Phosphoinositides Decrease Atp Sensitivity of the Cardiac Atp-Sensitive K+ Channel
Phosphoinositides Decrease Atp Sensitivity of the Cardiac Atp-Sensitive K+ Channel
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磷酸肌醇降低心脏 Atp 敏感 K 通道的 Atp 敏感性
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
J. Makielski
中科院分区：
文献类型：
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作者：
Z. Fan;J. Makielski
阴离子磷脂调节内向整流钾通道的活性（Fan，Z.，和J.C.马基尔斯基1997. J.Biol.Chem.272：5388-5395）。采用膜片钳技术研究了磷酸肌醇对三磷酸腺苷（ATP）抑制ATP敏感性钾通道（KATP）电流的影响，在心肌细胞和COS-1细胞中，磺酰脲受体的心脏亚型SUR 2与内向整流通道Kir6.2共表达。磷酸肌醇（1 mg/ml）在低[ATP]（1 μM）条件下30 s内增加KATP的开放概率。磷酸肌醇使ATP抑制脱敏，具有较长的起始时间（>3分钟），激活ATP（1 mM）抑制的通道。磷酸肌醇处理10 min，[ATP]（Ki）从35 μM增加到16 mM，在单通道水平，[ATP]增加导致平均开放时间缩短，平均关闭时间延长。磷酸肌醇延长了平均开放时间，缩短了平均关闭时间，并削弱了[ATP]的依赖性，这些参数导致在任何给定的[ATP]更高的开放概率。ATP结合的表观速率常数估计为0.8和0.02 mM−1 ms−1，在磷酸肌醇处理5分钟之前和之后，分别对应于35 μM和5.8 mM的Ki。磷酸肌醇不能使腺苷对KATP的抑制脱敏。在SUR 2的存在下，磷酸肌醇减弱了ATP抑制的MgATP拮抗作用。Kir6.2ΔC35是一个截短的Kir6.2，在没有SUR 2的情况下发挥作用，也表现出磷酸肌醇对ATP抑制的脱敏作用。这些数据表明：（a）磷酸肌醇在Kir6.2上的结合位点与ATP强烈竞争;（B）静电相互作用是这种竞争的特征性质;（c）与SUR 2结合，磷酸肌醇对ATP抑制产生额外的复杂作用。我们提出了一个模型的ATP结合位点，涉及带正电荷的残基上的COOH-末端的Kir6.2，与磷酸肌醇相互作用脱敏ATP抑制。
Anionic phospholipids modulate the activity of inwardly rectifying potassium channels (Fan, Z., and J.C. Makielski. 1997. J. Biol. Chem. 272:5388–5395). The effect of phosphoinositides on adenosine triphosphate (ATP) inhibition of ATP-sensitive potassium channel (KATP) currents was investigated using the inside-out patch clamp technique in cardiac myocytes and in COS-1 cells in which the cardiac isoform of the sulfonylurea receptor, SUR2, was coexpressed with the inwardly rectifying channel Kir6.2. Phosphoinositides (1 mg/ml) increased the open probability of KATP in low [ATP] (1 μM) within 30 s. Phosphoinositides desensitized ATP inhibition with a longer onset period (>3 min), activating channels inhibited by ATP (1 mM). Phosphoinositides treatment for 10 min shifted the half-inhibitory [ATP] (K i) from 35 μM to 16 mM. At the single-channel level, increased [ATP] caused a shorter mean open time and a longer mean closed time. Phosphoinositides prolonged the mean open time, shortened the mean closed time, and weakened the [ATP] dependence of these parameters resulting in a higher open probability at any given [ATP]. The apparent rate constants for ATP binding were estimated to be 0.8 and 0.02 mM−1 ms−1 before and after 5-min treatment with phosphoinositides, which corresponds to a K i of 35 μM and 5.8 mM, respectively. Phosphoinositides failed to desensitize adenosine inhibition of KATP. In the presence of SUR2, phosphoinositides attenuated MgATP antagonism of ATP inhibition. Kir6.2ΔC35, a truncated Kir6.2 that functions without SUR2, also exhibited phosphoinositide desensitization of ATP inhibition. These data suggest that (a) phosphoinositides strongly compete with ATP at a binding site residing on Kir6.2; (b) electrostatic interaction is a characteristic property of this competition; and (c) in conjunction with SUR2, phosphoinositides render additional, complex effects on ATP inhibition. We propose a model of the ATP binding site involving positively charged residues on the COOH-terminus of Kir6.2, with which phosphoinositides interact to desensitize ATP inhibition.
DOI：
10.1016/0065-2571(95)00005-4
发表时间：
1996-01-01
期刊：
ADVANCES IN ENZYME REGULATION, VOL 36
影响因子：
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作者：
Loijens, JC;Boronenkov, IV;Anderson, RA
通讯作者：
Anderson, RA
影响因子：
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作者：
GILLIS, KD;GEE, WM;MISLER, S
通讯作者：
MISLER, S
影响因子：
56.9
作者：
Shyng, SL;Nichols, CG
通讯作者：
Nichols, CG