Tfelt-Hansen J, MacLeod R J, Chattopadhyay N, Yano S, Quinn S, Ren X, Terwilliger E F, Schwarz P, Brown E M
Endocrine-Hypertension Division, Dept. of Medicine and Membrane Biology Program, Brigham and Women's Hospital and Harvard Medical School, 221 Longwood Ave., Boston, MA 02115, USA.
Am J Physiol Endocrinol Metab. 2003 Aug;285(2):E329-37. doi: 10.1152/ajpendo.00489.2002. Epub 2003 Apr 15.
Elevated extracellular calcium ([Ca2+]o) and other agonists potentially acting via the calcium-sensing receptor (CaR) increase parathyroid hormone-related peptide (PTHrP) release from H-500 Leydig cells. Here, we provide strong evidence for the CaR's involvement by using a dominant negative CaR that attenuates high [Ca2+]o-induced PTHrP release. This effect is likely transcriptional, because high [Ca2+]o upregulates the PTHrP transcript, an effect that is abolished by actinomycin D. Regulation of PTHrP release by the CaR involves activation of PKC as well as ERK1/2, p38 MAPK, and JNK pathways. However, we show for the first time that high [Ca2+]o-induced activation of the stress-activated protein kinase SEK1 is PKC independent, because there is an additive effect of a PKC inhibitor in combination with the JNK inhibitor on [Ca2+]o-stimulated PTHrP release. Furthermore, high [Ca2+]o, in a PKC-independent fashion, induces phosphorylation of ERK1/2, SEK1, p38 MAPK, and its downstream transcription factor ATF-2. We conclude that CaR regulation of PTHrP release in H-500 cells involves activation of PKC as well as the ERK1/2, p38 MAPK, and JNK pathways.
细胞外钙浓度升高（[Ca2+]o）以及其他可能通过钙敏感受体（CaR）起作用的激动剂会增加H - 500睾丸间质细胞中甲状旁腺激素相关肽（PTHrP）的释放。在此，我们通过使用一种显性负性CaR来减弱高[Ca2+]o诱导的PTHrP释放，从而为CaR的参与提供了有力证据。这种效应可能是转录性的，因为高[Ca2+]o会上调PTHrP转录本，而放线菌素D可消除这种效应。CaR对PTHrP释放的调节涉及蛋白激酶C（PKC）以及细胞外信号调节激酶1/2（ERK1/2）、p38丝裂原活化蛋白激酶（p38 MAPK）和应激活化蛋白激酶（JNK）途径的激活。然而，我们首次表明，高[Ca2+]o诱导的应激激活蛋白激酶SEK1的激活不依赖于PKC，因为PKC抑制剂与JNK抑制剂联合使用对[Ca2+]o刺激的PTHrP释放具有相加效应。此外，高[Ca2+]o以不依赖PKC的方式诱导ERK1/2、SEK1、p38 MAPK及其下游转录因子ATF - 2的磷酸化。我们得出结论，CaR对H - 500细胞中PTHrP释放的调节涉及PKC以及ERK1/2、p38 MAPK和JNK途径的激活。
