Monocyte chemotactic protein-induced protein-1 enhances DR5 degradation and negatively regulates DR5 activation-induced apoptosis through its deubiquitinase function

Monocyte chemotactic protein-induced protein-1 (MCPIP1; also called Regnase-1) encoded by the ZC3H12A gene critically regulates inflammatory responses and immune homeostasis primarily by RNase-dependent and - independent mechanisms. However, the relationship of MCPIP1 with apoptosis and cancer and the underlying mechanisms are largely unclear. The current study has demonstrated a previously uncovered connection between MCPIP1 and the negative regulation of death receptor 5 (DR5; also known as TRAIL-R2 or killer/DR5), a cell surface receptor for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), which is produced endogenously by various immune cells such as T cells. Our findings have revealed that MCPIP1 decreases both total cellular and cell surface DR5, primarily through modulating DUB-mediated protein autophagic/lysosomal degradation. Suppression of MCPIP1 by gene knockdown induces the formation of death-induced signaling complex (DISC) and enhances TRAIL or DR5 activation-induced apoptosis in cancer cells. Moreover, we demonstrated an inverse correlation between MCPIP1 expression and DR5 expression/cell sensitivity to DR5 activation-induced apoptosis in cancer cells. Our findings warrant future investigation of the roles of negative regulation of DR5 by MCPIP1 in cancer and in T-cell immunity.