Mechanisms of actin rearrangements mediating platelet activation.
Mechanisms of actin rearrangements mediating platelet activation.
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DOI：
10.1083/jcb.118.6.1421
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发表时间：
1992-09
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影响因子：
--
通讯作者：
Hartwig JH
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作者：
Hartwig JH
静止的人血小板的洗涤剂不溶性细胞骨架含有约2，000个肌动蛋白丝，其长度约为1微米，通过肌动蛋白结合蛋白以高角度交联，并结合到富含血影蛋白的亚膜层（Fox，J.，J. Boyles，M. Berndt，P. Steffen，and L.安德森。1988. 106：1525 - 1538; Hartwig，J.，和m.德西斯托1991. 112：407 - 425）。通过与玻璃接触激活血小板导致在30秒内细胞骨架的聚合肌动蛋白含量增加一倍，并出现两种不同的新肌动蛋白结构：丝状伪足内的长丝束，其终止于丝状伪足尖端（丝状伪足束）和片状伪足内正交排列的短长丝的圆周区（片状伪足网络）。在细胞松弛素B存在的情况下，暴露于玻璃的细胞中，这些结构都没有出现;相反，细胞骨架上有许多0.1 - 0.3微米长的肌动蛋白丝片段附着在膜层上。与玻璃诱导的形态学变化相同的时间过程中，细胞松弛素敏感的肌动蛋白成核活性，最初在静息血小板的细胞骨架中较低，在凝血酶活化的血小板的细胞骨架中增加10倍。这种活性随着与0.1 - 0.3微米长的肌动蛋白丝解聚一致的时间过程而衰减，鬼笔环肽抑制这种衰减。细胞松弛素不敏感和钙依赖性成核活性也显着增加血小板提取物后，凝血酶激活的细胞。预防细胞溶质Ca2+的上升通常与血小板活化的渗透性Ca2+螯合剂，Quin-2，抑制形成的lamelipodial网络，但不filopodial束后，玻璃接触，并减少细胞松弛素B敏感的成核活性的60%凝血酶处理后。然而，丝状伪足束是不正常的，因为它们不终止于丝状伪足尖端，而是形成环并返回到细胞体。添加钙螯合细胞恢复lamellipodial网络，钙加A23187结果在细胞骨架高度碎片化的肌动蛋白丝在几秒钟内。免疫胶体金标记的抗体对凝溶胶蛋白揭示凝溶胶蛋白分子在丝的末端附着在膜下层的静息细胞骨架和在一些丝的末端在lamellipodial网络和filepodial束的激活细胞骨架。此外，单体肌动蛋白的肌球蛋白亚片段1标记的活化的细胞骨架导致新的（未装饰的）丝生长的丝状伪足束和lamellipodial网络中的丝的末端。对这些发现的最简单的解释是凝溶胶蛋白覆盖了静息血小板中细丝的倒刺末端。在激活后，将这些细丝中的一些去帽，导致丝状伪足束。（400字处删节）
The detergent-insoluble cytoskeleton of the resting human blood platelet contains approximately 2,000 actin filaments approximately 1 micron in length crosslinked at high angles by actin-binding protein and which bind to a spectrin-rich submembrane lamina (Fox, J., J. Boyles, M. Berndt, P. Steffen, and L. Anderson. 1988. J. Cell Biol. 106:1525-1538; Hartwig, J., and M. DeSisto. 1991. J. Cell Biol. 112:407- 425). Activation of the platelets by contact with glass results within 30 s in a doubling of the polymerized actin content of the cytoskeleton and the appearance of two distinct new actin structures: bundles of long filaments within filopodia that end at the filopodial tips (filopodial bundles) and a circumferential zone of orthogonally arrayed short filaments within lamellipodia (lamellipodial network). Neither of these structures appears in cells exposed to glass with cytochalasin B present; instead the cytoskeletons have numerous 0.1-0.3-microns-long actin filament fragments attached to the membrane lamina. With the same time course as the glass-induced morphological changes, cytochalasin- sensitive actin nucleating activity, initially low in cytoskeletons of resting platelets, increases 10-fold in cytoskeletons of thrombin- activated platelets. This activity decays with a time course consistent with depolymerization of 0.1-0.3-microns-long actin filaments, and phalloidin inhibits this decay. Cytochalasin-insensitive and calcium- dependent nucleation activity also increases markedly in platelet extracts after thrombin activation of the cells. Prevention of the rise in cytosolic Ca2+ normally associated with platelet activation with the permeant Ca2+ chelator, Quin-2, inhibits formation of lamellipodial networks but not filopodial bundles after glass contact and reduces the cytochalasin B-sensitive nucleation activity by 60% after thrombin treatment. The filopodial bundles, however, are abnormal in that they do not end at the filopodial tips but form loops and return to the cell body. Addition of calcium to chelated cells restores lamellipodial networks, and calcium plus A23187 results in cytoskeletons with highly fragmented actin filaments within seconds. Immunogold labeling with antibodies against gelsolin reveals gelsolin molecules at the ends of filaments attached to the submembrane lamina of resting cytoskeletons and at the ends of some filaments in the lamellipodial networks and filopodial bundles of activated cytoskeletons. Addition of monomeric actin to myosin subfragment 1-labeled activated cytoskeletons leads to new (undecorated) filament growth off the ends of filaments in the filopodial bundles and the lamellipodial network. The simplest explanation for these findings is that gelsolin caps the barbed ends of the filaments in the resting platelet. Uncapping some of these filaments after activation leads to filopodial bundles.(ABSTRACT TRUNCATED AT 400 WORDS)