Increased nitration of sarcoplasmic reticulum Ca2+-ATPase in human heart failure.
BACKGROUND
Reduced sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA2a isoform) activity is a major determinant of reduced contractility in heart failure. Ca2+-ATPase inactivation can occur through SERCA2a nitration. We therefore investigated the role of SERCA2a nitration in heart failure.


RESULTS
We measured SERCA2a levels and nitrotyrosine levels in tissue from normal and failing human hearts using Western blots. We found that nitrotyrosine levels in idiopathic dilated cardiomyopathic (DCM) hearts were almost double those of control hearts in age-matched groups. Nitrotyrosine was dominantly present in a single protein with the molecular weight of SERCA2a, and immunoprecipitation confirmed that the protein recognized by the nitrotyrosine antibody was SERCA2a. There was a positive correlation between the time to half relaxation and the nitrotyrosine/SERCA2a content (P<0.01) in myocytes isolated from control and DCM hearts. In experiments with isolated SR vesicles from porcine hearts, we also showed that the Ca pump is inactivated by peroxynitrite exposure, and inactivation was prevented by protein kinase A pretreatment.


CONCLUSIONS
We conclude that SERCA2a inactivation by nitration may contribute to Ca pump failure and hence heart failure in DCM.
Lokuta
Andrew J
AJ
Department of Physiology, University of Wisconsin, Madison, USA.
Maertz
Nathan A
NA
Meethal
Sivan Vadakkadath
SV
Potter
Katherine T
KT
Kamp
Timothy J
TJ
Valdivia
Héctor H
HH
Haworth
Robert A
RA
D000293:Adolescent; D000328:Adult; D015153:Blotting, Western / Q000379:methods; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005260:Female; D006333:Heart Failure / Q000378:metabolism*; D006352:Heart Ventricles / Q000737:chemistry; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000737:chemistry / Q000201:enzymology; D032383:Myocytes, Cardiac / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D010766:Phosphorylation; D012519:Sarcoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
D007527:Isoenzymes; C002744:3-nitrotyrosine; D014443:Tyrosine; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases