Guanine nucleotide exchange factor (GEF), which can activate some, but not all, G-alpha proteins. Able to activate GNAI1, GNAO1 and GNAQ, but not GNAS by exchanging bound GDP for free GTP. Involved in regulation of microtubule pulling forces during mitotic movement of chromosomes by stimulating G(i)-alpha protein, possibly leading to release G(i)-alpha-GTP and NuMA proteins from the NuMA-GPSM2-G(i)-alpha-GDP complex. Also acts as an activator for G(q)-alpha (GNAQ) protein by enhancing the G(q)-coupled receptor-mediated ERK activation (By similarity). Interacts with GDP-bound G alpha proteins GNAI1, GNAO1 and GNAQ, and with GNA13 with lower affinity. Does not interact with G-alpha proteins when they are in complex with subunits beta and gamma. Interacts (via C-terminus) with RGS14; the interaction stimulates the dissociation of the complex between RGS14 and the active GTP-bound form of GNAI1 (By similarity). Colocalizes with RIC8A in CA2 hippocampal neurons. Colocalizes with GNAI1 and RGS14 at the plasma membrane (By similarity). Belongs to the synembryn family.