title: Disease-associated GPR56 mutations cause bilateral frontoparietal polymicrogyria via multiple mechanisms.
abstract: Loss-of-function mutations in the gene encoding G protein-coupled receptor 56 (GPR56) lead to bilateral frontoparietal polymicrogyria (BFPP), an autosomal recessive disorder affecting brain development. The GPR56 receptor is a member of the adhesion-GPCR family characterized by the chimeric composition of a long ectodomain (ECD), a GPCR proteolysis site (GPS), and a seven-pass transmembrane (7TM) moiety. Interestingly, all identified BFPP-associated missense mutations are located within the extracellular region of GPR56 including the ECD, GPS, and the extracellular loops of 7TM. In the present study, a detailed molecular and functional analysis of the wild-type GPR56 and BFPP-associated point mutants shows that individual GPR56 mutants most likely cause BFPP via different combination of multiple mechanisms. These include reduced surface receptor expression, loss of GPS proteolysis, reduced receptor shedding, inability to interact with a novel protein ligand, and differential distribution of the 7TM moiety in lipid rafts. These results provide novel insights into the cellular functions of GPR56 receptor and reveal molecular mechanisms whereby GPR56 mutations induce BFPP.
authors.affiliation: Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan, Taiwan.
authors.forename: Nien-Yi
authors.initials: NY
authors.lastname: Chiang
authors.forename: Cheng-Chih
authors.initials: CC
authors.lastname: Hsiao
authors.forename: Yi-Shu
authors.initials: YS
authors.lastname: Huang
authors.forename: Hsin-Yi
authors.initials: HY
authors.lastname: Chen
authors.forename: I-Ju
authors.initials: IJ
authors.lastname: Hsieh
authors.forename: Gin-Wen
authors.initials: GW
authors.lastname: Chang
authors.forename: Hsi-Hsien
authors.initials: HH
authors.lastname: Lin
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006025:Glycosaminoglycans / Q000737:chemistry; D006801:Humans; D054220:Malformations of Cortical Development / Q000235:genetics*; D021962:Membrane Microdomains; D051379:Mice; D009422:Nervous System Diseases / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding; D043562:Receptors, G-Protein-Coupled / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*
chemical_list: D006025:Glycosaminoglycans; D043562:Receptors, G-Protein-Coupled; C118925:ADGRG1 protein, human; C524781:Adgrg1 protein, mouse