Lipid Rafts Flashcards
What are lipid rafts?
Lipid-rich microdomains in the plasma membrane. They contain a lot of cholesterol and are detergent resistant.
Composition of lipid rafts
they contain two times more cholesterol than a normal membrane and are enriched in sphingolipids and glycolipids. They also contain glycolsylphophatidyl-inositol (GPI) anchors.
What is the function of cholesterol in relationship to lipid rafts?
cholesterol drives the formation of lipid rafts
Are lipid rafts permanent in one position or do they fluxuate?
Lipid rafts are in constant flux and exhibit heirarchy of organization.
What limits the size of lipid rafts?
Actin cytoskeleton
What are the functions of lipid rafts?
Signal transduction by receptors (TCR) Mechano-transduction through the cytoskeleton Endocytosis Cell polarity (apical membrane) Cell adhesion and migration Ion and metabolite transport Cell death
How do lipid rafts help in signalling?
Under resting conditions the T-cell receptor and the other adaptor/signaling molecules are kept apart. Upon TCR activation, the various components coalesce into a single raft. Same mechanism seems to happen for B-cell receptors.
How do lipid rafts help in adhesion?
Cell-matrix and cell-cell adhesion molecules congregate in lipid rafts.
What are the three types of endocytosis? and which ones are lipid-raft dependent
- Clathrin-dependent
- caveolin-dependent (use lipid rafts)
- clathrin- and caveolin-independent (use lipid rafts)
Why are caveolae important?
They are needed for caveolin-dependent endoctysois and they are also important for signaling. They can recruit other proteins to the site. Enzyme bound to caveolae keeps it in its inactive form but calcium will release this inhibition and activate the enzyme to produce NO.
Lipid rafts are important for the pathogenesis of which diseases?
Prion disease, cholera, neurodegenerative diseases, viral infection, parasite infection, cancer mtastasis
Potential treatment to disrupt lipid rafts:
cyclodextran
What is the connection between viral infection and lipid rafts?
Viruses utilize lipid raft-dependent endocytosis for entry into the cell. Protein on the coat of SV40 binds to a glycolipid within lipid raft and starts accumulating a lipid raft around itself, tirggering endocytosis to get into the cell.
Lipid-dependent endocytosis bypasses _____.
lysosomes
How do cancer cells migrate?
They need to detach their focal adhesions.This is mediated by complex signaling processes and involves a tyrosine kinase called FAK.
