Krishnan A V, Cramer S D, Bringhurst F R, Feldman D
Stanford University School of Medicine, California 95305.
Endocrinology. 1995 Feb;136(2):705-12. doi: 10.1210/endo.136.2.7835303.
The regulation of vitamin D receptor (VDR) abundance in MC3T3-E1 mouse osteoblasts and UMR 106-01 rat osteosarcoma cells by rat PTH 1-34, human PTH-related protein 1-34, and agents that activate specific signal transduction pathways was studied. Treatment of these cells with forskolin (FSK) caused up-regulation of VDR, whereas treatment with phorbol esters suppressed VDR levels. PTH or PTH-related protein treatment induced a 2- to 3-fold increase in VDR, which was equivalent to that elicited by FSK in UMR 106-01 cells but less than the FSK-induced increase (approximately 8-fold) in MC3T3-E1 cells. PTH treatment of MC3T3-E1 cells resulted in an approximately 3-fold increase in VDR levels with maximum stimulation occurring at 10(-9) M PTH after 4 h of treatment. In UMR 4-7 cells, a subclone of UMR 106-01 cells that express cAMP resistance due to regulated expression of a mutant form of the type 1 regulatory subunit of the cAMP-dependent protein kinase A (PKA), the up-regulation of VDR abundance due to FSK and PTH treatment was mostly prevented. Pretreatment of MC3T3-E1 cells with staurosporine, an inhibitor of PKC, resulted in an approximately 3-fold increase in basal VDR levels but did not enhance the PTH-mediated up-regulation of VDR. Collectively, these data suggest that the increase in VDR abundance observed in these target cells is mainly due to the activation of the PKA signal transduction pathway. Treatment of UMR 106-01 cells with PTH for 4 h before exposure of the cells to 1,25-dihydroxyvitamin D3 resulted in a 2-fold increase in the induction of 25-hydroxyvitamin D3-24 hydroxylase messenger RNA. Thus, exposure of target cells to PTH augments their response to 1,25-dihydroxyvitamin D3 due to up-regulation of VDR abundance.
研究了大鼠甲状旁腺激素1-34、人甲状旁腺激素相关蛋白1-34以及激活特定信号转导途径的试剂对MC3T3-E1小鼠成骨细胞和UMR 106-01大鼠骨肉瘤细胞中维生素D受体（VDR）丰度的调节作用。用福司可林（FSK）处理这些细胞会导致VDR上调，而用佛波酯处理则会抑制VDR水平。甲状旁腺激素或甲状旁腺激素相关蛋白处理可使VDR增加2至3倍，这与FSK在UMR 106-01细胞中引起的增加相当，但低于FSK在MC3T3-E1细胞中引起的增加（约8倍）。用甲状旁腺激素处理MC3T3-E1细胞导致VDR水平增加约3倍，在处理4小时后，10(-9) M甲状旁腺激素时刺激达到最大值。在UMR 4-7细胞中，UMR 106-01细胞的一个亚克隆，由于环磷酸腺苷依赖性蛋白激酶A（PKA）1型调节亚基的突变形式的表达受到调控而表现出对环磷酸腺苷的抗性，FSK和甲状旁腺激素处理导致的VDR丰度上调大多被阻止。用蛋白激酶C（PKC）抑制剂星形孢菌素预处理MC3T3-E1细胞，导致基础VDR水平增加约3倍，但并未增强甲状旁腺激素介导的VDR上调。总体而言，这些数据表明，在这些靶细胞中观察到的VDR丰度增加主要是由于PKA信号转导途径的激活。在将UMR 106-01细胞暴露于1,25-二羟基维生素D3之前，先用甲状旁腺激素处理4小时，导致25-羟基维生素D3-24羟化酶信使核糖核酸的诱导增加2倍。因此，靶细胞暴露于甲状旁腺激素会由于VDR丰度的上调而增强其对1,25-二羟基维生素D3的反应。
