Identification of a mitotic Rac-GEF, Trio, that counteracts MgcRacGAP function during cytokinesis.
Bottom Line: Moreover, Trio depletion specifically rescues the cytokinesis failure induced by MgcRacGAP depletion.Of importance, we demonstrate that this rescue is mediated by the Trio-Rac1 pathway, using GEF-dead mutants of Trio and a specific inhibitor of Rac1 activation by Trio.Overall this work identifies for the first time a GEF controlling Rac1 activation in dividing cells that counteracts MgcRacGAP function in cytokinesis.
Affiliation: Signaling and Cytoskeleton Dynamics Group, University of Montpellier, 34293 Montpellier, France.Show MeSH
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Mentions: To confirm that Trio activates Rac1 to control F-actin remodeling in dividing cells, we performed rescue experiments using the GEFD1 domain of Trio (green fluorescent protein [GFP]–DH1PH1; Figure 4, A–C, and Supplemental Figure S3). This domain was previously shown to strongly activate Rac1 (Bellanger et al., 1998). Expression of GFP-DH1PH1, insensitive to Trio siRNAs (Supplemental Figure S3), efficiently rescued the F-actin cytoskeleton remodeling defects observed in Trio-depleted anaphase cells (Figure 4, A–C). To demonstrate further the involvement of the Trio-Rac1 pathway in controlling F-actin remodeling in dividing cells, we used ITX3, a specific inhibitor of Rac1 activation by Trio (Bouquier et al., 2009). ITX3 treatment phenocopied Trio depletion (Figure 4D). Taken together, these results demonstrate that Trio functions as a GEF of Rac1 during cell division and that the Trio-Rac1-Arp2/3 pathway is important to control F-actin cytoskeleton remodeling in dividing cells.
Affiliation: Signaling and Cytoskeleton Dynamics Group, University of Montpellier, 34293 Montpellier, France.