Adhesion G protein-coupled receptors (aGPCRs) play critical roles in diverse neurobiological processes including brain development, synaptogenesis, and myelination. The aGPCR GPR56/ADGRG1 regulates both oligodendrocyte and cortical development. The N-terminal domain of GPR56 has low sequence identity and a fold that likely diverged from the PTX and LNS domains. It also has a conserved motif (HphiC91xxWxxxxG) that was identified among canonical PTX domains. Thus, it is termed the Pentraxin/Laminin/neurexin/sex-hormone-binding-globulin-Like (PLL) domain. Truncation-based analyses suggest that the regions of GPR56 responsible for binding TG2 and collagen III are within the PLL domain, most likely in the surface-exposed conserved patch. Furthermore, it is suggested that the conserved patch of the PLL domain mediates an essential function in CNS myelination [1].

1: Structural Basis for Regulation of GPR56/ADGRG1 by Its Alternatively Spliced Extracellular Domains. Salzman GS, Ackerman SD, Ding C, Koide A, Leon K, Luo R, Stoveken HM, Fernandez CG, Tall GG, Piao X, Monk KR, Koide S, Arac D; Neuron. 2016;91:1292-1304. PMID:27657451