Yamaguchi D T, Kleeman C R, Muallem S
Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048.
J Biol Chem. 1987 Nov 5;262(31):14967-73.
The effects of protein kinase C stimulation on free cytosolic Ca2+ [( Ca2+]i) were studied in Fura 2-loaded UMR-106 cells. Stimulation of the protein kinase C with the tumor-promoting phorbol esters 12-O-tetradecanoylphorbol 13-acetate (TPA) and phorbol 12,13-diacetate or 1-oleoyl-2-acetylglycerol was followed by an increase in [Ca2+]i. The protein kinase C-induced increase in [Ca2+]i has a lag period, the duration of which was dependent on the stimulant and medium Ca2+ concentrations. With 2 microM TPA, the rise in [Ca2+]i peaked within 1.5 min, after which [Ca2+]i returned partially toward base line. The increase in [Ca2+]i was absolutely dependent on the presence of medium Ca2+ and was inhibited by the Ca2+ channel blockers nicardipine and verapamil. Cell stimulation also results in Ca2+ release from intracellular pool(s) which appears to be mediated by a Ca2+-dependent Ca2+ release mechanism. The reduction in [Ca2+]i was due to channel inactivation. Pretreatment of the cells with 1 nM TPA, 2 units/ml parathyroid hormone (PTH), or 15 microM forskolin blocked the effect of 2 microM TPA on [Ca2+]i. TPA and PTH were more potent inhibitors than was forskolin. The properties of this channel are compared to the cAMP-independent PTH-stimulated Ca2+ channel present in these cells.
在用Fura 2加载的UMR-106细胞中研究了蛋白激酶C刺激对游离胞质Ca2+[Ca2+]i的影响。用促肿瘤佛波酯12-O-十四酰佛波醇13-乙酸酯（TPA）、佛波醇12,13-二乙酸酯或1-油酰-2-乙酰甘油刺激蛋白激酶C后，[Ca2+]i增加。蛋白激酶C诱导的[Ca2+]i增加有一个延迟期，其持续时间取决于刺激物和培养基Ca2+浓度。用2 microM TPA时，[Ca2+]i在1.5分钟内达到峰值，之后[Ca2+]i部分回到基线。[Ca2+]i的增加绝对依赖于培养基Ca2+的存在，并被Ca2+通道阻滞剂尼卡地平、维拉帕米抑制。细胞刺激还导致细胞内钙库释放Ca2+，这似乎是由一种Ca2+依赖性Ca2+释放机制介导的。[Ca2+]i的降低是由于通道失活。用1 nM TPA、2单位/毫升甲状旁腺激素（PTH）或15 microM福斯高林预处理细胞可阻断2 microM TPA对[Ca2+]i的影响。TPA和PTH比福斯高林是更有效的抑制剂。将该通道的特性与这些细胞中存在的不依赖cAMP的PTH刺激的Ca2+通道进行了比较。
