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Losada JC, Triana H, Vanegas E, Caro A, Rodríguez-López A, Espejo-Mojica AJ, Alméciga-Diaz CJ. Identification of Orthosteric and Allosteric Pharmacological Chaperones for Mucopolysaccharidosis Type IIIB. Chembiochem 2024; 25:e202400081. [PMID: 38830828 DOI: 10.1002/cbic.202400081] [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: 01/29/2024] [Revised: 05/28/2024] [Accepted: 06/03/2024] [Indexed: 06/05/2024]
Abstract
Mucopolysaccharidosis type IIIB (MPS IIIB) is an autosomal inherited disease caused by mutations in gene encoding the lysosomal enzyme N-acetyl-alpha-glucosaminidase (NAGLU). These mutations result in reduced NAGLU activity, preventing it from catalyzing the hydrolysis of the glycosaminoglycan heparan sulfate (HS). There are currently no approved treatments for MPS IIIB. A novel approach in the treatment of lysosomal storage diseases is the use of pharmacological chaperones (PC). In this study, we used a drug repurposing approach to identify and characterize novel potential PCs for NAGLU enzyme. We modeled the interaction of natural and artificial substrates within the active cavity of NAGLU (orthosteric site) and predicted potential allosteric sites. We performed a virtual screening for both the orthosteric and the predicted allosteric site against a curated database of human tested molecules. Considering the binding affinity and predicted blood-brain barrier permeability and gastrointestinal absorption, we selected atovaquone and piperaquine as orthosteric and allosteric PCs. The PCs were evaluated by their capacity to bind NAGLU and the ability to restore the enzymatic activity in human MPS IIIB fibroblasts These results represent novel PCs described for MPS IIIB and demonstrate the potential to develop novel therapeutic alternatives for this and other protein deficiency diseases.
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Affiliation(s)
- Juan Camilo Losada
- Institute for the Study of Inborn Errors of Metabolism, Faculty of Science, Pontificia Universidad Javeriana, Cra. 7 No. 43-82 Building 54, Lab 305 A., Bogotá D.C., 110231, Colombia
| | - Heidy Triana
- Institute for the Study of Inborn Errors of Metabolism, Faculty of Science, Pontificia Universidad Javeriana, Cra. 7 No. 43-82 Building 54, Lab 305 A., Bogotá D.C., 110231, Colombia
| | - Egdda Vanegas
- Chemistry Department, Faculty of Science, Pontificia Universidad Javeriana, Cra. 7 No. 43-82 Building 52, Room 110 305 A., Bogotá D.C., 110231, Colombia
| | - Angela Caro
- Chemistry Department, Faculty of Science, Pontificia Universidad Javeriana, Cra. 7 No. 43-82 Building 52, Room 110 305 A., Bogotá D.C., 110231, Colombia
| | - Alexander Rodríguez-López
- Institute for the Study of Inborn Errors of Metabolism, Faculty of Science, Pontificia Universidad Javeriana, Cra. 7 No. 43-82 Building 54, Lab 305 A., Bogotá D.C., 110231, Colombia
- Dogma Biotech, Cr 13 A No. 127 A-84, Bogotá D.C., 110111, Colombia
| | - Angela Johana Espejo-Mojica
- Institute for the Study of Inborn Errors of Metabolism, Faculty of Science, Pontificia Universidad Javeriana, Cra. 7 No. 43-82 Building 54, Lab 305 A., Bogotá D.C., 110231, Colombia
| | - Carlos Javier Alméciga-Diaz
- Institute for the Study of Inborn Errors of Metabolism, Faculty of Science, Pontificia Universidad Javeriana, Cra. 7 No. 43-82 Building 54, Lab 305 A., Bogotá D.C., 110231, Colombia
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Radomsky T, Anderson RC, Millar RP, Newton CL. Restoring function to inactivating G protein-coupled receptor variants in the hypothalamic-pituitary-gonadal axis 1. J Neuroendocrinol 2024:e13418. [PMID: 38852954 DOI: 10.1111/jne.13418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 03/30/2024] [Accepted: 05/15/2024] [Indexed: 06/11/2024]
Abstract
G protein-coupled receptors (GPCRs) are central to the functioning of the hypothalamic-pituitary-gonadal axis (HPG axis) and include the rhodopsin-like GPCR family members, neurokinin 3 receptor, kappa-opioid receptor, kisspeptin 1 receptor, gonadotropin-releasing hormone receptor, and the gonadotropin receptors, luteinizing hormone/choriogonadotropin receptor and follicle-stimulating hormone receptor. Unsurprisingly, inactivating variants of these receptors have been implicated in a spectrum of reproductive phenotypes, including failure to undergo puberty, and infertility. Clinical induction of puberty in patients harbouring such variants is possible, but restoration of fertility is not always a realisable outcome, particularly for those patients suffering from primary hypogonadism. Thus, novel pharmaceuticals and/or a fundamental change in approach to treating these patients are required. The increasing wealth of data describing the effects of coding-region genetic variants on GPCR function has highlighted that the majority appear to be dysfunctional as a result of misfolding of the encoded receptor protein, which, in turn, results in impaired receptor trafficking through the secretory pathway to the cell surface. As such, these intracellularly retained receptors may be amenable to 'rescue' using a pharmacological chaperone (PC)-based approach. PCs are small, cell permeant molecules hypothesised to interact with misfolded intracellularly retained proteins, stabilising their folding and promoting their trafficking through the secretory pathway. In support of the use of this approach as a viable therapeutic option, it has been observed that many rescued variant GPCRs retain at least a degree of functionality when 'rescued' to the cell surface. In this review, we examine the GPCR PC research landscape, focussing on the rescue of inactivating variant GPCRs with important roles in the HPG axis, and describe what is known regarding the mechanisms by which PCs restore trafficking and function. We also discuss some of the merits and obstacles associated with taking this approach forward into a clinical setting.
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Affiliation(s)
- Tarryn Radomsky
- Centre for Neuroendocrinology, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Ross C Anderson
- Centre for Neuroendocrinology, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Robert P Millar
- Centre for Neuroendocrinology, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Deanery of Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Faculty of Health Sciences, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
- School of Medicine, University of St Andrews, St Andrews, UK
| | - Claire L Newton
- Centre for Neuroendocrinology, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Deanery of Biomedical Sciences, University of Edinburgh, Edinburgh, UK
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Losada Díaz JC, Cepeda del Castillo J, Rodriguez-López EA, Alméciga-Díaz CJ. Advances in the Development of Pharmacological Chaperones for the Mucopolysaccharidoses. Int J Mol Sci 2019; 21:ijms21010232. [PMID: 31905715 PMCID: PMC6981736 DOI: 10.3390/ijms21010232] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 11/21/2019] [Accepted: 11/25/2019] [Indexed: 12/20/2022] Open
Abstract
The mucopolysaccharidoses (MPS) are a group of 11 lysosomal storage diseases (LSDs) produced by mutations in the enzymes involved in the lysosomal catabolism of glycosaminoglycans. Most of the mutations affecting these enzymes may lead to changes in processing, folding, glycosylation, pH stability, protein aggregation, and defective transport to the lysosomes. It this sense, it has been proposed that the use of small molecules, called pharmacological chaperones (PCs), can restore the folding, trafficking, and biological activity of mutated enzymes. PCs have the advantages of wide tissue distribution, potential oral administration, lower production cost, and fewer issues of immunogenicity than enzyme replacement therapy. In this paper, we will review the advances in the identification and characterization of PCs for the MPS. These molecules have been described for MPS II, IVA, and IVB, showing a mutation-dependent enhancement of the mutated enzymes. Although the results show the potential of this strategy, further studies should focus in the development of disease-specific cellular models that allow a proper screening and evaluation of PCs. In addition, in vivo evaluation, both pre-clinical and clinical, should be performed, before they can become a real therapeutic strategy for the treatment of MPS patients.
