Transient Confinement of a Glycosylphosphatidylinositol-Anchored Protein in the Plasma Membrane
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- 作者：Erin D. Sheets ; Greta M. Lee ; Rudolf Simson ; and Ken Jacobson
- 刊名：Biochemistry
- 出版年：1997
- 出版时间：October 14, 1997
- 年：1997
- 卷：36
- 期：41
- 页码：12449 - 12458
- 全文大小：244K
- 年卷期：v.36,no.41(October 14, 1997)
- ISSN：1520-4995
文摘
Glycosylphosphatidylinositol (GPI)-anchored proteins participatein many cell surface functions;however, the molecular associations of these lipid-linked proteinswithin the plasma membrane are notwell understood. Recent biochemical analyses of detergentinsoluble membrane fractions have suggestedthat GPI-anchored proteins may be associated with glycosphingolipid(GSL)-enriched domains that alsocontain cholesterol and signaling molecules such as Src family kinasesand, in some cases, caveolae.The movements of two components of the putative GSL-enricheddomains, Thy-1, a GPI-anchored protein,and GM1, a GSL, were followed with single particle tracking on C3H10T1/2 cell surfaces and categorizedinto four modes of lateral transport, fast diffusion, slow anomalousdiffusion, diffusion confined to 325-370 nm diameter regions, and a fraction of molecules that wasessentially stationary on the 6.6 s timescale. Longer observations (60 s) showed that Thy-1 and GM1 aretransiently confined for 7-9 s toregions averaging 260-330 nm in diameter. Approximately35-37% of both Thy-1 and GM1 undergoconfined diffusion, whereas only 16% of fluoresceinphosphatidylethanolamine, a phospholipid analogwhich is not expected to be found in the GSL domains, experienceconfined diffusion to regions averaging~230 nm in diameter. Further, when glycosphingolipid expressionwas reduced ~40% with theglucosylceramide synthase inhibitor,D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol,thepercentage of trajectories exhibiting confinement and the size of theconfining domain for Thy-1 werereduced ~1.5-fold. In contrast, extraction of cells with TritonX-100 leaves the fraction of moleculesconfined and the domain sizes of Thy-1 and GM1 unchanged. Ourresults are consistent with thepreferential association of GPI-anchored proteins withglycosphingolipid-enriched domains and suggestthat the confining domains may be the in vivoequivalent of the detergent insoluble membrane fractions.