Caveolins: structure and function in signal transduction.

The caveolin family proteins are typically associated with microdomains that are found in the plasma membrane of numerous cells. These microdomains are referred to as/called caveolae. Caveolins are small proteins (18-24 kDa) that have a hairpin loop conformation with both the N and C termini exposed to the cytoplasm. Apart from having a structural function within caveolae, these proteins have the capacity to bind cholesterol as well as a variety of proteins, such as receptors, Src-like kinases, G-proteins, H-Ras, MEK/ERK kinases and nitric oxide synthases, which are involved in signal transduction processes. Considerable data allow the assumption to be made that the majority of the interactions with signaling molecules hold them in an inactive or repressed state. The activity of caveolins seems to be dependent on its specific post-translation modifications. It is suggested that caveolins fulfill a role in the modulation of cellular signaling cascades.