A disease-associated mutation in the adhesion GPCR BAI2 (ADGRB2) increases receptor signaling activity

Abstract

Mutations in G protein-coupled receptors (GPCRs) that increase constitutive signaling activity can cause human disease. A de novo C-terminal mutation (R1465W) in the adhesion GPCR BAI2 (also known as ADGRB2) was identified in a patient suffering from progressive spastic paraparesis and other neurological symptoms. In vitro studies revealed that this mutation strongly increases the constitutive signaling activity of an N-terminally cleaved form of BAI2, which represents the activated form of the receptor. Further studies dissecting the mechanism(s) underling this effect revealed that wild-type BAI2 primarily couples to Gαz, with the R1465W mutation conferring increased coupling to Gαi. The R1465W mutation also increases the total and surface expression of BAI2. The mutation has no effect on receptor binding to β-arrestins, but does perturb binding to the endocytic protein endophilin A1, identified here as a novel interacting partner for BAI2. These studies provide new insights into the signaling capabilities of the adhesion GPCR BAI2/ADGRB2 and shed light on how an apparent gain-of-function mutation to the receptor’s C-terminus may lead to human disease.

A Comprehensive Mutagenesis Screen of the Adhesion GPCR Latrophilin-1/ADGRL1

“…Mutant GPCRs are often overexpressed and constitutively active in various cancers ( Dorsam and Gutkind, 2007 , Kan et al., 2010 , O'Hayre et al., 2013 ). Disease-associated mutations were previously reported to change other adhesion GPCR signaling ( Kishore and Hall, 2017 , Purcell et al., 2017 ). We tested cancer-associated mutations of Lphns reported in different types of carcinomas ( Kan et al., 2010 , O'Hayre et al., 2013 ) and found that the cancer-associated mutations affected basal activity and/or peptide response ( Figure 4 E).…”

Arrestin‐independent constitutive endocytosis of GPR125/ADGRA3

“…After internalization, the receptors are either targeted for degradation or recycled back to the cell surface where they can be stimulated again by their ligands . To our knowledge, little is known about intracellular trafficking of aGPCRs compared with class A, B1, and C receptors, apart from certain aGPCR's interaction with β‐arrestin and endosomal proteins . The arrestin family consists of four members: arrestin‐1 and arrestin‐4, also known as visual arrestins, are exclusively expressed in the retina, whereas the two β‐arrestin isoforms, β‐arrestin‐1 and β‐arrestin‐2 (also named arrestin‐2 and arrestin‐3, respectively), are ubiquitously expressed in most tissues …”

Orphan G Protein Coupled Receptors in Affective Disorders

“…In vitro, once the extracellular region is cleaved at the GPCR proteolytic site, truncated ADGRB2 specifically activates the Nuclear Factor of Activated T-cells (NFAT) luciferase reporter, suggesting a coupling to Gαq [ 101 ]. However, following signaling and biochemical studies of the activating mutation R1465W, it was revealed that ADGRB2 stimulates the NFAT pathway by Gβγ liberation and the activation of calcium channels and not through Gq [ 102 ]. Further in vitro analysis using the G protein inhibitors, pertussis toxin (PTX) and gallein, pointed instead to a coupling to Gαi/o/z family members, with a preference for Gαz [ 102 ].…”