Human heart failure: cAMP stimulation of SR Ca(2+)-ATPase activity and phosphorylation level of phospholamban.
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.
Schmidt
U
U
Integrated Physiology Research Laboratories, Cardiovascular Division, Department of Cardiovascular Medicine, Boston University School of Medicine, Boston 02118, MA, USA.
Hajjar
R J
RJ
Kim
C S
CS
Lebeche
D
D
Doye
A A
AA
Gwathmey
J K
JK
D000328:Adult; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002303:Cardiac Output, Low / Q000201:enzymology / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000494:pharmacology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D000099211:Phospholamban
D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000099211:Phospholamban