Cell-specific signaling and structure-activity relations of parathyroid hormone analogs in mouse kidney cells
Cell-specific signaling and structure-activity relations of parathyroid hormone analogs in mouse kidney cells
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DOI：
10.1210/en.140.1.301
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发表时间：
1999-01-01
期刊：
影响因子：
4.8
通讯作者：
Willick, GE
中科院分区：
文献类型：
--
作者：
Friedman, PA;Gesek, FA;Willick, GE
甲状旁腺激素是一种含有84个氨基酸的蛋白质。其同源受体的占用通常导致腺苷酸环化酶和/或磷酸肌醇特异性磷脂酶C β (PLC β)的激活。在肾脏中，PTH受体存在于近端和远端小管细胞上。在近端小管中，PTH诱导钙信号传导，典型表现为细胞内钙（[Ca2+](i)）和肌醇三磷酸形成的短暂升高，但不影响钙的吸收。相比之下，在远端小管中，甲状旁腺激素增加钙吸收，这与[Ca2+](i)的缓慢和持续上升有关，但不刺激磷脂酶C （PLC）或引起肌醇三磷酸积累。尽管如此，远端钙转运的刺激需要激活蛋白激酶C （PKC）和蛋白激酶a。我们现在通过使用合成的优先激活腺苷酸环化酶和/或PLC β的人类PTH类似物来表征配体占用差异效应的起源。我们进一步验证了磷脂酶D负责远端小管细胞PKC激活的假设。PTH-(1-31)在远端小管细胞中增加[Ca2+](i)，而在近端小管细胞中没有增加，而PTH-(3-34)在近端细胞中引起[Ca2+](i)的部分增加，但在远端细胞中没有影响。PTH-(7-34)阻断了PTH-(1-34)和PTH（1-31）刺激的远端小管细胞中[Ca2+](i)的增加。PLC抑制剂U73122消除了pth诱导的近端小管细胞[Ca2+](i)和肌醇三磷酸形成的升高，但对pth刺激的远端小管细胞Ca2+摄取没有影响。这些结果支持了PTH在远端小管细胞中激活PKC与PLC β无关的观点。然而，甲状旁腺素确实激活了磷脂酶D，并在远端细胞中形成了二酰基甘油。由于PTH诱导钙转运需要激活PKC，因此我们得出结论，PTH受体能够激活多种磷脂酶，并且这种激活的结构要求在近端和远端小管细胞中有所不同。
PTH is an 84-amino acid protein. Occupancy of its cognate receptor generally results in activation of adenylyl cyclase and/or phosphoinositide-specific phospholipase C beta (PLC beta). In the kidney, PTH receptors are present on proximal and distal tubule cells. In proximal tubules, PTH induces calcium signaling, typified by a transient rise in intracellular calcium ([Ca2+](i)) and inositol trisphosphate formation, but does not affect calcium absorption. By contrast, in distal tubules, PTH increases calcium absorption that is associated with a slow and sustained rise in [Ca2+](i), but does not stimulate phospholipase C (PLC) or cause inositol trisphosphate accumulation. Nonetheless, stimulation of distal calcium transport requires activation of protein kinase C (PKC) and protein kinase A. We now characterize the origin of the differential effects of ligand occupancy by using synthetic human PTH analogs that preferentially activate adenylyl cyclase and/or PLC beta. We further tested the hypothesis that phospholipase D is responsible for PKC activation in distal tubule cells. PTH-(1-31) increased [Ca2+](i) in distal tubule but not in proximal tubule cells, whereas PTH-(3-34) caused a partial increase in [Ca2+](i) in proximal cells, but had no effect in distal cells. PTH-(7-34) blocked increases in [Ca2+](i) in distal tubule cells stimulated by PTH-(1-34) and PTH(1-31). The PLC inhibitor U73122 abolished the PTH-induced rise in [Ca2+](i) and inositol trisphosphate formation by proximal tubule cells, but had no effect on PTH-stimulated Ca2+ uptake by distal tubule cells. These results support the view that activation of PKC by PTH in distal tubule cells does not involve PLC beta. PTH did, however, activate phospholipase D with attendant formation of diacylglycerol in distal cells. As activation of PKC is required for induction of calcium transport by PTH, we conclude that PTH receptors are capable of activating multiple phospholipases and that the structural requirements for such activation differ in proximal and distal tubule cells.