Cholesterol facilitates the native mechanism of Ca2+-triggered membrane fusion

被引:143
作者
Churchward, MA
Rogasevskaia, T
Höfgen, J
Bau, J
Coorssen, JR [1 ]
机构
[1] Univ Calgary, Hlth Sci Ctr, Fac Med, Dept Physiol & Biophys, Calgary, AB T2N 4N1, Canada
[2] Univ Calgary, Hlth Sci Ctr, Fac Med, Dept Biochem & Mol Biol, Calgary, AB T2N 4N1, Canada
[3] Univ Calgary, Hlth Sci Ctr, Fac Med, Dept Cell Biol & Anat,Hotchkiss Brain Inst, Calgary, AB T2N 4N1, Canada
关键词
sterol; negative curvature; vitamin E; secretory vesicles; exocytosis; polyene antibiotics;
D O I
10.1242/jcs.02601
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
The process of regulated exocytosis is defined by the Ca2+- triggered fusion of two apposed membranes, enabling the release of vesicular contents. This fusion step involves a number of energetically complex steps and requires both protein and lipid membrane components. The role of cholesterol has been investigated using isolated release-ready native cortical secretory vesicles to analyze the Ca2+- triggered fusion step of exocytosis. Cholesterol is a major component of vesicle membranes and we show here that selective removal from membranes, selective sequestering within membranes, or enzymatic modification causes a significant inhibition of the extent, Ca2+ sensitivity and kinetics of fusion. Depending upon the amount incorporated, addition of exogenous cholesterol to cholesterol-depleted membranes consistently recovers the extent, but not the Ca2+ sensitivity or kinetics of fusion. Membrane components of comparable negative curvature selectively recover the ability to fuse, but are unable to recover the kinetics and Ca2+ sensitivity of vesicle fusion. This indicates at least two specific positive roles for cholesterol in the process of membrane fusion: as a local membrane organizer contributing to the efficiency of fusion, and, by virtue of its intrinsic negative curvature, as a specific molecule working in concert with protein factors to facilitate the minimal molecular machinery for fast Ca2+- triggered fusion.
引用
收藏
页码:4833 / 4848
页数:16
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