP, Khelashvili G, Sezgin E, Levitz J, Menon AK. A cholesterol switch controls phospholipid scrambling by G protein-coupled receptors. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.11.24.568580. [PMID: 38045315 PMCID: PMC10690279 DOI: 10.1101/2023.11.24.568580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Class A G protein-coupled receptors (GPCRs), a superfamily of cell membrane signaling receptors, moonlight as constitutively active phospholipid scramblases. The plasma membrane of metazoan cells is replete with GPCRs, yet has a strong resting trans-bilayer phospholipid asymmetry, with the signaling lipid phosphatidylserine confined to the cytoplasmic leaflet. To account for the persistence of this lipid asymmetry in the presence of GPCR scramblases, we hypothesized that GPCR-mediated lipid scrambling is regulated by cholesterol, a major constituent of the plasma membrane. We now present a technique whereby synthetic vesicles reconstituted with GPCRs can be supplemented with cholesterol to a level similar to that of the plasma membrane and show that the scramblase activity of two prototypical GPCRs, opsin and the β1-adrenergic receptor, is impaired upon cholesterol loading. Our data suggest that cholesterol acts as a switch, inhibiting scrambling above a receptor-specific threshold concentration to disable GPCR scramblases at the plasma membrane.
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Affiliation(s)
- Indu Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Taras Sych
- Science for Life Laboratory, Department of Women’s and Children’s Health, Karolinska Institutet, 17165 Solna, Sweden
| | - Yeeun Son
- Graduate program in Biochemistry, Cell and Molecular Biology, Weill Cornell Graduate School, New York, NY 10065, USA
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Takefumi Morizumi
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
| | - Joon Lee
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Oliver P. Ernst
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada M5S 1A8
| | - George Khelashvili
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA
- Institute of Computational Biomedicine, Weill Cornell Medical College, New York, NY 10065, USA
| | - Erdinc Sezgin
- Graduate program in Biochemistry, Cell and Molecular Biology, Weill Cornell Graduate School, New York, NY 10065, USA
| | - Joshua Levitz
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Anant K. Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
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4
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Gutorov R, Katz B, Peters M, Minke B. Membrane lipid modulations by methyl-β-cyclodextrin uncouple the Drosophila light-activated phospholipase C from TRP and TRPL channel gating. J Biol Chem 2024; 300:105484. [PMID: 37992804 PMCID: PMC10770611 DOI: 10.1016/j.jbc.2023.105484] [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] [Received: 08/30/2023] [Revised: 11/05/2023] [Accepted: 11/14/2023] [Indexed: 11/24/2023] Open
Abstract
Sterols are hydrophobic molecules, known to cluster signaling membrane-proteins in lipid rafts, while methyl-β-cyclodextrin (MβCD) has been a major tool for modulating membrane-sterol content for studying its effect on membrane proteins, including the transient receptor potential (TRP) channels. The Drosophila light-sensitive TRP channels are activated downstream of a G-protein-coupled phospholipase Cβ (PLC) cascade. In phototransduction, PLC is an enzyme that hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) generating diacylglycerol, inositol-tris-phosphate, and protons, leading to TRP and TRP-like (TRPL) channel openings. Here, we studied the effects of MβCD on Drosophila phototransduction using electrophysiology while fluorescently monitoring PIP2 hydrolysis, aiming to examine the effects of sterol modulation on PIP2 hydrolysis and the ensuing light-response in the native system. Incubation of photoreceptor cells with MβCD dramatically reduced the amplitude and kinetics of the TRP/TRPL-mediated light response. MβCD also suppressed PLC-dependent TRP/TRPL constitutive channel activity in the dark induced by mitochondrial uncouplers, but PLC-independent activation of the channels by linoleic acid was not affected. Furthermore, MβCD suppressed a constitutively active TRP mutant-channel, trpP365, suggesting that TRP channel activity is a target of MβCD action. Importantly, whole-cell voltage-clamp measurements from photoreceptors and simultaneously monitored PIP2-hydrolysis by translocation of fluorescently tagged Tubby protein domain, from the plasma membrane to the cytosol, revealed that MβCD virtually abolished the light response when having little effect on the light-activated PLC. Together, MβCD uncoupled TRP/TRPL channel gating from light-activated PLC and PIP2-hydrolysis suggesting the involvement of distinct nanoscopic lipid domains such as lipid rafts and PIP2 clusters in TRP/TRPL channel gating.
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Affiliation(s)
- Rita Gutorov
- Faculty of Medicine, Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University, Jerusalem, Israel
| | - Ben Katz
- Faculty of Medicine, Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University, Jerusalem, Israel
| | - Maximilian Peters
- Faculty of Medicine, Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University, Jerusalem, Israel
| | - Baruch Minke
- Faculty of Medicine, Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University, Jerusalem, Israel.
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5
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Kovacs T, Nagy P, Panyi G, Szente L, Varga Z, Zakany F. Cyclodextrins: Only Pharmaceutical Excipients or Full-Fledged Drug Candidates? Pharmaceutics 2022; 14:pharmaceutics14122559. [PMID: 36559052 PMCID: PMC9788615 DOI: 10.3390/pharmaceutics14122559] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 11/15/2022] [Accepted: 11/18/2022] [Indexed: 11/23/2022] Open
Abstract
Cyclodextrins, representing a versatile family of cyclic oligosaccharides, have extensive pharmaceutical applications due to their unique truncated cone-shaped structure with a hydrophilic outer surface and a hydrophobic cavity, which enables them to form non-covalent host-guest inclusion complexes in pharmaceutical formulations to enhance the solubility, stability and bioavailability of numerous drug molecules. As a result, cyclodextrins are mostly considered as inert carriers during their medical application, while their ability to interact not only with small molecules but also with lipids and proteins is largely neglected. By forming inclusion complexes with cholesterol, cyclodextrins deplete cholesterol from cellular membranes and thereby influence protein function indirectly through alterations in biophysical properties and lateral heterogeneity of bilayers. In this review, we summarize the general chemical principles of direct cyclodextrin-protein interactions and highlight, through relevant examples, how these interactions can modify protein functions in vivo, which, despite their huge potential, have been completely unexploited in therapy so far. Finally, we give a brief overview of disorders such as Niemann-Pick type C disease, atherosclerosis, Alzheimer's and Parkinson's disease, in which cyclodextrins already have or could have the potential to be active therapeutic agents due to their cholesterol-complexing or direct protein-targeting properties.
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Affiliation(s)
- Tamas Kovacs
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, H-4032 Debrecen, Hungary
| | - Peter Nagy
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, H-4032 Debrecen, Hungary
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, H-4032 Debrecen, Hungary
| | - Lajos Szente
- CycloLab Cyclodextrin R & D Laboratory Ltd., H-1097 Budapest, Hungary
| | - Zoltan Varga
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, H-4032 Debrecen, Hungary
| | - Florina Zakany
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, H-4032 Debrecen, Hungary
- Correspondence:
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6
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The Role of Membrane Lipids in Light-Activation of Drosophila TRP Channels. Biomolecules 2022; 12:biom12030382. [PMID: 35327573 PMCID: PMC8945425 DOI: 10.3390/biom12030382] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 02/21/2022] [Accepted: 02/23/2022] [Indexed: 12/28/2022] Open
Abstract
Transient Receptor Potential (TRP) channels constitute a large superfamily of polymodal channel proteins with diverse roles in many physiological and sensory systems that function both as ionotropic and metabotropic receptors. From the early days of TRP channel discovery, membrane lipids were suggested to play a fundamental role in channel activation and regulation. A prominent example is the Drosophila TRP and TRP-like (TRPL) channels, which are predominantly expressed in the visual system of Drosophila. Light activation of the TRP and TRPL channels, the founding members of the TRP channel superfamily, requires activation of phospholipase Cβ (PLC), which hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) into Diacylglycerol (DAG) and Inositol 1, 4,5-trisphosphate (IP3). However, the events required for channel gating downstream of PLC activation are still under debate and led to several hypotheses regarding the mechanisms by which lipids gate the channels. Despite many efforts, compelling evidence of the involvement of DAG accumulation, PIP2 depletion or IP3-mediated Ca2+ release in light activation of the TRP/TRPL channels are still lacking. Exogeneous application of poly unsaturated fatty acids (PUFAs), a product of DAG hydrolysis was demonstrated as an efficient way to activate the Drosophila TRP/TRPL channels. However, compelling evidence for the involvement of PUFAs in physiological light-activation of the TRP/TRPL channels is still lacking. Light-induced mechanical force generation was measured in photoreceptor cells prior to channel opening. This mechanical force depends on PLC activity, suggesting that the enzymatic activity of PLC converting PIP2 into DAG generates membrane tension, leading to mechanical gating of the channels. In this review, we will present the roles of membrane lipids in light activation of Drosophila TRP channels and present the many advantages of this model system in the exploration of TRP channel activation under physiological conditions.
