1
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Xu X, Wu G. Human C1orf27 protein interacts with α 2A-adrenergic receptor and regulates its anterograde transport. J Biol Chem 2022; 298:102021. [PMID: 35551911 PMCID: PMC9168726 DOI: 10.1016/j.jbc.2022.102021] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 05/02/2022] [Accepted: 05/04/2022] [Indexed: 11/25/2022] Open
Abstract
The molecular mechanisms underlying the anterograde surface transport of G protein–coupled receptors (GPCRs) after their synthesis in the endoplasmic reticulum (ER) are not well defined. In C. elegans, odorant response abnormal 4 has been implicated in the delivery of olfactory GPCRs to the cilia of chemosensory neurons. However, the function and regulation of its human homolog, C1orf27, in GPCR transport or in general membrane trafficking remain unknown. Here, we demonstrate that siRNA-mediated knockdown of C1orf27 markedly impedes the ER-to-Golgi export kinetics of newly synthesized α2A-adrenergic receptor (α2A-AR), a prototypic GPCR, with the half-time being prolonged by more than 65%, in mammalian cells in retention using the selective hooks assays. Using modified bioluminescence resonance energy transfer assays and ELISAs, we also show that C1orf27 knockdown significantly inhibits the surface transport of α2A-AR. Similarly, C1orf27 knockout by CRISPR-Cas9 markedly suppresses the ER–Golgi-surface transport of α2A-AR. In addition, we demonstrate that C1orf27 depletion attenuates the export of β2-AR and dopamine D2 receptor but not of epidermal growth factor receptor. We further show that C1orf27 physically associates with α2A-AR, specifically via its third intracellular loop and C terminus. Taken together, these data demonstrate an important role of C1orf27 in the trafficking of nascent GPCRs from the ER to the cell surface through the Golgi and provide novel insights into the regulation of the biosynthesis and anterograde transport of the GPCR family members.
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Affiliation(s)
- Xin Xu
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Guangyu Wu
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA.
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2
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Vasudevan S, Park PSH. Differential Aggregation Properties of Mutant Human and Bovine Rhodopsin. Biochemistry 2020; 60:6-18. [PMID: 33356167 DOI: 10.1021/acs.biochem.0c00733] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rhodopsin is the light receptor required for the function and health of photoreceptor cells. Mutations in rhodopsin can cause misfolding and aggregation of the receptor, which leads to retinal degeneration. Bovine rhodopsin is often used as a model to understand the effect of pathogenic mutations in rhodopsin due to the abundance of structural information on the bovine form of the receptor. It is unclear whether or not the bovine rhodopsin template is adequate in predicting the effect of these mutations occurring in human retinal disease or in predicting the efficacy of therapeutic strategies. To better understand the extent to which bovine rhodopsin can serve as a model, human and bovine P23H rhodopsin mutants expressed heterologously in cells were examined. The aggregation properties and cellular localization of the mutant receptors were determined by Förster resonance energy transfer and confocal microscopy. The potential therapeutic effects of the pharmacological compounds 9-cis retinal and metformin were also examined. Human and bovine P23H rhodopsin mutants exhibited different aggregation properties and responses to the pharmacological compounds tested. These observations would lead to different predictions on the severity of the phenotype and divergent predictions on the benefit of the therapeutic compounds tested. The bovine rhodopsin template does not appear to adequately model the effects of the P23H mutation in the human form of the receptor.
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Affiliation(s)
- Sreelakshmi Vasudevan
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio 44106, United States
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3
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Krebs MP, Collin GB, Hicks WL, Yu M, Charette JR, Shi LY, Wang J, Naggert JK, Peachey NS, Nishina PM. Mouse models of human ocular disease for translational research. PLoS One 2017; 12:e0183837. [PMID: 28859131 PMCID: PMC5578669 DOI: 10.1371/journal.pone.0183837] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 08/12/2017] [Indexed: 01/24/2023] Open
Abstract
Mouse models provide a valuable tool for exploring pathogenic mechanisms underlying inherited human disease. Here, we describe seven mouse models identified through the Translational Vision Research Models (TVRM) program, each carrying a new allele of a gene previously linked to retinal developmental and/or degenerative disease. The mutations include four alleles of three genes linked to human nonsyndromic ocular diseases (Aipl1tvrm119, Aipl1tvrm127, Rpgrip1tvrm111, RhoTvrm334) and three alleles of genes associated with human syndromic diseases that exhibit ocular phentoypes (Alms1tvrm102, Clcn2nmf289, Fkrptvrm53). Phenotypic characterization of each model is provided in the context of existing literature, in some cases refining our current understanding of specific disease attributes. These murine models, on fixed genetic backgrounds, are available for distribution upon request and may be useful for understanding the function of the gene in the retina, the pathological mechanisms induced by its disruption, and for testing experimental approaches to treat the corresponding human ocular diseases.
