Chizmadzhev Y A, Cohen F S, Shcherbakov A, Zimmerberg J
Frumkin Institute of Electrochemistry, Moscow, Russia.
Biophys J. 1995 Dec;69(6):2489-500. doi: 10.1016/S0006-3495(95)80119-0.
Once formed, fusion pores rapidly enlarge to semi-stable conductance values. The membranes lining the fusion pore are continuous bilayer structures, so variations of conductance in time reflect bending and stretching of membranes. We therefore modeled the evolution of fusion pores using the theory of the mechanics of deforming homogeneous membranes. We calculated the changes in length and width of theoretical fusion pores according to standard dynamical equations of motion. Theoretical fusion pores quickly achieve semi-stable dimensions, which correspond to energy minima located in a canyon between energy barriers. The height of the barrier preventing pore expansion diminishes along the dimensions of length and width. The bottom of the canyon slopes gently downward along increasing length. As a consequence, theoretical fusion pores slowly lengthen and widen as the dimensions migrate along the bottom of the canyon, until the barrier vanishes and the pore rapidly enlarges. The dynamics of growth is sensitive to tension, spontaneous curvature, bending elasticity, and mobilities. This sensitivity can account for the quantitative differences in pore evolution observed in two experimental systems: HA-expressing cells fusing to planar bilayer membranes and beige mouse mast cell degranulation. We conclude that the mechanics of membranes could cause the phenomenon of stagewise growth of fusion pores.
一旦形成，融合孔会迅速扩大到半稳定的电导值。融合孔内衬的膜是连续的双层结构，因此电导随时间的变化反映了膜的弯曲和拉伸。因此，我们使用均匀膜变形力学理论对融合孔的演化进行了建模。我们根据标准的动力学运动方程计算了理论融合孔的长度和宽度变化。理论融合孔很快达到半稳定尺寸，这对应于位于能垒之间峡谷中的能量最小值。阻止孔扩张的能垒高度沿长度和宽度方向减小。峡谷底部随着长度增加而缓缓向下倾斜。因此，随着尺寸沿着峡谷底部移动，理论融合孔会缓慢变长和变宽，直到能垒消失且孔迅速扩大。生长动力学对张力、自发曲率、弯曲弹性和迁移率敏感。这种敏感性可以解释在两个实验系统中观察到的孔演化的定量差异：表达HA的细胞与平面双层膜融合以及米色小鼠肥大细胞脱颗粒。我们得出结论，膜的力学特性可能导致融合孔的阶段性生长现象。
