Phosphorylation Of Pkc Delta By Fer Tips The Balance From Egfr Degradation To Recycling

Receptor degradation terminates signaling by activated receptor tyrosine kinases. Degradation of EGFR occurs in lysosomes and requires the switching of RAB5 for RAB7 on late endosomes to enable their fusion with the lysosome, but what controls this critical switching is poorly understood. We show that the tyrosine kinase FER alters PKC delta function by phosphorylating it on Y374, and that phospho-Y374-PKC delta prevents RAB5 release from nascent late endosomes, thereby inhibiting EGFR degradation and promoting the recycling of endosomal EGFR to the cell surface. The rapid association of phospho-Y374-PKCd with EGFR-containing endosomes is diminished by PTPN14, which dephosphorylates phospho-Y374-PKC delta. In triple-negative breast cancer cells, the FER-dependent phosphorylation of PKCd enhances EGFR signaling and promotes anchorage-independent cell growth. Importantly, increased Y374-PKC delta phosphorylation correlating with arrested late endosome maturation was identified in similar to 25% of triple-negative breast cancer patients, suggesting that dysregulation of this pathway may contribute to their pathology.