Dominant negative RAC1 attenuates paclitaxel-induced apoptosis in human melanoma cells through upregulation of heat shock protein 27: A functional proteomics analysis

Abstract

GTPase Rac1 regulates a variety of cellular processes. More recent data suggest a role of Rac1 in the regulation of cell apoptosis. In the present study, I investigated the functional effects of Rac1 activation/inhibition on cancer cell apoptosis sensitivity and the underlying molecular mechanism by using three genetically modified stable human melanoma M14 cell lines. These cell lines are pIRES, V12Rac1, and N17Rac1. I found that N17Rac1 cells were more resistant to paclitaxel-evoked apoptosis compared to V12Rac1 and pIRES. Proteomic analysis revealed two proteins differentially displayed amongst the protein compositions of the three cell lines. One was upregulated in N17Rac1 cells, which was identified as HSP27. The second peptide spot was present only in N17Rac1, which was identified as ARL6IP4 also known as SR25. In order to examine the possible contribution of HSP27 upregulation to resistance against paclitaxel-elicited apoptosis in N17Rac1 cells, I used siRNA to knockdown HSP27 protein and determine ita??s influence on apoptotic triggering. I found that knockdown of HSP27 significantly increased the sensitivity of N17Rac1 cells to paclitaxel-evoked apoptosis.