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Affiliation(s)
- Juan Camilo Losada Díaz
- Institute for the Study of Inborn Errors of Metabolism, Faculty of Science, Pontificia Universidad Javeriana, Bogotá D.C. 110231, Colombia; (J.C.L.D.); (J.C.d.C.); (E.A.R.-L.)
| | - Jacobo Cepeda del Castillo
- Institute for the Study of Inborn Errors of Metabolism, Faculty of Science, Pontificia Universidad Javeriana, Bogotá D.C. 110231, Colombia; (J.C.L.D.); (J.C.d.C.); (E.A.R.-L.)
| | - Edwin Alexander Rodriguez-López
- Institute for the Study of Inborn Errors of Metabolism, Faculty of Science, Pontificia Universidad Javeriana, Bogotá D.C. 110231, Colombia; (J.C.L.D.); (J.C.d.C.); (E.A.R.-L.)
- Chemistry Department, Faculty of Science, Pontificia Universidad Javeriana, Bogotá D.C. 110231, Colombia
| | - Carlos J. Alméciga-Díaz
- Institute for the Study of Inborn Errors of Metabolism, Faculty of Science, Pontificia Universidad Javeriana, Bogotá D.C. 110231, Colombia; (J.C.L.D.); (J.C.d.C.); (E.A.R.-L.)
- Correspondence: ; Tel.: +57-1-3208320 (ext. 4140); Fax: +57-1-3208320 (ext. 4099)
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Marinko J, Huang H, Penn WD, Capra JA, Schlebach JP, Sanders CR. Folding and Misfolding of Human Membrane Proteins in Health and Disease: From Single Molecules to Cellular Proteostasis. Chem Rev 2019; 119:5537-5606. [PMID: 30608666 PMCID: PMC6506414 DOI: 10.1021/acs.chemrev.8b00532] [Citation(s) in RCA: 153] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Indexed: 12/13/2022]
Abstract
Advances over the past 25 years have revealed much about how the structural properties of membranes and associated proteins are linked to the thermodynamics and kinetics of membrane protein (MP) folding. At the same time biochemical progress has outlined how cellular proteostasis networks mediate MP folding and manage misfolding in the cell. When combined with results from genomic sequencing, these studies have established paradigms for how MP folding and misfolding are linked to the molecular etiologies of a variety of diseases. This emerging framework has paved the way for the development of a new class of small molecule "pharmacological chaperones" that bind to and stabilize misfolded MP variants, some of which are now in clinical use. In this review, we comprehensively outline current perspectives on the folding and misfolding of integral MPs as well as the mechanisms of cellular MP quality control. Based on these perspectives, we highlight new opportunities for innovations that bridge our molecular understanding of the energetics of MP folding with the nuanced complexity of biological systems. Given the many linkages between MP misfolding and human disease, we also examine some of the exciting opportunities to leverage these advances to address emerging challenges in the development of therapeutics and precision medicine.
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Affiliation(s)
- Justin
T. Marinko
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Hui Huang
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Wesley D. Penn
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - John A. Capra
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
- Department
of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37245, United States
| | - Jonathan P. Schlebach
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Charles R. Sanders
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
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5
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Tao YX, Conn PM. Pharmacoperones as Novel Therapeutics for Diverse Protein Conformational Diseases. Physiol Rev 2018; 98:697-725. [PMID: 29442594 DOI: 10.1152/physrev.00029.2016] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
After synthesis, proteins are folded into their native conformations aided by molecular chaperones. Dysfunction in folding caused by genetic mutations in numerous genes causes protein conformational diseases. Membrane proteins are more prone to misfolding due to their more intricate folding than soluble proteins. Misfolded proteins are detected by the cellular quality control systems, especially in the endoplasmic reticulum, and proteins may be retained there for eventual degradation by the ubiquitin-proteasome system or through autophagy. Some misfolded proteins aggregate, leading to pathologies in numerous neurological diseases. In vitro, modulating mutant protein folding by altering molecular chaperone expression can ameliorate some misfolding. Some small molecules known as chemical chaperones also correct mutant protein misfolding in vitro and in vivo. However, due to their lack of specificity, their potential as therapeutics is limited. Another class of compounds, known as pharmacological chaperones (pharmacoperones), binds with high specificity to misfolded proteins, either as enzyme substrates or receptor ligands, leading to decreased folding energy barriers and correction of the misfolding. Because many of the misfolded proteins are misrouted but do not have defects in function per se, pharmacoperones have promising potential in advancing to the clinic as therapeutics, since correcting routing may ameliorate the underlying mechanism of disease. This review will comprehensively summarize this exciting area of research, surveying the literature from in vitro studies in cell lines to transgenic animal models and clinical trials in several protein misfolding diseases.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University , Auburn, Alabama ; and Departments of Internal Medicine and Cell Biology, Texas Tech University Health Science Center , Lubbock, Texas
| | - P Michael Conn
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University , Auburn, Alabama ; and Departments of Internal Medicine and Cell Biology, Texas Tech University Health Science Center , Lubbock, Texas
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6
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Chemical validation and optimization of pharmacoperones targeting vasopressin type 2 receptor mutant. Biochem J 2018; 475:2941-2953. [PMID: 30068530 DOI: 10.1042/bcj20180065] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 07/09/2018] [Accepted: 07/31/2018] [Indexed: 11/17/2022]
Abstract
A series of compounds formerly identified by high-throughput screening was studied for their ability to serve as pharmacoperones for the vasopressin type 2 receptor (V2R) mutant L83Q, which is known to cause nephrogenic diabetes insipidus (NDI). Three compounds were particularly effective in rerouting the mutant receptor in a concentration-dependent manner, were neither agonists nor antagonists, and displayed low cellular toxicity. Compound 1 was most effective and can be used as a molecular probe for future studies of how small molecules may affect NDI caused by mutant V2R. These compounds, however, failed to rescue the V2R Y128S mutant, indicating that the compounds described may not work in the rescue of all known mutants of V2R. Taken collectively, the present studies have now identified a promising lead compound that could function as a pharmacoperone to correct the trafficking defect of the NDI-associated mutant V2R L83Q and thus has the therapeutic potential for the treatment of NDI.
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7
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Hou ZS, Ulloa-Aguirre A, Tao YX. Pharmacoperone drugs: targeting misfolded proteins causing lysosomal storage-, ion channels-, and G protein-coupled receptors-associated conformational disorders. Expert Rev Clin Pharmacol 2018; 11:611-624. [DOI: 10.1080/17512433.2018.1480367] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Zhi-Shuai Hou
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Alabama, USA
| | - Alfredo Ulloa-Aguirre
- Red de Apoyo a la Investigación (RAI), Universidad Nacional Autónoma de México (UNAM) and Instituto Nacional de Ciencias Médicas y Nutrición SZ, Mexico City, Mexico
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Alabama, USA
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8
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Abstract
The gonadotropin receptors (luteinising hormone receptor; LHR and follicle-stimulating hormone receptor; FSHR) are G protein-coupled receptors (GPCRs) that play an important role in the endocrine control of reproduction. Thus genetic mutations that cause impaired function of these receptors have been implicated in a number of reproductive disorders. Disease-causing genetic mutations in GPCRs frequently result in intracellular retention and degradation of the nascent protein through misfolding and subsequent recognition by cellular quality control machinery. The discovery and development of novel compounds termed pharmacological chaperones (pharmacoperones) that can stabilise misfolded receptors and restore trafficking and plasma membrane expression are therefore of great interest clinically, and promising in vitro data describing the pharmacoperone rescue of a number of intracellularly retained mutant GPCRs has provided a platform for taking these compounds into in vivo trials. Thienopyrimidine small molecule allosteric gonadotropin receptor agonists (Org 42599 and Org 41841) have been demonstrated to have pharmacoperone activity. These compounds can rescue cell surface expression and in many cases, hormone responsiveness, of a range of retained mutant gonadotropin receptors. Should gonadotropin receptor selectivity of these compounds be improved, they could offer therapeutic benefit to subsets of patients suffering from reproductive disorders attributed to defective gonadotropin receptor trafficking.
