In biology, caveolae, which are a special type of lipid raft, are small invaginations of the plasma membrane in the cells of many vertebrates. They are the most abundant surface feature of many vertebrate cell types, especially endothelial cells, adipocytes and embryonic notochord cells. They were originally discovered by E. Yamada in 1955.
The plasma membranes of cells contain combinations of glycosphingolipids, cholesterol and protein receptors organised in glycolipoprotein lipid microdomains termed lipid rafts. Their existence in cellular membranes remains somewhat controversial. It has been proposed that they are specialized membrane microdomains which compartmentalize cellular processes by serving as organising centers for the assembly of signaling molecules, allowing a closer interaction of protein receptors and their effectors to promote kinetically favorable interactions necessary for the signal transduction. Lipid rafts influence membrane fluidity and membrane protein trafficking, thereby regulating neurotransmission and receptor trafficking. Lipid rafts are more ordered and tightly packed than the surrounding bilayer, but float freely within the membrane bilayer. Although more common in the cell membrane, lipid rafts have also been reported in other parts of the cell, such as the Golgi apparatus and lysosomes.
In molecular biology, caveolins are a family of integral membrane proteins that are the principal components of caveolae membranes and involved in receptor-independent endocytosis. Caveolins may act as scaffolding proteins within caveolar membranes by compartmentalizing and concentrating signaling molecules. They also induce positive (inward) membrane curvature by way of oligomerization, and hairpin insertion. Various classes of signaling molecules, including G-protein subunits, receptor and non-receptor tyrosine kinases, endothelial nitric oxide synthase (eNOS), and small GTPases, bind Cav-1 through its 'caveolin-scaffolding domain'.
Lipid signaling, broadly defined, refers to any biological signaling event involving a lipid messenger that binds a protein target, such as a receptor, kinase or phosphatase, which in turn mediate the effects of these lipids on specific cellular responses. Lipid signaling is thought to be qualitatively different from other classical signaling paradigms because lipids can freely diffuse through membranes. One consequence of this is that lipid messengers cannot be stored in vesicles prior to release and so are often biosynthesized "on demand" at their intended site of action. As such, many lipid signaling molecules cannot circulate freely in solution but, rather, exist bound to special carrier proteins in serum.
BMP and activin membrane-bound inhibitor homolog , also known as BAMBI, is a protein which in humans is encoded by the BAMBI gene.
Leukosialin also known as sialophorin or CD43 is a transmembrane cell surface protein that in humans is encoded by the SPN (sialophorin) gene.
Caveolin-1 is a protein that in humans is encoded by the CAV1 gene.
Ephrin-B1 is a protein that in humans is encoded by the EFNB1 gene. It is a member of the ephrin family. The encoded protein is a type I membrane protein and a ligand of Eph-related receptor tyrosine kinases. It may play a role in cell adhesion and function in the development or maintenance of the nervous system.
Melanotransferrin is a protein that in humans is encoded by the MFI2 gene. MFI2 has also recently been designated CD228.
Lysophosphatidic acid receptor 1 also known as LPA1 is a protein that in humans is encoded by the LPAR1 gene. LPA1 is a G protein-coupled receptor that binds the lipid signaling molecule lysophosphatidic acid (LPA).
Flotillin-1 is a protein that in humans is encoded by the FLOT1 gene.
Autocrine motility factor receptor, isoform 2 is a protein that in humans is encoded by the AMFR gene.
Matrix metalloproteinase-16 is an enzyme that in humans is encoded by the MMP16 gene.
Prion protein 2 (dublet), also known as PRND, or Doppel protein, is a protein which in humans is encoded by the PRND gene.
Potassium channel subfamily K member 2 is a protein that in humans is encoded by the KCNK2 gene.
Vesicle-associated membrane protein 8 is a protein that in humans is encoded by the VAMP8 gene.
Glutamate receptor-interacting protein 1 is a protein that in humans is encoded by the GRIP1 gene.
Pancreatic secretory granule membrane major glycoprotein GP2 is a protein that in humans is encoded by the GP2 gene.
Caveolin-2 is a protein that in humans is encoded by the CAV2 gene.
Potocytosis is a type of receptor-mediated endocytosis in which small molecules are transported across the plasma membrane of a cell. The molecules are transported by caveolae and are deposited directly into the cytosol.
