Palmitoylation of CKAP4 by DHHC2 regulates APF‐mediated signaling

Abstract

We identified CKAP4 as a major substrate of the palmitoyl acyl transferase DHHC2 using a novel proteomic method called Palmitoyl‐cysteine Identification, Capture and Analysis (PICA). CKAP4 is a reversibly palmitoylated and phosphorylated protein that links the ER to the cytoskeleton. It is also a high‐affinity receptor for APF, a small glycosylated peptide secreted from bladder epithelial cells of patients with interstitial cystitis. The ability of DHHC2‐mediated palmitoylation of CKAP4 to regulate the antiproliferative effects of APF in HeLa cells was investigated. Our data show that siRNA‐mediated knockdown of DHHC2 expression and consequent suppression of CKAP4 palmitoylation blocks the ability of APF to regulate proliferation. Immunocytochemistry revealed inhibition of CKAP4 trafficking to the plasma membrane following DHHC2 knockdown. Stable expression of a palmitoylation‐incompetent form of CKAP4 showed reduced binding to microtubules and significantly increased the rate of cell migration. These data suggest an important role for DHHC2‐mediated palmitoylation of CKAP4 in cancer‐related cellular behaviors and support the idea that DHHC2 is a tumor suppressor.