Horowitz B, Hensley C B, Quintero M, Azuma K K, Putnam D, McDonough A A
Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles 90033.
J Biol Chem. 1990 Aug 25;265(24):14308-14.
The purpose of this study was to determine the effect of thyroid status on the Na,K-ATPase alpha isoforms and beta in rat heart, skeletal muscle, kidney, and brain at the levels of mRNA, protein abundance, and enzymatic activity. Northern and dot-blot analysis of RNA (euthyroid, hypothyroid, and triiodothyronine-injected hypothyroids = hyperthyroids) and immunoblot analysis of protein (euthyroid and hypothyroid) revealed isoform-specific regulation of Na,K-ATPase by thyroid status in kidney, heart, and skeletal muscle and no regulation of sodium pump subunit levels in the brain. In general, in the transition from euthyroid to hypothyroid alpha 1 mRNA and protein levels are unchanged in kidney and skeletal muscle and slightly decreased in heart, while alpha 2 mRNA and protein are decreased significantly in heart and skeletal muscle. In hypothyroid heart and skeletal muscle, the decrease in alpha 2 protein levels was much greater than the decrease in alpha 2 mRNA levels relative to euthyroid indicating translational or post-translational regulation of alpha 2 protein abundance by triiodothyronine status in these tissues. The regulation of beta subunit by thyroid status is tissue-dependent. In hypothyroid kidney beta mRNA levels do not change, but immunodetectable beta protein levels decrease relative to euthyroid, and the decrease parallels the decrease in Na,K-ATPase activity. In hypothyroid heart and skeletal muscle beta mRNA levels decrease; beta protein decreases in heart and was not detected in the skeletal muscle. These findings demonstrate that the euthyroid levels of expression of alpha 1 in heart, alpha 2 in heart and skeletal muscle, and beta in kidney, heart, and skeletal muscle are dependent on the presence of thyroid hormone.
本研究的目的是在mRNA、蛋白质丰度和酶活性水平上，确定甲状腺状态对大鼠心脏、骨骼肌、肾脏和大脑中钠钾ATP酶α亚型和β亚型的影响。对RNA（正常甲状腺、甲状腺功能减退和注射三碘甲状腺原氨酸的甲状腺功能减退 = 甲状腺功能亢进）进行Northern和斑点印迹分析，以及对蛋白质（正常甲状腺和甲状腺功能减退）进行免疫印迹分析，结果显示肾脏、心脏和骨骼肌中钠钾ATP酶受甲状腺状态的亚型特异性调节，而大脑中钠泵亚基水平不受调节。一般来说，从正常甲状腺状态转变为甲状腺功能减退状态时，肾脏和骨骼肌中α1 mRNA和蛋白质水平不变，心脏中略有下降，而心脏和骨骼肌中α2 mRNA和蛋白质显著下降。在甲状腺功能减退的心脏和骨骼肌中，相对于正常甲状腺状态，α2蛋白质水平的下降远大于α2 mRNA水平的下降，表明这些组织中三碘甲状腺原氨酸状态对α2蛋白质丰度有翻译或翻译后调节作用。β亚基受甲状腺状态的调节具有组织依赖性。在甲状腺功能减退的肾脏中，β mRNA水平不变，但相对于正常甲状腺状态，免疫可检测的β蛋白质水平下降，且这种下降与钠钾ATP酶活性的下降平行。在甲状腺功能减退的心脏和骨骼肌中，β mRNA水平下降；心脏中β蛋白质下降，而骨骼肌中未检测到。这些发现表明，心脏中α1、心脏和骨骼肌中α2以及肾脏、心脏和骨骼肌中β的正常甲状腺表达水平依赖于甲状腺激素的存在。