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Affiliation(s)
- Mark P. Krebs
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Gayle B. Collin
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Wanda L. Hicks
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Minzhong Yu
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio, United States of America
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, United States of America
| | | | - Lan Ying Shi
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Jieping Wang
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | | | - Neal S. Peachey
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio, United States of America
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, United States of America
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio, United States of America
| | - Patsy M. Nishina
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
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4
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Chen Y, Brooks MJ, Gieser L, Swaroop A, Palczewski K. Transcriptome profiling of NIH3T3 cell lines expressing opsin and the P23H opsin mutant identifies candidate drugs for the treatment of retinitis pigmentosa. Pharmacol Res 2016; 115:1-13. [PMID: 27838510 DOI: 10.1016/j.phrs.2016.10.031] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 10/18/2016] [Accepted: 10/26/2016] [Indexed: 01/01/2023]
Abstract
Mammalian cells are commonly employed in screening assays to identify active compounds that could potentially affect the progression of different human diseases including retinitis pigmentosa (RP), a class of inherited diseases causing retinal degeneration with compromised vision. Using transcriptome analysis, we compared NIH3T3 cells expressing wildtype (WT) rod opsin with a retinal disease-causing single P23H mutation. Surprisingly, heterologous expression of WT opsin in NIH3T3 cells caused more than a 2-fold change in 783 out of 16,888 protein coding transcripts. The perturbed genes encoded extracellular matrix proteins, growth factors, cytoskeleton proteins, glycoproteins and metalloproteases involved in cell adhesion, morphology and migration. A different set of 347 transcripts was either up- or down-regulated when the P23H mutant opsin was expressed suggesting an altered molecular perturbation compared to WT opsin. Transcriptome perturbations elicited by drug candidates aimed at mitigating the effects of the mutant protein revealed that different drugs targeted distinct molecular pathways that resulted in a similar phenotype selected by a cell-based high-throughput screen. Thus, transcriptome profiling can provide essential information about the therapeutic potential of a candidate drug to restore normal gene expression in pathological conditions.
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Affiliation(s)
- Yuanyuan Chen
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, United States
| | - Matthew J Brooks
- Neurobiology-Neurodegeneration & Repair Laboratory (N-NRL), National Eye Institute (NEI), National Institutes of Health (NIH), Bethesda, MD 20892, United States
| | - Linn Gieser
- Neurobiology-Neurodegeneration & Repair Laboratory (N-NRL), National Eye Institute (NEI), National Institutes of Health (NIH), Bethesda, MD 20892, United States
| | - Anand Swaroop
- Neurobiology-Neurodegeneration & Repair Laboratory (N-NRL), National Eye Institute (NEI), National Institutes of Health (NIH), Bethesda, MD 20892, United States
| | - Krzysztof Palczewski
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, United States.
