Regulation of an inwardly rectifying ATP-sensitive K+ channel in the basolateral membrane of renal proximal tubule.
Regulation of an inwardly rectifying ATP-sensitive K+ channel in the basolateral membrane of renal proximal tubule.
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DOI：
10.1085/jgp.111.1.161
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发表时间：
1998-01
期刊：
影响因子：
--
通讯作者：
Segal AS
中科院分区：
文献类型：
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作者：
Mauerer UR;Boulpaep EL;Segal AS
Na+，K +-ATP酶泵活性与基底外侧膜（BLM）K+电导的功能偶联对于维持近端小管中的运输至关重要。心尖钠进入刺激泵活性，降低胞质[ATP]，这反过来又解除ATP敏感性K+（KATP）通道的抑制。这些KATP通道的开放介导BLM的超极化，这促进持续Na+，K +-ATP酶泵周转所需的Na+重吸收和K+再循环。尽管它的生理重要性，很少有人知道这个通道的调节。本研究的重点是调节BLM KATP通道的第二信使和蛋白激酶使用膜补丁从解离，极化钝口螈近端小管细胞。该通道由蛋白激酶A和C调节，但方向相反。该通道在细胞贴附（c/a）贴片中由毛喉素激活，在由内而外（i/o）膜贴片中由PKA激活。然而，PKA的磷酸化作用不足以防止通道下降。相比之下，在c/a斑中，通道被佛波酯抑制，并且PKC降低i/o斑中的通道活性（pk10）。该通道是pH敏感的，并且降低胞质pH会降低BPO。增加c/a斑块中的细胞内[Ca2 +]（[Ca2 +] i）降低了β-淀粉样蛋白，并且这种作用是直接的，因为[Ca2 +] i抑制β-淀粉样蛋白，在i/o斑块中Ki为170 nM。膜拉伸和低渗肿胀不显着影响通道的行为，但通道似乎是由肌动蛋白细胞骨架调节。最后，该BLM KATP通道的活性与跨细胞转运偶联。在c/a斑贴中，抑制Na+，K +-ATP酶泵周转的操作减少了ATP，推测是由于细胞内[ATP]的升高，尽管不能排除相关的细胞去极化是可能的原因。相反，刺激转运（从而导致泵周转）会导致细胞内ATP水平的下降。这些结果表明，近端小管BLM中的内向整流KATP通道是将细胞代谢与转运活性联系起来的反馈系统中的关键元件。我们的结论是，耦合这KATP通道的Na+，K +-ATP酶泵的活性是一种机制，通过这种机制，可以维持稳态NaCl重吸收在近端小管。
Functional coupling of Na+,K+-ATPase pump activity to a basolateral membrane (BLM) K+ conductance is crucial for sustaining transport in the proximal tubule. Apical sodium entry stimulates pump activity, lowering cytosolic [ATP], which in turn disinhibits ATP-sensitive K+ (KATP) channels. Opening of these KATP channels mediates hyperpolarization of the BLM that facilitates Na+ reabsorption and K+ recycling required for continued Na+,K+-ATPase pump turnover. Despite its physiological importance, little is known about the regulation of this channel. The present study focuses on the regulation of the BLM KATP channel by second messengers and protein kinases using membrane patches from dissociated, polarized Ambystoma proximal tubule cells. The channel is regulated by protein kinases A and C, but in opposing directions. The channel is activated by forskolin in cell-attached (c/a) patches, and by PKA in inside-out (i/o) membrane patches. However, phosphorylation by PKA is not sufficient to prevent channel rundown. In contrast, the channel is inhibited by phorbol ester in c/a patches, and PKC decreases channel activity (nP o) in i/o patches. The channel is pH sensitive, and lowering cytosolic pH reduces nP o. Increasing intracellular [Ca2+] ([Ca2+]i) in c/a patches decreases nP o, and this effect is direct since [Ca2+]i inhibits nP o with a K i of ∼170 nM in i/o patches. Membrane stretch and hypotonic swelling do not significantly affect channel behavior, but the channel appears to be regulated by the actin cytoskeleton. Finally, the activity of this BLM KATP channel is coupled to transcellular transport. In c/a patches, maneuvers that inhibit turnover of the Na+,K+-ATPase pump reduce nP o, presumably due to a rise in intracellular [ATP], although the associated cell depolarization cannot be ruled out as the possible cause. Conversely, stimulation of transport (and thus pump turnover) leads to increases in nP o, presumably due to a fall in intracellular [ATP]. These results show that the inwardly rectifying KATP channel in the BLM of the proximal tubule is a key element in the feedback system that links cellular metabolism with transport activity. We conclude that coupling of this KATP channel to the activity of the Na+,K+-ATPase pump is a mechanism by which steady state NaCl reabsorption in the proximal tubule may be maintained.