Figure 1.

Summary of the existing mechanisms of insulin receptor (INSR) endocytosis, sorting, endosomal trafficking, and recycling. Insulin-INSR complex is internalized via clathrin-dependent and -independent pathways. The complex is broken down in early endosome (EE). Insulin is relocated into late endosome for degradation. INSR is either trafficked to late endosome for degradation or recycled back to the plasma membrane. INSR can be recycled directly from EE via a rapid recycling mechanism or go through the endosomal recycling compartment via a slow recycling process. Proteins involved in different processes are indicated on their corresponding positions.