Localization of RhoGEF2 during Drosophila cellularization is developmentally controlled by slam

Abstract

Essential for proper function of small GTPases of the Rho family, which control many aspects of cytoskeletal and membrane dynamics, is their temporal and spatial control by activating GDP exchange factors (GEFs) and deactivating GTPase-activating-proteins (GAPs). The regulatory mechanisms controlling these factors are not well understood, especially during development, when the organization and behaviour of cells change in a stage dependent manner. During Drosophila cellularization Rho signalling and RhoGEF2 are involved in furrow canal formation and the organization of actin and myosin. Here we analyze, how RhoGEF2 is localized at the sites of membrane invagination. We show that the PDZ domain is necessary for localization and function of RhoGEF2 and identify Slam as a factor that is necessary for RhoGEF2 localization. We also demonstrate that Slam can recruit RhoGEF2 to ectopic sites. Furthermore we find that the PDZ domain of RhoGEF2 can form a complex with Slam invivo and that Slam transcripts and protein colocalize at the furrow canal and in basal particles. Based on these findings, we propose that accumulation of slam mRNA and protein at the presumptive invagination site provides a spatial and temporal trigger for RhoGEF2-Rho1 signalling.

Septins promote F-actin ring formation by crosslinking actin filaments into curved bundles

“…3c). Consistent with previous reports [28][29][30] , FCs in DRhoGEF2 mutants failed to constrict (Fig. 3a).…”

Genetic Evidence for Antagonism Between Pak Protein Kinase and Rho1 Small GTPase Signaling in Regulation of the Actin Cytoskeleton During Drosophila Oogenesis

“…A protein similar to RhoGEF2 in mammals, P115-RhoGEF, appears to be negatively regulated by Pak binding to its DH-PH domain but we have been unable to find a similar physical interaction between Pak and the RhoGEF2 DH-PH, nor have we detected an effect of Pak on Rho1-GTP levels, although it is possible that there could be an effect not detectable by our assays (Rosenfeldt et al 2006). A recent study showed that the PDZ domain of RhoGEF2 is required for its localization at the furrow canal during cellularization (Wenzl et al 2010). Furthermore, the novel protein Slam, which complexes with the RhoGEF2 PDZ domain, is required for RhoGEF2 localization during cellularization, and it will be of interest to determine if Pak regulation of RhoGEF2 localization in the follicular epithelium involves the PDZ domain and/or Slam (Wenzl et al 2010).…”

“…A recent study showed that the PDZ domain of RhoGEF2 is required for its localization at the furrow canal during cellularization (Wenzl et al 2010). Furthermore, the novel protein Slam, which complexes with the RhoGEF2 PDZ domain, is required for RhoGEF2 localization during cellularization, and it will be of interest to determine if Pak regulation of RhoGEF2 localization in the follicular epithelium involves the PDZ domain and/or Slam (Wenzl et al 2010). Another possibility is that Pak regulates RhoGEF2 through a trimeric G-protein interaction.…”

Flow-dependent myosin recruitment during Drosophila cellularization requires zygotic dunk activity

“…Interestingly, Slam has also been shown to promote the accumulation of myosin at the invagination front (Lecuit et al, 2002;Acharya et al, 2014). Slam directly binds to RhoGEF2 and is required for recruitment of RhoGEF2 to the invagination front (Wenzl et al, 2010). RhoGEF2 is a guanine nucleotide exchange factor for Rho1 and has been shown to promote actin assembly and myosin activation at the invagination front through Rho1 and its downstream effectors (Crawford et al, 1998;Padash Barmchi et al, 2005;Grosshans et al, 2005).…”