IRTKS (insulin receptor tyrosine kinase substrate) or BAIAP2L1 (brain-specific angiogenesis inhibitor 1-associated protein 2-like protein 1) is widely expressed, serves as a substrate for the insulin receptor, and binds the small GTPase Rac []]. It plays a role in regulating the actin cytoskeleton and colocalizes with F-actin, cortactin, VASP, and vinculin. BAIAP2L1 expression leads to the formation of short actin bundles, distinct from filopodia-like protrusions induced by the expression of the related protein IRSp53 []. IRTKS mediates the recruitment of effector proteins Tir and EspFu, which regulate host cell actin reorganization, to bacterial attachment sites [].IRTKS contains an N-terminal IMD or Inverse-Bin/Amphiphysin/Rvs (I-BAR) domain, an SH3 domain, and a WASP homology 2 (WH2) actin-binding motif at the C terminus. The SH3 domain of IRTKS has been shown to bind the proline-rich C terminus of EspFu [].