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5
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Regulation of GPCR Anterograde Trafficking by Molecular Chaperones and Motifs. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 132:289-305. [PMID: 26055064 DOI: 10.1016/bs.pmbts.2015.02.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
G protein-coupled receptors (GPCRs) make up a superfamily of integral membrane proteins that respond to a wide variety of extracellular stimuli, giving them an important role in cell function and survival. They have also proven to be valuable targets in the fight against various diseases. As such, GPCR signal regulation has received considerable attention over the last few decades. With the amplitude of signaling being determined in large part by receptor density at the plasma membrane, several endogenous mechanisms for modulating GPCR expression at the cell surface have come to light. It has been shown that cell surface expression is determined by both exocytic and endocytic processes. However, the body of knowledge surrounding GPCR trafficking from the endoplasmic reticulum to the plasma membrane, commonly known as anterograde trafficking, has considerable room for growth. We focus here on the current paradigms of anterograde GPCR trafficking. We will discuss the regulatory role of both the general and "nonclassical private" chaperone systems in GPCR trafficking as well as conserved motifs that serve as modulators of GPCR export from the endoplasmic reticulum and Golgi apparatus. Together, these topics summarize some of the known mechanisms by which the cell regulates anterograde GPCR trafficking.
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6
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Bianchini E, Testoni S, Gentile A, Calì T, Ottolini D, Villa A, Brini M, Betto R, Mascarello F, Nissen P, Sandonà D, Sacchetto R. Inhibition of ubiquitin proteasome system rescues the defective sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA1) protein causing Chianina cattle pseudomyotonia. J Biol Chem 2014; 289:33073-82. [PMID: 25288803 DOI: 10.1074/jbc.m114.576157] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
A missense mutation in ATP2A1 gene, encoding sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA1) protein, causes Chianina cattle congenital pseudomyotonia, an exercise-induced impairment of muscle relaxation. Skeletal muscles of affected cattle are characterized by a selective reduction of SERCA1 in sarcoplasmic reticulum membranes. In this study, we provide evidence that the ubiquitin proteasome system is involved in the reduced density of mutated SERCA1. The treatment with MG132, an inhibitor of ubiquitin proteasome system, rescues the expression level and membrane localization of the SERCA1 mutant in a heterologous cellular model. Cells co-transfected with the Ca(2+)-sensitive probe aequorin show that the rescued SERCA1 mutant exhibits the same ability of wild type to maintain Ca(2+) homeostasis within cells. These data have been confirmed by those obtained ex vivo on adult skeletal muscle fibers from a biopsy from a pseudomyotonia-affected subject. Our data show that the mutation generates a protein most likely corrupted in proper folding but not in catalytic activity. Rescue of mutated SERCA1 to sarcoplasmic reticulum membrane can re-establish resting cytosolic Ca(2+) concentration and prevent the appearance of pathological signs of cattle pseudomyotonia.
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Affiliation(s)
| | | | - Arcangelo Gentile
- the Department of Veterinary Medical Sciences, University of Bologna, 40064 Bologna, Italy
| | - Tito Calì
- Biology, University of Padova, 35131 Padova, Italy
| | | | - Antonello Villa
- the Consorzio M.I.A., University of Milano Bicocca, 20900 Monza, Italy
| | - Marisa Brini
- Biology, University of Padova, 35131 Padova, Italy
| | - Romeo Betto
- the Neuroscience Institute, Consiglio Nazionale delle Ricerche Padova, 35131 Padova, Italy, and
| | - Francesco Mascarello
- Comparative Biomedicine and Food Science, University of Padova,35020 Legnaro (Padova), Italy
| | - Poul Nissen
- the Department of Molecular Biology and Genetics, Centre for Membrane Pumps in Cells and Disease, Aarhus University, 8000 Aarhus, Denmark
| | | | - Roberta Sacchetto
- Comparative Biomedicine and Food Science, University of Padova,35020 Legnaro (Padova), Italy,
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7
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Tao YX, Conn PM. Chaperoning G protein-coupled receptors: from cell biology to therapeutics. Endocr Rev 2014; 35:602-47. [PMID: 24661201 PMCID: PMC4105357 DOI: 10.1210/er.2013-1121] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 03/14/2014] [Indexed: 12/13/2022]
Abstract