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7
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Feng X, Yang F, Rabenstein M, Wang Z, Frech MJ, Wree A, Bräuer AU, Witt M, Gläser A, Hermann A, Rolfs A, Luo J. Stimulation of mGluR1/5 Improves Defective Internalization of AMPA Receptors in NPC1 Mutant Mouse. Cereb Cortex 2021; 30:1465-1480. [PMID: 31599924 DOI: 10.1093/cercor/bhz179] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Niemann-Pick type C1 (NPC1) disease is characterized by neurodegeneration caused by cholesterol accumulation in the late endosome/lysosome. In this study, a defective basal and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-stimulated internalization of GluR2-containing AMPA receptors in NPC1-/- cortical neurons was detected. Our results show that the amount of cholesterol and group I metabotropic glutamate receptors (mGluR1/5) in lipid rafts of NPC1-/- cortical tissue and neurons are decreased and their downstream signals of p-ERK are defective, which are restored by a rebalance of cholesterol homeostasis through β-cyclodextrin (β-CD) treatment. Application of 3,5-dihydroxyphenylglycine (DHPG)-a mGluR1/5 agonist-and β-CD markedly increases the internalization of AMPA receptors and decreases over-influx of calcium in NPC1-/- neurons, respectively. Furthermore, the defective phosphorylated GluR2 and protein kinase C signals are ameliorated by the treatment with DHPG and β-CD, respectively, suggesting an involvement of them in internalization dysfunction. Taken together, our data imply that abnormal internalization of AMPA receptors is a critical mechanism for neuronal dysfunction and the correction of dysfunctional mGluR1/5 is a potential therapeutic strategy for NPC1 disease.
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Affiliation(s)
- Xiao Feng
- Translational Neurodegeneration Section "Albrecht Kossel", Department of Neurology, University Medical Center Rostock, Rostock 18147, Germany
| | - Fan Yang
- Translational Neurodegeneration Section "Albrecht Kossel", Department of Neurology, University Medical Center Rostock, Rostock 18147, Germany
| | - Michael Rabenstein
- Translational Neurodegeneration Section "Albrecht Kossel", Department of Neurology, University Medical Center Rostock, Rostock 18147, Germany
| | - Zhen Wang
- Max Delbrück Center for Molecular Medicine, Berlin 13125, Germany
| | - Moritz J Frech
- Translational Neurodegeneration Section "Albrecht Kossel", Department of Neurology, University Medical Center Rostock, Rostock 18147, Germany.,Center for Transdisciplinary Neurosciences Rostock (CTNR), University Medical Center Rostock, University of Rostock, Rostock 18147, Germany
| | - Andreas Wree
- Center for Transdisciplinary Neurosciences Rostock (CTNR), University Medical Center Rostock, University of Rostock, Rostock 18147, Germany.,Institute of Anatomy, University Medical Center Rostock, Rostock 18055, Germany
| | - Anja U Bräuer
- Institute of Anatomy, University Medical Center Rostock, Rostock 18055, Germany.,Research Group Anatomy, School of Medicine and Health Sciences, Carl von Ossietzky University, Oldenburg 26129, Germany.,Research Center for Neurosensory Science, Carl von Ossietzky University, Oldenburg 26129, Germany
| | - Martin Witt
- Institute of Anatomy, University Medical Center Rostock, Rostock 18055, Germany
| | - Anne Gläser
- Institute of Anatomy, University Medical Center Rostock, Rostock 18055, Germany
| | - Andreas Hermann
- Translational Neurodegeneration Section "Albrecht Kossel", Department of Neurology, University Medical Center Rostock, Rostock 18147, Germany.,Center for Transdisciplinary Neurosciences Rostock (CTNR), University Medical Center Rostock, University of Rostock, Rostock 18147, Germany.,German Center for Neurodegenerative Diseases (DZNE), Rostock/Greifswald, Rostock 18147, Germany
| | | | - Jiankai Luo
- Translational Neurodegeneration Section "Albrecht Kossel", Department of Neurology, University Medical Center Rostock, Rostock 18147, Germany.,Center for Transdisciplinary Neurosciences Rostock (CTNR), University Medical Center Rostock, University of Rostock, Rostock 18147, Germany
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8
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Kurth M, Lolicato F, Sandoval-Perez A, Amaya-Espinosa H, Teslenko A, Sinning I, Beck R, Brügger B, Aponte-Santamaría C. Cholesterol Localization around the Metabotropic Glutamate Receptor 2. J Phys Chem B 2020; 124:9061-9078. [PMID: 32954729 DOI: 10.1021/acs.jpcb.0c05264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The metabotropic glutamate receptor (mGluR) 2 plays a key role in the central nervous system. mGluR2 has been shown to be regulated by its surrounding lipid environment, especially by cholesterol, by an unknown mechanism. Here, using a combination of biochemical approaches, photo-cross-linking experiments, and molecular dynamics simulations we show the interaction of cholesterol with at least two, but potentially five more, preferential sites on the mGluR2 transmembrane domain. Our simulations demonstrate that surface matching, rather than electrostatic interactions with specific amino acids, is the main factor defining cholesterol localization. Moreover, the cholesterol localization observed here is similar to the sterol-binding pattern previously described in silico for other members of the mGluR family. Biochemical assays suggest little influence of cholesterol on trafficking or dimerization of mGluR2. Nevertheless, simulations revealed a significant reduction of residue-residue contacts together with an alteration in the internal mechanical stress at the cytoplasmic side of the helical bundle when cholesterol was present in the membrane. These alterations may be related to destabilization of the basal state of mGluR2. Due to the high sequence conservation of the transmembrane domains of mGluRs, the molecular interaction of cholesterol and mGluR2 described here is also likely to be relevant for other members of the mGLuR family.
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Affiliation(s)
- Markus Kurth
- Biochemistry Center (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Fabio Lolicato
- Biochemistry Center (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Angelica Sandoval-Perez
- Max Planck Tandem Group in Computational Biophysics, University of Los Andes, Bogotá, Colombia
| | - Helman Amaya-Espinosa
- Max Planck Tandem Group in Computational Biophysics, University of Los Andes, Bogotá, Colombia
| | - Alexandra Teslenko
- Biochemistry Center (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Irmgard Sinning
- Biochemistry Center (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Rainer Beck
- Biochemistry Center (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Britta Brügger
- Biochemistry Center (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Camilo Aponte-Santamaría
- Max Planck Tandem Group in Computational Biophysics, University of Los Andes, Bogotá, Colombia.,Interdisciplinary Center for Scientific Computing, University of Heidelberg, Heidelberg, Germany
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9
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Direct and indirect cholesterol effects on membrane proteins with special focus on potassium channels. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1865:158706. [DOI: 10.1016/j.bbalip.2020.158706] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 03/19/2020] [Accepted: 03/30/2020] [Indexed: 12/16/2022]
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10
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Bolla JR, Agasid MT, Mehmood S, Robinson CV. Membrane Protein-Lipid Interactions Probed Using Mass Spectrometry. Annu Rev Biochem 2019; 88:85-111. [PMID: 30901263 DOI: 10.1146/annurev-biochem-013118-111508] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Membrane proteins that exist in lipid bilayers are not isolated molecular entities. The lipid molecules that surround them play crucial roles in maintaining their full structural and functional integrity. Research directed at investigating these critical lipid-protein interactions is developing rapidly. Advancements in both instrumentation and software, as well as in key biophysical and biochemical techniques, are accelerating the field. In this review, we provide a brief outline of structural techniques used to probe protein-lipid interactions and focus on the molecular aspects of these interactions obtained from native mass spectrometry (native MS). We highlight examples in which lipids have been shown to modulate membrane protein structure and show how native MS has emerged as a complementary technique to X-ray crystallography and cryo-electron microscopy. We conclude with a short perspective on future developments that aim to better understand protein-lipid interactions in the native environment.
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Affiliation(s)
- Jani Reddy Bolla
- Department of Chemistry, University of Oxford, Oxford OX1 3QZ, United Kingdom;
| | - Mark T Agasid
- Department of Chemistry, University of Oxford, Oxford OX1 3QZ, United Kingdom;
| | - Shahid Mehmood
- Department of Chemistry, University of Oxford, Oxford OX1 3QZ, United Kingdom;
| | - Carol V Robinson
- Department of Chemistry, University of Oxford, Oxford OX1 3QZ, United Kingdom;
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11
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Cholesterol and the Safety Factor for Neuromuscular Transmission. Int J Mol Sci 2019; 20:ijms20051046. [PMID: 30823359 PMCID: PMC6429197 DOI: 10.3390/ijms20051046] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 02/23/2019] [Accepted: 02/24/2019] [Indexed: 12/12/2022] Open
Abstract
A present review is devoted to the analysis of literature data and results of own research. Skeletal muscle neuromuscular junction is specialized to trigger the striated muscle fiber contraction in response to motor neuron activity. The safety factor at the neuromuscular junction strongly depends on a variety of pre- and postsynaptic factors. The review focuses on the crucial role of membrane cholesterol to maintain a high efficiency of neuromuscular transmission. Cholesterol metabolism in the neuromuscular junction, its role in the synaptic vesicle cycle and neurotransmitter release, endplate electrogenesis, as well as contribution of cholesterol to the synaptogenesis, synaptic integrity, and motor disorders are discussed.
