Clathrin-mediated endocytosis (CME), the major endocytic pathway, regulates the rates of internalization of receptors as well as their downstream signaling activities. Recently, our lab has discovered that signaling can reciprocally regulate CME in cancer cells. The crosstalk between signaling and CME contributes to abnormal trafficking of signaling receptors and altered downstream signaling, leading to enhanced cancer metastasis. Accordingly, it is important to understand the nature and extent of interactions between CME and intracellular signaling in cancer cell biology. To address this issue, we targeted a set of prioritized kinases that are often implicated in cancer-relevant signaling pathways using validated pharmacologic inhibitors and compared their effects on CME function using different models for human noncancerous and cancer cells. We found that inhibition of several kinases selectively affected CME function in cancer cells. Notably, ERK inhibition had the most significant and consistent effects on CME activity across different types of cancer cells, while not affecting CME in several noncancerous cell lines tested. We established that a second ERK inhibitor, and importantly inhibition of the essential upstream kinase MEK, had the same cancer cell-specific effects on CME activity. Furthermore, we found that inhibition of ERK dramatically reduced the rate of clathrin-coated pit (CCP) initiation selectively in cancer cells. Characterization of one potential ERK substrate, FCHSD2, showed that knockdown of FCHSD2 had the similar cancer cell-specific effects on CME activity and on CCP initiation rate and that the cells depleted for FCHSD2 were insensitive to ERK inhibition. Surprisingly, the expression level of FCHSD2 is positively correlated with higher cancer patient survival rate, suggesting that FCHSD2 might be a tumor suppressor regulated by ERK. Our study provides new insight into the mechanisms and consequences of the reciprocal regulation of signaling and CME in cancer cells.

Citation Format: Guan-Yu Xiao, Sandra Schmid. Oncogenic signaling pathways differentially regulate clathrin-mediated endocytosis in cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 966.