ICAP-1 is a serine/threonine-rich protein that binds to the cytoplasmic domains of beta-1 integrins in a highly specific manner, binding to a NPXY sequence motif on the beta-1 integrin. The cytoplasmic domains of integrins are essential for cell adhesion, and the fact that phosphorylation of ICAP-1 by interaction with the cell-matrix implies an important role of ICAP-1 during integrin-dependent cell adhesion [1]. Overexpression of ICAP-1 strongly reduces the integrin-mediated cell spreading on extracellular matrix and inhibits both Cdc42 and Rac1. In addition, ICAP-1 induces release of Cdc42 from cellular membranes and prevents the dissociation of GDP from this GTPase [2]. An additional function of ICAP-1 is to promote differentiation of osteoprogenitors by supporting their condensation through modulating the integrin high affinity state [3],

1: ICAP-1, a novel beta1 integrin cytoplasmic domain-associated protein, binds to a conserved and functionally important NPXY sequence motif of beta1 integrin. Chang DD, Wong C, Smith H, Liu J; J Cell Biol. 1997;138:1149-1157. PMID:9281591

2: The integrin cytoplasmic domain-associated protein ICAP-1 binds and regulates Rho family GTPases during cell spreading. Degani S, Balzac F, Brancaccio M, Guazzone S, Retta SF, Silengo L, Eva A, Tarone G; J Cell Biol. 2002;156:377-387. PMID:11807099

3: Defective osteoblast function in ICAP-1-deficient mice. Bouvard D, Aszodi A, Kostka G, Block MR, Albiges-Rizo C, Fassler R; Development. 2007;134:2615-2625. PMID:17567669