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Affiliation(s)
- Claire L Newton
- Centre for Neuroendocrinology and Department of Immunology, Faculty of Health Sciences, University of Pretoria, PO Box 2034, Pretoria, 0001, South Africa.
| | - Ross C Anderson
- Centre for Neuroendocrinology and Department of Immunology, Faculty of Health Sciences, University of Pretoria, PO Box 2034, Pretoria, 0001, South Africa
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9
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Janovick JA, Spicer TP, Bannister TD, Scampavia L, Conn PM. Pharmacoperone rescue of vasopressin 2 receptor mutants reveals unexpected constitutive activity and coupling bias. PLoS One 2017; 12:e0181830. [PMID: 28767678 PMCID: PMC5540481 DOI: 10.1371/journal.pone.0181830] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 07/08/2017] [Indexed: 12/30/2022] Open
Abstract
Pharmacoperones are small molecules that diffuse into cells and rescue misfolded, mistrafficked protein mutants, restoring their function. These substances act with high target specificity, serving as templates to fold (or refold) receptors, enzymes, ion channels or other proteins and enable them to pass the scrutiny of the cellular quality control system ("rescue"). In the present study we demonstrate that a rescued mutant (L83Q) of the vasopressin type 2 receptor (V2R), shows a strong bias for Gs coupling unlike the WT V2 receptor, which couples to both Gs and Gq/11. Failure of the mutant to couple to Gq/11 was not due to a limiting quantity of G-proteins since other Gq/11-coupled receptors (WT V2R, histamine receptor and muscarinic receptor) responded appropriately to their ligands. Transfection with DNA encoding Gq enabled the V2 receptor mutant to couple to this G protein, but only modestly compared with the WT receptor. Fourteen V2R mutant pharmacoperones, of multiple chemical classes, obtained from a high throughput screen of a 660,000 structure library, and one V2R peptidomimetic antagonist rescues L83Q. The rescued mutant shows similar bias with all pharmacoperones identified, suggesting that the bias is intrinsic to the mutant protein's structure, rather than due to the chemical class of the pharmacoperone. In the case of V2R mutant Y128S, rescue with a pharmacoperone revealed constitutive activity, also with bias for Gs, although both IP and cAMP were produced in response to agonist. These results suggest that particular rescued receptor mutants show functional characteristics that differ from the WT receptor; a finding that may be important to consider as pharmacoperones are developed as therapeutic agents.
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Affiliation(s)
- Jo Ann Janovick
- Departments of Internal Medicine and Cell Biology/Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
| | - Timothy P. Spicer
- Lead Identification Division, Translational Research Institute and Department of Molecular Therapeutics, Scripps Research Institute, Jupiter, Florida, United States of America
| | - Thomas D. Bannister
- Department of Chemistry, Scripps Research Institute, Jupiter, Florida, United States of America
| | - Louis Scampavia
- Lead Identification Division, Translational Research Institute and Department of Molecular Therapeutics, Scripps Research Institute, Jupiter, Florida, United States of America
| | - P. Michael Conn
- Departments of Internal Medicine and Cell Biology/Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
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Volmar CH, Wahlestedt C, Brothers SP. Orphan diseases: state of the drug discovery art. Wien Med Wochenschr 2017; 167:197-204. [PMID: 26819216 PMCID: PMC4963293 DOI: 10.1007/s10354-015-0423-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 12/21/2015] [Indexed: 01/08/2023]
Abstract
Since 1983 more than 300 drugs have been developed and approved for orphan diseases. However, considering the development of novel diagnosis tools, the number of rare diseases vastly outpaces therapeutic discovery. Academic centers and nonprofit institutes are now at the forefront of rare disease R&D, partnering with pharmaceutical companies when academic researchers discover novel drugs or targets for specific diseases, thus reducing the failure risk and cost for pharmaceutical companies. Considerable progress has occurred in the art of orphan drug discovery, and a symbiotic relationship now exists between pharmaceutical industry, academia, and philanthropists that provides a useful framework for orphan disease therapeutic discovery. Here, the current state-of-the-art of drug discovery for orphan diseases is reviewed. Current technological approaches and challenges for drug discovery are considered, some of which can present somewhat unique challenges and opportunities in orphan diseases, including the potential for personalized medicine, gene therapy, and phenotypic screening.
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Affiliation(s)
- Claude-Henry Volmar
- Center for Therapeutic Innovation (CTI), Department of Psychiatry and Behavioral Sciences, University of Miami Miller School of Medicine, 1501 NW 10th Ave, BRB #416 (M860), 33136, Miami, FL, USA
| | - Claes Wahlestedt
- Center for Therapeutic Innovation (CTI), Department of Psychiatry and Behavioral Sciences, University of Miami Miller School of Medicine, 1501 NW 10th Ave, BRB #416 (M860), 33136, Miami, FL, USA
| | - Shaun P Brothers
- Center for Therapeutic Innovation (CTI), Department of Psychiatry and Behavioral Sciences, University of Miami Miller School of Medicine, 1501 NW 10th Ave, BRB #416 (M860), 33136, Miami, FL, USA.
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11
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Janovick JA, Spicer TP, Smith E, Bannister TD, Kenakin T, Scampavia L, Conn PM. Receptor antagonism/agonism can be uncoupled from pharmacoperone activity. Mol Cell Endocrinol 2016; 434:176-85. [PMID: 27389877 PMCID: PMC4983495 DOI: 10.1016/j.mce.2016.07.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 07/01/2016] [Accepted: 07/01/2016] [Indexed: 10/21/2022]
Abstract
Pharmacoperones rescue misrouted mutants of the vasopressin receptor type 2 (V2R) and enable them to traffic to the correct biological locus where they function. Previously, a library of nearly 645,000 structures was interrogated with a high throughput screen; pharmacoperones were identified for V2R mutants with a view toward correcting the underlying mutational defects in nephrogenic diabetes insipidus. In the present study, an orthologous assay was used to evaluate hits from the earlier study. We found no consistent relation between antagonism or agonism and pharmacoperone activity. Active pharmacoperones were identified which had minimal antagonistic activity. This increases the therapeutic reach of these drugs, since virtually all pharmacoperone drugs reported to date were selected from peptidomimetic antagonists. Such mixed-activity drugs have a complex pharmacology limiting their therapeutic utility and requiring their removal prior to stimulation of the receptor with agonist.
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Affiliation(s)
- Jo Ann Janovick
- Departments of Internal Medicine and Cell Biology/Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Timothy P Spicer
- Scripps Research Institute Molecular Screening Center, Department of Molecular Therapeutics, Scripps Research Institute, Jupiter, FL, United States
| | - Emery Smith
- Scripps Research Institute Molecular Screening Center, Department of Molecular Therapeutics, Scripps Research Institute, Jupiter, FL, United States
| | - Thomas D Bannister
- Department of Chemistry, Scripps Research Institute, Jupiter, FL, United States
| | - Terry Kenakin
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC, United States
| | - Louis Scampavia
- Scripps Research Institute Molecular Screening Center, Department of Molecular Therapeutics, Scripps Research Institute, Jupiter, FL, United States
| | - P Michael Conn
- Departments of Internal Medicine and Cell Biology/Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX, United States.
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12
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Conn PM, Spicer TP, Scampavia L, Janovick JA. Assay strategies for identification of therapeutic leads that target protein trafficking. Trends Pharmacol Sci 2015; 36:498-505. [PMID: 26067100 DOI: 10.1016/j.tips.2015.05.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2015] [Revised: 05/09/2015] [Accepted: 05/13/2015] [Indexed: 12/12/2022]
Abstract
Receptors, enzymes, and ion channels are traditional targets of therapeutic development. A common strategy is to target these proteins with agents that either activate or suppress their activity with ligands or substrates that occupy orthosteric sites or have allosteric interactions. An alternative approach involves regulation of protein trafficking. In principle, this approach enables 'rescue' of misfolded and misrouted mutant proteins to restore function, 'shipwrecking' of undesirable proteins by targeting them for destruction, and regulation of levels of partially expressed wild type (WT) proteins at their functional sites of action. Here, we present drug discovery strategies that identify 'pharmacoperones', which are small molecules that serve as molecular templates and cause otherwise misfolded mutant proteins to fold and route correctly.