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12
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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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13
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Desai AJ, Miller LJ. Changes in the plasma membrane in metabolic disease: impact of the membrane environment on G protein-coupled receptor structure and function. Br J Pharmacol 2017; 175:4009-4025. [PMID: 28691227 DOI: 10.1111/bph.13943] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 06/08/2017] [Accepted: 07/04/2017] [Indexed: 12/11/2022] Open
Abstract
Drug development targeting GPCRs often utilizes model heterologous cell expression systems, reflecting an implicit assumption that the membrane environment has little functional impact on these receptors or on their responsiveness to drugs. However, much recent data have illustrated that membrane components can have an important functional impact on intrinsic membrane proteins. This review is directed toward gaining a better understanding of the structure of the plasma membrane in health and disease, and how this organelle can influence GPCR structure, function and regulation. It is important to recognize that the membrane provides a potential mode of lateral allosteric regulation of GPCRs and can affect the effectiveness of drugs and their biological responses in various disease states, which can even vary among individuals across the population. The type 1 cholecystokinin receptor is reviewed as an exemplar of a class A GPCR that is affected in this way by changes in the plasma membrane. LINKED ARTICLES This article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.21/issuetoc.
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Affiliation(s)
- Aditya J Desai
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ, USA
| | - Laurence J Miller
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ, USA
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14
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Javadi A, Deevi RK, Evergren E, Blondel-Tepaz E, Baillie GS, Scott MGH, Campbell FC. PTEN controls glandular morphogenesis through a juxtamembrane β-Arrestin1/ARHGAP21 scaffolding complex. eLife 2017; 6:e24578. [PMID: 28749339 PMCID: PMC5576923 DOI: 10.7554/elife.24578] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 07/24/2017] [Indexed: 01/01/2023] Open
Abstract
PTEN controls three-dimensional (3D) glandular morphogenesis by coupling juxtamembrane signaling to mitotic spindle machinery. While molecular mechanisms remain unclear, PTEN interacts through its C2 membrane-binding domain with the scaffold protein β-Arrestin1. Because β-Arrestin1 binds and suppresses the Cdc42 GTPase-activating protein ARHGAP21, we hypothesize that PTEN controls Cdc42 -dependent morphogenic processes through a β-Arrestin1-ARHGAP21 complex. Here, we show that PTEN knockdown (KD) impairs β-Arrestin1 membrane localization, β-Arrestin1-ARHGAP21 interactions, Cdc42 activation, mitotic spindle orientation and 3D glandular morphogenesis. Effects of PTEN deficiency were phenocopied by β-Arrestin1 KD or inhibition of β-Arrestin1-ARHGAP21 interactions. Conversely, silencing of ARHGAP21 enhanced Cdc42 activation and rescued aberrant morphogenic processes of PTEN-deficient cultures. Expression of the PTEN C2 domain mimicked effects of full-length PTEN but a membrane-binding defective mutant of the C2 domain abrogated these properties. Our results show that PTEN controls multicellular assembly through a membrane-associated regulatory protein complex composed of β-Arrestin1, ARHGAP21 and Cdc42.
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Affiliation(s)
- Arman Javadi
- Centre for Cancer Research and Cell BiologyQueen’s University of BelfastBelfastUnited Kingdom
| | - Ravi K Deevi
- Centre for Cancer Research and Cell BiologyQueen’s University of BelfastBelfastUnited Kingdom
| | - Emma Evergren
- Centre for Cancer Research and Cell BiologyQueen’s University of BelfastBelfastUnited Kingdom
| | - Elodie Blondel-Tepaz
- Inserm, U1016, Institut CochinParisFrance
- CNRS, UMR8104ParisFrance
- Univ. Paris Descartes, Sorbonne Paris CitéParisFrance
| | - George S Baillie
- Institute of Cardiovascular and Medical Science, College of Medical, Veterinary and Life SciencesUniversity of GlasgowGlasgowScotland
| | - Mark GH Scott
- Inserm, U1016, Institut CochinParisFrance
- CNRS, UMR8104ParisFrance
- Univ. Paris Descartes, Sorbonne Paris CitéParisFrance
| | - Frederick C Campbell
- Centre for Cancer Research and Cell BiologyQueen’s University of BelfastBelfastUnited Kingdom
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15
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Hacke M, Björkholm P, Hellwig A, Himmels P, Ruiz de Almodóvar C, Brügger B, Wieland F, Ernst AM. Inhibition of Ebola virus glycoprotein-mediated cytotoxicity by targeting its transmembrane domain and cholesterol. Nat Commun 2015; 6:7688. [PMID: 26158910 DOI: 10.1038/ncomms8688] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 05/29/2015] [Indexed: 11/10/2022] Open
Abstract
The high pathogenicity of the Ebola virus reflects multiple concurrent processes on infection. Among other important determinants, Ebola fusogenic glycoprotein (GP) has been associated with the detachment of infected cells and eventually leads to vascular leakage and haemorrhagic fever. Here we report that the membrane-anchored GP is sufficient to induce the detachment of adherent cells. The results show that the detachment induced through either full-length GP1,2 or the subunit GP2 depends on cholesterol and the structure of the transmembrane domain. These data reveal a novel molecular mechanism in which GP regulates Ebola virus assembly and suggest that cholesterol-reducing agents could be useful as therapeutics to counteract GP-mediated cell detachment.
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Affiliation(s)
- Moritz Hacke
- Heidelberg University Biochemistry Center (BZH), 69120 Heidelberg, Germany
| | - Patrik Björkholm
- Department of Molecular Evolution, Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, 75124 Uppsala, Sweden
| | - Andrea Hellwig
- Interdisciplinary Center for Neurosciences, Heidelberg University, Heidelberg 69120, Germany
| | - Patricia Himmels
- Heidelberg University Biochemistry Center (BZH), 69120 Heidelberg, Germany
| | | | - Britta Brügger
- Heidelberg University Biochemistry Center (BZH), 69120 Heidelberg, Germany
| | - Felix Wieland
- Heidelberg University Biochemistry Center (BZH), 69120 Heidelberg, Germany
| | - Andreas M Ernst
- Heidelberg University Biochemistry Center (BZH), 69120 Heidelberg, Germany
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16
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van der Westhuizen ET, Valant C, Sexton PM, Christopoulos A. Endogenous Allosteric Modulators of G Protein–Coupled Receptors. J Pharmacol Exp Ther 2015; 353:246-60. [DOI: 10.1124/jpet.114.221606] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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17
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Expression of Membrane Proteins in the Eyes of Transgenic Drosophila melanogaster. Methods Enzymol 2015; 556:219-39. [DOI: 10.1016/bs.mie.2014.12.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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18
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Krivoi II. Functional interactions of Na,K-ATPase with molecular environment. Biophysics (Nagoya-shi) 2014. [DOI: 10.1134/s000635091405011x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
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19
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Christopoulos A. Advances in G protein-coupled receptor allostery: from function to structure. Mol Pharmacol 2014; 86:463-78. [PMID: 25061106 DOI: 10.1124/mol.114.094342] [Citation(s) in RCA: 170] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
It is now widely accepted that G protein-coupled receptors (GPCRs) are highly dynamic proteins that adopt multiple active states linked to distinct functional outcomes. Furthermore, these states can be differentially stabilized not only by orthosteric ligands but also by allosteric ligands acting at spatially distinct binding sites. The key pharmacologic characteristics of GPCR allostery include improved selectivity due to either greater sequence divergence between receptor subtypes and/or subtype-selective cooperativity, a ceiling level to the effect, probe dependence (whereby the magnitude and direction of the allosteric effect change with the nature of the interacting ligands), and the potential for biased signaling. Recent chemical biology developments are beginning to demonstrate how the incorporation of analytical pharmacology and operational modeling into the experimental workflow can enrich structure-activity studies of allostery and bias, and have also led to the discovery of a new class of hybrid orthosteric/allosteric (bitopic) molecules. The potential for endogenous allosteric modulators to play a role in physiology and disease remains to be fully appreciated but will likely represent an important area for future studies. Finally, breakthroughs in structural and computational biology are beginning to unravel the mechanistic basis of GPCR allosteric modulation at the molecular level.
