Regulation of secretion, exocytosis and membrane fusion by vesicular lipids

许多分子(如荷尔蒙)由细胞分泌，用于细胞间的交流，在细胞内被包装成小泡(每个小泡被包含大量胆固醇的脂膜包围)。细胞分泌的打包信号分子涉及囊泡与细胞表面的融合(细胞表面也被一层脂膜包围，其胆固醇密度约为囊膜的三分之一)；这一过程始于形成一个非常小的孔，将囊泡内部与细胞表面连接起来。

Many molecules (e.g. hormones) that are secreted by cells for communications between cells are packaged into small vesicles (each surrounded by a lipid membrane that includes lots of cholesterol) within the cell. The secretion of the packaged signaling molecules from a cell involves the fusion of the vesicle with the cell's surface (which is also surrounded by a lipid membrane whose density of cholesterol is about 1/3 that of the vesicular membrane); this process starts with the formation of a very small pore that connects the inside of a vesicle with the cell's surface.