Yamaji Satoshi, Suzuki Atsushi, Kanamori Heiwa, Mishima Wataru, Takabayashi Maki, Fujimaki Katsumichi, Tomita Naoto, Fujisawa Shin, Ohno Shigeo, Ishigatsubo Yoshiaki
The First Department of Internal Medicine, Yokohama City University School of Medicine, 3-9 Fuku-ura, Kanazawa-ku, 236-0004, Yokohama, Japan.
Biochem Biophys Res Commun. 2002 Oct 11;297(5):1324-31. doi: 10.1016/s0006-291x(02)02381-1.
Integrin-mediated adhesion induces the formation of focal adhesions that link the extracellular matrix and intracellular actin cytoskeletal networks. We previously showed that integrin-linked kinase (ILK), which can interact with beta1 and beta3 integrins, and its interacting protein, affixin, play an essential role in the initial assembly of focal adhesion structures and actin stress fibers. Although the relevant structures are also observed in integrin alphaIIbbeta3 in platelets, the precise underlying molecular mechanism remains unclarified. Here, we found that ILK stably forms a complex with ss-affixin in platelets. Thrombin stimulation induces their association with integrin beta3, which is followed by their incorporation into the Triton-insoluble membrane-cytoskeletal fraction. During the course of thrombin-induced platelet aggregation, ILK activity was enhanced within 90s to 2.1-fold of the basal level, independent of phosphatidylinositol 3-kinase. Taken together with the observation that the treatment with an anti-integrin beta3 antibody stimulates ILK activity without inducing platelet aggregation, these results suggest that the outside-in signaling induced by fibrinogen binding to integrin enhances ILK activity and results in the initial phase to reorganize the actin cytoskeleton.
整合素介导的黏附诱导黏着斑的形成，黏着斑连接细胞外基质和细胞内肌动蛋白细胞骨架网络。我们之前表明，可与β1和β3整合素相互作用的整合素连接激酶（ILK）及其相互作用蛋白亲和素，在黏着斑结构和肌动蛋白应力纤维的初始组装中起重要作用。尽管在血小板的整合素αIIbβ3中也观察到了相关结构，但其确切的潜在分子机制仍不清楚。在这里，我们发现ILK在血小板中与ss-亲和素稳定形成复合物。凝血酶刺激诱导它们与整合素β3结合，随后它们被整合到不溶于曲拉通的膜-细胞骨架组分中。在凝血酶诱导的血小板聚集过程中，ILK活性在90秒内增强至基础水平的2.1倍，这与磷脂酰肌醇3激酶无关。结合用抗整合素β3抗体处理可刺激ILK活性而不诱导血小板聚集这一观察结果，这些结果表明纤维蛋白原与整合素结合诱导的外向内信号增强了ILK活性，并导致肌动蛋白细胞骨架重组的初始阶段。
