Glucose-stimulated insulin secretion is controlled by both exocytosis and endocytosis in pancreatic β-cells. Although endocytosis is a fundamental step to maintain cellular responses to the secretagogue, the molecular mechanism of endocytosis remains poorly defined. Kimura et al. have demonstrated the regulatory mechanisms of the IQGAP1/GDP-bound Rab27a endocytic machinery. PKCε, which was activated by glucose stimulation, phosphorylated IQGAP1 on Ser-1443, thereby promoting the dissociation of the IQGAP1/GDP-bound Rab27a complex in pancreatic β-cells. Insulin secretion is controlled by stage-specific complex formation and the dissociation of IQGAP1 from its specific binding partners.