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Affiliation(s)
- Arthur Christopoulos
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria, Australia
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20
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Wu H, Wang C, Gregory KJ, Han GW, Cho HP, Xia Y, Niswender CM, Katritch V, Meiler J, Cherezov V, Conn PJ, Stevens RC. Structure of a class C GPCR metabotropic glutamate receptor 1 bound to an allosteric modulator. Science 2014; 344:58-64. [PMID: 24603153 DOI: 10.1126/science.1249489] [Citation(s) in RCA: 394] [Impact Index Per Article: 39.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The excitatory neurotransmitter glutamate induces modulatory actions via the metabotropic glutamate receptors (mGlus), which are class C G protein-coupled receptors (GPCRs). We determined the structure of the human mGlu1 receptor seven-transmembrane (7TM) domain bound to a negative allosteric modulator, FITM, at a resolution of 2.8 angstroms. The modulator binding site partially overlaps with the orthosteric binding sites of class A GPCRs but is more restricted than most other GPCRs. We observed a parallel 7TM dimer mediated by cholesterols, which suggests that signaling initiated by glutamate's interaction with the extracellular domain might be mediated via 7TM interactions within the full-length receptor dimer. A combination of crystallography, structure-activity relationships, mutagenesis, and full-length dimer modeling provides insights about the allosteric modulation and activation mechanism of class C GPCRs.
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Affiliation(s)
- Huixian Wu
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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21
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Roh SE, Hong YH, Jang DC, Kim J, Kim SJ. Lipid rafts serve as signaling platforms for mGlu1 receptor-mediated calcium signaling in association with caveolin. Mol Brain 2014; 7:9. [PMID: 24512690 PMCID: PMC3937055 DOI: 10.1186/1756-6606-7-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 01/30/2014] [Indexed: 11/24/2022] Open
Abstract
Background Group I metabotropic glutamate receptors (mGlu1/5 receptors) have important roles in synaptic activity in the central nervous system. They modulate neuronal excitability by mobilizing intracellular Ca2+ following receptor activation. Also, accumulating evidence has indicated the association of Ca2+ signaling with lipid rafts. Caveolin, an adaptor protein found in a specialized subset of lipid rafts, has been reported to promote the localization of membrane proteins to lipid rafts. Results In the present study, we investigated the role of lipid rafts on the mGlu1α receptor-mediated Ca2+ signaling in association with caveolin in hippocampal primary neurons and HEK293 cells. We show that the disruption of lipid rafts using methyl-β-cyclodextrin markedly decreased mGlu1α receptor-mediated Ca2+ transients and lipid rafts localization of the receptor. Furthermore, transfection of mGlu1α receptor with mutated caveolin-binding domain reduced localization of the receptor to lipid rafts. Also, application of a peptide blocker of mGlu1α receptor and caveolin binding reduced the Ca2+ signaling and the lipid rafts localization. Conclusions Taken together, these results suggest that the binding of mGlu1α receptor to caveolin is crucial for its lipid rafts localization and mGlu1α receptor-mediated Ca2+ transients.
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Affiliation(s)
| | | | | | | | - Sang Jeong Kim
- Department of Physiology, Seoul National University College of Medicine, 28, Yeongeon-dong, Jongno-gu, Seoul 110-799, Korea.
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Mondal S, Khelashvili G, Johner N, Weinstein H. How the dynamic properties and functional mechanisms of GPCRs are modulated by their coupling to the membrane environment. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 796:55-74. [PMID: 24158801 DOI: 10.1007/978-94-007-7423-0_4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Experimental observations of the dependence of function and organization of G protein-coupled receptors (GPCRs) on their lipid environment have stimulated new quantitative studies of the coupling between the proteins and the membrane. It is important to develop such a quantitative understanding at the molecular level because the effects of the coupling are seen to be physiologically and clinically significant. Here we review findings that offer insight into how membrane-GPCR coupling is connected to the structural characteristics of the GPCR, from sequence to 3D structural detail, and how this coupling is involved in the actions of ligands on the receptor. The application of a recently developed computational approach designed for quantitative evaluation of membrane remodeling and the energetics of membrane-protein interactions brings to light the importance of the radial asymmetry of the membrane-facing surface of GPCRs in their interaction with the surrounding membrane. As the radial asymmetry creates adjacencies of hydrophobic and polar residues at specific sites of the GPCR, the ability of membrane remodeling to achieve complete hydrophobic matching is limited, and the residual mismatch carries a significant energy cost. The adjacencies are shown to be affected by ligand-induced conformational changes. Thus, functionally important organization of GPCRs in the cell membrane can depend both on ligand-determined properties and on the lipid composition of various membrane regions with different remodeling capacities. That this functionally important reorganization can be driven by oligomerization patterns that reduce the energy cost of the residual mismatch, suggests a new perspective on GPCR dimerization and ligand-GPCR interactions. The relation between the modulatory effects on GPCRs from the binding of specific cell-membrane components, e.g., cholesterol, and those produced by the non-local energetics of hydrophobic mismatch are discussed in this context.
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Affiliation(s)
- Sayan Mondal
- Department of Physiology and Biophysics, Weill Cornell Medical College, Cornell University, Room E-509, 1300 York Avenue, 10065, New York City, NY, USA
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23
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Kumari R, Castillo C, Francesconi A. Agonist-dependent signaling by group I metabotropic glutamate receptors is regulated by association with lipid domains. J Biol Chem 2013; 288:32004-19. [PMID: 24045944 DOI: 10.1074/jbc.m113.475863] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Group I metabotropic glutamate receptors (mGluRs), mGluR1 and mGluR5, play critical functions in forms of activity-dependent synaptic plasticity and synapse remodeling in physiological and pathological states. Importantly, in animal models of fragile X syndrome, group I mGluR activity is abnormally enhanced, a dysfunction that may partly underlie cognitive deficits in the condition. Lipid rafts are cholesterol- and sphingolipid-enriched membrane domains that are thought to form transient signaling platforms for ligand-activated receptors. Many G protein-coupled receptors, including group I mGluRs, are present in lipid rafts, but the mechanisms underlying recruitment to these membrane domains remain incompletely understood. Here, we show that mGluR1 recruitment to lipid rafts is enhanced by agonist binding and is supported at least in part by an intact cholesterol recognition/interaction amino acid consensus (CRAC) motif in the receptor. Substitutions of critical residues in the motif reduce mGluR1 association with lipid rafts and agonist-induced, mGluR1-dependent activation of extracellular-signal-activated kinase1/2 MAP kinase (ERK-MAPK). We find that alteration of membrane cholesterol content or perturbation of lipid rafts regulates agonist-dependent activation of ERK-MAPK by group I mGluRs, suggesting a potential function for cholesterol as a positive allosteric modulator of receptor function(s). Together, these findings suggest that drugs that alter membrane cholesterol levels or directed to the receptor-cholesterol interface could be employed to modulate abnormal group I mGluR activity in neuropsychiatric conditions, including fragile X syndrome.
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Affiliation(s)
- Ranju Kumari
- From the Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
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24
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Membrane-sensitive conformational states of helix 8 in the metabotropic Glu2 receptor, a class C GPCR. PLoS One 2012; 7:e42023. [PMID: 22870276 PMCID: PMC3411606 DOI: 10.1371/journal.pone.0042023] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 06/29/2012] [Indexed: 11/19/2022] Open
Abstract
The recent elucidation of the X-ray structure of several class A GPCRs clearly indicates that the amphipathic helix 8 (H8) is a conserved structural domain in most crystallized GPCRs. Very little is known about the presence and the possible role of an analogous H8 domain in the distantly related class C GPCRs. In this study, we investigated the structural properties for the H8 domain of the mGluR2 receptor, a class C GPCR, by applying extended molecular dynamics simulations. Our study indicates that the amphipathic H8 adopts membrane-sensitive conformational states, which depend on the membrane composition. Cholesterol-rich membranes stabilize the helical structure of H8 whereas cholesterol-depleted membranes induce a disruption of H8. The observed link between membrane cholesterol levels and H8 conformational states suggests that H8 behaves as a sensor of cholesterol concentration.
