Fukayama S, Lanske B, Guo J, Kronenberg H M, Bringhurst F R
Endocrine Unit, Massachusetts General Hospital, Boston 02114, USA.
Am J Physiol. 1996 Jul;271(1 Pt 1):C121-9. doi: 10.1152/ajpcell.1996.271.1.C121.
Parathyroid hormone (PTH) activates both adenylate cyclase and phospholipase C in target cells, and cloned PTH/PTH-related protein (PTHrP) receptor can mediate both responses when expressed in host cells such as LLC-PK1 renal epithelial cells. Because calcitonin (CT) is known to augment 70-kDa heat shock protein (HSP70) mRNA by an adenosine 3',5'-cyclic monophosphate (cAMP)-independent mechanism in LLC-PK1 cells, we examined regulation of HSP70 transcription by PTH in these cells. Like CT, human PTH-(1-34) [hPTH-(1-34); 10(-10) to 10(-7) M)] increased porcine HSP70 mRNA and human HSP70 promoter-chloramphenicol acetyltransferase (CAT) expression within 4 h in LLC-PK1 cells that stably express > or = 100,000 PTH/PTHrP receptors per cell. The effect of PTH on HSP70 mRNA was not mimicked by cAMP analogues, forskolin, phorbol esters, Ca2+ ionophores, or alpha-thrombin; was insensitive to pertussis toxin; and was not due to increased mRNA stability. The upregulation of HSP70 gene transcription by hPTH (and CT) was clearly observed even after deletion of the functional heat shock consensus element in the promoter region of the human HSP70/CAT reporter. Upregulation of HSP70 transcription via endogenous PTH receptors also was observed in the osteoblastic cell lines SaOS-2 and ROS 17/2.8. Regulation of HSP70 gene transcription by PTH may be a common cellular response to the hormone, which, in some cells, may not be mediated by activation of adenylate cyclase or protein kinase C.
甲状旁腺激素（PTH）可激活靶细胞中的腺苷酸环化酶和磷脂酶C，克隆的PTH/甲状旁腺激素相关蛋白（PTHrP）受体在宿主细胞如LLC-PK1肾上皮细胞中表达时，可介导这两种反应。由于已知降钙素（CT）可通过一种不依赖于3',5'-环磷酸腺苷（cAMP）的机制增加LLC-PK1细胞中70-kDa热休克蛋白（HSP70）的mRNA，因此我们研究了PTH对这些细胞中HSP70转录的调控。与CT一样，人PTH-(1-34) [hPTH-(1-34)；10⁻¹⁰至10⁻⁷ M]在每细胞稳定表达≥100,000个PTH/PTHrP受体的LLC-PK1细胞中，4小时内可增加猪HSP70 mRNA和人HSP70启动子-氯霉素乙酰转移酶（CAT）的表达。cAMP类似物、福斯可林、佛波酯、Ca²⁺离子载体或α-凝血酶不能模拟PTH对HSP70 mRNA的作用；对百日咳毒素不敏感；且不是由于mRNA稳定性增加所致。即使在人HSP70/CAT报告基因启动子区域的功能性热休克共有元件缺失后，仍可清楚地观察到hPTH（和CT）对HSP70基因转录的上调作用。在成骨细胞系SaOS-2和ROS 17/2.8中也观察到了内源性PTH受体介导的HSP70转录上调。PTH对HSP70基因转录的调控可能是细胞对该激素的一种常见反应，在某些细胞中，这种反应可能不是由腺苷酸环化酶或蛋白激酶C的激活介导的。
