Paul Benjamin Z S, Kim Soochong, Dangelmaier Carol, Nagaswami Chandrasekaran, Jin Jianguo, Hartwig John H, Weisel John W, Daniel James L, Kunapuli Satya P
Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Platelets. 2003 May;14(3):159-69. doi: 10.1080/0953710031000092794.
Platelet shape change is an extremely rapid process mediated by both the calcium-sensitive and p160ROCK pathways. The present study examines how different features of shape change studied by scanning electron microscopy clearly correlate to changes in the pattern of light absorbance measured in an aggregometer. Platelets change shape from the initial 'disc' form by producing: membrane 'blebs', sphere formation (cell-rounding), filopodia extension, and surface membrane folding. The presentation of these features was dramatically slower in the absence of intracellular calcium mobilization. In the presence of the p160ROCK-inhibitor, Y-27632, shape change was initially normal but platelets rapidly transformed back to smooth discs with extended filopodia. The reappearance of the disc shape is reflected by an increase in the amplitude of oscillations in the aggregometer shape change tracing. The kinetics of actin/cytoskeleton association correlated with filopodia formation but not with disc to sphere transformation. Changes in the level of tubulin polymerization correlated with changes from disc to sphere morphology. These experiments are consistent with a role for a RhoA/Rho kinase-regulated pathway in the maintenance of a spherical platelet shape after agonist-dependent activation. Continued disruption of the cytoskeletal microtubule ring, appears to be a Rhokinase-dependent event involved in the transformation of discoid platelets into spheres.
血小板形状改变是一个由钙敏感途径和p160ROCK途径介导的极其快速的过程。本研究探讨了通过扫描电子显微镜研究的形状改变的不同特征如何与在凝集仪中测量的吸光度模式的变化明显相关。血小板通过产生以下变化从最初的“圆盘”形式改变形状：膜“泡”、球体形成（细胞变圆）、丝状伪足延伸和表面膜折叠。在没有细胞内钙动员的情况下，这些特征的呈现明显较慢。在存在p160ROCK抑制剂Y-27632的情况下，形状改变最初是正常的，但血小板迅速变回带有延伸丝状伪足的光滑圆盘。圆盘形状的重新出现通过凝集仪形状改变追踪中振荡幅度的增加来反映。肌动蛋白/细胞骨架结合的动力学与丝状伪足形成相关，但与圆盘到球体的转变无关。微管蛋白聚合水平的变化与从圆盘到球体形态的变化相关。这些实验与RhoA/Rho激酶调节的途径在激动剂依赖性激活后维持球形血小板形状中的作用一致。细胞骨架微管环的持续破坏似乎是一个涉及盘状血小板向球体转变的Rho激酶依赖性事件。
