Although caveolae are sometimes considered to be synonymous with lipid rafts, it is now clear that they represent only a subset of rafts whose properties are defined by their major protein components belonging to the caveolin family and denoted Cav-1, Cav-2, and Cav-3 (Parton and Simons, 1995, 2007) . The characterization of PTRF (polymerase I and transcript release factor, originally identified as an RNA Pol I transcription factor, also called Cav-P60 and now termed cavin-1) and subsequently of other cavin family members as important constituents in caveolae formation has revealed new levels of complexity in the biogenesis of these plasma membrane invaginations (Briand et al., 2011) . Like the rafts themselves, the caveolae are enriched in cholesterol, glycosphingolipids, and SM. They are the site of several important protein-protein interactions, for example, the neurotrophin receptors, TrkA and p75(NTR), whose respective interactions with caveolin regulates neurotrophin signaling in the brain (Bilderback et al., 1999) . Caveolins also regulate G-proteins, MAPK, PI3K, and Src tyrosine kinases (Marin, 2011) .