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25
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Oddi S, Dainese E, Sandiford S, Fezza F, Lanuti M, Chiurchiù V, Totaro A, Catanzaro G, Barcaroli D, De Laurenzi V, Centonze D, Mukhopadhyay S, Selent J, Howlett AC, Maccarrone M. Effects of palmitoylation of Cys(415) in helix 8 of the CB(1) cannabinoid receptor on membrane localization and signalling. Br J Pharmacol 2012; 165:2635-51. [PMID: 21895628 PMCID: PMC3423250 DOI: 10.1111/j.1476-5381.2011.01658.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 07/15/2011] [Accepted: 08/05/2011] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE The CB(1) cannabinoid receptor is regulated by its association with membrane microdomains such as lipid rafts. Here, we investigated the role of palmitoylation of the CB(1) receptor by analysing the functional consequences of site-specific mutation of Cys(415) , the likely site of palmitoylation at the end of helix 8, in terms of membrane association, raft targeting and signalling. EXPERIMENTAL APPROACH The palmitoylation state of CB(1) receptors in rat forebrain was assessed by depalmitoylation/repalmitoylation experiments. Cys(415) was replaced with alanine by site-directed mutagenesis. Green fluorescence protein chimeras of both wild-type and mutant receptors were transiently expressed and functionally characterized in SH-SY5Y cells and HEK-293 cells by means of confocal microscopy, cytofluorimetry and competitive binding assays. Confocal fluorescence recovery after photobleaching was used to assess receptor membrane dynamics, whereas signalling activity was assessed by [(35) S]GTPγS, cAMP and co-immunoprecipitation assays. KEY RESULTS Endogenous CB(1) receptors in rat brain were palmitoylated. Mutation of Cys(415) prevented the palmitoylation of the receptor in transfected cells and reduced its recruitment to plasma membrane and lipid rafts; it also increased protein diffusional mobility. The same mutation markedly reduced the functional coupling of CB(1) receptors with G-proteins and adenylyl cyclase, whereas depalmitoylation abolished receptor association with a specific subset of G-proteins. CONCLUSIONS AND IMPLICATIONS CB(1) receptors were post-translationally modified by palmitoylation. Mutation of Cys(415) provides a receptor that is functionally impaired in terms of membrane targeting and signalling. LINKED ARTICLES This article is part of a themed section on Cannabinoids in Biology and Medicine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-8. To view Part I of Cannabinoids in Biology and Medicine visit http://dx.doi.org/10.1111/bph.2011.163.issue-7.
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Affiliation(s)
- Sergio Oddi
- Department of Biomedical Sciences, University of TeramoTeramo, Italy
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
| | - Enrico Dainese
- Department of Biomedical Sciences, University of TeramoTeramo, Italy
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
| | - Simone Sandiford
- Neuroscience/Drug Abuse Research Program, Biomedical Biotechnology Research Institute, North Carolina Central UniversityDurham, NC, USA
| | - Filomena Fezza
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
- Department of Experimental Medicine and Biochemical Sciences, University of Rome ‘Tor Vergata’Rome, Italy
| | - Mirko Lanuti
- Department of Biomedical Sciences, University of TeramoTeramo, Italy
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
| | - Valerio Chiurchiù
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
| | - Antonio Totaro
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
| | - Giuseppina Catanzaro
- Department of Biomedical Sciences, University of TeramoTeramo, Italy
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
| | - Daniela Barcaroli
- Department of Biomedical Sciences, University of Chieti-Pescara ‘G. d'Annunzio’Chieti, Italy
| | - Vincenzo De Laurenzi
- Department of Biomedical Sciences, University of Chieti-Pescara ‘G. d'Annunzio’Chieti, Italy
| | - Diego Centonze
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
- Department of Neurosciences, University of Rome ‘Tor Vergata’Rome, Italy
| | - Somnath Mukhopadhyay
- Neuroscience/Drug Abuse Research Program, Biomedical Biotechnology Research Institute, North Carolina Central UniversityDurham, NC, USA
| | - Jana Selent
- Research Group of biomedical Informatics (GRIB-IMIM), University of Pompeu Fabra, Barcelona Biomedical Research Park (PRBB)Barcelona, Spain
| | - Allyn C Howlett
- Department of Physiology and Pharmacology, Wake Forest University Health SciencesWinston-Salem, NC, USA
| | - Mauro Maccarrone
- Department of Biomedical Sciences, University of TeramoTeramo, Italy
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
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Lieu MH, Vallejos MJ, Michael E, Tsunoda S. Mechanisms underlying stage-1 TRPL channel translocation in Drosophila photoreceptors. PLoS One 2012; 7:e31622. [PMID: 22363689 PMCID: PMC3282777 DOI: 10.1371/journal.pone.0031622] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Accepted: 01/16/2012] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND TRP channels function as key mediators of sensory transduction and other cellular signaling pathways. In Drosophila, TRP and TRPL are the light-activated channels in photoreceptors. While TRP is statically localized in the signaling compartment of the cell (the rhabdomere), TRPL localization is regulated by light. TRPL channels translocate out of the rhabdomere in two distinct stages, returning to the rhabdomere with dark-incubation. Translocation of TRPL channels regulates their availability, and thereby the gain of the signal. Little, however, is known about the mechanisms underlying this trafficking of TRPL channels. METHODOLOGY/PRINCIPAL FINDINGS We first examine the involvement of de novo protein synthesis in TRPL translocation. We feed flies cycloheximide, verify inhibition of protein synthesis, and test for TRPL translocation in photoreceptors. We find that protein synthesis is not involved in either stage of TRPL translocation out of the rhabdomere, but that re-localization to the rhabdomere from stage-1, but not stage-2, depends on protein synthesis. We also characterize an ex vivo eye preparation that is amenable to biochemical and genetic manipulation. We use this preparation to examine mechanisms of stage-1 TRPL translocation. We find that stage-1 translocation is: induced with ATP depletion, unaltered with perturbation of the actin cytoskeleton or inhibition of endocytosis, and slowed with increased membrane sterol content. CONCLUSIONS/SIGNIFICANCE Our results indicate that translocation of TRPL out of the rhabdomere is likely due to protein transport, and not degradation/re-synthesis. Re-localization from each stage to the rhabdomere likely involves different strategies. Since TRPL channels can translocate to stage-1 in the absence of ATP, with no major requirement of the cytoskeleton, we suggest that stage-1 translocation involves simple diffusion through the apical membrane, which may be regulated by release of a light-dependent anchor in the rhabdomere.
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Affiliation(s)
- Minh-Ha Lieu
- Department of Biology, Boston University, Boston, Massachusetts, United States of America
| | - Maximiliano J. Vallejos
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
| | - Emily Michael
- Department of Biology, Boston University, Boston, Massachusetts, United States of America
| | - Susan Tsunoda
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
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Distribution of metabotropic receptors of serotonin, dopamine, GABA, glutamate, and short neuropeptide F in the central complex of Drosophila. Neuroscience 2012; 208:11-26. [PMID: 22361394 DOI: 10.1016/j.neuroscience.2012.02.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 01/19/2012] [Accepted: 02/07/2012] [Indexed: 01/19/2023]
Abstract
The central complex is a prominent set of midline neuropils in the insect brain, known to be a higher locomotor control center that integrates visual inputs and modulates motor outputs. It is composed of four major neuropil structures, the ellipsoid body (EB), fan-shaped body (FB), noduli (NO), and protocerebral bridge (PB). In Drosophila different types of central complex neurons have been shown to express multiple neuropeptides and neurotransmitters; however, the distribution of corresponding receptors is not known. Here, we have mapped metabotropic, G-protein-coupled receptors (GPCRs) of several neurotransmitters to neurons of the central complex. By combining immunocytochemistry with GAL4 driven green fluorescent protein, we examined the distribution patterns of six different GPCRs: two serotonin receptor subtypes (5-HT(1B) and 5-HT(7)), a dopamine receptor (DopR), the metabotropic GABA(B) receptor (GABA(B)R), the metabotropic glutamate receptor (DmGluR(A)) and a short neuropeptide F receptor (sNPFR1). Five of the six GPCRs were mapped to different neurons in the EB (sNPFR1 was not seen). Different layers of the FB express DopR, GABA(B)R, DmGluR(A,) and sNPFR1, whereas only GABA(B)R and DmGluR(A) were localized to the PB. Finally, strong expression of DopR and DmGluR(A) was detected in the NO. In most cases the distribution patterns of the GPCRs matched the expression of markers for their respective ligands. In some nonmatching regions it is likely that other types of dopamine and serotonin receptors or ionotropic GABA and glutamate receptors are expressed. Our data suggest that chemical signaling and signal modulation are diverse and highly complex in the different compartments and circuits of the Drosophila central complex. The information provided here, on receptor distribution, will be very useful for future analysis of functional circuits in the central complex, based on targeted interference with receptor expression.
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Desai AJ, Miller LJ. Sensitivity of cholecystokinin receptors to membrane cholesterol content. Front Endocrinol (Lausanne) 2012; 3:123. [PMID: 23087674 PMCID: PMC3475150 DOI: 10.3389/fendo.2012.00123] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Accepted: 10/01/2012] [Indexed: 12/18/2022] Open
Abstract
Cholesterol represents a structurally and functionally important component of the eukaryotic cell membrane, where it increases lipid order, affects permeability, and influences the lateral mobility and conformation of membrane proteins. Several G protein-coupled receptors have been shown to be affected by the cholesterol content of the membrane, with functional impact on their ligand binding and signal transduction characteristics. The effects of cholesterol can be mediated directly by specific molecular interactions with the receptor and/or indirectly by altering the physical properties of the membrane. This review focuses on the importance and differential effects of membrane cholesterol on the activity of cholecystokinin (CCK) receptors. The type 1 CCK receptor is quite sensitive to its cholesterol environment, while the type 2 CCK receptor is not. The possible structural basis for this differential impact is explored and the implications of pathological states, such as metabolic syndrome, in which membrane cholesterol may be increased and CCK1R function may be abnormal are discussed. This is believed to have substantial potential importance for the development of drugs targeting the CCK receptor.
