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Bolinger AA, Frazier A, La JH, Allen JA, Zhou J. Orphan G Protein-Coupled Receptor GPR37 as an Emerging Therapeutic Target. ACS Chem Neurosci 2023; 14:3318-3334. [PMID: 37676000 PMCID: PMC11144446 DOI: 10.1021/acschemneuro.3c00479] [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] [Indexed: 09/08/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are successful druggable targets, making up around 35% of all FDA-approved medications. However, a large number of receptors remain orphaned, with no known endogenous ligand, representing a challenging but untapped area to discover new therapeutic targets. Among orphan GPCRs (oGPCRs) of interest, G protein-coupled receptor 37 (GPR37) is highly expressed in the central nervous system (CNS), particularly in the spinal cord and oligodendrocytes. While its cellular signaling mechanisms and endogenous receptor ligands remain elusive, GPR37 has been implicated in several important neurological conditions, including Parkinson's disease (PD), inflammation, pain, autism, and brain tumors. GPR37 structure, signaling, emerging physiology, and pharmacology are reviewed while integrating a discussion on potential therapeutic indications and opportunities.
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Affiliation(s)
- Andrew A. Bolinger
- Department of Pharmacology and Toxicology, Center for Addiction Sciences and Therapeutics, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Andrew Frazier
- Department of Pharmacology and Toxicology, Center for Addiction Sciences and Therapeutics, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Jun-Ho La
- Department of Neurobiology, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - John A. Allen
- Department of Pharmacology and Toxicology, Center for Addiction Sciences and Therapeutics, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Jia Zhou
- Department of Pharmacology and Toxicology, Center for Addiction Sciences and Therapeutics, University of Texas Medical Branch, Galveston, Texas 77555, United States
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Fuyuki A, Yamamoto S, Sohel MSH, Homma T, Kitamura K, Onouchi S, Saito S. Expression of prosaposin and its G protein-coupled receptor (GPR) 37 in mouse cochlear and vestibular nuclei. J Vet Med Sci 2023; 85:266-270. [PMID: 36696997 PMCID: PMC10076190 DOI: 10.1292/jvms.22-0552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Prosaposin is a precursor of lysosomal hydrolases activator proteins, saposins, and also acts as a secretory protein that is not processed into saposins. Prosaposin elicits neurotrophic function via G protein-coupled receptor (GPR) 37, and prosaposin deficiency causes abnormal vestibuloauditory end-organ development. In this study, immunohistochemistry was used to examine prosaposin and GPR37 expression patterns in the mouse cochlear and vestibular nuclei. Prosaposin immunoreactivity was observed in neurons and glial cells in both nuclei. GPR37 immunoreactivity was observed in only some neurons, and its immunoreactivity in the vestibular nucleus was weaker than that in the cochlear nucleus. This study suggests a possibility that prosaposin deficiency affects not only the end-organs but also the first center of the vestibuloauditory system.
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Affiliation(s)
- Aimi Fuyuki
- Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan
| | - Saki Yamamoto
- Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan
| | - Md Shahriar Hasan Sohel
- Laboratory of Veterinary Anatomy, The Joint Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - Takeshi Homma
- Laboratory of Veterinary Anatomy, The Joint Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - Kai Kitamura
- Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan
| | - Sawa Onouchi
- Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan.,Laboratory of Veterinary Anatomy, The Joint Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - Shouichiro Saito
- Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan.,Laboratory of Veterinary Anatomy, The Joint Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
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Sarkar S, Homma T, Onouchi S, Shimizu Y, Shiina T, Nabeka H, Matsuda S, Saito S. Expression of the G protein-coupled receptor (GPR) 37 and GPR37L1 in the mouse digestive system. J Vet Med Sci 2020; 83:1-8. [PMID: 33208571 PMCID: PMC7870391 DOI: 10.1292/jvms.20-0603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G protein-coupled receptor (GPR) 37 and GPR37L1 are known to modulate the dopaminergic neuron activity, and recently, they are identified as candidate prosaposin receptors. Intercellular prosaposin is proteolytically processed into four saposins, each of which acts as a sphingolipid hydrolase activator in the lysosome. In contrast, extracellular prosaposin exerts a trophic effect on neurons via GPR37 and GPR37L1. In this study, the expression patterns of GPR37 and GPR37L1 in the mouse digestive system were examined immunohistochemically. The islets of Langerhans of the pancreas showed intense immunoreactivity for GPR37 and GPR37L1. Weak immunoreactivity for GPR37 and GPR37L1 was found in the nerve plexuses of the esophagus and small and large intestines. Colocalization of GPR37 and tyrosine hydroxylase immunoreactivity was observed in the neuron of the nerve plexus of the large intestine. This study suggests the possibility that prosaposin affects the function of islet-secreting cells. Also, the expression of GPR37 and GPR37L1 in the nerve plexus suggests that prosaposin exerts a trophic effect not only in the central nervous system, but also in the enteric nervous system.
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Affiliation(s)
- Sonjoy Sarkar
- Laboratory of Veterinary Anatomy, The United Graduate School of Veterinary Science, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
| | - Takeshi Homma
- Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu 501-1193, Japan
| | - Sawa Onouchi
- Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu 501-1193, Japan
| | - Yasutake Shimizu
- Laboratory of Veterinary Physiology, The Joint Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan
| | - Takahiko Shiina
- Laboratory of Veterinary Physiology, The Joint Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan
| | - Hiroaki Nabeka
- Department of Anatomy and Embryology, Ehime University Graduate School of Medicine, Toon, Ehime 791-0295, Japan
| | - Seiji Matsuda
- Department of Anatomy and Embryology, Ehime University Graduate School of Medicine, Toon, Ehime 791-0295, Japan
| | - Shouichiro Saito
- Laboratory of Veterinary Anatomy, The United Graduate School of Veterinary Science, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.,Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu 501-1193, Japan.,Laboratory of Veterinary Anatomy, The Joint Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan
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GPR37 and GPR37L1 are receptors for the neuroprotective and glioprotective factors prosaptide and prosaposin. Proc Natl Acad Sci U S A 2013; 110:9529-34. [PMID: 23690594 DOI: 10.1073/pnas.1219004110] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
GPR37 (also known as Pael-R) and GPR37L1 are orphan G protein-coupled receptors that are almost exclusively expressed in the nervous system. We screened these receptors for potential activation by various orphan neuropeptides, and these screens yielded a single positive hit: prosaptide, which promoted the endocytosis of GPR37 and GPR37L1, bound to both receptors and activated signaling in a GPR37- and GPR37L1-dependent manner. Prosaptide stimulation of cells transfected with GPR37 or GPR37L1 induced the phosphorylation of ERK in a pertussis toxin-sensitive manner, stimulated (35)S-GTPγS binding, and promoted the inhibition of forskolin-stimulated cAMP production. Because prosaptide is the active fragment of the secreted neuroprotective and glioprotective factor prosaposin (also known as sulfated glycoprotein-1), we purified full-length prosaposin and found that it also stimulated GPR37 and GPR37L1 signaling. Moreover, both prosaptide and prosaposin were found to protect primary astrocytes against oxidative stress, with these protective effects being attenuated by siRNA-mediated knockdown of endogenous astrocytic GPR37 or GPR37L1. These data reveal that GPR37 and GPR37L1 are receptors for the neuroprotective and glioprotective factors prosaptide and prosaposin.
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