Peter J. Newman, PhD, Blood Research Institute, Blood Center of Wisconsin, Milwaukee, 53711 WI, USA, E-mail:
Cunji Gao, PhD, Chronic Disease Research Institute, Department of Nutrition and Food Hygiene, Zhejiang University School of Public Health, 310058 Hangzhou, China, Tel: +86 571 882 066 00, Fax: +86 571 882 066 00, E-mail:
Thromb Haemost. 2016 Oct 28;116(5):918-930. doi: 10.1160/TH16-02-0096. Epub 2016 Jul 28.
Integrin-αIIbβ3-mediated outside-in signalling is widely accepted as an amplifier of platelet activation; accumulating evidence suggests that outside-in signalling can, under certain conditions, also function as an inhibitor of platelet activation. The role of integrin-αIIbβ3-mediated outside-in signalling in platelet activation is disputable. We employed flow cytometry, aggregometry, immunoprecipitation, and immunoblotting to investigate the role of integrin-αIIbβ3-mediated outside-in signalling in platelet activation. Integrin αIIbβ3 inhibition enhances agonist-induced platelet ATP secretion. Human platelets lacking expression of αIIbβ3 exhibited more platelet ATP secretion than their wild-type counterparts. Moreover, integrin-αIIbβ3-mediated outside-in signals activate SHIP-1, which in turn mediates p-Akt dephosphorylation, leading to inactivation of PI3K/Akt signalling. Furthermore, 3AC (SHIP-1 inhibitor) inhibits platelet disaggregation, and promotes platelet ATP secretion. Upon ADP stimulation, Talin is recruited to αIIbβ3, and it is dissociated from αIIbβ3 when platelets disaggregate. In addition, treatment with RUC2, an inhibitor of αIIbβ3, which blocks αIIbβ3-mediated outside-in signalling, can markedly prevent the dissociation of talin from integrin. SHIP1 Inhibitor 3AC inhibits the dissociation of talin from integrin-β3. These results suggest that integrin-αIIbβ3-mediated outside-in signalling can serve as a brake to restrict unnecessary platelet activation by activated SHIP-1, which mediated the disassociation of talin from β3, leading to integrin inactivation and blocking of PI3K/Akt signalling to restrict platelet ATP secretion.
整合素-αIIbβ3 介导的外向信号转导被广泛认为是血小板激活的放大器；越来越多的证据表明，在某些情况下，外向信号转导也可以作为血小板激活的抑制剂。整合素-αIIbβ3 介导的外向信号转导在血小板激活中的作用存在争议。我们采用流式细胞术、聚集测定法、免疫沉淀和免疫印迹法来研究整合素-αIIbβ3 介导的外向信号转导在血小板激活中的作用。整合素αIIbβ3 抑制增强激动剂诱导的血小板 ATP 分泌。缺乏αIIbβ3 表达的人血小板表现出比其野生型对应物更多的血小板 ATP 分泌。此外，整合素-αIIbβ3 介导的外向信号转导激活 SHIP-1，进而介导 p-Akt 去磷酸化，导致 PI3K/Akt 信号转导失活。此外，3AC（SHIP-1 抑制剂）抑制血小板解聚，并促进血小板 ATP 分泌。在 ADP 刺激下，Talin 被招募到αIIbβ3 上，当血小板解聚时，它与αIIbβ3 分离。此外，用 RUC2（一种阻断αIIbβ3 介导的外向信号转导的抑制剂）处理可以显著防止 talin 从整合素-β3 上解离。SHIP1 抑制剂 3AC 抑制 talin 从整合素-β3 上的解离。这些结果表明，整合素-αIIbβ3 介导的外向信号转导可以作为制动器，通过激活的 SHIP-1 来限制不必要的血小板激活，该抑制剂介导 talin 与β3 的分离，导致整合素失活并阻断 PI3K/Akt 信号转导，从而限制血小板 ATP 分泌。
