Inoue Osamu, Suzuki-Inoue Katsue, McCarty Owen J T, Moroi Masaaki, Ruggeri Zaverio M, Kunicki Thomas J, Ozaki Yukio, Watson Steve P
Department of Clinical and Laboratory Medicine, Yamanashi Medical University, 1110 Shimokato Tamaho Nakakoma, Yamanashi 409-3898, Japan.
Blood. 2006 Feb 15;107(4):1405-12. doi: 10.1182/blood-2005-06-2406. Epub 2005 Oct 11.
The extracellular matrix protein, laminin, supports platelet adhesion through binding to integrin alpha6beta1 In the present study, we demonstrate that human laminin, purified from placenta, also stimulates formation of filopodia and lamellipodia in human and mouse platelets through a pathway that is dependent on alpha6beta1 and the collagen receptor GPVI. The integrin alpha6beta1 is essential for adhesion to laminin, as demonstrated using an alpha6-blocking antibody, whereas GPVI is dispensable for this response, as shown using "knockout" mouse platelets. On the other hand, lamellipodia formation on laminin is completely inhibited in the absence of GPVI, although filopodia formation remains and is presumably mediated via alpha6beta1 Lamellipodia and filopodia formation are inhibited in Syk-deficient platelets, demonstrating a key role for the kinase in signaling downstream of GPVI and integrin alpha6beta1 GPVI was confirmed as a receptor for laminin using surface plasmon resonance spectroscopy and by demonstration of lamellipodia formation on laminin in the presence of collagenase. These results identify GPVI as a novel receptor for laminin and support a model in which integrin alpha6beta1 brings laminin to GPVI, which in turn mediates lamellipodia formation. We speculate that laminin contributes to platelet spreading in vivo through a direct interaction with GPVI.
细胞外基质蛋白层粘连蛋白通过与整合素α6β1结合来支持血小板黏附。在本研究中，我们证明从胎盘中纯化的人层粘连蛋白还通过一条依赖于α6β1和胶原受体GPVI的途径刺激人和小鼠血小板中丝状伪足和片状伪足的形成。使用α6阻断抗体证明，整合素α6β1对于黏附层粘连蛋白至关重要，而使用“基因敲除”小鼠血小板表明，GPVI对于这种反应是可有可无的。另一方面，在没有GPVI的情况下，层粘连蛋白上的片状伪足形成被完全抑制，尽管丝状伪足形成仍然存在，并且推测是通过α6β1介导的。在缺乏Syk的血小板中，片状伪足和丝状伪足的形成受到抑制，这表明该激酶在GPVI和整合素α6β1下游信号传导中起关键作用。使用表面等离子体共振光谱并通过证明在胶原酶存在的情况下层粘连蛋白上片状伪足的形成，证实GPVI是层粘连蛋白的受体。这些结果确定GPVI是层粘连蛋白的一种新型受体，并支持一种模型，即整合素α6β1将层粘连蛋白带到GPVI，后者进而介导片状伪足的形成。我们推测层粘连蛋白通过与GPVI的直接相互作用在体内促进血小板铺展。
