Pestina T I, Jackson C W, Stenberg P E
Department of Hematology/Oncology, St Jude Children's Research Hospital, Memphis, TN 38105, USA.
Blood. 1995 May 1;85(9):2436-46.
The roles of most cytoskeletal proteins in platelet formation and function remain largely undefined. We earlier detected megakaryocyte membrane blebbing and a unique antigenic determinant associated with a missense mutation in the cytoskeletal protein, talin, in an animal model of hereditary macrothrombocytopenia, the Wistar Furth (WF) rat, which led us to examine the distribution of talin and other cytoskeletal proteins in resting normal and WF rat platelets. In contrast to the conclusions of an earlier ultrastructural analysis, our biochemical and ultrastructural immunogold studies indicate a significant membrane-association of talin in both resting normal and WF rat platelets as found earlier for rat megakaryocytes. Talin was associated with plasma membranes, membranes of the surface-connected canalicular system, and with alpha-granule membranes of both normal and WF rat platelets, but as in WF megakaryocytes, talin was absent from the large membrane complexes of WF platelets. An even more striking difference was seen in the distribution of myosin in subcellular fractions of normal and WF rat platelets separated in density gradients, in which the proportion of myosin in the least dense WF rat platelet membrane fraction was one half that in the same normal platelet fraction. This difference was balanced by a fourfold increase in myosin in the most dense WF rat subcellular fraction, which is highly enriched for alpha-granules. These results support our hypothesis that the platelet abnormalities of the WF rat are related to defects in the megakaryocyte-platelet cytoskeleton.
大多数细胞骨架蛋白在血小板形成和功能中的作用仍 largely 未明确。我们之前在遗传性大血小板减少症的动物模型——Wistar Furth（WF）大鼠中检测到巨核细胞膜泡化以及与细胞骨架蛋白踝蛋白中的错义突变相关的独特抗原决定簇，这促使我们研究踝蛋白和其他细胞骨架蛋白在静息正常和 WF 大鼠血小板中的分布。与早期超微结构分析的结论相反，我们的生化和超微结构免疫金研究表明，踝蛋白在静息正常和 WF 大鼠血小板中均与膜有显著关联，这与之前在大鼠巨核细胞中发现的情况相同。踝蛋白与质膜、表面连接小管系统的膜以及正常和 WF 大鼠血小板的α-颗粒膜相关，但与 WF 巨核细胞一样，WF 血小板的大膜复合物中不存在踝蛋白。在通过密度梯度分离的正常和 WF 大鼠血小板亚细胞组分中肌球蛋白的分布上观察到了更显著的差异，其中最不致密的 WF 大鼠血小板膜组分中肌球蛋白的比例是相同正常血小板组分中的一半。这种差异通过最致密的 WF 大鼠亚细胞组分中肌球蛋白增加四倍得到平衡，该组分高度富集α-颗粒。这些结果支持了我们的假设，即 WF 大鼠的血小板异常与巨核细胞 - 血小板细胞骨架的缺陷有关。
