This family features the C-terminal regions of various plexins (e.g. Swiss:P51805). Plexins are receptors for semaphorins, and plexin signalling is important in path finding and patterning of both neurons and developing blood vessels [1,2]. The cytoplasmic region, which has been called a SEX domain in some members of this family [3], is involved in downstream signalling pathways, by interaction with proteins such as Rac1, RhoD, Rnd1 and other plexins [4]. This domain acts as a RasGAP domain [5].

1: Semaphorin-plexin signaling guides patterning of the developing vasculature. Torres-Vazquez J, Gitler AD, Fraser SD, Berk JD, Van N Pham, Fishman MC, Childs S, Epstein JA, Weinstein BM; Dev Cell 2004;7:117-123. PMID:15239959

2: Caenorhabditis elegans PlexinA, PLX-1, interacts with transmembrane semaphorins and regulates epidermal morphogenesis. Fujii T, Nakao F, Shibata Y, Shioi G, Kodama E, Fujisawa H, Takagi S; Development 2002;129:2053-2063. PMID:11959816

3: A family of transmembrane proteins with homology to the MET-hepatocyte growth factor receptor. Maestrini E, Tamagnone L, Longati P, Cremona O, Gulisano M, Bione S, Tamanini F, Neel BG, Toniolo D, Comoglio PM; Proc Natl Acad Sci U S A 1996;93:674-678. PMID:8570614

4: Plexin-A1 and plexin-B1 specifically interact at their cytoplasmic domains. Usui H, Taniguchi M, Yokomizo T, Shimizu T; Biochem Biophys Res Commun 2003;300:927-931. PMID:12559962

5: The semaphorin 3A receptor may directly regulate the activity of small GTPases. Rohm B, Rahim B, Kleiber B, Hovatta I, Puschel AW; FEBS Lett. 2000;486:68-72. PMID:11108845