Multifunctionality of proteins is one of the mechanisms accounting for the complexity of interactome networks in higher eukaryotes. Reports in the literature suggest that during oncogenesis and other pathologic conditions many proteins perform additional functions without changes in three dimensional structures. One such multifunctional protein is S29 ribosomal protein. The S29 ribosomal protein is not only involved in ribosome assembly but its enhanced expression has been shown to possess antitumor properties in NSCLC H520 cells. Moreover, S29 ribosomal protein increases tumor suppressor activity of K rev-1 gene on v-K ras-transformed NIH3T3 cells. Recently conservation and multifunctional nature of ribosomal protein S29 has urged the search for mechanism behind its function. In this study we made an attempt to investigate the antiproliferative potential of S29 ribosomal protein on human laryngeal carcinoma cells (Hep2) by adopting biochemical and proteomic approaches. Apoptosis was examined by Hoechst 33342 staining, FACS, increased expression of pro-apoptotic protein Bax, decreased expression of anti-apoptotic proteins Bcl-2 and Bcl-xL_, release of apoptogenic cytochrome c and activation of initiator and effector caspases followed by cleavage of nuclear substrate poly (ADP-ribose) polymerase. There was also non-involvement of p53 in S29 ribosomal protein induced apoptosis. p38 and JNK inhibitors significantly protected cells from S29-induced apoptosis. Further, our proteomic results also support that JNK and p38 activation appears to play a critical role in S29-induced apoptosis in Hep2 cells. These findings demonstrate for the first time the potential of anti-human laryngeal activity of S29 ribosomal protein in Hep2 cells. Further this study raises the possibility of using S29 ribosomal protein as a promising approach to carcinoma therapy.

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