Modulation of hepatocellular swelling-activated K+ currents by phosphoinositide pathway-dependent protein kinase C
Modulation of hepatocellular swelling-activated K+ currents by phosphoinositide pathway-dependent protein kinase C
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DOI：
10.1152/ajpcell.00602.2005
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发表时间：
2006-07-01
影响因子：
5.5
通讯作者：
Hill, Ceredwyn E.
中科院分区：
文献类型：
--
作者：
Lan, Wen-Zhi;Wang, Penny Y. T.;Hill, Ceredwyn E.
K+通道参与伴随肝细胞营养摄取和胆汁形成的调节性体积减少（RVD）。我们最近发现KCNQ1是肝细胞肿胀激活K+电流（I-KVol）的一个重要部分的候选分子。我们已经证明KCNQ1抑制剂chromanol 293B显著抑制离体灌注大鼠肝脏中rvd相关的K+通量，并使用膜片钳技术确定将肿胀与I-KVol激活联系起来的信号通路。用维持或增加磷脂酰肌醇4,5-二磷酸（PIP2）的溶液进行肝细胞贴片电极透析可增加I-KVol，而降低细胞PIP2的条件会降低I-KVol。GTP和AlF4-刺激了I-KVol的发育，提示G蛋白和磷脂酶C （PLC）在其中起作用。PLC阻断剂U-73122降低了I-KVol，抑制了对PIP2或GTP的刺激反应。蛋白激酶C （PKC）参与其中，因为K+电流被1-油基-2-乙酰基- cn -甘油增强，并在PKC被12-肉豆蔻酸13-乙酸phorbol （PMA）或PKC抑制剂GF 109203X慢性刺激后被抑制。细胞松弛素D或GF 109203X均可阻断I-KVol和随之增加的膜电容。急性PMA并没有消除细胞松弛素D的抑制，这表明pkc介导的I-KVol激活涉及细胞骨架。在等渗条件下，类似于I-KVol的缓慢发展的K+电流被PIP2、脂质磷酸酶抑制剂（以对抗PIP2耗竭）、plc偶联α(1)-肾上腺素能受体激动剂或PKC激活剂激活，并被PKC抑制而抑制，这表明低渗性是通过PIP2/PKC依赖性途径激活I-KVol的一系列刺激之一。结果表明，PIP2通过涉及PKC激活的细胞骨架重排间接激活肝细胞kcnq1样通道。
K+ channels participate in the regulatory volume decrease (RVD) accompanying hepatocellular nutrient uptake and bile formation. We recently identified KCNQ1 as a molecular candidate for a significant fraction of the hepatocellular swelling-activated K+ current (I-KVol). We have shown that the KCNQ1 inhibitor chromanol 293B significantly inhibited RVD-associated K+ flux in isolated perfused rat liver and used patch-clamp techniques to define the signaling pathway linking swelling to I-KVol activation. Patch-electrode dialysis of hepatocytes with solutions that maintain or increase phosphatidylinositol 4,5-bisphosphate (PIP2) increased I-KVol, whereas conditions that decrease cellular PIP2 decreased I-KVol. GTP and AlF4- stimulated I-KVol development, suggesting a role for G proteins and phospholipase C (PLC). Supporting this, the PLC blocker U-73122 decreased I-KVol and inhibited the stimulatory response to PIP2 or GTP. Protein kinase C (PKC) is involved, because K+ current was enhanced by 1-oleoyl-2-acetyl-sn-glycerol and inhibited after chronic PKC stimulation with phorbol 12-myristate 13-acetate (PMA) or the PKC inhibitor GF 109203X. Both I-KVol and the accompanying membrane capacitance increase were blocked by cytochalasin D or GF 109203X. Acute PMA did not eliminate the cytochalasin D inhibition, suggesting that PKC-mediated I-KVol activation involves the cytoskeleton. Under isotonic conditions, a slowly developing K+ current similar to I-KVol was activated by PIP2, lipid phosphatase inhibitors to counter PIP2 depletion, a PLC-coupled alpha(1)-adrenoceptor agonist, or PKC activators and was depressed by PKC inhibition, suggesting that hypotonicity is one of a set of stimuli that can activate I-KVol through a PIP2/PKC-dependent pathway. The results indicate that PIP2 indirectly activates hepatocellular KCNQ1-like channels via cytoskeletal rearrangement involving PKC activation.