Caveolin 1, a component of caveolae, regulates signalling pathways compartmentalization interacting with tyrosine kinase receptors and their substrates. The role of caveolin I in the Insulin Receptor (IR) signalling has been well investigated. On the contrary, the functional link between caveolin I and IGF-I Receptor (IGF-IR) remains largely unknown. Here we show that (1) IGF-IR colocalizes with caveolin I in the lipid rafts enriched fractions on plasmamembrane in R-IGF-IRWT Cells, (2) IGF-I induces caveolin I phosphorylation at the level of tyrosine 14, (3) this effect is rapid and results in the translocation of caveolin I and in the formation of membrane patches on cell surface. These actions are IGF-I specific since we did not detect caveolin I redistribution in insulin stimulated R- cells overexpressing IRs. (C) 2002 Elsevier Science (USA). All rights reserved.