L-type calcium channel activity in osteoblast cells is regulated by the actin cytoskeleton independent of protein trafficking
L-type calcium channel activity in osteoblast cells is regulated by the actin cytoskeleton independent of protein trafficking
复制标题
成骨细胞中的 L 型钙通道活性由肌动蛋白细胞骨架调节，与蛋白质运输无关
DOI：
10.1007/s00774-010-0252-6
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发表时间：
2011-09-01
影响因子：
3.3
通讯作者：
Zhang, Xuemei
中科院分区：
文献类型：
--
作者：
Li, Fangping;Wang, Wenwei;Zhang, Xuemei
电压依赖性L型钙通道在许多细胞过程中发挥着重要作用。在不可兴奋的细胞中，肌动蛋白细胞骨架与通道的相互作用还不是很清楚。我们对不同的成骨细胞进行了全细胞膜片钳表面生物素化和钙成像，以分别确定通道动力学、幅度、表面丰度和细胞内钙。膜片钳研究表明，鬼臼乙素引起的肌动蛋白聚合使ICa的峰电流密度增加，而细胞松弛素D(CD)引起的肌动蛋白解聚使电流幅度显著降低。这一结果与钙显像结果一致，表明镉能显著降低Bay K8644诱导的细胞内钙升高。表面生物素化研究表明，Cd不能影响成孔亚基α1C的表面表达。有趣的是，Cd的应用引起了ICa稳态失活动力学的显著负移。半最大失活时的电压下降，且呈剂量依赖关系。Cd还可降低活化维生素D3(1α，25-D3)对VDCC和细胞内钙离子的影响。我们认为，在成骨细胞中，肌动蛋白细胞骨架通过改变通道动力学性质而不是改变表面表达来影响α1C，并且它能够通过α调节1，25-D3信号。我们的研究为成骨细胞的钙调节提供了新的视角，成骨细胞在许多生理功能中都是必不可少的。
Voltage-dependent L-type calcium channels (VDCC) play important roles in many cellular processes. The interaction of the actin cytoskeleton with the channel in nonexcitable cells is less well understood. We performed whole-cell patch-clamp surface biotinylation and calcium imaging on different osteoblast cells to determine channel kinetics, amplitude, surface abundance, and intracellular calcium, respectively. Patch-clamp studies showed that actin polymerization by phalloidin increased the peak current density ofICa, whereas actin depolymerization by cytochalasin D (CD) significantly decreased the current amplitude. This result is consistent with calcium imaging, which showed that CD significantly decreased Bay K8644-induced intracellular calcium increase. Surface biotinylation studies showed that CD is not able to affect the surface expression of the pore-forming subunit α1C. Interestingly, application of CD caused a significantly negative shift in the steady-state inactivation kinetics ofICa. There were decreases in the voltage at half-maximal inactivation that changed in a dose-dependent manner. CD also reduced the effect of activated vitamin D3(1α,25-D3) on VDCC and intracellular calcium. We conclude that in osteoblasts the actin cytoskeleton affects α1Cby altering the channel kinetic properties, instead of changing the surface expression, and it is able to regulate 1α,25-D3 signaling through VDCC. Our study provides a new insight into calcium regulation in osteoblasts, which are essential in many physiological functions of this cell.