Cholesterol facilitates the native mechanism of Ca2+-triggered membrane fusion
Cholesterol facilitates the native mechanism of Ca2+-triggered membrane fusion
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DOI：
10.1242/jcs.02601
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发表时间：
2005-10-15
影响因子：
4
通讯作者：
Coorssen, JR
中科院分区：
文献类型：
--
作者：
Churchward, MA;Rogasevskaia, T;Coorssen, JR
调节胞吐作用的过程由两个并列膜的Ca2+触发融合定义，从而能够释放囊泡内容物。该融合步骤涉及许多能量复杂的步骤，并且需要蛋白质和脂质膜组分。胆固醇的作用已被调查使用分离的释放准备好本地皮质分泌囊泡分析的Ca2+触发的融合步骤的胞吐。胆固醇是囊泡膜的主要组成部分，我们在这里表明，从膜的选择性去除，膜内的选择性螯合，或酶促修饰导致的程度，Ca2+的敏感性和动力学的融合显着抑制。取决于掺入量，将外源性胆固醇添加到胆固醇耗尽的膜中始终恢复融合的程度，但不恢复Ca2+敏感性或融合动力学。可比较的负曲率的膜组分选择性地恢复融合的能力，但不能恢复囊泡融合的动力学和Ca2+敏感性。这表明胆固醇在膜融合过程中至少有两个特定的积极作用：作为局部膜组织者有助于融合的效率，以及凭借其固有的负曲率，作为一种特定的分子与蛋白质因子协同工作，以促进快速Ca2+触发融合的最小分子机制。
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.