RasGAP is a multifunctional protein that controls Ras activity and that is found in chromosomal passenger complexes. It also negatively or positively regulates apoptosis depending on the extent of its cleavage by caspase-3. RasGAP has been reported to bind to G3BP1 (RasGAP SH3-domain-binding protein 1), a protein regulating mRNA stability and stress granule formation. The region of RasGAP (amino acids 317-326) thought to bind to G3BP1 corresponds exactly to the sequence within fragment N2, a caspase-3-generated fragment of RasGAP, that mediates sensitization of tumor cells to genotoxins. While assessing the contribution of G3BP1 in the anti-cancer function of a cell-permeable peptide containing the 317-326 sequence of RasGAP (TAT-RasGAP(3)(1)(7)(-)(3)(2)(6)), we found that, in conditions where G3BP1 and RasGAP bind to known partners, no interaction between G3BP1 and RasGAP could be detected. TAT-RasGAP(3)(1)(7)(-)(3)(2)(6) did not modulate binding of G3BP1 to USP10, stress granule formation or c-myc mRNA levels. Finally, TAT-RasGAP(3)(1)(7)(-)(3)(2)(6) was able to sensitize G3BP1 knock-out cells to cisplatin-induced apoptosis. Collectively these results indicate that G3BP1 and its putative RasGAP binding region have no functional influence on each other. Importantly, our data provide arguments against G3BP1 being a genuine RasGAP-binding partner. Hence, G3BP1-mediated signaling may not involve RasGAP.
Revisiting G3BP1 as a RasGAP binding protein: sensitization of tumor cells to chemotherapy by the RasGAP 317-326 sequence does not involve G3BP1
Annibaldi, A.; Dousse, A.; Martin, S.; Tazi, J.; Widmann, C.
2011 / vol 6 / pages e29024
10.1371/journal.pone.0029024 PONE-D-11-15805 [pii]
1932-6203 (Electronic) 1932-6203 (Linking)
Cell Line, Tumor; Humans; Animals; Mice; Amino Acid Sequence; Protein Binding; Apoptosis/drug effects; Carrier Proteins/*metabolism; Cricetinae; Drug Resistance, Neoplasm/drug effects; Mutagens/pharmacology; Peptide Fragments/chemistry/*pharmacology; ras GTPase-Activating Proteins/*chemistry/*metabolism