The Journal of Cell Biology
Geisel School of Medicine
Fibroblast growth factor 2 (FGF2) is a major regulator of developmental, pathological, and therapeutic angiogenesis. Its activity is partially mediated by binding to syndecan 4 (S4), a proteoglycan receptor. Angiogenesis requires polarized activation of the small guanosine triphosphatase Rac1, which involves localized dissociation from RhoGDI1 and association with the plasma membrane. Previous work has shown that genetic deletion of S4 or its adapter, synectin, leads to depolarized Rac activation, decreased endothelial migration, and other physiological defects. In this study, we show that Rac1 activation downstream of S4 is mediated by the RhoG activation pathway. RhoG is maintained in an inactive state by RhoGDI1, which is found in a ternary complex with synectin and S4. Binding of S4 to synectin increases the latter's binding to RhoGDI1, which in turn enhances RhoGDI1's affinity for RhoG. S4 clustering activates PKCα, which phosphorylates RhoGDI1 at Ser96. This phosphorylation triggers release of RhoG, leading to polarized activation of Rac1. Thus, FGF2-induced Rac1 activation depends on the suppression of RhoG by a previously uncharacterized ternary S4–synectin–RhoGDI1 protein complex and activation via PKCα.
Elfenbein A, Rhodes JM, Meller J, Schwartz MA, Matsuda M, Simons M. Suppression of RhoG activity is mediated by a syndecan 4-synectin-RhoGDI1 complex and is reversed by PKCalpha in a Rac1 activation pathway. J Cell Biol. 2009 Jul 13;186(1):75-83. doi: 10.1083/jcb.200810179. Epub 2009 Jul 6. PMID: 19581409; PMCID: PMC2712988.
Dartmouth Digital Commons Citation
Elfenbein, Arye; Rhodes, John M.; Meller, Julia; Schwartz, Martin A.; Matsuda, Michiyuki; and Simons, Michael, "Suppression of RhoG activity is Mediated by a Syndecan 4–Synectin–RhoGDI1 Complex and is Reversed by PKCα in a Rac1 Activation Pathway" (2009). Dartmouth Scholarship. 3301.