The integrin cytoplasmic domain-associated protein ICAP-1 binds and regulates Rho family GTPases during cell spreading

J Cell Biol. 2002 Jan 21;156(2):377-87. doi: 10.1083/jcb.200108030. Epub 2002 Jan 21.


Using two-hybrid screening, we isolated the integrin cytoplasmic domain-associated protein (ICAP-1), an interactor for the COOH terminal region of the beta1A integrin cytoplasmic domain. To investigate the role of ICAP-1 in integrin-mediated adhesive function, we expressed the full-length molecule in NIH3T3 cells. ICAP-1 expression strongly prevents NIH3T3 cell spreading on extracellular matrix. This inhibition is transient and can be counteracted by coexpression of a constitutively activated mutant of Cdc42, suggesting that ICAP-1 acts upstream of this GTPase. In addition, we found that ICAP-1 binds both to Cdc42 and Rac1 in vitro, and its expression markedly inhibits activation of these GTPases during integrin-mediated cell adhesion to fibronectin as detected by PAK binding assay. In the attempt to define the molecular mechanism of this inhibition, we show that ICAP-1 reduces both the intrinsic and the exchange factor-induced dissociation of GDP from Cdc42; moreover, purified ICAP-1 displaces this GTPase from cellular membranes. Together, these data show for the first time that ICAP-1 regulates Rho family GTPases during integrin-mediated cell matrix adhesion, acting as guanine dissociation inhibitor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Adaptor Proteins, Signal Transducing
  • Amino Acid Sequence
  • Animals
  • COS Cells
  • Carrier Proteins / metabolism*
  • Cell Division
  • Cell Size
  • Guanosine Diphosphate / metabolism
  • Integrins / metabolism
  • Intracellular Signaling Peptides and Proteins*
  • Membrane Proteins*
  • Mice
  • Molecular Sequence Data
  • Protein Binding
  • Rats
  • Sequence Homology, Amino Acid
  • Structure-Activity Relationship
  • Substrate Specificity
  • Time Factors
  • Two-Hybrid System Techniques
  • cdc42 GTP-Binding Protein / antagonists & inhibitors
  • cdc42 GTP-Binding Protein / genetics
  • cdc42 GTP-Binding Protein / metabolism
  • rac1 GTP-Binding Protein / antagonists & inhibitors
  • rac1 GTP-Binding Protein / metabolism
  • rho GTP-Binding Proteins / antagonists & inhibitors
  • rho GTP-Binding Proteins / metabolism*
  • rhoA GTP-Binding Protein / metabolism


  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • ITGB1BP1 protein, human
  • Integrins
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Guanosine Diphosphate
  • cdc42 GTP-Binding Protein
  • rac1 GTP-Binding Protein
  • rho GTP-Binding Proteins
  • rhoA GTP-Binding Protein