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Affiliation(s)
- P Michael Conn
- Department of Internal Medicine, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, USA; Department of Cell Biology/Biochemistry, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, USA.
| | - Timothy P Spicer
- Lead Identification Division, Translational Research Institute and Department of Molecular Therapeutics, Scripps Research Institute, Jupiter, FL, USA
| | - Louis Scampavia
- Lead Identification Division, Translational Research Institute and Department of Molecular Therapeutics, Scripps Research Institute, Jupiter, FL, USA
| | - Jo Ann Janovick
- Department of Internal Medicine, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, USA; Department of Cell Biology/Biochemistry, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, USA
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13
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Conn PM, Smith E, Spicer T, Chase P, Scampavia L, Janovick JA. A phenotypic high throughput screening assay for the identification of pharmacoperones for the gonadotropin releasing hormone receptor. Assay Drug Dev Technol 2015; 12:238-46. [PMID: 24831790 DOI: 10.1089/adt.2014.576] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We describe a phenotypic high throughput screening (HTS) calcium flux assay designed to identify pharmacoperones for the gonadotropin releasing hormone receptor (GnRHR). Pharmacoperones are target-specific, small molecules that diffuse into cells, rescue misfolded protein mutants, and restore them to function. Rescue is based on correcting the trafficking of mutants that would otherwise be retained in the endoplasmic reticulum and unable to function correctly. This approach identifies drugs with a significant degree of novelty, relying on cellular mechanisms that are not currently exploited. Development of such assays is important, since the extensive use of agonist/antagonist screens alone means that useful chemical structures may be present in existing libraries but have not been previously identified using existing methods. Our assay utilizes cell lines stably expressing a GnRHR mutant under the control of a tetracycline (OFF) transactivator. This allows us to quantitate the level of functional and properly trafficked G protein coupled receptors present in each test well. Furthermore, since we are able to turn receptor expression on and off, we can rapidly eliminate the majority of false positives from our screening results. Our data show that this approach is likely to be successful in identifying hits from large chemical libraries.
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Affiliation(s)
- P Michael Conn
- 1 Departments of Internal Medicine and Cell Biology/Biochemistry, Texas Tech University Health Sciences Center , Lubbock, Texas
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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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Pharmacological chaperoning: a primer on mechanism and pharmacology. Pharmacol Res 2014; 83:10-9. [PMID: 24530489 DOI: 10.1016/j.phrs.2014.01.005] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 01/29/2014] [Indexed: 12/26/2022]
Abstract
Approximately forty percent of diseases are attributable to protein misfolding, including those for which genetic mutation produces misfolding mutants. Intriguingly, many of these mutants are not terminally misfolded since native-like folding, and subsequent trafficking to functional locations, can be induced by target-specific, small molecules variably termed pharmacological chaperones, pharmacoperones, or pharmacochaperones (PCs). PC targets include enzymes, receptors, transporters, and ion channels, revealing the breadth of proteins that can be engaged by ligand-assisted folding. The purpose of this review is to provide an integrated primer of the diverse mechanisms and pharmacology of PCs. In this regard, we examine the structural mechanisms that underlie PC rescue of misfolding mutants, including the ability of PCs to act as surrogates for defective intramolecular interactions and, at the intermolecular level, overcome oligomerization deficiencies and dominant negative effects, as well as influence the subunit stoichiometry of heteropentameric receptors. Not surprisingly, PC-mediated structural correction of misfolding mutants normalizes interactions with molecular chaperones that participate in protein quality control and forward-trafficking. A variety of small molecules have proven to be efficacious PCs and the advantages and disadvantages of employing orthostatic antagonists, active-site inhibitors, orthostatic agonists, and allosteric modulator PCs are considered. Also examined is the possibility that several therapeutic agents may have unrecognized activity as PCs, and this chaperoning activity may mediate/contribute to therapeutic action and/or account for adverse effects. Lastly, we explore evidence that pharmacological chaperoning exploits intrinsic ligand-assisted folding mechanisms. Given the widespread applicability of PC rescue of mutants associated with protein folding disorders, both in vitro and in vivo, the therapeutic potential of PCs is vast. This is most evident in the treatment of lysosomal storage disorders, cystic fibrosis, and nephrogenic diabetes insipidus, for which proof of principle in humans has been demonstrated.
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Conn PM, Smithson DC, Hodder PS, Stewart MD, Behringer RR, Smith E, Ulloa-Aguirre A, Janovick JA. Transitioning pharmacoperones to therapeutic use: in vivo proof-of-principle and design of high throughput screens. Pharmacol Res 2013; 83:38-51. [PMID: 24373832 DOI: 10.1016/j.phrs.2013.12.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 12/16/2013] [Accepted: 12/16/2013] [Indexed: 12/26/2022]
Abstract
A pharmacoperone (from "pharmacological chaperone") is a small molecule that enters cells and serves as molecular scaffolding in order to cause otherwise-misfolded mutant proteins to fold and route correctly within the cell. Pharmacoperones have broad therapeutic applicability since a large number of diseases have their genesis in the misfolding of proteins and resultant misrouting within the cell. Misrouting may result in loss-of-function and, potentially, the accumulation of defective mutants in cellular compartments. Most known pharmacoperones were initially derived from receptor antagonist screens and, for this reason, present a complex pharmacology, although these are highly target specific. In this summary, we describe efforts to produce high throughput screens that identify these molecules from chemical libraries as well as a mouse model which provides proof-of-principle for in vivo protein rescue using existing pharmacoperones.
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Affiliation(s)
- P Michael Conn
- Department of Internal Medicine, Texas Tech University Health Science Center, 3601 4th Street, Lubbock, TX 79430, United States; Department of Cell Biology, Texas Tech University Health Science Center, 3601 4th Street, Lubbock, TX 79430, United States.
| | - David C Smithson
- Oregon Translational Research and Drug Development Institute (OTRADI), Portland, OR 97201, United States
| | - Peter S Hodder
- Translational Research Institute, Scripps Research Institute, Jupiter, FL 33458, United States
| | - M David Stewart
- Department of Genetics, University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, United States; Department of Biology and Biochemistry, University of Houston, Houston, TX 77204, United States
| | - Richard R Behringer
- Department of Genetics, University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, United States
| | - Emery Smith
- Translational Research Institute, Scripps Research Institute, Jupiter, FL 33458, United States
| | - Alfredo Ulloa-Aguirre
- Research Support Network, Instituto Nacional de Ciencias Medicas y Nutricion, S-Z Universidad Autonoma de Mexico, Mexico, D.F., Mexico
| | - Jo Ann Janovick
- Department of Internal Medicine, Texas Tech University Health Science Center, 3601 4th Street, Lubbock, TX 79430, United States; Department of Cell Biology, Texas Tech University Health Science Center, 3601 4th Street, Lubbock, TX 79430, United States
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Restoration of testis function in hypogonadotropic hypogonadal mice harboring a misfolded GnRHR mutant by pharmacoperone drug therapy. Proc Natl Acad Sci U S A 2013; 110:21030-5. [PMID: 24324164 DOI: 10.1073/pnas.1315194110] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Mutations in receptors, ion channels, and enzymes are frequently recognized by the cellular quality control system as misfolded and retained in the endoplasmic reticulum (ER) or otherwise misrouted. Retention results in loss of function at the normal site of biological activity and disease. Pharmacoperones are target-specific small molecules that diffuse into cells and serve as folding templates that enable mutant proteins to pass the criteria of the quality control system and route to their physiologic site of action. Pharmacoperones of the gonadotropin releasing hormone receptor (GnRHR) have efficacy in cell culture systems, and their cellular and biochemical mechanisms of action are known. Here, we show the efficacy of a pharmacoperone drug in a small animal model, a knock-in mouse, expressing a mutant GnRHR. This recessive mutation (GnRHR E(90)K) causes hypogonadotropic hypogonadism (failed puberty associated with low or apulsatile luteinizing hormone) in both humans and in the mouse model described. We find that pulsatile pharmacoperone therapy restores E(90)K from ER retention to the plasma membrane, concurrently with responsiveness to the endogenous natural ligand, gonadotropin releasing hormone, and an agonist that is specific for the mutant. Spermatogenesis, proteins associated with steroid transport and steroidogenesis, and androgen levels were restored in mutant male mice following pharmacoperone therapy. These results show the efficacy of pharmacoperone therapy in vivo by using physiological, molecular, genetic, endocrine and biochemical markers and optimization of pulsatile administration. We expect that this newly appreciated approach of protein rescue will benefit other disorders sharing pathologies based on misrouting of misfolded protein mutants.
