Burgos M, Pastor M D, González J C, Martinez-Galan J R, Vaquero C F, Fradejas N, Benavides A, Hernández-Guijo J M, Tranque P, Calvo S
Unidad de Fisiología, Facultad de Medicina y Centro Regional de Investigaciones Biomedicas, Universidad de Castilla La Mancha, Albacete, Spain.
Glia. 2007 Nov 1;55(14):1437-48. doi: 10.1002/glia.20555.
Astrocytes express voltage-gated calcium channels (VGCCs) that are upregulated in the context of the reactive astrogliosis occurring in several CNS pathologies. Moreover, the ability of selective calcium channel blockers to inhibit reactive astrogliosis has been revealed in a variety of experimental models. However, the functions and regulation of VGCC in astrocytes are still poorly understood. Interestingly, protein kinase C epsilon (PKCepsilon), one of the known regulators of VGCC in several cell types, induces in astrocytes a stellated morphology similar to that associated to gliosis. Thereby, here we explored the possible regulation of VGCC by adenovirally expressed PKCepsilon in astrocytes. We found that PKCepsilon potently increases the mRNA levels of two different calcium channel alpha(1) subunits, Ca(V)1.2 (L-type channel) and Ca(V)2.1 (P/Q-type channel). The mRNA upregulation was followed by a robust increase in the corresponding peptides. Moreover, the new calcium channels formed as a consequence of PKCepsilon activation are functional, since overexpression of constitutively-active PKCepsilon increased significantly the calcium current density in astrocytes. PKCepsilon raised currents carried by both L- and P/Q-type channels. However, the effect on the P/Q-type channel was more prominent since an increase of the relative contribution of this channel to the whole cell calcium current was observed. Finally, we found that PKCepsilon-induced stellation was significantly reduced by the specific L-type channel blocker nifedipine, indicating that calcium influx through VGCC mediates the change in astrocyte morphology induced by PKCepsilon. Therefore, here we describe a novel regulatory pathway involving VGCC that participates in PKCepsilon-dependent astrocyte activation.
星形胶质细胞表达电压门控钙通道(VGCCs),在几种中枢神经系统疾病中发生的反应性星形胶质细胞增生的情况下,这些通道会上调。此外,在多种实验模型中已经揭示了选择性钙通道阻滞剂抑制反应性星形胶质细胞增生的能力。然而,星形胶质细胞中VGCC的功能和调节仍知之甚少。有趣的是,蛋白激酶Cε(PKCε)是几种细胞类型中已知的VGCC调节因子之一,它在星形胶质细胞中诱导出类似于与胶质增生相关的星形形态。因此,我们在此探索了腺病毒表达的PKCε对星形胶质细胞中VGCC的可能调节作用。我们发现PKCε有力地增加了两种不同钙通道α(1)亚基Ca(V)1.2(L型通道)和Ca(V)2.1(P/Q型通道)的mRNA水平。mRNA上调之后,相应的肽段也显著增加。此外,由于PKCε激活而形成的新钙通道具有功能,因为组成型活性PKCε的过表达显著增加了星形胶质细胞中的钙电流密度。PKCε增加了L型和P/Q型通道携带的电流。然而,对P/Q型通道的影响更为突出,因为观察到该通道对全细胞钙电流的相对贡献增加。最后,我们发现特异性L型通道阻滞剂硝苯地平显著降低了PKCε诱导的星形化,表明通过VGCC的钙内流介导了PKCε诱导的星形胶质细胞形态变化。因此,我们在此描述了一种涉及VGCC的新型调节途径,该途径参与了PKCε依赖性星形胶质细胞的激活。