※ Caspy/SIP family introduction

    SIP (CacyBP/SIP) was originally identified in Ehrilich ascities tumor cells. SIP has been show to interact with a variety of ligands, including S100, Skp1, tubulin, Siah-1, actin and ERK1/2. Studies show that binding with tubulin is essential for cytoskeleton rearrangement during the differentiation of NB2a cells. SIP interacts with ERK1/2 will lead to the ELK-1 activation and plays an important role in cell differentiation. SIP has also been found to contain phosphatase activity recently and one substrate is ERK1/2. E217K mutant will lead to the drop of phosphatase activity toward ERK1/2, which suggests that the C-terminal domain act as a phosphatase like domain (1).

Reference
1. Kilanczyk, E., Filipek, S. and Filipek, A. (2011) ERK1/2 is dephosphorylated by a novel phosphatase--CacyBP/SIP. Biochem Biophys Res Commun, 404, 179-183. PMID: 21110948