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Conn PM, Smith E, Hodder P, Janovick JA, Smithson DC. High-throughput screen for pharmacoperones of the vasopressin type 2 receptor. ACTA ACUST UNITED AC 2013; 18:930-7. [PMID: 23640875 DOI: 10.1177/1087057113483559] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Pharmacoperone drugs correct the folding of misfolded protein mutants and restore function (i.e., "rescue") by correcting the routing of (otherwise) misrouted mutants. Assays for pharmacoperones have not been applied to screen large libraries previously. Currently, most pharmacoperones possess intrinsic agonist or antagonist activities since these were identified using high-throughput screens aimed at discovering direct agonists or antagonists. Here we describe an ultra-high-throughput compatible no-wash assay system designed to specifically identify pharmacoperones of the vasopressin type 2 receptor (V2R). Development of such assays is important and novel since useful chemical structures with the ability to control cellular trafficking but lacking intrinsic agonist or antagonist properties have not likely been identified using existing screens. In the described assay, the level of functional human V2R (hV2R) (mutant) present in each test well is quantitated by stimulation with saturating levels of agonist followed by use of a luminescent-based cyclic adenosine monophosphate assay. This allows the assay to identify compounds that increase the trafficking of mutant hV2R[L(83)Q] in our model system.
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Affiliation(s)
- P Michael Conn
- Divisions of Reproductive Sciences and Neuroscience, Oregon National Primate Research Center, Beaverton, OR 97006, USA.
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Janovick JA, Pogozheva ID, Mosberg HI, Cornea A, Conn PM. Rescue of misrouted GnRHR mutants reveals its constitutive activity. Mol Endocrinol 2012; 26:1179-88. [PMID: 22595961 DOI: 10.1210/me.2012-1089] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
G protein-coupled receptors (GPCR) play central roles in almost all physiological functions, and mutations in GPCR are responsible for over 30 hereditary diseases associated with loss or gain of receptor function. Gain of function mutants are frequently described as having constitutive activity (CA), that is, they activate effectors in the absence of agonist occupancy. Although many GPCR have mutants with CA, the GnRH receptor (GnRHR) was not, until 2010, associated with any CA mutants. The explanation for the failure to observe CA appears to be that the quality control system of the cell recognizes CA mutants of GnRHR as misfolded and retains them in the endoplasmic reticulum. In the present study, we identified several human (h)GnRHR mutants with substitutions in transmembrane helix 6 (F(272)K, F(272)Q, Y(284)F, C(279)A, and C(279)S) that demonstrate varying levels of CA after being rescued by pharmacoperones from different chemical classes and/or deletion of residue K(191), a modification that increases trafficking to the plasma membrane. The movement of the mutants from the endoplasmic reticulum (unrescued) to the plasma membrane (after rescue) is supported by confocal microscopy. Judging from the receptor-stimulated inositol phosphate production, mutants F(272)K and F(272)Q, after rescue, display the largest level of CA, an amount that is comparable with agonist-stimulated activation. Because mutations in other GPCR are, like the hGnRHR, scrutinized by the quality control system, this general approach may reveal CA in receptor mutants from other systems. A computer model of the hGnRHR and these mutants was used to evaluate the conformation associated with CA.
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Affiliation(s)
- Jo Ann Janovick
- Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, Oregon 97006-3448, USA
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Ulloa-Aguirre A, Michael Conn P. Pharmacoperones: a new therapeutic approach for diseases caused by misfolded G protein-coupled receptors. ACTA ACUST UNITED AC 2012; 5:13-24. [PMID: 22074574 DOI: 10.2174/187221411794351851] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 11/13/2010] [Indexed: 01/10/2023]
Abstract
G Protein-coupled receptors (GPCRs) are cell membrane proteins that recognize specific chemical signals such as drugs and hormones and transduce these signals into cellular responses by activating G-proteins. As is the case for all newly synthesized proteins, GPCRs are subjected to conformational scrutiny at the endoplasmic reticulum prior to processing and trafficking to the cell surface membrane. Because of this stringent quality control screening mechanism, mutations that result in protein misfolding frequently lead to retention in the endoplasmic reticulum, aggregation or other misrouting and, eventually, to disease. This article reviews some patents and new therapeutic opportunities based on the misfolding and retention of otherwise functional GPCRs that represent promising approaches to correct conformational abnormalities leading to distinct disease states.
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Affiliation(s)
- Alfredo Ulloa-Aguirre
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia Luis Castelazo Ayala, Instituto Mexicano del Seguro Social, Av. Rio Magdalena 289, 60. piso, Col. Tizapan San Angel, C.P. 01090, Mexico D.F., Mexico.
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Pharmacological chaperones correct misfolded GPCRs and rescue function: protein trafficking as a therapeutic target. Subcell Biochem 2012; 63:263-89. [PMID: 23161143 DOI: 10.1007/978-94-007-4765-4_14] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
G-protein-coupled receptors (GPCRs) are a large superfamily of plasma membrane proteins that play central roles in transducing endocrine, neural and -sensory signals. In humans, more than 30 disorders are associated with mutations in GPCRs and these proteins are common drug development targets, with 30-50% of drugs targeting them. GPCR mutants are frequently misfolded, recognized as defective by the cellular quality control system, retained in the endoplasmic reticulum and do not traffic to the plasma membrane. The use of small molecules chaperones (pharmacological chaperones or "pharmacoperones") to rescue misfolded GPCRs has provided a new approach for treatment of human diseases caused by misfolding and misrouting. This chapter provides an overview of the molecular basis of this approach using the human gonadotropin-releasing hormone receptor (hGnRHR) as model for treatment of conformational diseases provoked by -misfolded GPCRs.
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Forfar R, Lu ZL. Role of the transmembrane domain 4/extracellular loop 2 junction of the human gonadotropin-releasing hormone receptor in ligand binding and receptor conformational selection. J Biol Chem 2011; 286:34617-26. [PMID: 21832286 DOI: 10.1074/jbc.m111.240341] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recent crystal structures of G protein-coupled receptors (GPCRs) show the remarkable structural diversity of extracellular loop 2 (ECL2), implying its potential role in ligand binding and ligand-induced receptor conformational selectivity. Here we have applied molecular modeling and mutagenesis studies to the TM4/ECL2 junction (residues Pro(174(4.59))-Met(180(4.66))) of the human gonadotropin-releasing hormone (GnRH) receptor, which uniquely has one functional type of receptor but two endogenous ligands in humans. We suggest that the above residues assume an α-helical extension of TM4 in which the side chains of Gln(174(4.60)) and Phe(178(4.64)) face toward the central ligand binding pocket to make H-bond and aromatic contacts with pGlu(1) and Trp(3) of both GnRH I and GnRH II, respectively. The interaction between the side chains of Phe(178(4.64)) of the receptor and Trp(3) of the GnRHs was supported by reciprocal mutations of the interacting residues. Interestingly, alanine mutations of Leu(175(4.61)), Ile(177(4.63)), and Met(180(4.66)) decreased mutant receptor affinity for GnRH I but, in contrast, increased affinity for GnRH II. This suggests that these residues make intramolecular or intermolecular contacts with residues of transmembrane (TM) domain 3, TM5, or the phospholipid bilayer, which couple the ligand structure to specific receptor conformational switches. The marked decrease in signaling efficacy of I177A and F178A also indicates that IIe(177(4.63)) and Phe(178(4.64)) are important in stabilizing receptor-active conformations. These findings suggest that the TM4/ECL2 junction is crucial for peptide ligand binding and, consequently, for ligand-induced receptor conformational selection.
