Revisiting G3BP1 as a RasGAP binding protein: sensitization of tumor cells to chemotherapy by the RasGAP 317-326 sequence does not involve G3BP1.
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-RasGAP₃₁₇₋₃₂₆), we found that, in conditions where G3BP1 and RasGAP bind to known partners, no interaction between G3BP1 and RasGAP could be detected. TAT-RasGAP₃₁₇₋₃₂₆ did not modulate binding of G3BP1 to USP10, stress granule formation or c-myc mRNA levels. Finally, TAT-RasGAP₃₁₇₋₃₂₆ 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.
Department of Physiology, University of Lausanne, Lausanne, Switzerland.
Alessandro
A
Annibaldi
Aline
A
Dousse
Sophie
S
Martin
Jamal
J
Tazi
Christian
C
Widmann
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D006224:Cricetinae; D004265:DNA Helicases; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D006801:Humans; D051379:Mice; D009153:Mutagens / Q000494:pharmacology; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D000075223:Poly-ADP-Ribose Binding Proteins; D011485:Protein Binding; D020365:RNA Helicases; D000067776:RNA Recognition Motif Proteins; D020703:ras GTPase-Activating Proteins / Q000737:chemistry* / Q000378:metabolism*
D002352:Carrier Proteins; D009153:Mutagens; D010446:Peptide Fragments; D000075223:Poly-ADP-Ribose Binding Proteins; D000067776:RNA Recognition Motif Proteins; D020703:ras GTPase-Activating Proteins; D004265:DNA Helicases; C492055:G3bp1 protein, mouse; D020365:RNA Helicases