G protein-coupled receptors (GPCRs) are membrane proteins that traverse the plasma membrane seven times (hence, are also called 7TM receptors). The polytopic structure of GPCRs makes the folding of GPCRs difficult and complex. Indeed, many wild-type GPCRs are not folded optimally, and defects in folding are the most common cause of genetic diseases due to GPCR mutations. Both general and receptor-specific molecular chaperones aid the folding of GPCRs. Chemical chaperones have been shown to be able to correct the misfolding in mutant GPCRs, proving to be important tools for studying the structure-function relationship of GPCRs. However, their potential therapeutic value is very limited. Pharmacological chaperones (pharmacoperones) are potentially important novel therapeutics for treating genetic diseases caused by mutations in GPCR genes that resulted in misfolded mutant proteins. Pharmacoperones also increase cell surface expression of wild-type GPCRs; therefore, they could be used to treat diseases that do not harbor mutations in GPCRs. Recent studies have shown that indeed pharmacoperones work in both experimental animals and patients. High-throughput assays have been developed to identify new pharmacoperones that could be used as therapeutics for a number of endocrine and other genetic diseases.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology, and Pharmacology (Y.-X.T.), College of Veterinary Medicine, Auburn University, Auburn, Alabama 36849-5519; and Departments of Internal Medicine and Cell Biology (P.M.C.), Texas Tech University Health Science Center, Lubbock, Texas 79430-6252
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8
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Chen Y, Jastrzebska B, Cao P, Zhang J, Wang B, Sun W, Yuan Y, Feng Z, Palczewski K. Inherent instability of the retinitis pigmentosa P23H mutant opsin. J Biol Chem 2014; 289:9288-303. [PMID: 24515108 PMCID: PMC3979360 DOI: 10.1074/jbc.m114.551713] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 02/05/2014] [Indexed: 11/06/2022] Open
Abstract
The P23H opsin mutation is the most common cause of autosomal dominant retinitis pigmentosa. Even though the pathobiology of the resulting retinal degeneration has been characterized in several animal models, its complex molecular mechanism is not well understood. Here, we expressed P23H bovine rod opsin in the nervous system of Caenorhabditis elegans. Expression was low due to enhanced protein degradation. The mutant opsin was glycosylated, but the polysaccharide size differed from that of the normal protein. Although P23H opsin aggregated in the nervous system of C. elegans, the pharmacological chaperone 9-cis-retinal stabilized it during biogenesis, producing a variant of rhodopsin called P23H isorhodopsin. In vitro, P23H isorhodopsin folded correctly, formed the appropriate disulfide bond, could be photoactivated but with reduced sensitivity, and underwent Meta II decay at a rate similar to wild type isorhodopsin. In worm neurons, P23H isorhodopsin initiated phototransduction by coupling with the endogenous Gi/o signaling cascade that induced loss of locomotion. Using pharmacological interventions affecting protein synthesis and degradation, we showed that the chromophore could be incorporated either during or after mutant protein translation. However, regeneration of P23H isorhodopsin with chromophore was significantly slower than that of wild type isorhodopsin. This effect, combined with the inherent instability of P23H rhodopsin, could lead to the structural cellular changes and photoreceptor death found in autosomal dominant retinitis pigmentosa. These results also suggest that slow regeneration of P23H rhodopsin could prevent endogenous chromophore-mediated stabilization of rhodopsin in the retina.
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Affiliation(s)
| | | | | | | | - Benlian Wang
- Center for Proteomics and Bioinformatics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965 and
| | - Wenyu Sun
- Polgenix Inc., Cleveland, Ohio 44106
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9
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Zhang N, Kolesnikov AV, Jastrzebska B, Mustafi D, Sawada O, Maeda T, Genoud C, Engel A, Kefalov VJ, Palczewski K. Autosomal recessive retinitis pigmentosa E150K opsin mice exhibit photoreceptor disorganization. J Clin Invest 2012; 123:121-37. [PMID: 23221340 DOI: 10.1172/jci66176] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 10/04/2012] [Indexed: 12/13/2022] Open
Abstract
The pathophysiology of the E150K mutation in the rod opsin gene associated with autosomal recessive retinitis pigmentosa (arRP) has yet to be determined. We generated knock-in mice carrying a single nucleotide change in exon 2 of the rod opsin gene resulting in the E150K mutation. This novel mouse model displayed severe retinal degeneration affecting rhodopsin's stabilization of rod outer segments (ROS). Homozygous E150K (KK) mice exhibited early-onset retinal degeneration, with disorganized ROS structures, autofluorescent deposits in the subretinal space, and aberrant photoreceptor phagocytosis. Heterozygous (EK) mice displayed a delayed-onset milder retinal degeneration. Further, mutant receptors were mislocalized to the inner segments and perinuclear region. Though KK mouse rods displayed markedly decreased phototransduction, biochemical studies of the mutant rhodopsin revealed only minimally affected chromophore binding and G protein activation. Ablation of the chromophore by crossing KK mice with mice lacking the critical visual cycle protein LRAT slowed retinal degeneration, whereas blocking phototransduction by crossing KK mice with GNAT1-deficient mice slightly accelerated this process. This study highlights the importance of proper higher-order organization of rhodopsin in the native tissue and provides information about the signaling properties of this mutant rhodopsin. Additionally, these results suggest that patients heterozygous for the E150K mutation should be periodically reevaluated for delayed-onset retinal degeneration.
