Synaptojanin-2 is a ubiquitously expressed central regulatory enzyme in the phosphoinositide-signaling cascade []. As a novel Rac1 effector regulating an early step of clathrin-mediated endocytosis, synaptojanin-2 acts as a polyphosphoinositide phosphatase, directly and specifically interacting with Rac1 in a GTP-dependent manner. It mediates the inhibitory effect of Rac1 on endocytosis and plays an important role in the Rac1-mediated control of cell growth []. Synaptojanin-2 shows high sequence homology to the N-terminal Sac1p homology domain [], the central inositol 5-phosphatase domain, and the putative RNA recognition motif (RRM) of synaptojanin-1, but differs in the proline-rich region.