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Affiliation(s)
| | - Laurence J. Miller
- *Correspondence: Laurence J. Miller, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, 13400 E. Shea Blvd., Scottsdale, AZ 85259, USA. e-mail:
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Meinertzhagen IA, Lee CH. The genetic analysis of functional connectomics in Drosophila. ADVANCES IN GENETICS 2012; 80:99-151. [PMID: 23084874 DOI: 10.1016/b978-0-12-404742-6.00003-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Fly and vertebrate nervous systems share many organizational features, such as layers, columns and glomeruli, and utilize similar synaptic components, such as ion channels and receptors. Both also exhibit similar network features. Recent technological advances, especially in electron microscopy, now allow us to determine synaptic circuits and identify pathways cell-by-cell, as part of the fly's connectome. Genetic tools provide the means to identify synaptic components, as well as to record and manipulate neuronal activity, adding function to the connectome. This review discusses technical advances in these emerging areas of functional connectomics, offering prognoses in each and identifying the challenges in bridging structural connectomics to molecular biology and synaptic physiology, thereby determining fundamental mechanisms of neural computation that underlie behavior.
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Affiliation(s)
- Ian A Meinertzhagen
- Department of Psychology and Neuroscience, Life Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4R2.
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Localisation to lipid rafts correlates with increased function of the Gal/GalNAc lectin in the human protozoan parasite, Entamoeba histolytica. Int J Parasitol 2011; 41:1409-19. [PMID: 22085647 DOI: 10.1016/j.ijpara.2011.10.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Revised: 09/23/2011] [Accepted: 10/06/2011] [Indexed: 11/24/2022]
Abstract
Entamoeba histolytica is the causative agent of dysentery and liver abscess and is prevalent in developing countries. Adhesion to the host is critical to infection and is mediated by amoebic surface receptors. One such receptor, the Gal/GalNAc lectin, binds to galactose or N-acetylgalactosamine residues on host components and consists of heavy (Hgl), light (Lgl) and intermediate (Igl) subunits. The mechanism by which the lectin assembles into a functional complex is not known. The parasite also relies on cholesterol-rich domains (lipid rafts) for adhesion. Therefore, it is conceivable that rafts regulate the assembly or function of the lectin. To test this, amoebae were loaded with cholesterol and lipid rafts were purified and characterised. Western blotting showed that cholesterol loading resulted in co-compartmentalisation of all three subunits in rafts. This co-compartmentalisation was accompanied by an increase in the ability of the amoebae to bind to host cells in a galactose-specific manner, suggesting that there is a correlation between location and function of the Gal/GalNAc lectin. Cholesterol loading did not increase the surface levels of the lectin subunits. Therefore, the cholesterol-induced increase in adhesion was not the result of externalisation of an internal pool of subunits. A mutant cell line that modestly responded to cholesterol with a slight increase in adhesion exhibited only a slight enrichment of Hgl and Lgl in rafts. This supports the connection between location and function of the Gal/GalNAc lectin. Actin can also influence the interaction of proteins with rafts. Therefore, the sub-membrane distribution of the lectin subunits was also assessed after treatment with an actin depolymerising agent, cytochalasin D. Cytochalasin D-treatment had no effect on the submembrane distribution of the subunits, suggesting that actin does not prevent the association of lectin subunits with rafts in this system. Together, these data provide insight into the molecular mechanisms regulating the location and function of this adhesin.
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Intrinsic membrane association of the cytoplasmic tail of influenza virus M2 protein and lateral membrane sorting regulated by cholesterol binding and palmitoylation. Biochem J 2011; 437:389-97. [PMID: 21592088 DOI: 10.1042/bj20110706] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The influenza virus transmembrane protein M2 is a proton channel, but also plays a role in the scission of nascent virus particles from the plasma membrane. An amphiphilic helix in the CT (cytoplasmic tail) of M2 is supposed to insert into the lipid bilayer, thereby inducing curvature. Palmitoylation of the helix and binding to cholesterol via putative CRAC (cholesterol recognition/interaction amino acid consensus) motifs are believed to target M2 to the edge of rafts, the viral-budding site. In the present study, we tested pre-conditions of this model, i.e. that the CT interacts with membranes, and that acylation and cholesterol binding affect targeting of M2. M2-CT, purified as a glutathione transferase fusion protein, associated with [3H]photocholesterol and with liposomes. Mutation of tyrosine residues in the CRAC motifs prevented [(3)H]photocholesterol labelling and reduced liposome binding. M2-CT fused to the yellow fluorescent protein localized to the Golgi in transfected cells; membrane targeting was dependent on CRAC and (to a lesser extent) on palmitoylation. Preparation of giant plasma membrane vesicles from cells expressing full-length M2-GFP (green fluorescent protein) showed that the protein is partly present in the raft domain. Raft targeting required palmitoylation, but not the CRAC motifs. Thus palmitoylation and cholesterol binding differentially affect the intrinsic membrane binding of the amphiphilic helix.
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Contreras FX, Ernst AM, Wieland F, Brügger B. Specificity of intramembrane protein-lipid interactions. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a004705. [PMID: 21536707 DOI: 10.1101/cshperspect.a004705] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Our concept of biological membranes has markedly changed, from the fluid mosaic model to the current model that lipids and proteins have the ability to separate into microdomains, differing in their protein and lipid compositions. Since the breakthrough in crystallizing membrane proteins, the most powerful method to define lipid-binding sites on proteins has been X-ray and electron crystallography. More recently, chemical biology approaches have been developed to analyze protein-lipid interactions. Such methods have the advantage of providing highly specific cellular probes. With the advent of novel tools to study functions of individual lipid species in membranes together with structural analysis and simulations at the atomistic resolution, a growing number of specific protein-lipid complexes are defined and their functions explored. In the present article, we discuss the various modes of intramembrane protein-lipid interactions in cellular membranes, including examples for both annular and nonannular bound lipids. Furthermore, we will discuss possible functional roles of such specific protein-lipid interactions as well as roles of lipids as chaperones in protein folding and transport.
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Panneels V, Kock I, Krijnse-Locker J, Rezgaoui M, Sinning I. Drosophila photoreceptor cells exploited for the production of eukaryotic membrane proteins: receptors, transporters and channels. PLoS One 2011; 6:e18478. [PMID: 21494623 PMCID: PMC3072989 DOI: 10.1371/journal.pone.0018478] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Accepted: 03/01/2011] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Membrane proteins (MPs) play key roles in signal transduction. However, understanding their function at a molecular level is mostly hampered by the lack of protein in suitable amount and quality. Despite impressive developments in the expression of prokaryotic MPs, eukaryotic MP production has lagged behind and there is a need for new expression strategies. In a pilot study, we produced a Drosophila glutamate receptor specifically in the eyes of transgenic flies, exploiting the naturally abundant membrane stacks in the photoreceptor cells (PRCs). Now we address the question whether the PRCs also process different classes of medically relevant target MPs which were so far notoriously difficult to handle with conventional expression strategies. PRINCIPAL FINDINGS We describe the homologous and heterologous expression of 10 different targets from the three major MP classes--G protein-coupled receptors (GPCRs), transporters and channels in Drosophila eyes. PRCs offered an extraordinary capacity to produce, fold and accommodate massive amounts of MPs. The expression of some MPs reached similar levels as the endogenous rhodopsin, indicating that the PRC membranes were almost unsaturable. Expression of endogenous rhodopsin was not affected by the target MPs and both could coexist in the membrane stacks. Heterologous expression levels reached about 270 to 500 pmol/mg total MP, resulting in 0.2-0.4 mg purified target MP from 1 g of fly heads. The metabotropic glutamate receptor and human serotonin transporter--both involved in synaptic transmission--showed native pharmacological characteristics and could be purified to homogeneity as a prerequisite for further studies. SIGNIFICANCE We demonstrate expression in Drosophila PRCs as an efficient and inexpensive tool for the large scale production of functional eukaryotic MPs. The fly eye system offers a number of advantages over conventional expression systems and paves the way for in-depth analyses of eukaryotic MPs that have so far not been accessible to biochemical and biophysical studies.
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Affiliation(s)
- Valérie Panneels
- Department of Structural Biology, Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Ines Kock
- Department of Structural Biology, Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Jacomine Krijnse-Locker
- Department of Infectious Diseases and Core Facility Electron Microscopy (EMCF), University of Heidelberg, Heidelberg, Germany
| | - Meriem Rezgaoui
- Department of Structural Biology, Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Irmgard Sinning
- Department of Structural Biology, Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
- * E-mail:
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Das J. Aliphatic diazirines as photoaffinity probes for proteins: recent developments. Chem Rev 2011; 111:4405-17. [PMID: 21466226 DOI: 10.1021/cr1002722] [Citation(s) in RCA: 200] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Joydip Das
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas 77204, USA.
