Sun Der-Shan, Lo Szecheng J, Lin Chi-Hung, Yu Mei-Shiuan, Huang Ching-Yi, Chen Yao-Fong, Chang Hsin-Hou
Institute of Molecular and Cellular Biology, Tzu-Chi University, Hualien, Taiwan.
J Biomed Sci. 2005;12(2):321-33. doi: 10.1007/s11373-005-0979-6.
The frequency of calcium oscillation reveals the platelet activation status, however, the biological significance of the periodic calcium responses and methods of communication with other integrin-mediated signals are not clear. RGD-containing disintegrin rhodostomin coated substrates were employed to enhance platelet spreading and calcium oscillation through direct binding and clustering of the receptor integrin alpha(IIb)beta3. The results showed that the activation of phosphatidylinositol 3-kinase (PI3-K) and internal calcium pathways were crucial for alpha(IIb)beta3 outside-in signaling. PI3-K antagonists wortmannin and LY294002 inhibited disintegrin substrates and induced platelet spreading and calcium oscillation. At the same time, pretreatment of platelets with the microsomal calcium-ATPase inhibitor thapsigargin to deplete internal calcium stores severely impaired the calcium oscillation as well as PI3-K activation and spreading on disintegrin substrates. Because inhibition of one pathway could inhibit the other, our data indicates that PI3-K and calcium oscillation are synergistically operated and form a positive-feedback regulation in integrin alpha(IIb)beta3-mediated outside-in signaling.
钙振荡的频率揭示了血小板的活化状态，然而，周期性钙反应的生物学意义以及与其他整合素介导信号的通讯方式尚不清楚。含RGD的去整合素罗豆素包被的底物通过受体整合素α（IIb）β3的直接结合和聚集来增强血小板铺展和钙振荡。结果表明，磷脂酰肌醇3激酶（PI3-K）和细胞内钙途径的激活对于α（IIb）β3外向信号转导至关重要。PI3-K拮抗剂渥曼青霉素和LY294002抑制去整合素底物并诱导血小板铺展和钙振荡。同时，用微粒体钙-ATP酶抑制剂毒胡萝卜素预处理血小板以耗尽细胞内钙储存，严重损害了钙振荡以及PI3-K激活和在去整合素底物上的铺展。由于抑制一条途径可抑制另一条途径，我们的数据表明PI3-K和钙振荡协同运作，并在整合素α（IIb）β3介导的外向信号转导中形成正反馈调节。
