P-glycoprotein attenuates DNA repair activity in multidrug-resistant cells by acting through the Cbp-Csk-Src cascade
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Li-Fang Lin1, Ming-Hsi Wu1, Vijaya Kumar Pidugu1,2, I-Ching Ho1, Tsann-Long Su1 and Te-Chang Lee1,2,3
1Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
2Taiwan International Graduate Program in Molecular Medicine, National Yang-Ming University, Academia Sinica, Taipei 11529, Taiwan
3Institute of Pharmacology, National Yang-Ming University, Taipei 11221, Taiwan
Te-Chang Lee, email: [email protected]
Keywords: P-glycoprotein, multidrug resistance, Cbp-Csk-Src cascade, DNA repair proteins
Received: October 07, 2016 Accepted: January 24, 2017 Published: February 03, 2017
Recent studies have demonstrated that P-glycoprotein (P-gp) expression impairs DNA interstrand cross-linking agent-induced DNA repair efficiency in multidrug-resistant (MDR) cells. To date, the detailed molecular mechanisms underlying how P-gp interferes with Src activation and subsequent DNA repair activity remain unclear. In this study, we determined that the C-terminal Src kinase-binding protein (Cbp) signaling pathway involved in the negative control of Src activation is enhanced in MDR cells. We also demonstrated that cells that ectopically express P-gp exhibit reduced activation of DNA damage response regulators, such as ATM, Chk2, Braca1 and Nbs1 and hence attenuated DNA double-strand break repair capacity and become more susceptible than vector control cells to DNA interstrand cross-linking (ICL) agents. Moreover, we demonstrated that P-gp can not only interact with Cbp and Src but also enhance the formation of inhibitory C-terminal Src kinase (Csk)-Cbp complexes that reduce phosphorylation of the Src activation residue Y416 and increase phosphorylation of the Src negative regulatory residue Y527. Notably, suppression of Cbp expression in MDR cells restores cisplatin-induced Src activation, improves DNA repair capacity, and increases resistance to ICL agents. Ectopic expression of Cbp attenuates cisplatin-induced Src activation and increases the susceptibility of cells to ICL agents. Together, the current results indicate that P-gp inhibits DNA repair activity by modulating Src activation via Cbp-Csk-Src cascade. These results suggest that DNA ICL agents are likely to have therapeutic potential against MDR cells with P-gp-overexpression.
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