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Abstract
The last 10 years have seen a rebirth of interest in lipid biology in the fields of Drosophila development and neurobiology, and sphingolipids have emerged as controlling many processes that have not previously been studied from the viewpoint of lipid biochemistry. Mutations in sphingolipid regulatory enzymes have been pinpointed as affecting cell survival and growth in tissues ranging from muscle to retina. Specification of cell types are also influenced by sphingolipid regulatory pathways, as genetic interactions of glycosphingolipid biosynthetic enzymes with many well-known signaling receptors such as Notch and epidermal growth factor receptor reveal. Furthermore, studies in flies are now uncovering unexpected roles of sphingolipids in controlling lipid storage and response to nutrient availability. The sophisticated genetics of Drosophila is particularly well suited to uncover the roles of sphingolipid regulatory enzymes in development and metabolism, especially in light of conserved pathways that are present in both flies and mammals. The challenges that remain in the field of sphingolipid biology in Drosophila are to combine traditional developmental genetics with more analytical biochemical and biophysical methods, to quantify and localize the responses of these lipids to genetic and metabolic perturbations.
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Affiliation(s)
- Rachel Kraut
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
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Abstract
Synaptic vesicles have a high sterol content, but the importance of vesicular sterols during vesicle recycling is unclear. We used the Drosophila temperature-sensitive dynamin mutant, shibire-ts1, to block endocytosis of recycling synaptic vesicles and to trap them reversibly at the plasma membrane where they were accessible to sterol extraction. Depletion of sterols from trapped vesicles prevented recovery of synaptic transmission after removal of the endocytic block. Measurement of vesicle recycling with synaptopHluorin, FM1-43, and FM4-64 demonstrated impaired membrane retrieval after vesicular sterol depletion. When plasma membrane sterols were extracted before vesicle trapping, no vesicle recycling defects were observed. Ultrastructural analysis indicated accumulation of endosomes and a defect in the formation of synaptic vesicles in synaptic terminals subjected to vesicular sterol depletion. Our results demonstrate the importance of a high vesicular sterol concentration for endocytosis and suggest that vesicular and membrane sterol pools do not readily intermingle during vesicle recycling.
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The fusion of synaptic vesicle membranes studied by lipid mixing: the R18 fluorescence assay validity. Chem Phys Lipids 2010; 163:778-86. [DOI: 10.1016/j.chemphyslip.2010.09.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 09/03/2010] [Accepted: 09/07/2010] [Indexed: 12/27/2022]
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Diverse Presynaptic Mechanisms Underlying Methyl-β-Cyclodextrin-Mediated Changes in Glutamate Transport. Cell Mol Neurobiol 2010; 30:1013-23. [DOI: 10.1007/s10571-010-9532-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2009] [Accepted: 05/13/2010] [Indexed: 02/05/2023]
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Masood MA, Yuan C, Acharya JK, Veenstra TD, Blonder J. Quantitation of ceramide phosphorylethanolamines containing saturated and unsaturated sphingoid base cores. Anal Biochem 2010; 400:259-69. [PMID: 20122889 PMCID: PMC3020903 DOI: 10.1016/j.ab.2010.01.033] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Accepted: 01/27/2010] [Indexed: 01/19/2023]
Abstract
Sphingomyelin (SM) and ceramide-phosphoethanolamines (cer-PEs) are related lipids present in mammals and insects, respectively. Owing to the critical roles that cer-PEs play in eukaryotic cellular function, there is a need to develop methods that provide accurate quantitation of these compounds. Results obtained in this study demonstrate that Drosophila contains cer-PEs with unsaturated sphingoid base cores as well as low levels of cer-PEs that possess saturated sphingoid base cores. Specifically, the method developed in this study enabled the quantitation of picogram amounts of cer-PE containing both unsaturated d14:1(Delta4) and d16:1(Delta4) and saturated d14:0 sphingoid base cores. Using this method, cer-PE compounds with both saturated and unsaturated sphingoid base cores were initially identified by neutral loss scanning, followed by quantitation using selected reaction monitoring (SRM) scans. The SRM scans measured a product ion originating from the sphingoid base backbone, rather than from the head group, increasing the specificity and sensitivity of the quantitation measurement.
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Affiliation(s)
- M Athar Masood
- Laboratory of Proteomics and Analytical Technologies, Advanced Technology Program, SAIC-Frederick, NCI-Frederick, Frederick, MD 21702, USA.
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Khanna MR, Stanley BA, Thomas GH. Towards a membrane proteome in Drosophila: a method for the isolation of plasma membrane. BMC Genomics 2010; 11:302. [PMID: 20462449 PMCID: PMC2876126 DOI: 10.1186/1471-2164-11-302] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Accepted: 05/12/2010] [Indexed: 12/27/2022] Open
Abstract
Background The plasma membrane (PM) is a compartment of significant interest because cell surface proteins influence the way in which a cell interacts with its neighbours and its extracellular environment. However, PM is hard to isolate because of its low abundance. Aqueous two-phase affinity purification (2PAP), based on PEG/Dextran two-phase fractionation and lectin affinity for PM-derived microsomes, is an emerging method for the isolation of high purity plasma membranes from several vertebrate sources. In contrast, PM isolation techniques in important invertebrate genetic model systems, such as Drosophila melanogaster, have relied upon enrichment by density gradient centrifugation. To facilitate genetic investigation of activities contributing to the content of the PM sub-proteome, we sought to adapt 2PAP to this invertebrate model to provide a robust PM isolation technique for Drosophila. Results We show that 2PAP alone does not completely remove contaminating endoplasmic reticulum and mitochondrial membrane. However, a novel combination of density gradient centrifugation plus 2PAP results in a robust PM preparation. To demonstrate the utility of this technique we isolated PM from fly heads and successfully identified 432 proteins using MudPIT, of which 37% are integral membrane proteins from all compartments. Of the 432 proteins, 22% have been previously assigned to the PM compartment, and a further 34% are currently unassigned to any compartment and represent candidates for assignment to the PM. The remainder have previous assignments to other compartments. Conclusion A combination of density gradient centrifugation and 2PAP results in a robust, high purity PM preparation from Drosophila, something neither technique can achieve on its own. This novel preparation should lay the groundwork for the proteomic investigation of the PM in different genetic backgrounds in Drosophila. Our results also identify two key steps in this procedure: The optimization of membrane partitioning in the PEG/Dextran mixture, and careful choice of the correct lectin for the affinity purification step in light of variations in bulk membrane lipid composition and glycosylation patterns respectively. This points the way for further adaptations into other systems.
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Affiliation(s)
- Mansi R Khanna
- Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA
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Cholesterol Depletion from the Plasma Membrane Impairs Proton and Glutamate Storage in Synaptic Vesicles of Nerve Terminals. J Mol Neurosci 2010; 41:358-67. [DOI: 10.1007/s12031-010-9351-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2009] [Accepted: 03/12/2010] [Indexed: 12/14/2022]
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Borisova T, Krisanova N, Sivko R, Borysov A. Cholesterol depletion attenuates tonic release but increases the ambient level of glutamate in rat brain synaptosomes. Neurochem Int 2010; 56:466-78. [DOI: 10.1016/j.neuint.2009.12.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 12/07/2009] [Accepted: 12/11/2009] [Indexed: 10/20/2022]
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Ernst AM, Contreras FX, Brügger B, Wieland F. Determinants of specificity at the protein-lipid interface in membranes. FEBS Lett 2010; 584:1713-20. [PMID: 20085759 DOI: 10.1016/j.febslet.2009.12.060] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 12/22/2009] [Accepted: 12/22/2009] [Indexed: 02/06/2023]
Abstract
The complexity of pro- and eukaryotic lipidomes is increasingly appreciated mainly owing to the advance of mass spectrometric methods. Biophysical approaches have revealed that the large number of lipid classes and molecular species detected have implications for the self-organizing potential of biological membranes, resulting in the formation of lateral heterogeneous phases. How membrane proteins are able to adapt specifically to their surrounding heterogeneous matrix, and whether this environment affects protein targeting and function, is therefore a matter of particular interest. Here, we review specific protein-lipid interactions, focusing on the molecular mechanisms that determine specificity at the protein-lipid interface, and on membrane proteins that require lipids as cofactors for their architecture and function.
