Roles of Phospholipid Molecular Species in Cell Signaling

研究了磷脂分子种类在细胞信号转导中的作用。质量变化的各种分子种类的磷脂测定刺激后的人血小板与凝血酶和胶原蛋白。刺激后，磷脂酰肌醇和磷脂酰丝氨酸的每一个分子物种同样水解，而磷脂酰胆碱和二酰基-和烯基酰基-磷脂酰乙醇嗪含有花生四烯酸的分子物种被选择性水解。Ca^<2+>浓度影响活化人血小板磷脂分子种类的差异降解，血栓素A_2拮抗剂ONO 3708可完全抑制胶原活化人血小板胞浆游离Ca^<2+>的增加。半数最大Ca^2+释放和内流分别需要3和4 nM STA_2，STA_2是一种稳定的血栓烷A_2模拟物。然而，磷脂酶C的半数最大激活需要约18 nM STA_2。Ca^<2+>通道阻断剂， ...更多信息 硝苯地平是一种二氢吡啶衍生物，可抑制由胶原蛋白或低浓度STA_2（10 nM）引起的Ca^2+内流和内贮释放，但不能抑制由凝血酶或高浓度STA_2（100 nM）引起的内流和内贮释放。这些结果表明，在人血小板中存在两种不同的钙通道，对二氢吡啶敏感的和不敏感的钙通道依赖于激动剂的浓度和种类。<125>在4 ℃与细胞表面受体结合后，在37 ℃孵育8 min期间，I标记的表皮生长因子掺入中国仓鼠V79-UF细胞的内体中并高度浓缩。从标记的细胞中，通过在Percoll密度梯度和蔗糖密度梯度上等容离心分离内体。发现内体膜在磷脂组成上不同于质膜。含有两个单烯脂肪酸的二酰基磷脂酰胆碱和二酰基磷脂酰乙醇胺的分子种类在核内体中的含量低于质膜。无论磷脂分子种类在质膜中的比例是否改变，内体和质膜之间磷脂的极性头基和分子种类组成的差异没有改变。少

Roles of phospholipid molecular species in cell signaling were studied. Mass changes in the various molecular species of phospholipids were determined after stimulation of human platelets with thrombin and collagen. Upon stimulation, every molecular species of phosphatidylinositol and phosphatidylserine was equally hydrolyzed, whereas the molecular species of phosphatidylcholine and diacyl- and alkenylacyl-phosphatidylethanolazine containing arachidonic acid were selectively hydrolyzed. The Ca^<2+> concentration affects the differential degradation of phospholipid molecular species in activated human platelets.The thromboxane A_2 antagonist, ONO3708, completely inhibited the increase in cytosolic free Ca^<2+> in human platelets during activation with collagen. Half-maximal Ca^<2+> release and influx required about 3 and 4 nM STA_2, a stable thromboxane A_2 mimetic, respectively. However, half-maximal activation of phospholipase C required about 18 nM STA_2.The Ca^<2+> channel blocker, … More nifedipine, a dihydropyridine derivative, inhibited the Ca^<2+> influx and release from internal stores caused by collagen or a low concentration of STA_2 (10 nM), but did not inhibit those caused by thrombin or a high concentration of STA_2 (100 nM). These results indicate the presence of two distinct, dihydropyridine-sensitive and insensitive, Ca^<2+> channels dependent on the concentrations and classes of agonists in human platelets.^<125>I-labeled epidermal growth factor was incorporated into and highly concentrated in endosomes of Chinese hamster V79-UF cells during incubation at 37ﾟC for 8 min after binding to its receptors on the cell surface at 4ﾟC. From the labeled cells, endosomes were isolated by isopyenic centrifugation on a Percoll density gradient and then sucrose density gradients. Endosome membranes were found to differ from plasma membranes in the phospholipid composition. The contents of molecular species of diacylphosphatidyleholine and diacylphosphatidylethanolamine with two monoenoic fatty acids were lower in endosomes than in plasma membranes. The differences in the polar head group and molecular species compositions of phospholipids between endosomes and plasma membranes did not change, regardless of whether or not the proportions of phospholipid molecular species in plasma membranes changed. Less