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Affiliation(s)
- Ning Zhang
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44160, USA
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10
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Li C, Fan Y, Lan TH, Lambert NA, Wu G. Rab26 modulates the cell surface transport of α2-adrenergic receptors from the Golgi. J Biol Chem 2012; 287:42784-94. [PMID: 23105096 DOI: 10.1074/jbc.m112.410936] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The molecular mechanisms underlying the transport from the Golgi to the cell surface of G protein-coupled receptors remain poorly elucidated. Here we determined the role of Rab26, a Ras-like small GTPase involved in vesicle-mediated secretion, in the cell surface export of α(2)-adrenergic receptors. We found that transient expression of Rab26 mutants and siRNA-mediated depletion of Rab26 significantly attenuated the cell surface numbers of α(2A)-AR and α(2B)-AR, as well as ERK1/2 activation by α(2B)-AR. Furthermore, the receptors were extensively arrested in the Golgi by Rab26 mutants and siRNA. Moreover, Rab26 directly and activation-dependently interacted with α(2B)-AR, specifically the third intracellular loop. These data demonstrate that the small GTPase Rab26 regulates the Golgi to cell surface traffic of α(2)-adrenergic receptors, likely through a physical interaction. These data also provide the first evidence implicating an important function of Rab26 in coordinating plasma membrane protein transport.
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Affiliation(s)
- Chunman Li
- Department of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, Georgia 30912, USA
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Anterograde trafficking of nascent α(2B)-adrenergic receptor: structural basis, roles of small GTPases. CURRENT TOPICS IN MEMBRANES 2012; 67:79-100. [PMID: 21771486 DOI: 10.1016/b978-0-12-384921-2.00004-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
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12
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Abstract
Anterograde trafficking of newly synthesized G protein-coupled -receptors (GPCRs) from the endoplasmic reticulum to the cell surface represents a crucial checkpoint in controlling the amount of the functional receptors at the cell surface and the strength of signaling initiated by the receptors. In contrast to the extensively studied, well-understood endocytic and recycling pathways, the molecular mechanisms underlying the cell-surface targeting of the receptors remain poorly defined. In this chapter, I will discuss current advances in understanding post-Golgi transport of GPCRs by focusing on specific motifs or sequences that may function as sorting signals regulating export from the Golgi and subsequent transport to the plasma membrane of GPCRs.
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13
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Abstract
The visual pigment rhodopsin (rh1) constitutes the first step in the sensory transduction cascade in the rod photoreceptors of the vertebrate eye, forming the basis of vision at low light levels. In most vertebrates, rhodopsin is a single-copy gene whose function in rod photoreceptors is highly conserved. We found evidence for a second rhodopsin-like gene (rh1-2) in the zebrafish genome. This novel gene was not the product of a zebrafish-specific gene duplication event and contains a number of unique amino acid substitutions. Despite these differences, expression of rh1-2 in vitro yielded a protein that not only bound chromophore, producing an absorption spectrum in the visible range (λmax ≈ 500 nm), but also activated in response to light. Unlike rh1, rh1-2 is not expressed during the first 4 days of embryonic development; it is expressed in the retina of adult fish but not the brain or muscle. Similar rh1-2 sequences were found in two other Danio species, as well as a more distantly related cyprinid, Epalzeorhynchos bicolor. While sequences were only identified in cyprinid fish, phylogenetic analyses suggest an older origin for this gene family. Our study suggests that rh1-2 is a functional opsin gene that is expressed in the retina later in development. The discovery of a new previously uncharacterized opsin gene in zebrafish retina is surprising given its status as a model system for studies of vertebrate vision and visual development.