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Affiliation(s)
- Rachel Forfar
- MRC Technology, Mill Hill, London NW7 1AD, United Kingdom
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Ng DP, Poulsen BE, Deber CM. Membrane protein misassembly in disease. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1115-22. [PMID: 21840297 DOI: 10.1016/j.bbamem.2011.07.046] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 07/28/2011] [Accepted: 07/29/2011] [Indexed: 11/19/2022]
Abstract
Helix-helix interactions play a central role in the folding and assembly of integral α-helical membrane proteins and are fundamentally dictated by the amino acid sequence of the TM domain. It is not surprising then that missense mutations that target these residues are often linked to disease. In this review, we focus on the molecular mechanisms through which missense mutations lead to aberrant folding and/or assembly of these proteins, and then discuss pharmacological approaches that may potentially mitigate or reverse the negative effects of these mutations. Improving our understanding of how missense mutations affect the interactions between TM α-helices will increase our capability to develop effective therapeutic approaches to counter the misassembly of these proteins and, ultimately, disease. This article is part of a Special Issue entitled: Protein Folding in Membranes.
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Affiliation(s)
- Derek P Ng
- Division of Molecular Structure & Function, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
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Janovick JA, Pogozheva ID, Mosberg HI, Conn PM. Salt bridges overlapping the gonadotropin-releasing hormone receptor agonist binding site reveal a coincidence detector for G protein-coupled receptor activation. J Pharmacol Exp Ther 2011; 338:430-42. [PMID: 21527534 DOI: 10.1124/jpet.111.180869] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
G protein-coupled receptors (GPCRs) play central roles in most physiological functions, and mutations in them cause heritable diseases. Whereas crystal structures provide details about the structure of GPCRs, there is little information that identifies structural features that permit receptors to pass the cellular quality control system or are involved in transition from the ground state to the ligand-activated state. The gonadotropin-releasing hormone receptor (GnRHR), because of its small size among GPCRs, is amenable to molecular biological approaches and to computer modeling. These techniques and interspecies comparisons are used to identify structural features that are important for both intracellular trafficking and GnRHR activation yet distinguish between these processes. Our model features two salt (Arg(38)-Asp(98) and Glu(90)-Lys(121)) and two disulfide (Cys(14)-Cys(200) and Cys(114)-Cys(196)) bridges, all of which are required for the human GnRHR to traffic to the plasma membrane. This study reveals that both constitutive and ligand-induced activation are associated with a "coincidence detector" that occurs when an agonist binds. The observed constitutive activation of receptors lacking Glu(90)-Lys(121), but not Arg(38)-Asp(98) ionic bridge, suggests that the role of the former connection is holding the receptor in the inactive conformation. Both the aromatic ring and hydroxyl group of Tyr(284) and the hydrogen bonding of Ser(217) are important for efficient receptor activation. Our modeling results, supported by the observed influence of Lys(191) from extracellular loop 2 (EL2) and a four-residue motif surrounding this loop on ligand binding and receptor activation, suggest that the positioning of EL2 within the seven-α-helical bundle regulates receptor stability, proper trafficking, and function.
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Affiliation(s)
- Jo Ann Janovick
- Division of Reproductive Sciences, Oregon National Primate Research Center, Beaverton, Oregon, USA
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Abstract
G protein-coupled receptors (GPCRs), which includes the gonadotropin releasing hormone (GnRH) receptor (GnRHR), comprises the largest family of validated drug targets-more than half of all approved drugs derive their benefits by selective targeting of GPCRs. Most drugs in this class are either agonists or antagonists of GPCRs and high throughput screens (HTSs) have typically been designed and performed with a view toward identification of such compounds as lead drug candidates. This manuscript presents the case that valuable drugs which effect the trafficking of GPCRs may have been overlooked because pharmacoperones have been selected from existing screens that identify agonists and antagonists. A "gain of activity assay" is proposed; this assay relies on the expression of a mutant of the GnRHR that is known to be rescuable by pharmacoperone drugs, and which is restored to activity in their presence. Accordingly, "hits" are identified by the appearance of activity. The gene for the mutant is under control of tetracycline and may be prevented from being expressed. This is a valuable feature since it allows false positives to be identified. Such drugs will show apparent activity whether or not the mutant is expressed. This assay will enable identification of these drugs from chemical libraries and does not rely on their activity as agonists or antagonists.
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Affiliation(s)
- P. Michael Conn
- Division of Reproductive Sciences, Oregon National Primate Research Center, Oregon Health and Science UniversityBeaverton, OR, USA
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science UniversityBeaverton, OR, USA
- Department of Physiology and Pharmacology, Oregon Health and Science UniversityBeaverton, OR, USA
- Department of Cell Biology and Development, Oregon Health and Science UniversityBeaverton, OR, USA
- Department of Obstetrics and Gynecology, Oregon Health and Science UniversityBeaverton, OR, USA
- *Correspondence: P. Michael Conn, Oregon National Primate Research Center, Oregon Health and Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA. e-mail:
| | - Jo Ann Janovick
- Division of Reproductive Sciences, Oregon National Primate Research Center, Oregon Health and Science UniversityBeaverton, OR, USA
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science UniversityBeaverton, OR, USA
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Conn PM, Ulloa-Aguirre A. Pharmacological chaperones for misfolded gonadotropin-releasing hormone receptors. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2011; 62:109-41. [PMID: 21907908 DOI: 10.1016/b978-0-12-385952-5.00008-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Structural alterations provoked by mutations or genetic variations in the gene sequence of G protein-coupled receptors (GPCRs) may lead to abnormal function of the receptor molecule. Frequently, this leads to disease. While some mutations lead to changes in domains involved in agonist binding, receptor activation, or coupling to effectors, others may cause misfolding and lead to retention/degradation of the protein molecule by the quality control system of the cell. Several strategies, including genetic, chemical, and pharmacological approaches, have been shown to rescue function of trafficking-defective misfolded GPCRs. Among these, pharmacological strategies offer the most promising therapeutic tool to promote proper trafficking of misfolded proteins to the plasma membrane (PM). Pharmacological chaperones or "pharmacoperones" are small compounds that permeate the PM, enter cells, and bind selectively to misfolded proteins and correct folding allowing routing of the target protein to the PM, where the receptor may bind and respond to agonist stimulation. In this review, we describe new therapeutic opportunities based on mislocalization of otherwise functional human gonadotropin-releasing hormone receptors. This particular receptor is highly sensitive to single changes in chemical charge, and its intracellular traffic is delicately balanced between expression at the PM or retention/degradation in the endoplasmic reticulum; it is, therefore, a particularly instructive model to understand both the protein routing and the molecular mechanisms, whereby pharmacoperones rescue misfolded intermediates or conformationally defective receptors.
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Affiliation(s)
- P Michael Conn
- Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
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Re M, Pampillo M, Savard M, Dubuc C, McArdle CA, Millar RP, Conn PM, Gobeil F, Bhattacharya M, Babwah AV. The human gonadotropin releasing hormone type I receptor is a functional intracellular GPCR expressed on the nuclear membrane. PLoS One 2010; 5:e11489. [PMID: 20628612 PMCID: PMC2900216 DOI: 10.1371/journal.pone.0011489] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 06/11/2010] [Indexed: 12/02/2022] Open
Abstract
The mammalian type I gonadotropin releasing hormone receptor (GnRH-R) is a structurally unique G protein-coupled receptor (GPCR) that lacks cytoplasmic tail sequences and displays inefficient plasma membrane expression (PME). Compared to its murine counterparts, the primate type I receptor is inefficiently folded and retained in the endoplasmic reticulum (ER) leading to a further reduction in PME. The decrease in PME and concomitant increase in intracellular localization of the mammalian GnRH-RI led us to characterize the spatial distribution of the human and mouse GnRH receptors in two human cell lines, HEK 293 and HTR-8/SVneo. In both human cell lines we found the receptors were expressed in the cytoplasm and were associated with the ER and nuclear membrane. A molecular analysis of the receptor protein sequence led us to identify a putative monopartite nuclear localization sequence (NLS) in the first intracellular loop of GnRH-RI. Surprisingly, however, neither the deletion of the NLS nor the addition of the Xenopus GnRH-R cytoplasmic tail sequences to the human receptor altered its spatial distribution. Finally, we demonstrate that GnRH treatment of nuclei isolated from HEK 293 cells expressing exogenous GnRH-RI triggers a significant increase in the acetylation and phosphorylation of histone H3, thereby revealing that the nuclear-localized receptor is functional. Based on our findings, we conclude that the mammalian GnRH-RI is an intracellular GPCR that is expressed on the nuclear membrane. This major and novel discovery causes us to reassess the signaling potential of this physiologically and clinically important receptor.
