Adhesion G Protein-Coupled Receptor G1 (ADGRG1/GPR56) and Pancreatic ß-Cell Function.

ABSTRACT

CONTEXT Adhesion G protein-coupled receptor (GPCR)-G1 (ADGRG1) is the most abundant GPCR in human pancreatic islets, but its role in islet function is unclear. OBJECTIVE: Investigate how ADGRG1 expression and activation by its ligand, collagen III, impacts ß-cell function in normal and type 2 diabetic (T2D) islets. DESIGN: Genes associated with the ADGRG1 in human islets was probed by RNA-sequencing of human pancreatic islet isolated from cadaveric donors, followed by functional studies on ß-cell proliferation, apoptosis, and insulin secretion in human and mouse islets and in INS-1 cells. MAIN OUTCOME MEASURES: Changes in ß-cell gene expression, proliferation, apoptosis, and insulin secretion were quantified by RNA-sequencing, qPCR, Thymidine incorporation, Western blotting, and RIA, respectively. RESULTS: ADGRG1 is the most abundant GPCR mRNA in both human and mouse islets, and its expression in human islets strongly correlates with genes important for ß-cell function and T2D risk. The expression of ADGRG1 was reduced in islets of T2D donors, in db/db mouse islets, and in isolated human islets exposed to chronic hyperglycemia. Beneficial effects of collagen type III on ß-cell function via activation of the cAMP/protein kinase A pathway, suppression of RhoA and caspase-3 activity, increased ß-cell viability, and proliferation were abolished when ADGRG1 was down-regulated in ß-cells. CONCLUSIONS: We demonstrate a mechanistic link between ADGRG1 expression and ß-cell function. Pharmacological agents that promote expression or activation of the ADGRG1 receptor may represent a novel approach for the treatment of T2D.