Phosphorylation of S1505 in the cardiac Na+ channel inactivation gate is required for modulation by protein kinase C.
Phosphorylation of S1505 in the cardiac Na+ channel inactivation gate is required for modulation by protein kinase C.
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DOI：
10.1085/jgp.108.5.375
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发表时间：
1996-11
期刊：
影响因子：
--
通讯作者：
Scheuer T
中科院分区：
文献类型：
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作者：
Qu Y;Rogers JC;Tanada TN;Catterall WA;Scheuer T
脑和心脏Na+通道的失活都是通过蛋白激酶C （PKC）的激活来调节的，但方式不同。先前的实验表明，在连接脑Na+通道α亚基的同源结构域III和IV （LIII/IV）的高度保守环中，丝氨酸1506的磷酸化对于PKC的所有作用是必要的。在这里，我们研究了类似丝氨酸对rH1心脏Na+通道的不同调制的重要性。将rH1的丝氨酸1505突变为丙氨酸以阻止其磷酸化，由此产生的突变通道在1610个细胞中表达。这些突变通道的电生理特性与野生型（WT） rH1通道没有区别。当保持电位为-94 mV时，1-油基-2-乙酰基-sn-甘油（OAG）激活PKC可使WT Na+电流降低49.3 +/- 4.2% (P < 0.01)，而S1505A突变体电流仅降低8.5 +/- 5.4% （P = 0.29）。PKC激活还导致WT通道稳态失活的电压依赖性偏移-17 mv，这在突变体中被消除。因此，丝氨酸1505的磷酸化对于失活曲线的负移和PKC对Na+电流的降低都是必需的。S1505/1506的磷酸化在脑和心脏Na+通道中具有共同和不同的作用。在脑和心脏的Na+通道中，PKC对该位点的磷酸化是降低Na+电流峰值所必需的。然而，脑Na+通道中S1506的磷酸化会减缓和破坏开放通道的失活。Na+通道在心脏的S1505磷酸化，而在大脑的S1506不磷酸化，导致失活曲线的负移，表明它稳定了关闭状态的失活。由于含有S1505/S1506的LIII/IV是完全保守的，磷酸化丝氨酸与通道其他区域的相互作用在两种通道类型中一定是不同的。
Inactivation of both brain and cardiac Na+ channels is modulated by activation of protein kinase C (PKC) but in different ways. Previous experiments had shown that phosphorylation of serine 1506 in the highly conserved loop connecting homologous domains III and IV (LIII/IV) of the brain Na+ channel alpha subunit is necessary for all effects of PKC. Here we examine the importance of the analogous serine for the different modulation of the rH1 cardiac Na+ channel. Serine 1505 of rH1 was mutated to alanine to prevent its phosphorylation, and the resulting mutant channel was expressed in 1610 cells. Electrophysiological properties of these mutant channels were indistinguishable from those of wild-type (WT) rH1 channels. Activation of PKC with 1-oleoyl-2-acetyl-sn-glycerol (OAG) reduced WT Na+ current by 49.3 +/- 4.2% (P < 0.01) but S1505A mutant current was reduced by only 8.5 +/- 5.4% (P = 0.29) when the holding potential was -94 mV. PKC activation also caused a -17-mV shift in the voltage dependence of steady-state inactivation of the WT channel which was abolished in the mutant. Thus, phosphorylation of serine 1505 is required for both the negative shift in the inactivation curve and the reduction in Na+ current by PKC. Phosphorylation of S1505/1506 has common and divergent effects in brain and cardiac Na+ channels. In both brain and cardiac Na+ channels, phosphorylation of this site by PKC is required for reduction of peak Na+ current. However, phosphorylation of S1506 in brain Na+ channels slows and destabilizes inactivation of the open channel. Phosphorylation of S1505 in cardiac, but not S1506 in brain, Na+ channels causes a negative shift in the inactivation curve, indicating that it stabilizes inactivation from closed states. Since LIII/IV containing S1505/S1506 is completely conserved, interaction of the phosphorylated serine with other regions of the channel must differ in the two channel types.