EVENTS LEADING TO THE OPENING AND CLOSING OF THE EXOCYTOTIC FUSION PORE HAVE MARKEDLY DIFFERENT TEMPERATURE DEPENDENCIES - KINETIC-ANALYSIS OF SINGLE FUSION EVENTS IN PATCH-CLAMPED MOUSE MAST-CELLS
EVENTS LEADING TO THE OPENING AND CLOSING OF THE EXOCYTOTIC FUSION PORE HAVE MARKEDLY DIFFERENT TEMPERATURE DEPENDENCIES - KINETIC-ANALYSIS OF SINGLE FUSION EVENTS IN PATCH-CLAMPED MOUSE MAST-CELLS
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DOI：
10.1016/s0006-3495(92)81884-2
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发表时间：
1992-03-01
影响因子：
3.4
通讯作者：
FERNANDEZ, JM
中科院分区：
文献类型：
--
作者：
OBERHAUSER, AF;MONCK, JR;FERNANDEZ, JM
胞吐过程中最早的事件是融合孔的形成，这是一个水通道，连接分泌颗粒的管腔和细胞外空间。在gtp - γ -s刺激的胞外融合过程中，我们可以通过测量贴片夹紧肥大细胞导纳的变化来观察单个融合孔的形成及其随后的扩张或关闭。为了研究融合孔的分子结构，我们研究了融合孔形成和关闭的速率常数与温度的关系。融合孔形成速率的阿伦尼乌斯图与表观活化能23 kcal/mol呈简单的线性关系。相比之下，融合孔闭合速率的阿伦尼乌斯图是不连续的，在13℃左右断裂。在断点以上，闭合速率对温度有较弱的依赖性（7千卡/摩尔），而在13℃以下，闭合速率与温度无关。这种类型的温度依赖性是在经历流固相转变的脂相中依赖于扩散的事件的特征。我们提出融合孔的形成是由具有高活化能的分子结构的构象变化调节的，而融合孔的关闭是由在13℃时相分离的脂质调节的。
The earliest event in exocytosis is the formation of a fusion pore, an aqueous channel that connects the lumen of a secretory granule with the extracellular space. We can observe the formation of individual fusion pores and their subsequent dilation or closure by measuring the changes in the admittance of patch-clamped mast cells during GTP-gamma-S-stimulated exocytotic fusion. To investigate the molecular structure of the fusion pore, we have studied the temperature dependency of the rate constants for fusion pore formation and closure. An Arrhenius plot of the rate of fusion pore formation shows a simple linear relationship with an apparent activation energy of 23 kcal/mol. In contrast, the Arrhenius plot of the rate of closure of the fusion pore is discontinuous, with the break at approximately 13-degrees-C. Above the break point, the rate of closure has a weak temperature dependence (7 kcal/mol), whereas below 13-degrees-C the rate of closure is temperature independent. This type of temperature dependency is characteristic of events that depend on diffusion in a lipid phase that undergoes a fluid-solid phase transition. We propose that the formation of the fusion pore is regulated by the conformational change of a molecular structure with a high activation energy, whereas the closure of the fusion pore is regulated by lipids that become phase separated at 13-degrees-C.