title: The differential protein and lipid compositions of noncaveolar lipid microdomains and caveolae.
abstract: Morphologically, caveolae and lipid rafts are two different membrane structures. They are often reported to share similar lipid and protein compositions, and are considered to be two subtypes of membrane lipid microdomains. By modifying sucrose density gradient flotation centrifugation, which is used to isolate lipid microdomains, we were able to separate caveolae and noncaveolar lipid microdomains into two distinct fractions. The caveolar membranes are membrane vesicles of 100-nm diameter, enriched with caveolin-1 and flotillin-1. The noncaveolar lipid microdomains are amorphous membranes and most likely the coalescence of heterogeneous lipid rafts. They are depleted of caveolin-1 and are more enriched with cholesterol and sphingolipids than the caveolae. Many membrane proteins, such as insulin-like growth factor-1 receptor (membrane receptor), aquaporin-1 (membrane transporter), Thy-1 and N-cadherin (glycosylphosphatidylinositol-anchored membrane protein and membrane glycoprotein), are specifically associated with noncaveolar lipid microdomains, but not with caveolae. These results indicate that the lipid and protein compositions of caveolae differ from those of noncaveolar lipid microdomains. The difference in their protein compositions implies that these two membrane microdomains may have different cellular functions.
authors.affiliation: State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Yao
authors.forename: Shangyu
authors.initials: S
authors.lastname: Hong
authors.forename: Hu
authors.initials: H
authors.lastname: Zhou
authors.forename: Taichang
authors.initials: T
authors.lastname: Yuan
authors.forename: Rong
authors.initials: R
authors.lastname: Zeng
authors.forename: Kan
authors.initials: K
authors.lastname: Liao
mesh_terms: D041721:3T3-L1 Cells; D000818:Animals; D021941:Caveolae / Q000737:chemistry*; D051242:Caveolin 1 / Q000032:analysis; D002458:Cell Fractionation; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D002784:Cholesterol / Q000032:analysis; D008055:Lipids / Q000032:analysis* / Q000737:chemistry; D021962:Membrane Microdomains / Q000737:chemistry*; D008565:Membrane Proteins / Q000032:analysis*; D051379:Mice; D013107:Sphingolipids / Q000032:analysis
chemical_list: D051242:Caveolin 1; D008055:Lipids; D008565:Membrane Proteins; D013107:Sphingolipids; C106354:flotillins; D002784:Cholesterol