This family consists of Rap1 GTPase-GDP dissociation stimulator 1 (RAP1GDS1, SmgGDS) from vertebrates and its homologues from fungi and Drosophila, GTPase-GDP dissociation stimulator vimar. RAP1GDS1 acts as a guanine exchange factor (GEFs) acting on small GTPases RhoA and RhoC through a distinct exchange mechanism compared with canonical GEFs []. RAP1GDS1 promotes both cell proliferation and migration and is up-regulated in several types of cancer [, ]. RAP1GDS1 plays a role in mitochondria morphology, as it regulates mitochondrial dynamics by controlling RHOT function to promote mitochondrial fission during high calcium conditions []. The Saccharomyces cerevisiae orthologue is known as Bem4. Bem4 interacts with Rho-type GTPases, including Cdc42p, and regulates the filamentous-growth mitogen-activated protein kinase pathway [, ].
