Differential distribution and regulation of mouse cardiac Na+/K+-ATPase α1 and α2 subunits in T-tubule and surface sarcolemmal membranes
Differential distribution and regulation of mouse cardiac Na+/K+-ATPase α1 and α2 subunits in T-tubule and surface sarcolemmal membranes
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DOI：
10.1016/j.cardiores.2006.11.006
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发表时间：
2007-01-01
影响因子：
10.8
通讯作者：
Shattock, Michael J.
中科院分区：
文献类型：
--
作者：
Berry, Roger G.;Despa, Sanda;Shattock, Michael J.
目的：两种 Na+/K+-ATP 酶 (NKA) α 亚基亚型 α(1) 和 α(2) 在成年小鼠心脏中表达。这些异构体在 T 管和表面肌膜 (SSL) 膜中的亚细胞分布及其受 cAMP 依赖性蛋白激酶 (PKA) 的调节尚不清楚。方法：我们使用甲酰胺诱导的小鼠心室肌细胞去管，通过测量 NKA 电流（I 泵）和 NKA 介导的 Na+，研究 T 管与 SSL 膜中 α(1) 和 α(2) 的 PKA 差异功能分布和调节流出量 (-d[Na](i)/dt)。结果：I-泵由 88% α(1) 介导的 I-泵 (I alpha(1)) 和 12% alpha(2) 介导的 I-泵 (I alpha(2)) 组成。 α(1) 和 α(2) 亚基表现出不同的哇巴因亲和力（分别为 105 +/- 6 和 0.3 +/- 0.1 mu mol/L），但对细胞内 Na+ 的亲和力相似（K1/2Na+ 分别为 16.6 +/- 0.8 和 16.7 +/- 2.6 mmol/L）。去管降低了 (i) I 泵密度（1.42 +/- 0.1 至 1.20 +/- 0.04 pA/pF），(ii) 电池电容（181 +/- 12 至 127 +/- 17 pF），以及 (iii) I α(2) 贡献（12 至 6%）。 T 管中的总 I 泵密度（1.94 pA/pF，推导）与 SSL 膜相比高出 60%。尽管 T 管膜仅占总表面积的 30%，但它们产生的 I α(2) 大约为 70%，I α(1) 大约为 37%。 SSL 中 I α(1) 密度显着高于 I α(2)（I α(1):I α(2) = 16:1），但在 T 管 (4:1) 中明显降低。除了差异定位之外，异丙肾上腺素（ISO，1 mu mol/L）还显着增加了α（1）介导的NKA Na+亲和力（从16.6 +/- 0.8到13.3 +/- 1.4 mmol/L），并导致最大NKA Na+流出率小幅增加。 ISO 对 α(2) 介导的 NKA 活性没有影响。结论：这些数据表明，NKA α(1) 和 α(2) 亚基在 T 管和 SSL 膜中差异定位并受 PKA 调节，并且可能在心脏兴奋-收缩耦合中具有不同的调节作用。 (c) 2006 年欧洲心脏病学会。由 Elsevier B.V. 出版。保留所有权利。
Objectives: Two Na+/K+-ATPase (NKA) alpha-subunit isoforms, alpha(1) and alpha(2), are expressed in the adult mouse heart. The subcellular distribution of these isoforms in T-tubule and surface sarcolemmal (SSL) membranes and their regulation by cAMP-dependent protein kinase (PKA) is unclear.Methods: We used formamide-induced detubulation of mouse ventricular myocytes to investigate differential functional distribution and regulation by PKA of alpha(1) and alpha(2) in T-tubule versus SSL membranes by measuring NKA current (I-pump) and NKA-mediated Na+ efflux (-d[Na](i)/dt).Results: I-pump is composed of 88% alpha(1)-mediated I-pump (I alpha(1)) and 12% alpha(2)-mediated I-pump (I alpha(2)). alpha(1) and alpha(2) subunits demonstrate distinct ouabain affinities (105 +/- 6 and 0.3 +/- 0.1 mu mol/L respectively) but similar affinity for intracellular Na+ (K1/2Na+ of 16.6 +/- 0.8 and 16.7 +/- 2.6 mmol/L respectively). Detubulation reduced (i) I-pump density (1.42 +/- 0.1 to 1.20 +/- 0.04 pA/pF), (ii) cell capacitance (181 +/- 12 to 127 +/- 17 pF), and (iii) I alpha(2) contribution (12 to 6%). Total I-pump density was similar to 60% higher in T-tubule (1.94 pA/pF, derived) vs. SSL membranes. Although T-tubule membranes represent only 30% of total surface area, they generate similar to 70% of I alpha(2) and similar to 37% of I alpha(1). I alpha(1) density was substantially higher than I alpha(2) in SSL (I alpha(1):I alpha(2) = 16:1) but this was markedly reduced in T-tubules (4:1). In addition to differential localisation, isoprenaline (ISO, 1 mu mol/L) significantly increased alpha(1)-mediated NKA Na+ affinity (from 16.6 +/- 0.8 to 13.3 +/- 1.4 mmol/L) and caused a small increase in maximal NKA Na+ efflux rate. ISO had no effect on alpha(2)-mediated NKA activity.Conclusion: These data suggest that NKA alpha(1) and alpha(2) subunits are differentially localised and regulated by PKA in T-tubule and SSL membranes and may have distinct regulatory roles in cardiac excitation-contraction coupling. (c) 2006 European Society of Cardiology. Published by Elsevier B.V. All rights reserved.