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Affiliation(s)
- Andreas M Ernst
- Heidelberg University, Biochemistry Center, Heidelberg, Germany. \
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Paila YD, Chattopadhyay A. Membrane cholesterol in the function and organization of G-protein coupled receptors. Subcell Biochem 2010; 51:439-66. [PMID: 20213554 DOI: 10.1007/978-90-481-8622-8_16] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cholesterol is an essential component of higher eukaryotic membranes and plays a crucial role in membrane organization, dynamics and function. The G-protein coupled receptors (GPCRs) are the largest class of molecules involved in signal transduction across membranes, and represent major targets in the development of novel drug candidates in all clinical areas. Membrane cholesterol has been reported to have a modulatory role in the function of a number of GPCRs. Two possible mechanisms have been previously suggested by which membrane cholesterol could influence the structure and function of GPCRs (i) through a direct/specific interaction with GPCRs, or (ii) through an indirect way by altering membrane physical properties in which the receptor is embedded, or due to a combination of both. Recently reported crystal structures of GPCRs have shown structural evidence of cholesterol binding sites. Against this backdrop, we recently proposed a novel mechanism by which membrane cholesterol could affect structure and function of GPCRs. According to our hypothesis, cholesterol binding sites in GPCRs could represent 'nonannular' binding sites. Interestingly, previous work from our laboratory has demonstrated that membrane cholesterol is required for the function of the serotonin(1A) receptor (a representative GPCR), which could be due to specific interaction of the receptor with cholesterol. Based on these results, we envisage that there could be specific/nonannular cholesterol binding site(s) in the serotonin(1A) receptor. We have analyzed putative cholesterol binding sites from protein databases in the serotonin(1A) receptor. Our analysis shows that cholesterol binding sites are inherent characteristic features of serotonin(1A) receptors and are conserved through natural evolution. Progress in deciphering molecular details of the GPCR-cholesterol interaction in the membrane would lead to better insight into our overall understanding of GPCR function in health and disease, thereby enhancing our ability to design better therapeutic strategies to combat diseases related to malfunctioning of GPCRs.
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Affiliation(s)
- Yamuna Devi Paila
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Hyderabad, 500 007, India
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Abstract
Cholesterol is a major constituent of the plasma membrane in eukaryotic cells. It regulates the physical state of the phospholipid bilayer and is crucially involved in the formation of membrane microdomains. Cholesterol also affects the activity of several membrane proteins, and is the precursor for steroid hormones and bile acids. Here, methods are described that are used to explore the binding and/or interaction of proteins to cholesterol. For this purpose, a variety of cholesterol probes bearing radio-, spin-, photoaffinity- or fluorescent labels are currently available. Examples of proven cholesterol binding molecules are polyene compounds, cholesterol-dependent cytolysins, enzymes accepting cholesterol as substrate, and proteins with cholesterol binding motifs. Main topics of this report are the localization of candidate membrane proteins in cholesterol-rich microdomains, the issue of specificity of cholesterol- protein interactions, and applications of the various cholesterol probes for these studies.
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Affiliation(s)
- Gerald Gimpl
- Institut für Biochemie, Johannes Gutenberg-Universität, Johann-Joachim-Becherweg 30, Mainz, Germany.
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Abstract
Eukaryotic membrane proteins are often difficult to obtain in sufficient amounts for structural studies using classical cell culture overexpression systems. This could be due to incomplete protein maturation and insufficient trafficking to the plasma membrane or to a cytotoxic effect of the recombinant membrane protein changing the overall metabolism. The method presented here takes advantage of the membrane stacks in the retina, where rhodopsin resides. The idea is to direct G protein-coupled receptors (GPCRs) and transporters to these membrane stacks and to express the target proteins in the retina of transgenic Drosophila melanogaster. Drosophila was chosen since fly genetics are well established and rather easily accessible. Metabotropic glutamate receptor mGluRa from Drosophila was among the first examples for GPCRs expressed in this system. It showed high expression yield, functionality and high homogeneity. When the same protein was expressed in Sf9 cells, however, contamination by immature protein was a problem. Encouraged by this success, the fly system is now successfully used for a larger variety of membrane proteins, including mammalian GPCRs and transporters.
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Abstract
Up to now less than a handful of viral cholesterol-binding proteins have been characterized, in HIV, influenza virus and Semliki Forest virus. These are proteins with roles in virus entry or morphogenesis. In the case of the HIV fusion protein gp41 cholesterol binding is attributed to a cholesterol recognition consensus (CRAC) motif in a flexible domain of the ectodomain preceding the trans-membrane segment. This specific CRAC sequence mediates gp41 binding to a cholesterol affinity column. Mutations in this motif arrest virus fusion at the hemifusion stage and modify the ability of the isolated CRAC peptide to induce segregation of cholesterol in artificial membranes.Influenza A virus M2 protein co-purifies with cholesterol. Its proton translocation activity, responsible for virus uncoating, is not cholesterol-dependent, and the transmembrane channel appears too short for integral raft insertion. Cholesterol binding may be mediated by CRAC motifs in the flexible post-TM domain, which harbours three determinants of binding to membrane rafts. Mutation of the CRAC motif of the WSN strain attenuates virulence for mice. Its affinity to the raft-non-raft interface is predicted to target M2 protein to the periphery of lipid raft microdomains, the sites of virus assembly. Its influence on the morphology of budding virus implicates M2 as factor in virus fission at the raft boundary. Moreover, M2 is an essential factor in sorting the segmented genome into virus particles, indicating that M2 also has a role in priming the outgrowth of virus buds.SFV E1 protein is the first viral type-II fusion protein demonstrated to directly bind cholesterol when the fusion peptide loop locks into the target membrane. Cholesterol binding is modulated by another, proximal loop, which is also important during virus budding and as a host range determinant, as shown by mutational studies.
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Affiliation(s)
- Cornelia Schroeder
- Max Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, D-01307, Dresden, Germany.
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Haberkant P, van Meer G. Protein-lipid interactions: paparazzi hunting for snap-shots. Biol Chem 2009; 390:795-803. [PMID: 19426134 DOI: 10.1515/bc.2009.074] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Photoactivatable groups meeting the criterion of minimal perturbance allow the investigation of interactions in biological samples. Here, we review the application of photoactivatable groups in lipids enabling the study of protein-lipid interactions in (biological) membranes. The chemistry of various photoactivatable groups is summarized and the specificity of the interactions detected is discussed. The recent introduction of 'click chemistry' in photocrosslinking of membrane proteins by photo-activatable lipids opens new possibilities for the analysis of crosslinked products and will help to close the gap between proteomics and lipidomics.
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Affiliation(s)
- Per Haberkant
- Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, Utrecht University, NL-3584 CH Utrecht, The Netherlands.
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Wang X, Rao RP, Kosakowska-Cholody T, Masood MA, Southon E, Zhang H, Berthet C, Nagashim K, Veenstra TK, Tessarollo L, Acharya U, Acharya JK. Mitochondrial degeneration and not apoptosis is the primary cause of embryonic lethality in ceramide transfer protein mutant mice. ACTA ACUST UNITED AC 2009; 184:143-58. [PMID: 19139267 PMCID: PMC2615084 DOI: 10.1083/jcb.200807176] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Ceramide transfer protein (CERT) functions in the transfer of ceramide from the endoplasmic reticulum (ER) to the Golgi. In this study, we show that CERT is an essential gene for mouse development and embryonic survival and, quite strikingly, is critical for mitochondrial integrity. CERT mutant embryos accumulate ceramide in the ER but also mislocalize ceramide to the mitochondria, compromising their function. Cells in mutant embryos show abnormal dilation of the ER and degenerating mitochondria. These subcellular changes manifest as heart defects and cause severely compromised cardiac function and embryonic death around embryonic day 11.5. In spite of ceramide accumulation, CERT mutant mice do not die as a result of enhanced apoptosis. Instead, cell proliferation is impaired, and expression levels of cell cycle–associated proteins are altered. Individual cells survive, perhaps because cell survival mechanisms are activated. Thus, global compromise of ER and mitochondrial integrity caused by ceramide accumulation in CERT mutant mice primarily affects organogenesis rather than causing cell death via apoptotic pathways.
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Affiliation(s)
- Xin Wang
- Laboratory of Cell and Developmental Signaling, National Cancer Institute at Frederick, Frederick, MD 21702, USA
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Mackiewicz M, Zimmerman JE, Shockley KR, Churchill GA, Pack AI. What are microarrays teaching us about sleep? Trends Mol Med 2009; 15:79-87. [PMID: 19162550 DOI: 10.1016/j.molmed.2008.12.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Revised: 12/09/2008] [Accepted: 12/09/2008] [Indexed: 01/10/2023]
Abstract
Many fundamental questions about sleep remain unanswered. The presence of sleep across phyla suggests that it must serve a basic cellular and/or molecular function. Microarray studies, performed in several model systems, have identified classes of genes that are sleep-state regulated. This has led to the following concepts: first, a function of sleep is to maintain synaptic homeostasis; second, sleep is a stage of macromolecule biosynthesis; third, extending wakefulness leads to downregulation of several important metabolic pathways; and, fourth, extending wakefulness leads to endoplasmic reticulum stress. In human studies, microarrays are being applied to the identification of biomarkers for sleepiness and for the common debilitating condition of obstructive sleep apnea.
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