Cleavage of epidermal growth factor receptor by caspase during apoptosis is independent of its internalization

Abstract

Epidermal growth factor receptor (EGFR) plays a critical role in cell proliferation, differentiation, and transformation. EGFR downregulation attenuates its signaling intensity and duration to maintain cellular homeostasis. Here, we report that during apoptosis EGFR is cleaved by activated caspase-3 or related proteases at its C-terminus domain. EGFR downregulation by activation of caspases is neither stimulus- nor cell type-specific. EGFR internalization during apoptosis required dynamin and cholesterol since dominant-negative dynamin (K44A) or cholesterol depletion by methyl--cyclodextrin prevented EGFR internalization. However, EGFR downregulation did not require its internalization. The EGFR cleavage fragment was detected in the membrane blebs in addition to the cell pellets. Mutations at the consensus sequence (DXXD) at the C-terminus domain revealed that DVVD1012 and to a lesser extent DNPD1172 may be target sites for active recombinant caspase-3 in vitro and activated caspase-3 or related proteases in vivo. We have detected the N-terminus and C-terminus fragments in vitro and in vivo. A cleavage-deficient EGFR mutant delayed apoptosis process. We conclude that the evolutionarily conserved C-terminus domain of EGFR is the target of caspases and subjected to degradation during apoptosis to shut down its signaling.