Acts as a guanine nucleotide exchange factor (GEF) for RAN GTPase (By similarity). May play an essential role in hemostasis and in maintaining microtubule dynamics with respect to both platelet shape and function (By similarity). May act as an adapter protein to couple membrane receptors to intracellular signaling pathways. Enhances dihydrotestosterone-induced transactivation activity of AR, as well as dexamethasone-induced transactivation activity of NR3C1, but does not affect estrogen-induced transactivation. In contrast to RANBP9, does not interact with Sos and does not activate the Ras pathway.