Tripartite motif protein 23 (TRIM23) regulates degradation of epidermal growth factor receptor (EGFR)

Abstract

Tripartite motif protein 23 (TRIM23), also known as ADP‐ribosylation factor‐domain protein (ARD) 1, is a multi‐domain 64‐kDa protein that contains ADP‐ribosylation factor, GTPase‐activating protein, and E3 ubiquitin ligase sequences. That EGFR levels were higher in ARD1−/− than in wild type MEFs was known, but the mechanism responsible remained unknown. To explore that question, we used co‐immunoprecipitation (co‐IP) to evaluate possible interactions of ARD1 and EGFR. Endogenous ARD1 and EGFR in HeLa cells were each immunoprecipitated by antibodies against the other, as was cytohesin‐1, the only known activator of the ARD1 ARF domain. Overexpression of ARD1, intended to enhance the interaction between ARD1 and EGFR, decreased the total cell EGFR. We then found that EGFR levels were increased after ARD1 depletion in HeLa cells. It appears that the interaction of ARD1 and EGFR can be important in regulation of EGFR degradation, and thereby the EGFR content of HeLa cells as well as MEFs.