Regulation of KATP and Cl channel activity by AMPK, ATP and adenosine receptors: impact on membrane excitability during muscle activity and fatigue

AMPK、ATP 和腺苷受体对 KATP 和 Cl 通道活性的调节：对肌肉活动和疲劳期间膜兴奋性的影响

• 批准号: RGPIN-2015-04437
• 负责人: Renaud, JeanMarc
• 金额: $ 2.91万
• 依托单位: University of Ottawa
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612966
• 关键词: Regulation; KATP; Cl; channel; activity

Noteworthy are complex changes in ion channel activity in the cell membrane during skeletal muscle activity. The first change, occurring during Phase 1, starts at the onset of muscle activity and is characterized by a 70% decreases in ClC-1 Cl- channel activity. Phase 2 occurs is characterized by large increases ClC-1 and KATP channel activity up to 3-times above the pre-stimulation level. During moderate exercise, mean interstitial [K+] reaches 10 mM within 5 min. Our studies on K+ and Cl- effects on membrane excitability are providing evidence that the reduction in ClC-1 channel activity during Phase 1 is important not only to prevent any K+-induced force depression, but in fact to augment the capacity of K+ to potentiate force at 10 mM K+. The increase in ClC-1 and KATP channel activity during Phase 2 is believed to be associated with fatigue, known as the decrease in force or work when muscles are repetitively stimulated. It is now well accepted that a major factor in muscle fatigue involves a decrease in Ca2+ release by the sarcoplasmic reticulum, which in turn is in part due to a decreased membrane excitability. The decreased excitability is triggered by increase in ClC-1 activity changing the K+ effect from a potentiation to a depression, while the increase in K+ efflux through KATP channels reduces action potential amplitude to eventually reduce force sparing ATP.      The question is what controls the complex changes in the activity of ClC-1 and KATP channel activity from the onset of muscle activity (i.e., Phase 1) to the development of fatigue (i.e., Phase 2). It has been shown that the decrease in ClC-1 channel activity at the onset of exercise is related to a phosphorylation by PKC. It is also known that activation of ATP receptors reduce ClC-1 channel activity, but it remains to be determined whether these ATP receptors are involved at the onset of exercise. Under patch clamp conditions, the A1 adenosine receptors activate KATP channels, but it remains to be determined if the A1 receptors are involved in the activation of ClC-1 and KATP channels during fatigue. In cardiac muscle, AMPK, an important cell energy sensor, activate KATP channels; it is therefore possible that it also activates the ClC-1 and KATP channels during fatigue in skeletal muscle.      The long term objective is to study the intracellular signaling pathways that regulate membrane excitability from the onset of muscle activity to fatigue. The short term objectives of this proposal are to investigate i) the role of ATP and its receptors in optimizing muscle performance during Phase 1 and ii) the role of AMPK and adenosine in triggering fatigue (Phase 2). Two hypotheses are proposed: 1) “ATP receptors optimize muscle performance by lowering ClC-1 Cl- channel activity, activating Na+ K+ ATPase pump, and promoting K+-induced force potentiation” and 2) “AMPK and adenosine triggers fatigue by reducing the pump activity and activating KATP and ClC-1 channels”.

值得注意的是，在骨骼肌活动期间，细胞膜离子通道活性的复杂变化。第一个变化发生在第一阶段，开始于肌肉活动，其特征是ClC-1Cl-通道活性下降了70%。第二阶段的特点是ClC-1和KATP通道活性较刺激前大幅增加3倍。在中等强度的运动中，平均间质[K+]在5分钟内达到10 mm。我们对K+和Cl-对膜兴奋性的影响的研究提供了证据，证明在第一相中ClC-1通道活性的降低不仅对于防止K+诱导的力抑制是重要的，而且实际上增加了K+在10 mM K+时增强力的能力。第二阶段ClC-1和KATP通道活性的增加被认为与疲劳有关，疲劳是指当肌肉受到重复刺激时，力或功的减少。现在公认的是，肌肉疲劳的一个主要因素是肌浆网钙释放减少，这在一定程度上是由于膜兴奋性降低。兴奋性的降低是由ClC-1活性的增加引起的，将K+效应从增强改变为抑制，而K+通过KATP通道外流的增加降低了动作电位的幅度，最终减少了对力的节省。 现在的问题是，从肌肉活动开始(即第一阶段)到疲劳发展(即第二阶段)，是什么控制着CLC-1和KATP通道活性的复杂变化。已有研究表明，运动开始时ClC-1通道活性的降低与PKC的磷酸化有关。也已知，激活ATP受体会降低ClC-1通道的活性，但在运动开始时，这些ATP受体是否参与仍有待确定。在膜片钳条件下，A1腺苷受体激活KATP通道，但A1受体是否参与疲劳时ClC-1和KATP通道的激活仍有待确定。在心肌中，AMPK是一种重要的细胞能量感受器，它激活KATP通道；因此，在骨骼肌疲劳时，AMPK也可能激活ClC-1和KATP通道。 他说，长期目标是研究从肌肉活动开始到疲劳过程中调节膜兴奋性的细胞内信号通路。这项建议的短期目标是研究：1)在第一阶段和第二阶段，ATP及其受体在优化肌肉性能中的作用；第二，AMPK和腺苷在引发疲劳中的作用(第二阶段)。提出了两个假说：1)ATP受体通过降低ClC-1Cl-通道活性，激活Na+-K+-ATPase泵，促进K+诱导的力增强来优化肌肉表现；2)AMPK和腺苷通过降低泵活性和激活KATP和ClC-1通道来触发疲劳。