Furukawa K, Tawada Y, Shigekawa M
Department of Molecular Physiology, National Cardiovascular Center Research Institute, Osaka, Japan.
J Biol Chem. 1989 Mar 25;264(9):4844-9.
We examined the effect of phorbol myristate acetate (PMA), a potent activator of protein kinase C, on Ca2+ extrusion from cultured vascular smooth muscle cells (VSMCs) incubated in the absence of added extracellular Na+ (Na+o). Previously, strong experimental evidence was presented that the Na+o-independent Ca2+ extrusion from VSMCs is effected by the plasma membrane Ca2+ pump (Furukawa, K.-I., Tawada, Y., and Shigekawa, M. (1988) J. Biol. Chem. 263, 8058-8065). Brief (2 min) pretreatment of VSMCs with 30-300 nM PMA suppressed the intracellular Ca2+ transient induced with 1 microM ionomycin to about 60% of the control, whereas it accelerated the concomitant Na+o-independent 45Ca2+ extrusion by up to 20%. When the Ca2+ transient was induced with 0.1 microM angiotensin II, the PMA pretreatment markedly suppressed it and reduced also the rate of 45Ca2+ efflux from cells slightly. These effects of PMA were mimicked by 1-oleoyl-2-acetylglycerol, another protein kinase C activator, but were abolished by prior treatment of cells with staurosporine, an inhibitor of protein kinase C, or prior long incubation of cells with PMA. Analysis of the effect of PMA on [Ca2+]i dependence of the rate of Na+o-independent 45Ca2+ efflux revealed that PMA increased the maximum Ca2+ efflux rate without a significant change in the affinity for Ca2+. These results strongly suggest that the plasma membrane Ca2+ pump in VSMCs can be stimulated by PMA and that protein kinase C is involved in regulation of [Ca2+]i in intact VSMCs.
我们研究了佛波醇肉豆蔻酸酯乙酸酯（PMA）（一种蛋白激酶C的强效激活剂）对在无细胞外钠（Na⁺ₒ）添加情况下培养的血管平滑肌细胞（VSMC）中Ca²⁺外排的影响。此前，已有强有力的实验证据表明，VSMC中不依赖Na⁺ₒ的Ca²⁺外排是由质膜Ca²⁺泵介导的（古川，K.-I.，田田，Y.，和重川，M.（1988年）《生物化学杂志》263卷，8058 - 8065页）。用30 - 300 nM PMA对VSMC进行短暂（2分钟）预处理，可将1 μM离子霉素诱导的细胞内Ca²⁺瞬变抑制至对照的约60%，而同时它可使不依赖Na⁺ₒ的⁴⁵Ca²⁺外排加速高达20%。当用0.1 μM血管紧张素II诱导Ca²⁺瞬变时，PMA预处理可显著抑制该瞬变，并且也使细胞中⁴⁵Ca²⁺流出速率略有降低。PMA的这些作用可被另一种蛋白激酶C激活剂1 - 油酰基 - 2 - 乙酰甘油模拟，但在用蛋白激酶C抑制剂星形孢菌素预先处理细胞或用PMA对细胞进行长时间预先孵育后，这些作用消失。对PMA对不依赖Na⁺ₒ的⁴⁵Ca²⁺外排速率的[Ca²⁺]i依赖性影响的分析表明，PMA增加了最大Ca²⁺外排速率，而对Ca²⁺的亲和力没有显著变化。这些结果有力地表明，VSMC中的质膜Ca²⁺泵可被PMA刺激，并且蛋白激酶C参与完整VSMC中[Ca²⁺]i的调节。
