Inverse (I)-BAR, also known as the IRSp53/MIM homology Domain (IMD), of Insulin Receptor tyrosine kinase Substrate p53
The IMD domain, also called Inverse-Bin/Amphiphysin/Rvs (I-BAR) domain, is a dimerization and lipid-binding module that bends membranes and induces membrane protrusions. IRSp53 (Insulin Receptor tyrosine kinase Substrate p53) is also known as BAIAP2 (Brain-specific Angiogenesis Inhibitor 1-Associated Protein 2). It is a scaffolding protein that takes part in many signaling pathways including Cdc42-induced filopodia formation, Rac-mediated lamellipodia extension, and spine morphogenesis. IRSp53 exists as multiple splicing variants that differ mainly at the C-termini. One variant (T-form) is expressed exclusively in human breast cancer cells. The gene encoding IRSp53 is a putative susceptibility gene for Gilles de la Tourette syndrome. IRSp53 contains an N-terminal IMD, a CRIB (Cdc42 and Rac interactive binding motif), an SH3 domain, and a WASP homology 2 (WH2) actin-binding motif at the C-terminus. Its IMD domain binds and bundles actin filaments, binds membranes, and interacts with the small GTPase Rac.