Structural and functional analysis of GPR56 protein in human frontal cortex developmental disease BFPP: The role of disease‐associated mutations on receptor trafficking and functions

Abstract

G protein‐coupled receptor 56 (GPR56) plays a role in the development of neural progenitor cells and has been linked to the developmental malformations of human brain. Similar to other adhesion GPCRs, GPR56 contains a GPCR proteolytic site (GPS) motif. Genetic mutations in GPR56 cause a human brain cortical malformation called bilateral frontoparietal polymicrogyria (BFPP). However, it remains unclear how these mutations affect GPR56 function. We cloned the wild type GPR56 cDNA and disease‐associated point mutants, including R38W, Y88C, and C91S in the N terminal domain, two mutations (R565W, L640R) in the extracellular loop domain, and the two mutations in the GPS domain (C346S and W349S). We aim to investigate how the BFPP‐associated mutations affect the intracellular trafficking and cell surface expression of GPR56. We found that disease‐associated GPR56 missense mutations produce proteins with reduced intracellular trafficking and poor cell surface expression or impaired GPS cleavage that fail to traffic beyond the ER. Furthermore, we has produced recombinant GPR56 extracellular domain as a protein probe for ligand search on various cell lines. We have identified a potential novel cellular ligand for GPR56. NSC97‐2628‐B‐182‐030‐MY2