MOLECULAR MECHANISM OF MORPHOLOGICAL RESPONSE TO MECHANICAL STIMULI IN ENDOTHELIAL CELLS

内皮细胞呈纺锤形，其长度与血管走向平行。这种特殊的形状和排列方式对于防止细胞被血流剥离非常重要。然而，培养的内皮细胞不显示这样的形状和排列。那么，是什么机制导致了内皮细胞的这种适应性特征呢？已知通过脉动血流施加到细胞上的机械应力，如剪切应力和周期性周向应力，足以在内皮细胞中诱导这种形态学反应。本课题的最终目的是了解机械诱导内皮细胞形态学反应的内在分子机制。特别是我们的目标是证明我们的分子级联假说：周期性牵张 * 机械敏感通道的激活 * 细胞内Ca动员 * 应力纤维和粘着力的重组 * 形态学变化。 ...更多信息 的级联，并发现，介导的钙渗透机械敏感离子通道的激活细胞内钙动员是必要的形态反应。在第二年，我们分析了钙动员后细胞形态学变化与细胞骨架重组之间的关系。应力纤维（肌动蛋白束）的再聚过程可分为三个步骤：预聚的肌动蛋白纤维的脱聚、新肌动蛋白丝的形成、肌动蛋白纤维的伸长和成束。细胞的形态变化进行伴随着最后一步的细胞骨架reoganization，需要钙动员。事实上，在这一步骤中发生了粘着斑蛋白的钙依赖性酪氨酸磷酸化。当这种磷酸化被药物抑制时，细胞骨架的重组和形态学反应都被完全抑制。激酶和GTP结合蛋白在分子级联中的参与仍有待解决。少

Endothelial cells exhibit spindle like shape aligning their longtude parallel with vessel running. This peculiar shape and alignment is isgnificant to prevent the cells from being pealed off by blood flow. However, cultured endothelial cells do not show such shape and alignment. Then what mechanisms do bring about such an adaptive feature in endothelial cells? It is known that mechanical stresses onto the cells, like shear stress and periodic circumferential stetch, by pulsative blood flow are enough to induce such a morphological response in endothelial cells. The altimate goal of this project is to know the inderlying molecular mechanism in mechanically induced morphological response of endothlial cells. Partcularly we aimed to prove our hypothesis on the molecular cascade : periodic stretch*activation of mechanosensitive channels*intracellular Ca-mobilization*reorganization of stress fibers and forcal adhesion*morphological change.In the first year we concentrated on the early part … More of the cascade, and found that intacellular Ca-mobilization mediated by the activation of Ca-permeable mechanosensitive ion channels is necessary for the morphological response. In the second year we analyzed the relationship between the cell morphological change and the cytoskeletal reoganization following Ca-mobilization. The reoganization process of stress fibers (bundle of F-actins) could be disected into three steps : depolimerization of pre-exisiting F-actin fibers*formation of new actin filaments perpendicuraly to stretch axis*elongation and bundling of actin fibers. Morphological change of the cells proceeded concomitant with the last step of cytoskeletal reoganization that requires Ca-mobilization. In fact Ca-dependent tyrosine phosphorylation of focal adhesion proteins occured during this step. When this phosphorylation was inhibited by drugs, both the cytoskeletal reoganization and the morphological response was completely inhibited. Involvement of kinases and GTP binding proteins in the molecular cascade remains to be solved. Less