Schoutsen B, Blom J J, Verdouw P D, Lamers J M
Department of Biochemistry and Thoraxcentre, Erasmus University Rotterdam, The Netherlands.
J Mol Cell Cardiol. 1989 Jul;21(7):719-27. doi: 10.1016/0022-2828(89)90613-5.
The present study was designed to examine the relation between the loss of Ca2+ uptake activity and the change of protein phosphorylation in sarcoplasmic reticulum from ischemic myocardium. Ischemic (0.5, 1 and 2 h duration) and non-ischemic tissue samples were taken from the coronary-ligated porcine left ventricle and sarcoplasmic reticulum fractions were isolated. The membranes were tested for Ca2+ uptake and ATPase activities and phosphorylation of phospholamban. The in vitro 32P incorporation into phospholamban in the presence of cAMP plus the catalytic subunit of cyclic AMP dependent protein kinase became markedly reduced depending on the duration of ischemia. The activities of the Ca2+ pump (Ca2+ uptake and ATPase) were also decreased. The 32P incorporation into the myofibrillar component troponin I, which is also a specific substrate for catalytic subunit, was not affected by ischemia. The reduction of the Ca2+ pump activity correlated with the reduction of 32P incorporation into phospholamban. It is postulated that the ischemia induced inactivation of the Ca2+ pump is not only a consequence of specific loss of enzyme activity, but it is also caused by altered characteristics of phospholamban.
本研究旨在探讨缺血心肌肌浆网中钙离子摄取活性丧失与蛋白质磷酸化变化之间的关系。从冠状动脉结扎的猪左心室获取缺血（持续时间为0.5、1和2小时）和非缺血组织样本，并分离出肌浆网部分。检测膜的钙离子摄取和ATP酶活性以及受磷蛋白的磷酸化情况。在存在cAMP和环磷酸腺苷依赖性蛋白激酶催化亚基的情况下，体外32P掺入受磷蛋白的量根据缺血持续时间而显著减少。钙离子泵（钙离子摄取和ATP酶）的活性也降低。32P掺入肌原纤维成分肌钙蛋白I（其也是催化亚基的特异性底物）不受缺血影响。钙离子泵活性的降低与32P掺入受磷蛋白的减少相关。据推测，缺血诱导的钙离子泵失活不仅是酶活性特异性丧失的结果，也是由受磷蛋白特性改变引起的。
