High glucose-induced glucagon resistance and membrane distribution of GCGR revealed by super-resolution imaging

Summary: The glucagon receptor (GCGR) is a member of the class B G protein-coupled receptor family. Many research works have been carried out on GCGR structure, glucagon signaling pathway, and GCGR antagonists. However, the expression and fine distribution of GCGR proteins in response to glucagon under high glucose remain unclear. Using direct stochastic optical reconstruction microscopy (dSTORM) imaging, nanoscale GCGR clusters were observed on HepG2 cell membranes, and high glucose promoted GCGR expression and the formation of more and larger clusters. Moreover, glucagon stimulation under high glucose did not inhibit GCGR levels as significantly as that under low glucose and did not increase the downstream cyclic 3,5′-adenosine monophosphate-protein kinase A (cAMP-PKA) signal, and there were still large-size clusters on the membranes, indicating that high glucose induced glucagon resistance. In addition, high glucose induced stronger glucagon resistance in hepatoma cells compared with hepatic cells. Our work will pave a way to further our understanding of the pathogenesis of diabetes and develop more effective drugs targeting GCGR.