Barwe Sonali P, Jordan Maria C, Skay Anna, Inge Landon, Rajasekaran Sigrid A, Wolle Daniel, Johnson Christina L, Neco Patricia, Fang Kun, Rozengurt Nora, Goldhaber Joshua I, Roos Kenneth P, Rajasekaran Ayyappan K
Nemours Center for Childhood Cancer Research, Alfred I. duPont Hospital for Children, Rockland Center One, 1701 Rockland Road, Wilmington, DE 19803, USA.
J Mol Cell Cardiol. 2009 Oct;47(4):552-60. doi: 10.1016/j.yjmcc.2009.07.018. Epub 2009 Aug 15.
Na,K-ATPase is composed of two essential alpha- and beta-subunits, both of which have multiple isoforms. Evidence indicates that the Na,K-ATPase enzymatic activity as well as its alpha(1), alpha(3) and beta(1) isoforms are reduced in the failing human heart. The catalytic alpha-subunit is the receptor for cardiac glycosides such as digitalis, used for the treatment of congestive heart failure. The role of the Na,K-ATPase beta(1)-subunit (Na,K-beta(1)) in cardiac function is not known. We used Cre/loxP technology to inactivate the Na,K-beta(1) gene exclusively in the ventricular cardiomyocytes. Animals with homozygous Na,K-beta(1) gene excision were born at the expected Mendelian ratio, grew into adulthood, and appeared to be healthy until 10 months of age. At 13-14 months, these mice had 13% higher heart/body weight ratios, and reduced contractility as revealed by echocardiography compared to their wild-type (WT) littermates. Pressure overload by transverse aortic constriction (TAC) in younger mice, resulted in compensated hypertrophy in WT mice, but decompensation in the Na,K-beta(1) KO mice. The young KO survivors of TAC exhibited decreased contractile function and mimicked the effects of the Na,K-beta(1) KO in older mice. Further, we show that intact hearts of Na,K-beta(1) KO anesthetized mice as well as isolated cardiomyocytes were insensitive to ouabain-induced positive inotropy. This insensitivity was associated with a reduction in NCX1, one of the proteins involved in regulating cardiac contractility. In conclusion, our results demonstrate that Na,K-beta(1) plays an essential role in regulating cardiac contractility and that its loss is associated with significant pathophysiology of the heart.
钠钾ATP酶由两个必需的α和β亚基组成，这两个亚基都有多种同工型。有证据表明，在衰竭的人类心脏中，钠钾ATP酶的酶活性及其α(1)、α(3)和β(1)同工型均降低。催化性α亚基是洋地黄等强心苷的受体，用于治疗充血性心力衰竭。钠钾ATP酶β(1)亚基（Na,K-β(1)）在心脏功能中的作用尚不清楚。我们使用Cre/loxP技术仅在心室心肌细胞中使Na,K-β(1)基因失活。纯合缺失Na,K-β(1)基因的动物以预期的孟德尔比率出生，成长至成年，在10个月大之前看起来都很健康。在13 - 14个月时，与野生型（WT）同窝小鼠相比，这些小鼠的心脏/体重比高出13%，超声心动图显示其收缩力降低。年轻小鼠经横向主动脉缩窄（TAC）造成压力超负荷后，WT小鼠出现代偿性肥大，而Na,K-β(1)基因敲除（KO）小鼠则出现失代偿。TAC后存活的年轻KO小鼠表现出收缩功能下降，类似于老年Na,K-β(1) KO小鼠的效应。此外，我们发现麻醉的Na,K-β(1) KO小鼠的完整心脏以及分离的心肌细胞对哇巴因诱导的正性肌力作用不敏感。这种不敏感性与参与调节心脏收缩力的蛋白之一钠钙交换体1（NCX1）的减少有关。总之，我们的结果表明，Na,K-β(1)在调节心脏收缩力中起重要作用，其缺失与心脏的显著病理生理学变化相关。
