Cardiac Signaling Center, University of South Carolina, Charleston, South Carolina 29403, USA.
Ann N Y Acad Sci. 2010 Feb;1188:153-8. doi: 10.1111/j.1749-6632.2009.05095.x.
Acute oxygen sensing in the heart is thought to occur through redox regulation and phosphorylation of membrane channels. Here we report a novel O2-sensing mechanism involving the C-terminus of the L-type Ca2+ channel and regulated by PKA phosphorylation. In patch-clamped myocytes, oxygen deprivation decreased ICa within 40 s. The suppressive effect of anoxia was relieved by PKA-mediated phosphorylation only when Ca2+ was the charge carrier, whereas phosphorylated IBa remained sensitive to O2 withdrawal. Suppression of Ca2+ release by thapsigargin did not alter the response of ICa to anoxia, suggesting a mandatory role for Ca2+ influx and not Ca2+-induced Ca2+ release (CICR) in O2 regulation of the channel. Consistent with this idea, mutation of 80 amino acids in the Ca2+/CaM-binding domain of the recombinant alpha1C subunit that removes Ca2+ dependent inactivation (CDI) abolished O2 sensitivity of the channel. Our findings suggest that the Ca2+/CaM binding domain of the L-type Ca2+ may represent a molecular site for O2 sensing of the heart.
心脏中的急性氧感应被认为通过氧化还原调节和膜通道的磷酸化来发生。在这里，我们报告了一种涉及 L 型钙通道 C 末端的新型 O2 感应机制，该机制受 PKA 磷酸化调节。在膜片钳钳制的心肌细胞中，缺氧在 40 秒内降低 ICa。只有当 Ca2+ 作为电荷载体时，PKA 介导的磷酸化才能缓解缺氧的抑制作用，而磷酸化的 IBa 仍然对缺氧敏感。肌浆网钙释放抑制剂 thapsigargin 抑制 Ca2+ 释放不会改变 ICa 对缺氧的反应，这表明 Ca2+ 内流而不是 Ca2+-诱导的 Ca2+ 释放（CICR）在通道的 O2 调节中起强制性作用。与这一观点一致，去除钙依赖性失活（CDI）的重组 alpha1C 亚基钙/钙调蛋白结合域中的 80 个氨基酸的突变消除了通道对 O2 的敏感性。我们的研究结果表明，L 型钙通道的钙/钙调蛋白结合域可能代表心脏中 O2 感应的分子位点。
