A role for the non‐receptor tyrosine kinase ACK1 in TNF‐alpha‐mediated apoptosis and proliferation in human intestinal epithelial caco‐2 cells

摘要

Abstract The roles of tumor necrosis factor alpha (TNF‐alpha) and its mediators in cellular processes related to intestinal diseases remain elusive. In this study, we aimed to determine the biological role of activated Cdc42‐associated kinase 1 (ACK1) in TNF‐alpha‐mediated apoptosis and proliferation in Caco‐2 cells. ACK1 expression was knocked down using ACK1‐specific siRNAs, and ACK1 activity was disrupted using a small molecule ACK1 inhibitor. The Terminal deoxynucleotidyl transferase biotin‐dUTP Nick End Labeling (TUNEL) and the BrdU incorporation assays were used to measure apoptosis and cell proliferation, respectively. ACK1‐specific siRNA and the pharmacological ACK1 inhibitor significantly abrogated the TNF‐alpha‐mediated anti‐apoptotic effects and proliferation of Caco‐2 cells. Interestingly, TNF‐alpha activated ACK1 at tyrosine 284 (Tyr284), and the ErbB family of proteins was implicated in ACK1 activation in Caco‐2 cells. ACK1‐Tyr284 was required for protein kinase B (AKT) activation, and ACK1 signaling was mediated through recruiting and phosphorylating the down‐stream adaptor protein AKT, which likely promoted cell proliferation in response to TNF‐alpha. Moreover, ACK1 activated AKT and Src enhanced nuclear factor‐кB (NF‐кB) activity, suggesting a correlation between NF‐кB signaling and TNF‐alpha‐mediated apoptosis in Caco‐2 cells. Our results demonstrate that ACK1 plays an important role in modulating TNF‐alpha‐induced aberrant cell proliferation and apoptosis, mediated in part by ACK1 activation. ACK1 and its down‐stream effectors may hold promise as therapeutic targets in the prevention and treatment of gastrointestinal cancers, in particular, those induced by chronic intestinal inflammation.