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Affiliation(s)
- Michelle Re
- The Children's Health Research Institute, London, Canada
- Lawson Health Research Institute, London, Canada
- Department of Obstetrics and Gynaecology, The University of Western Ontario, London, Canada
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Canada
| | - Macarena Pampillo
- The Children's Health Research Institute, London, Canada
- Lawson Health Research Institute, London, Canada
- Department of Obstetrics and Gynaecology, The University of Western Ontario, London, Canada
| | - Martin Savard
- Department of Pharmacology, Université de Sherbrooke, Sherbrooke, Canada
| | - Céléna Dubuc
- Department of Pharmacology, Université de Sherbrooke, Sherbrooke, Canada
| | - Craig A. McArdle
- Laboratories for Integrated Neuroscience and Endocrinology, Department of Clinical Sciences at South Bristol, University of Bristol, Bristol, United Kingdom
| | - Robert P. Millar
- MRC Human Reproductive Sciences Unit, The Queen's Medical Research Institute, Edinburgh, United Kingdom
| | - P. Michael Conn
- Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, Oregon, United States of America
| | - Fernand Gobeil
- Department of Pharmacology, Université de Sherbrooke, Sherbrooke, Canada
| | - Moshmi Bhattacharya
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Canada
| | - Andy V. Babwah
- The Children's Health Research Institute, London, Canada
- Lawson Health Research Institute, London, Canada
- Department of Obstetrics and Gynaecology, The University of Western Ontario, London, Canada
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Canada
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Cavanaugh A, McKenna J, Stepanchick A, Breitwieser GE. Calcium-sensing receptor biosynthesis includes a cotranslational conformational checkpoint and endoplasmic reticulum retention. J Biol Chem 2010; 285:19854-64. [PMID: 20421307 DOI: 10.1074/jbc.m110.124792] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Metabolic labeling with [(35)S]cysteine was used to characterize early events in CaSR biosynthesis. [(35)S]CaSR is relatively stable (half-life approximately 8 h), but maturation to the final glycosylated form is slow and incomplete. Incorporation of [(35)S]cysteine is linear over 60 min, and the rate of [(35)S]CaSR biosynthesis is significantly increased by the membrane-permeant allosteric agonist NPS R-568, which acts as a cotranslational pharmacochaperone. The [(35)S]CaSR biosynthetic rate also varies as a function of conformational bias induced by loss- or gain-of-function mutations. In contrast, [(35)S]CaSR maturation to the plasma membrane was not significantly altered by exposure to the pharmacochaperone NPS R-568, the allosteric agonist neomycin, or the orthosteric agonist Ca(2+) (0.5 or 5 mm), suggesting that CaSR does not control its own release from the endoplasmic reticulum. A CaSR chimera containing the mGluR1alpha carboxyl terminus matures completely (half-time of approximately 8 h) and without a lag period, as does the truncation mutant CaSRDelta868 (half-time of approximately 16 h). CaSRDelta898 exhibits maturation comparable with full-length CaSR, suggesting that the CaSR carboxyl terminus between residues Thr(868) and Arg(898) limits maturation. Overall, these results suggest that CaSR is subject to cotranslational quality control, which includes a pharmacochaperone-sensitive conformational checkpoint. The CaSR carboxyl terminus is the chief determinant of intracellular retention of a significant fraction of total CaSR. Intracellular CaSR may reflect a rapidly mobilizable "storage form" of CaSR and/or may subserve distinct intracellular signaling roles that are sensitive to signaling-dependent changes in endoplasmic reticulum Ca(2+) and/or glutathione.
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Affiliation(s)
- Alice Cavanaugh
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822, USA
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Abstract
G protein-coupled receptors (GPCRs) play central roles in almost all physiological functions; mutations in GPCRs are responsible for more than 30 disorders. There is a great deal of information about GPCR structure but little information that directly relates structure to protein trafficking or to activation. The gonadotropin releasing hormone receptor, because of its small size among GPCRs, is amenable to preparation of mutants and was used in this study to establish the relation among a salt bridge, protein trafficking, and receptor activation. This bridge, between residues E(90) [located in transmembrane segment (TM) 2] and K(121) (TM3), is associated with correct trafficking to the plasma membrane. Agonists, but not antagonists, interact with residue K(121), and destabilize the TM2-TM3 association of the receptor in the plasma membrane. The hGnRHR mutant E(90)K has a broken salt bridge, which also destabilizes the TM2-TM3 association and is typically retained in the endoplasmic reticulum. We show that this mutant, if rescued to the plasma membrane by either of two different means, has constitutive activity and shows modified ligand specificity, revealing a role for the salt bridge in receptor activation, ligand specificity, trafficking, and structure. The data indicate that destabilizing the TM2-TM3 relation for receptor activation, while requiring an intact salt bridge for correct trafficking, provides a mechanism that protects the cell from plasma membrane expression of constitutive activity.
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Janovick JA, Conn PM. Use of pharmacoperones to reveal GPCR structural changes associated with constitutive activation and trafficking. Methods Enzymol 2010; 485:277-92. [PMID: 21050923 DOI: 10.1016/b978-0-12-381296-4.00016-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The gonadotropin-releasing hormone (GnRH) receptor (GnRHR), because of its small size among G-protein-coupled receptors (GPCRs), is amenable to facile preparation of mutants. This receptor is used in our laboratory as a structural model for this super-family of protein receptors and has helped us understand the requirements for proper trafficking. We have demonstrated that pharmacoperones ("pharmacological chaperones"), small target-specific drugs that diffuse into cells, are capable of rescuing misfolded and misrouted GnRHR mutants and restoring them to function. By rescuing these proteins, these drugs enable the plasma membrane expression of such mutants in living cells and allow examination of mutants that would otherwise be retained in the endoplasmic reticulum and would not be available for ligand binding and signal transduction. As an example of the efficacy of this method, we have shown that mutant E⁹⁰K, which breaks a salt bridge (E⁹⁰-K¹²¹) normally found in the GnRHR, results in constitutive activity when rescued by pharmacoperones. A second method of rescue, involving a mutation that increases the expression of GnRHRs, is shown to have a similar effect. Normally, in the absence of rescue by either of these methods, this mutant, associated with human hypogonadotropic hypogonadism, is misrouted and this constitutive activity has gone unrecognized. This observation [Janovick, J. A., and Conn, P. M. (2010). Salt bridge integrates GPCR activation with protein trafficking. Proc. Natl. Acad. Sci. USA107, 4454-4458.] showed that the cell normally recognizes this protein as defective and prevents its routing to the plasma membrane.
