Phosphatidylinositol 3,4,5-trisphosphate is formed from phosphatidylinositol 4,5-bisphosphate in thrombin-stimulated platelets.
Phosphatidylinositol 3,4,5-trisphosphate is formed from phosphatidylinositol 4,5-bisphosphate in thrombin-stimulated platelets.
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磷脂酰肌醇 3,4,5-三磷酸由凝血酶刺激的血小板中的磷脂酰肌醇 4,5-二磷酸形成。
DOI：
10.1042/bj3010415
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Rittenhouse,SE
中科院分区：
文献类型：
--
作者：
Carter,AN;Huang,R;Sorisky,A;Downes,CP;Rittenhouse,SE
血小板以GTP依赖性方式对凝血酶和凝血酶受体导向肽产生应答，从而积累PtdIns（3，4，5）P3和PtdIns（3，4）P2。这些磷酸肌醇被认为是多种细胞中信号传导事件的介质。我们已经研究了PtdIns（3，4，5）P3和PtdIns（3，4）P2合成的代谢途径，通过简单（10分钟）孵育血小板与高活性的[32 P]Pi，随后20或60 s暴露于凝血酶，并分析所得标记的PtdIns（3，4，5）P3和PtdIns（3，4）P2中各个磷酸基团的相对放射性。在这种非平衡标记条件下具有最高比活性的磷酸基团指示在代谢序列中最后添加的磷酸基团。凝血酶刺激PtdIns（3，4）P2的标记速率明显慢于PtdIns（3，4，5）P3。在60 s内未检测到标记PtdIns 3 P增加。PtdIns（3，4，5）P3和PtdIns（3，4）P2的测量相对放射性以3 > 5> 4>> 1的顺序降低。根据标记率和比放射性分析的结果，我们得出结论，PtdIns（3，4，5）Pa是由PtdIns（4，5）P2的3-OH磷酸化形成的，而PtdIns（3，4）P2可能是由PtdIns 4P的3-OH磷酸化和/或PtdIns（3，4，5）P3的去磷酸化形成的。这些发现指出磷酸肌醇3-激酶的激活是凝血酶刺激血小板中关键的受体调节步骤。
Platelets accumulate PtdIns(3,4,5)P3 and PtdIns(3,4)P2 in response to thrombin and thrombin-receptor-directed peptide in a GTP-dependent manner. These phosphoinositides are considered to be mediators of signaling events in a variety of cells. We have examined the metabolic route by which PtdIns(3,4,5)P3 and PtdIns(3,4)P2 are synthesized by briefly (10 min) incubating platelets with high activities of [32P]Pi, followed by 20 or 60 s exposure to thrombin, and analysing the relative radioactivities of the individual phosphate groups in the resulting labelled PtdIns(3,4,5)P3 and PtdIns(3,4)P2. The phosphate group possessing the highest specific activity under such non-equilibrium labelling conditions indicates the last one added in a metabolic sequence. The thrombin-stimulated rate of labelling of PtdIns(3,4)P2 was significantly slower than that of PtdIns(3,4,5)P3. Increased labelled PtdIns3P was not detected within 60 s. The measured relative radioactivities decreased in the order 3 > 5 > 4 >> 1 for PtdIns(3,4,5)P3 and 3 > 4 >> 1 for PtdIns(3,4)P2. On the basis of the results of both rate-of-labelling and specific radioactivity analyses we conclude that PtdIns(3,4,5)Pa is formed by 3-OH phosphorylation of PtdIns(4,5)P2, whereas PtdIns(3,4)P2, may be formed by 3-OH phosphorylation of PtdIns4P and/or dephosphorylation of PtdIns(3,4,5)P3. These findings point to the activation of phosphoinositide 3-kinase as a critical receptor-regulated step in thrombin-stimulated platelets.