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Pulagam LP, Palczewski K. Electrostatic compensation restores trafficking of the autosomal recessive retinitis pigmentosa E150K opsin mutant to the plasma membrane. J Biol Chem 2010; 285:29446-56. [PMID: 20628051 DOI: 10.1074/jbc.m110.151407] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rhodopsin is the rod photoreceptor G protein-coupled receptor responsible for capturing light. Mutations in the gene encoding this protein can lead to a blinding disease called retinitis pigmentosa, which is inherited frequently in an autosomal dominant manner. The E150K opsin mutant associated with rarely occurring autosomal recessive retinitis pigmentosa localizes to trans-Golgi network membranes rather than to plasma membranes of rod photoreceptor cells. We investigated the molecular mechanisms underlying opsin retention in the Golgi apparatus. Electrostatic calculations reveal that the E150K mutant features an overall accumulation of positive charges between helices H-IV and H-II. Human E150K and several other closely related opsin mutants were then expressed in HEK-293 cells. Spectral characteristics and functional biochemistry of each mutant were analyzed after reconstitution with the cis-retinoid chromophore. UV-visible spectra and rhodopsin/transducin activation assays revealed only minor differences between the purified wild type control and rhodopsin mutants. However, partial restoration of the surface electrostatic charge in the compensatory R69E/E150K double mutant rescues the plasma membrane localization of opsin. These findings emphasize the fundamental importance of electrostatic interactions for appropriate membrane trafficking of opsin and advance our understanding of the pathophysiology of autosomal recessive retinitis pigmentosa due to the E150K mutation.
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Affiliation(s)
- Lakshmi Padmavathi Pulagam
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
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15
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Dong C, Yang L, Zhang X, Gu H, Lam ML, Claycomb WC, Xia H, Wu G. Rab8 interacts with distinct motifs in alpha2B- and beta2-adrenergic receptors and differentially modulates their transport. J Biol Chem 2010; 285:20369-80. [PMID: 20424170 DOI: 10.1074/jbc.m109.081521] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The molecular mechanism underlying the post-Golgi transport of G protein-coupled receptors (GPCRs) remains poorly understood. Here we determine the role of Rab8 GTPase, which modulates vesicular protein transport between the trans-Golgi network (TGN) and the plasma membrane, in the cell surface targeting of alpha(2B)- and beta(2)-adrenergic receptors (AR). Transient expression of GDP- and GTP-bound Rab8 mutants and short hairpin RNA-mediated knockdown of Rab8 more potently inhibited the cell surface expression of alpha(2B)-AR than beta(2)-AR. The GDP-bound Rab8(T22N) mutant attenuated ERK1/2 activation by alpha(2B)-AR, but not beta(2)-AR, and arrested alpha(2B)-AR in the TGN compartment. Co-immunoprecipitation revealed that both alpha(2B)-AR and beta(2)-AR physically interacted with Rab8 and glutathione S-transferase fusion protein pulldown assays demonstrated that Rab8 interacted with the C termini of both receptors. Interestingly, mutation of the highly conserved membrane-proximal C terminus dileucine motif selectively blocked beta(2)-AR interaction with Rab8, whereas mutation of residues Val(431)-Phe(432)-Asn(433)-Gln(434), Pro(447)-Trp(448), Gln(450)-Thr(451), and Trp(453) in the C terminus impaired alpha(2B)-AR interaction with Rab8. Furthermore, transport inhibition by Rab8(T22N) of a chimeric beta(2)-AR carrying the alpha(2B)-AR C terminus was similar to alpha(2B)-AR. These data provide strong evidence indicating that Rab8 GTPase interacts with distinct motifs in the C termini of alpha(2B)-AR and beta(2)-AR and differentially modulates their traffic from the TGN to the cell surface.
