Schmidt U, Hajjar R J, Kim C S, Lebeche D, Doye A A, Gwathmey J K
Integrated Physiology Research Laboratories, Cardiovascular Division, Department of Cardiovascular Medicine, Boston University School of Medicine, Boston 02118, MA, USA.
Am J Physiol. 1999 Aug;277(2):H474-80. doi: 10.1152/ajpheart.1999.277.2.H474.
Failing human myocardium has been associated with decreased sarcoplasmic reticulum (SR) Ca(2+)-ATPase activity. There remains controversy as to whether the regulation of SR Ca(2+)-ATPase activity is altered in heart failure or whether decreased SR Ca(2+)-ATPase activity is due to changes in SR Ca(2+)-ATPase or phospholamban expression. We therefore investigated whether alterations in cAMP-dependent phosphorylation of phospholamban may be responsible for the reduced SR Ca(2+)-ATPase activity in human heart failure. Protein levels of phospholamban and SR Ca(2+)-ATPase, detected by Western blot, were unchanged in failing compared with nonfailing human myocardium. There was decreased responsiveness to the direct activation of the SR Ca(2+)-ATPase activity by either cAMP (0.01-100 micromol/l) or protein kinase A (1-30 microgram) in failing myocardium. Using the backphosphorylation technique, we observed a decrease of the cAMP-dependent phosphorylation level of phospholamban by 20 +/- 2%. It is concluded that the impaired SR function in human end-stage heart failure may be due, in part, to a reduced cAMP-dependent phosphorylation of phospholamban.
衰竭的人类心肌与肌浆网（SR）Ca²⁺ -ATP酶活性降低有关。关于心力衰竭时SR Ca²⁺ -ATP酶活性的调节是否改变，或者SR Ca²⁺ -ATP酶活性降低是否归因于SR Ca²⁺ -ATP酶或受磷蛋白表达的变化，仍存在争议。因此，我们研究了受磷蛋白的环磷酸腺苷（cAMP）依赖性磷酸化改变是否可能是人类心力衰竭中SR Ca²⁺ -ATP酶活性降低的原因。通过蛋白质印迹法检测，与非衰竭人类心肌相比，衰竭心肌中受磷蛋白和SR Ca²⁺ -ATP酶的蛋白质水平没有变化。在衰竭心肌中，cAMP（0.01 - 100微摩尔/升）或蛋白激酶A（1 - 30微克）对SR Ca²⁺ -ATP酶活性的直接激活反应性降低。使用反向磷酸化技术，我们观察到受磷蛋白的cAMP依赖性磷酸化水平降低了20±2%。结论是，人类终末期心力衰竭中SR功能受损可能部分归因于受磷蛋白的cAMP依赖性磷酸化降低。
