orphan adhesion receptor GPR56, member of the class B2 family of seven-transmembrane G protein-coupled receptors
GPR56 is an orphan receptor that has been classified as that belongs to the Group VIII of adhesion GPCRs. Other members of the Group VII include orphan GPCRs such as GPR64, GPR97, GPR112, GPR114, and GPR126. GPR56 is involved in the regulation of oligodendrocyte development and myelination in the central nervous system via coupling to G(12/13) proteins, which leads to the activation of RhoA GTPase. The adhesion receptors are characterized by the presence of large N-terminal extracellular domains containing multiple adhesion motifs, which play critical roles in cell-cell adhesion and cell-matrix interactions, that are coupled to a class B seven-transmembrane domain. Furthermore, almost all adhesion receptors, except GPR123, contain an evolutionarily conserved GPCR- autoproteolysis inducing (GAIN) domain that undergoes autoproteolytic processing at the GPCR proteolysis site (GPS) motif located immediately N-terminal to the first transmembrane region, to generate N- and C-terminal fragments (NTF and CTF), which may serve important biological functions.