Jorgacevski Jernej, Fosnaric Miha, Vardjan Nina, Stenovec Matjaz, Potokar Maja, Kreft Marko, Kralj-Iglic Veronika, Iglic Ales, Zorec Robert
Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
Mol Membr Biol. 2010 Apr;27(2-3):65-80. doi: 10.3109/09687681003597104.
It is believed that in regulated exocytosis the vesicle membrane fuses with the plasma membrane in response to a physiological stimulus. However, in the absence of stimulation, repetitive transient fusion events are also observed, reflecting a stable state. The mechanisms by which the initial fusion pore attains stability are poorly understood. We modelled energetic stability of the fusion pore by taking into account the anisotropic, intrinsic shape of the membrane constituents and their in-plane ordering in the local curvature of the membrane. We used cell-attached membrane capacitance techniques to monitor the appearance and conductance of single fusion pore events in cultured rat lactotrophs. The results revealed a bell-shaped distribution of the fusion pore conductance with a modal value of 25 pS. The experimentally observed increase of the fusion pore stability with decreasing fusion pore radius agrees well with the theoretical predictions. Moreover, the results revealed a correlation between the amplitude of transient capacitance increases and the fusion pore conductance, indicating that larger vesicles may attain a stable fusion pore with larger fusion pore diameters.
据信,在调节性胞吐作用中,囊泡膜会响应生理刺激与质膜融合。然而,在无刺激的情况下,也会观察到重复性的瞬时融合事件,这反映了一种稳定状态。初始融合孔达到稳定的机制目前还知之甚少。我们通过考虑膜成分的各向异性、固有形状及其在膜局部曲率中的面内有序性,对融合孔的能量稳定性进行了建模。我们使用细胞贴附膜电容技术来监测培养的大鼠促乳素细胞中单个融合孔事件的出现和电导。结果显示融合孔电导呈钟形分布,模态值为25 pS。实验观察到融合孔稳定性随融合孔半径减小而增加,这与理论预测非常吻合。此外,结果还揭示了瞬时电容增加幅度与融合孔电导之间的相关性,表明较大的囊泡可能会形成具有较大融合孔直径的稳定融合孔。