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Affiliation(s)
- Chunmin Dong
- Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA
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16
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Azam M, Khan MI, Gal A, Hussain A, Shah STA, Khan MS, Sadeque A, Bokhari H, Collin RW, Orth U, van Genderen MM, den Hollander A, Cremers FPM, Qamar R. A homozygous p.Glu150Lys mutation in the opsin gene of two Pakistani families with autosomal recessive retinitis pigmentosa. Mol Vis 2009; 15:2526-34. [PMID: 19960070 PMCID: PMC2787306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Accepted: 11/25/2009] [Indexed: 10/25/2022] Open
Abstract
PURPOSE To identify the gene mutations responsible for autosomal recessive retinitis pigmentosa (arRP) in Pakistani families. METHODS A cohort of consanguineous families with typical RP phenotype in patients was screened by homozygosity mapping using microsatellite markers that mapped close to 21 known arRP genes and five arRP loci. Mutation analysis was performed by direct sequencing of the candidate gene. RESULTS In two families, RP21 and RP53, homozygosity mapping suggested RHO, the gene encoding rhodopsin, as a candidate disease gene on chromosome 3q21. In six out of seven affected members from the two families, direct sequencing of RHO identified a homozygous c.448G>A mutation resulting in the p.Glu150Lys amino acid change. This variant was first reported in PMK197, an Indian arRP family. Single nucleotide polymorphism analysis in RP21, RP53, and PMK197 showed a common disease-associated haplotype in the three families. CONCLUSIONS In two consanguineous Pakistani families with typical arRP phenotype in the patients, we identified a disease-causing mutation (p.Glu150Lys) in the RHO gene. Single nucleotide polymorphism analysis suggests that the previously reported Indian family (PMK197) and the two Pakistani families studied here share the RHO p.Glu150Lys mutation due to a common ancestry.
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Affiliation(s)
- Maleeha Azam
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan,Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Muhammad Imran Khan
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | - Andreas Gal
- Department of Human Genetics, University Medical Centre Hamburg Eppendorf, Germany
| | - Alamdar Hussain
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | - Syed Tahir Abbas Shah
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | - Muhammad Shakil Khan
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan,Shifa College of Medicine, Islamabad, Pakistan
| | - Ahmed Sadeque
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | - Habib Bokhari
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | - Rob W.J. Collin
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands,Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Ulrike Orth
- Department of Human Genetics, University Medical Centre Hamburg Eppendorf, Germany
| | | | - A.I. den Hollander
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands,Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Frans P. M. Cremers
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan,Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands,Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Raheel Qamar
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan,Shifa College of Medicine, Islamabad, Pakistan
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Krebs MP, Holden DC, Joshi P, Clark CL, Lee AH, Kaushal S. Molecular mechanisms of rhodopsin retinitis pigmentosa and the efficacy of pharmacological rescue. J Mol Biol 2009; 395:1063-78. [PMID: 19913029 DOI: 10.1016/j.jmb.2009.11.015] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 11/05/2009] [Accepted: 11/05/2009] [Indexed: 11/24/2022]
Abstract
Variants of rhodopsin, a complex of 11-cis retinal and opsin, cause retinitis pigmentosa (RP), a degenerative disease of the retina. Trafficking defects due to rhodopsin misfolding have been proposed as the most likely basis of the disease, but other potentially overlapping mechanisms may also apply. Pharmacological therapies for RP must target the major disease mechanism and contend with overlap, if it occurs. To this end, we have explored the molecular basis of rhodopsin RP in the context of pharmacological rescue with 11-cis retinal. Stable inducible cell lines were constructed to express wild-type opsin; the pathogenic variants T4R, T17M, P23A, P23H, P23L, and C110Y; or the nonpathogenic variants F220L and A299S. Pharmacological rescue was measured as the fold increase in rhodopsin or opsin levels upon addition of 11-cis retinal during opsin expression. Only Pro23 and T17M variants were rescued significantly. C110Y opsin was produced at low levels and did not yield rhodopsin, whereas the T4R, F220L, and A299S proteins reached near-wild-type levels and changed little with 11-cis retinal. All of the mutant rhodopsins exhibited misfolding, which increased over a broad range in the order F220L, A299S, T4R, T17M, P23A, P23H, P23L, as determined by decreased thermal stability in the dark and increased hydroxylamine sensitivity. Pharmacological rescue increased as misfolding decreased, but was limited for the least misfolded variants. Significantly, pathogenic variants also showed abnormal photobleaching behavior, including an increased ratio of metarhodopsin-I-like species to metarhodopsin-II-like species and aberrant photoproduct accumulation with prolonged illumination. These results, combined with an analysis of published biochemical and clinical studies, suggest that many rhodopsin variants cause disease by affecting both biosynthesis and photoactivity. We conclude that pharmacological rescue is promising as a broadly effective therapy for rhodopsin RP, particularly if implemented in a way that minimizes the photoactivity of the mutant proteins.
