IRR is involved in glucose-induced endocytosis after insulin secretion

Endocytosis after insulin secretion plays a pivotal role in the regulation of insulin secretion in pancreatic β-cells. Our recent study suggested that EPI64, a GTPase activating protein for Rab27a, contributes to the regulation of glucose-induced endocytosis, which is mediated by the GDP-bound form of Rab27a. Here, we identified insulin receptor-related receptor (IRR) as an EPI64-interacting protein. Knockdown of IRR inhibited glucose-induced uptake of transferrin, a marker of endocytosis, translocation of the guanine-nucleotide-exchange factor ARNO to the plasma membrane, and generation of phosphatidylinositol 3,4,5-trisphosphate (PIP₃). These results suggest that IRR functions upstream of PIP₃ generation and controls endocytosis after insulin secretion.