51. Identification and functional characterisation of N-linked glycosylation of the orphan G protein-coupled receptor Gpr176
- Author
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Akira Hirasawa, Kaoru Goto, Yoshiaki Yamaguchi, Tianyu Wang, Genzui Setsu, Hitoshi Okamura, Masao Doi, Shumpei Nakagawa, Takahito Miyake, and Sumihiro Kunisue
- Subjects
Male ,Glycosylation ,Glycoside Hydrolases ,lcsh:Medicine ,Sequence Homology ,Hormone receptors ,medicine.disease_cause ,Article ,Receptors, G-Protein-Coupled ,chemistry.chemical_compound ,Mice ,N-linked glycosylation ,medicine ,Cyclic AMP ,Animals ,Amino Acid Sequence ,lcsh:Science ,Receptor ,Peptide sequence ,G protein-coupled receptor ,Mice, Knockout ,Mutation ,Multidisciplinary ,lcsh:R ,Cell biology ,carbohydrates (lipids) ,Mice, Inbred C57BL ,chemistry ,lcsh:Q ,lipids (amino acids, peptides, and proteins) ,Heterologous expression ,Signal transduction ,Circadian rhythms and sleep ,Protein Processing, Post-Translational ,Signal Transduction ,Post-translational modifications - Abstract
G-protein-coupled receptors (GPCRs) are important drug targets with diverse therapeutic applications. However, there are still more than a hundred orphan GPCRs, whose protein functions and biochemical features remain unidentified. Gpr176 encodes a class-A orphan GPCR that has a role in circadian clock regulation in mouse hypothalamus and is also implicated in human breast cancer transcriptional response. Here we show that Gpr176 is N-glycosylated. Peptide-N-glycosidase treatment of mouse hypothalamus extracts revealed that endogenous Gpr176 undergoes N-glycosylation. Using a heterologous expression system, we show that N-glycosylation occurs at four conserved asparagine residues in the N-terminal region of Gpr176. Deficient N-glycosylation due to mutation of these residues reduced the protein expression of Gpr176. At the molecular function level, Gpr176 has constitutive, agonist-independent activity that leads to reduced cAMP synthesis. Although deficient N-glycosylation did not compromise this intrinsic activity, the resultant reduction in protein expression was accompanied by attenuation of cAMP-repressive activity in the cells. We also demonstrate that human GPR176 is N-glycosylated. Importantly, missense variations in the conserved N-glycosylation sites of human GPR176 (rs1473415441; rs761894953) affected N-glycosylation and thereby attenuated protein expression and cAMP-repressive activity in the cells. We show that N-glycosylation is a prerequisite for the efficient protein expression of functional Gpr176/GPR176.
- Published
- 2019