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Affiliation(s)
- Mark P Krebs
- Department of Ophthalmology and the Charlie Mack Overstreet Laboratories for Retinal Diseases, College of Medicine, University of Florida, Gainesville, FL 32610, USA
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Gamundi MJ, Hernan I, Muntanyola M, Maseras M, López-Romero P, Álvarez R, Dopazo A, Borrego S, Carballo M. Transcriptional expression ofcis-acting andtrans-acting splicing mutations cause autosomal dominant retinitis pigmentosa. Hum Mutat 2008; 29:869-78. [DOI: 10.1002/humu.20747] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Dong C, Filipeanu CM, Duvernay MT, Wu G. Regulation of G protein-coupled receptor export trafficking. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1768:853-70. [PMID: 17074298 PMCID: PMC1885203 DOI: 10.1016/j.bbamem.2006.09.008] [Citation(s) in RCA: 204] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Revised: 09/14/2006] [Accepted: 09/18/2006] [Indexed: 12/26/2022]
Abstract
G protein-coupled receptors (GPCRs) constitute a superfamily of cell-surface receptors which share a common topology of seven transmembrane domains and modulate a variety of cell functions through coupling to heterotrimeric G proteins by responding to a vast array of stimuli. The magnitude of cellular response elicited by a given signal is dictated by the level of GPCR expression at the plasma membrane, which is the balance of elaborately regulated endocytic and exocytic trafficking. This review will cover recent advances in understanding the molecular mechanism underlying anterograde transport of the newly synthesized GPCRs from the endoplasmic reticulum (ER) through the Golgi to the plasma membrane. We will focus on recently identified motifs involved in GPCR exit from the ER and the Golgi, GPCR folding in the ER and the rescue of misfolded receptors from within, GPCR-interacting proteins that modulate receptor cell-surface targeting, pathways that mediate GPCR traffic, and the functional role of export in controlling GPCR signaling.
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Affiliation(s)
| | | | | | - Guangyu Wu
- * Corresponding author. Tel: +1 504 568 2236; Fax: +1 504 568 2361. E-mail address: (G. Wu)
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Hagemann IS, Nikiforovich GV, Baranski TJ. Comparison of the retinitis pigmentosa mutations in rhodopsin with a functional map of the C5a receptor. Vision Res 2006; 46:4519-31. [PMID: 16962629 DOI: 10.1016/j.visres.2006.07.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2006] [Revised: 07/14/2006] [Accepted: 07/19/2006] [Indexed: 10/24/2022]
Abstract
We compare the known retinitis pigmentosa (RP) mutations in rhodopsin with mutational data obtained for the complement factor 5a receptor (C5aR), a member of the rhodopsin-like family of G protein-coupled receptors (GPCRs). We have performed genetic analyses that define residues that are required for C5aR folding and function. The cognate residues in rhodopsin are not preferentially mutated in RP, suggesting that the predominant molecular defect in RP involves more than simple misfolding or inactivation. Energy calculations are performed to elucidate the structural effects of the RP mutations. Many of these mutations specifically disrupt the environment of the retinal prosthetic group of rhodopsin, and these do not correspond to essential residues in C5aR. This may be because a retinal group is present in rhodopsin but not in C5aR. Another subset of RP mutations is more generally important for receptor structure, and these mutations correlate with essential residues of C5aR.
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Affiliation(s)
- Ian S Hagemann
- Department of Medicine, Washington University in St. Louis, Campus Box 8127, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
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