Novel Mechanism for Suppression of Hyperpolarization-activated Cyclic Nucleotide-gated Pacemaker Channels by Receptor-like Tyrosine Phosphatase-α
Novel Mechanism for Suppression of Hyperpolarization-activated Cyclic Nucleotide-gated Pacemaker Channels by Receptor-like Tyrosine Phosphatase-α
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DOI：
10.1074/jbc.m804205200
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发表时间：
2008-10-31
影响因子：
4.8
通讯作者：
Yu, Han-Gang
中科院分区：
文献类型：
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作者：
Huang, Jianying;Huang, Aijie;Yu, Han-Gang
我们之前报道了Src增加酪氨酸磷酸化活性在调节超极化激活的环核苷酸门控（HCN）通道中的重要作用。在这里，我们提供的证据显示了酪氨酸磷酸化降低对HCN通道性质的新机制。我们发现受体样蛋白酪氨酸磷酸酶α (RPTP α)显著抑制或消除HEK293细胞中HCN2通道的表达。生化证据表明，rtp α显著降低了HCN2的表面表达，这与通道蛋白酪氨酸磷酸化的降低是平行的。共聚焦成像证实，rtp α抑制了HCN2通道的膜表面分布。此外，我们在心室中检测到RPTP α蛋白的存在，其表达水平在发育过程中发生了变化。氧化苯larsin或正钒酸钠对酪氨酸磷酸酶活性的抑制将心室超极化激活电流（I-f，由HCN通道产生）的激活从非生理电压转移到与加速激活动力学相关的生理电压。总之，我们发现RPTP α通过酪氨酸去磷酸化在HCN通道功能中起关键作用。这些发现对于HCN和RPTP α丰富表达的神经元也很重要。
We have previously reported an important role of increased tyrosine phosphorylation activity by Src in the modulation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Here we provide evidence showing a novel mechanism of decreased tyrosine phosphorylation on HCN channel properties. We found that the receptor-like protein-tyrosine phosphatase-alpha (RPTP alpha) significantly inhibited or eliminated HCN2 channel expression in HEK293 cells. Biochemical evidence showed that the surface expression of HCN2 was remarkably reduced by RPTP alpha, which was in parallel to the decreased tyrosine phosphorylation of the channel protein. Confocal imaging confirmed that the membrane surface distribution of the HCN2 channel was inhibited by RPTP alpha. Moreover, we detected the presence of RPTP alpha proteins in cardiac ventricles with expression levels changed during development. Inhibition of tyrosine phosphatase activity by phenylarsine oxide or sodium orthovanadate shifted ventricular hyperpolarization-activated current (I-f, generated by HCN channels) activation from nonphysiological voltages into physiological voltages associated with accelerated activation kinetics. In conclusion, we showed a critical role RPTP alpha plays in HCN channel function via tyrosine dephosphorylation. These findings are also important to neurons where HCN and RPTP alpha are richly expressed.