Pribluda V, Rotman A
Biochemistry. 1982 Jun 8;21(12):2825-32. doi: 10.1021/bi00541a003.
The dynamics of actin polymerization, cytoskeleton formation, and interaction with membrane and cytoplasmic proteins as a result of platelet activation by temperature. ADP, or thrombin were studied. The polymerization of about 30% of platelet DNase I available actin to a nonavailable state is rapid and complete within 10 s after platelet activation with ADP and thrombin. This polymerization might be related to shape change rather than to aggregation or secretion. A similar value of actin polymerization is obtained when platelets are induced to change shape by cooling. This polymerization is partially reversible upon deactivation of the platelets by apyrase, hirudin, or rewarming. Cycles of temperatures-mediated activation and deactivation show a cyclic variation in the state of actin, with a tendency to refractivity to further changes after a couple of cycles. No correlation is observed between microtubule integrity and actin polmerization when studies are performed with platelets pretreated with colchicine. Analysis of the Triton residue composition shows that the cytoskeleton of resting platelets is composed mainly of actin and myosin in a 4.5:1 ratio. Activation with ADP and thrombin leads to the association and incorporation of several other protein (actin binding protein, 95 000 daltons, three to four proteins in the 35 000-dalton region, and two proteins in the 17 000-dalton region with the cytoskeleton). The incorporation of these proteins has a dynamic nature that depends on both the state of aggregation and the reversibility of the activation. Activation leads to a significant increase in the total cytoskeletal proteins, and although low temperature also induces such an increase, the cytoskeletal pattern of cooled platelets is not different from that of resting platelets. A complete reversibility in morphology and amount of protein was observed with temperature cycling. In light of these results, the dynamic nature of the state of actin in platelets is discussed.
研究了温度、二磷酸腺苷（ADP）或凝血酶激活血小板后，肌动蛋白聚合、细胞骨架形成以及与膜蛋白和细胞质蛋白相互作用的动力学过程。在用ADP和凝血酶激活血小板后10秒内，约30%的血小板中可利用的脱氧核糖核酸酶I肌动蛋白迅速且完全地聚合成不可利用状态。这种聚合可能与形状改变有关，而非聚集或分泌。当通过冷却诱导血小板改变形状时，可获得类似的肌动蛋白聚合值。在用腺苷三磷酸双磷酸酶、水蛭素使血小板失活或复温后，这种聚合部分可逆。温度介导的激活和失活循环显示肌动蛋白状态呈周期性变化，经过几个循环后对进一步变化有折射倾向。当对用秋水仙碱预处理的血小板进行研究时，未观察到微管完整性与肌动蛋白聚合之间的相关性。对Triton残余物组成的分析表明，静息血小板的细胞骨架主要由肌动蛋白和肌球蛋白以4.5:1的比例组成。用ADP和凝血酶激活会导致几种其他蛋白质（肌动蛋白结合蛋白，95000道尔顿，在35000道尔顿区域有三到四种蛋白质，在17000道尔顿区域有两种蛋白质）与细胞骨架结合并整合。这些蛋白质的整合具有动态性质，取决于聚集状态和激活的可逆性。激活导致细胞骨架总蛋白显著增加，尽管低温也会诱导这种增加，但冷却血小板的细胞骨架模式与静息血小板的并无不同。通过温度循环观察到形态和蛋白量完全可逆。根据这些结果，讨论了血小板中肌动蛋白状态的动态性质。
