Mandla S, Boneh A, Tenenhouse H S
Department of Pediatrics, McGill University-Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada.
Endocrinology. 1990 Dec;127(6):2639-47. doi: 10.1210/endo-127-6-2639.
Although calcium-activated, phospholipid-dependent protein kinase (protein kinase C) has been implicated in the regulation of various steroidogenic pathways, comparatively little is known of its role in the metabolism of vitamin D. The present study was undertaken to determine whether protein kinase C is involved in the regulation of renal mitochondrial 25-hydroxyvitamin D3-24-hydroxylase (24-hydroxylase), the first enzyme in the C-24 oxidation pathway, a major catabolic pathway for vitamin D metabolites in kidney and other target tissues. We examined the effect of phorbol 12-myristate 13-acetate (PMA), a potent activator of protein kinase C, on 24-hydroxylase activity in fresh mouse renal tubules and correlated the changes in 24,25-dihydroxyvitamin D3 [24,25-(OH)2D3] production with translocation of protein kinase C and phosphorylation of mitochondrial proteins. PMA stimulated 24,25-(OH)2D3 synthesis, protein kinase C translocation from the cytosolic to the mitochondrial fraction, and phosphorylation of 30-35 K, 40 K, and 50 K mitochondrial proteins derived from 32P-labeled tubules. 4 alpha-Phorbol 12,13 didecanoate, an insert analog of PMA, did not elicit any of these effects. The synthetic diacylglycerol, oleoylacetyl glycerol, also stimulated 24,25-(OH)2D3 synthesis, whereas the protein kinase C inhibitors, H-7 and staurosporine, inhibited 24-hydroxylase activity. PMA did not further stimulate 24,25-(OH)2D3 production in tubules derived from mutant (Hyp) mice in which 24-hydroxylase and protein kinase C activities are elevated relative to normal. However, after treatment with H-7, 24-hydroxylase activity was reduced in both strains, and genotype differences were no longer apparent. Finally, H-7 failed to inhibit the induced renal 24-hydroxylase in tubules isolated from 1,25-dihydroxyvitamin D3-treated mice. These findings suggest a role for protein kinase C in the regulation of constitutive renal 24-hydroxylase and implicate the kinase in the aberrant expression of the hydroxylase in the Hyp mouse.
尽管钙激活的磷脂依赖性蛋白激酶（蛋白激酶C）参与了多种类固醇生成途径的调节，但对于其在维生素D代谢中的作用却知之甚少。本研究旨在确定蛋白激酶C是否参与肾线粒体25-羟基维生素D3-24-羟化酶（24-羟化酶）的调节，该酶是C-24氧化途径中的首个酶，是肾脏及其他靶组织中维生素D代谢产物的主要分解代谢途径。我们研究了蛋白激酶C的强效激活剂佛波酯12-肉豆蔻酸酯13-乙酸酯（PMA）对新鲜小鼠肾小管中24-羟化酶活性的影响，并将24,25-二羟基维生素D3[24,25-(OH)2D3]生成的变化与蛋白激酶C的易位及线粒体蛋白的磷酸化相关联。PMA刺激了24,25-(OH)2D3的合成、蛋白激酶C从胞质向线粒体部分的易位以及来自32P标记肾小管的30 - 35K、40K和50K线粒体蛋白的磷酸化。PMA的插入类似物4α-佛波醇12,13-二癸酸酯未引发任何这些效应。合成二酰甘油油酰乙酰甘油也刺激了24,25-(OH)2D3的合成，而蛋白激酶C抑制剂H-7和星形孢菌素则抑制了24-羟化酶活性。PMA并未进一步刺激来自突变（Hyp）小鼠的肾小管中24,25-(OH)2D3的生成，但在该突变小鼠中，24-羟化酶和蛋白激酶C的活性相对于正常小鼠有所升高。然而，用H-7处理后，两种品系的24-羟化酶活性均降低，基因型差异不再明显。最后，H-7未能抑制从1,25-二羟基维生素D3处理的小鼠中分离出的肾小管中诱导的肾24-羟化酶。这些发现表明蛋白激酶C在组成型肾24-羟化酶的调节中发挥作用，并提示该激酶与Hyp小鼠中羟化酶的异常表达有关。