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Affiliation(s)
- Jo Ann Janovick
- Divisions of Reproductive Sciences and Neuroscience (ONPRC), Beaverton, Oregon, USA
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Lucca-Junior W, Janovick JA, Conn PM. Participation of the endoplasmic reticulum protein chaperone thio-oxidoreductase in gonadotropin-releasing hormone receptor expression at the plasma membrane. Braz J Med Biol Res 2009; 42:164-7. [PMID: 19274343 DOI: 10.1590/s0100-879x2009000200003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2008] [Accepted: 12/11/2008] [Indexed: 11/22/2022] Open
Abstract
Chaperone members of the protein disulfide isomerase family can catalyze the thiol-disulfide exchange reaction with pairs of cysteines. There are 14 protein disulfide isomerase family members, but the ability to catalyze a thiol disulfide exchange reaction has not been demonstrated for all of them. Human endoplasmic reticulum protein chaperone thio-oxidoreductase (ERp18) shows partial oxidative activity as a protein disulfide isomerase. The aim of the present study was to evaluate the participation of ERp18 in gonadotropin-releasing hormone receptor (GnRHR) expression at the plasma membrane. Cos-7 cells were cultured, plated, and transfected with 25 ng (unless indicated) wild-type human GnRHR (hGnRHR) or mutant GnRHR (Cys14Ala and Cys200Ala) and pcDNA3.1 without insert (empty vector) or ERp18 cDNA (75 ng/well), pre-loaded for 18 h with 1 microCi myo-[2-3H(N)]-inositol in 0.25 mL DMEM and treated for 2 h with buserelin. We observed a decrease in maximal inositol phosphate (IP) production in response to buserelin in the cells co-transfected with hGnRHR, and a decrease from 20 to 75 ng of ERp18 compared with cells co-transfected with hGnRHR and empty vector. The decrease in maximal IP was proportional to the amount of ERp18 DNA over the range examined. Mutants (Cys14Ala and Cys200Ala) that could not form the Cys14-Cys200 bridge essential for plasma membrane routing of the hGnRHR did not modify maximal IP production when they were co-transfected with ERp18. These results suggest that ERp18 has a reduction role on disulfide bonds in wild-type hGnRHR folding.
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Affiliation(s)
- W Lucca-Junior
- Division of Neuroscience and Reproductive Sciences, Oregon National Primate Research Center, Oregon Health and Science University, ONPRC/OHSU, Beaverton, Oregon, USA.
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Conn PM, Janovick JA. Trafficking and quality control of the gonadotropin releasing hormone receptor in health and disease. Mol Cell Endocrinol 2009; 299:137-45. [PMID: 19059461 PMCID: PMC2655134 DOI: 10.1016/j.mce.2008.10.051] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Accepted: 10/27/2008] [Indexed: 01/09/2023]
Abstract
In order to serve as enzymes, receptors and ion channels, proteins require structural precision. This is monitored by a cellular quality control system (QCS) that rejects misfolded proteins and thereby protects the cell against aberrant activity. Misfolding can result in protein molecules that retain intrinsic function, yet become misrouted within the cell; these cease to perform normally and result in disease. A therapeutic opportunity exists to correct misrouting and rescue mutants using "pharmacoperones" (small molecular folding templates, often peptidomimetics, which promote correct folding and rescue) thereby restoring function and potentially curing the underlying disease. Because of its small size, the GnRH (gonadotropin-releasing hormone) receptor (GnRHR) is an excellent model for GPCR (G protein-coupled receptor) and has allowed elucidation of the precise biochemical mechanism of pharmacoperone action necessary for rational design of new therapeutic agents. This review summarizes what has been learned about the structural requirements of the GnRHR that govern its interaction with the QCS and now presents the potential for the rational design of pharmacoperones. Because of the role of protein processing, this approach is likely to be applicable to other GCPCs and other proteins in general.
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Affiliation(s)
- P Michael Conn
- Oregon National Primate Research Center and Departments of Physiology and Pharmacology and Cell Biology and Development, Oregon Health & Science University, United States.
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Janovick JA, Patny A, Mosley R, Goulet MT, Altman MD, Rush TS, Cornea A, Conn PM. Molecular mechanism of action of pharmacoperone rescue of misrouted GPCR mutants: the GnRH receptor. Mol Endocrinol 2009; 23:157-68. [PMID: 19095769 PMCID: PMC2646616 DOI: 10.1210/me.2008-0384] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Accepted: 12/08/2008] [Indexed: 12/22/2022] Open
Abstract
The human GnRH receptor (hGnRHR), a G protein-coupled receptor, is a useful model for studying pharmacological chaperones (pharmacoperones), drugs that rescue misfolded and misrouted protein mutants and restore them to function. This technique forms the basis of a therapeutic approach of rescuing mutants associated with human disease and restoring them to function. The present study relies on computational modeling, followed by site-directed mutagenesis, assessment of ligand binding, effector activation, and confocal microscopy. Our results show that two different chemical classes of pharmacoperones act to stabilize hGnRHR mutants by bridging residues D(98) and K(121). This ligand-mediated bridge serves as a surrogate for a naturally occurring and highly conserved salt bridge (E(90)-K(121)) that stabilizes the relation between transmembranes 2 and 3, which is required for passage of the receptor through the cellular quality control system and to the plasma membrane. Our model was used to reveal important pharmacophoric features, and then identify a novel chemical ligand, which was able to rescue a D(98) mutant of the hGnRHR that could not be rescued as effectively by previously known pharmacoperones.
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Affiliation(s)
- Jo Ann Janovick
- Oregon National Primate Research Center/Oregon Health Sciences University, Beaverton, Oregon 97006, USA
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Müller DJ, Wu N, Palczewski K. Vertebrate membrane proteins: structure, function, and insights from biophysical approaches. Pharmacol Rev 2008; 60:43-78. [PMID: 18321962 DOI: 10.1124/pr.107.07111] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Membrane proteins are key targets for pharmacological intervention because they are vital for cellular function. Here, we analyze recent progress made in the understanding of the structure and function of membrane proteins with a focus on rhodopsin and development of atomic force microscopy techniques to study biological membranes. Membrane proteins are compartmentalized to carry out extra- and intracellular processes. Biological membranes are densely populated with membrane proteins that occupy approximately 50% of their volume. In most cases membranes contain lipid rafts, protein patches, or paracrystalline formations that lack the higher-order symmetry that would allow them to be characterized by diffraction methods. Despite many technical difficulties, several crystal structures of membrane proteins that illustrate their internal structural organization have been determined. Moreover, high-resolution atomic force microscopy, near-field scanning optical microscopy, and other lower resolution techniques have been used to investigate these structures. Single-molecule force spectroscopy tracks interactions that stabilize membrane proteins and those that switch their functional state; this spectroscopy can be applied to locate a ligand-binding site. Recent development of this technique also reveals the energy landscape of a membrane protein, defining its folding, reaction pathways, and kinetics. Future development and application of novel approaches during the coming years should provide even greater insights to the understanding of biological membrane organization and function.
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Affiliation(s)
- Daniel J Müller
- Biotechnology Center, University of Technology, Dresden, Germany
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Conn PM, Ulloa-Aguirre A, Ito J, Janovick JA. G Protein-Coupled Receptor Trafficking in Health and Disease: Lessons Learned to Prepare for Therapeutic Mutant Rescue in Vivo. Pharmacol Rev 2007; 59:225-50. [PMID: 17878512 DOI: 10.1124/pr.59.3.2] [Citation(s) in RCA: 200] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
G protein-coupled receptors (GPCR) comprise the largest family of drug targets. This is not surprising as many signaling systems rely on this class of receptor to convert external and internal stimuli to intracellular responses. As is the case with other membrane proteins, GPCRs are subjected to a stringent quality control mechanism at the endoplasmic reticulum, which ensures that only correctly folded proteins enter the secretory pathway. Because of this quality control system, point mutations resulting in protein sequence variations may result in the production of misfolded and disease-causing proteins that are unable to reach their functional destinations in the cell. There is now a wealth of information demonstrating the functional rescue of misfolded mutant receptors by small nonpeptide molecules originally designed to serve as receptor antagonists; these small molecules ("pharmacoperones") serve as molecular templates, promoting correct folding and allowing the mutants to pass the scrutiny of the cellular quality control system and be expressed at the cell surface membrane. Two of these systems are especially well characterized: the gonadotropin-releasing hormone and the vasopressin type 2 receptors, which play important roles in regulating reproduction and water homeostasis, respectively. Mutations in these receptors can lead to well defined diseases that are recognized as being caused by receptor misfolding that may potentially be amenable to treatment with pharmacoperones. This review is focused on protein misfolding and misrouting related to various disease states, with special emphasis on these two receptors, which have proved to be of value for development of drugs potentially useful in regulating GPCR trafficking in healthy and disease states.
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Affiliation(s)
- P Michael Conn
- Divisions of Neuroscience and Reproductive Biology, ONPRC/OHSU, Beaverton, OR 97006, USA.
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