A SERCA2 pump with an increased Ca2+ affinity can lead to severe cardiac hypertrophy, stress intolerance and reduced life span.
Abnormal Ca(2+) cycling in the failing heart might be corrected by enhancing the activity of the cardiac Ca(2+) pump, the sarco(endo)plasmic reticulum Ca(2+)-ATPase 2a (SERCA2a) isoform. This can be obtained by increasing the pump's affinity for Ca(2+) by suppressing phospholamban (PLB) activity, the in vivo inhibitor of SERCA2a. In SKO mice, gene-targeted replacement of SERCA2a by SERCA2b, a pump with a higher Ca(2+) affinity, results in cardiac hypertrophy and dysfunction. The stronger PLB inhibition on cardiac morphology and performance observed in SKO was investigated here in DKO mice, which were obtained by crossing SKO with PLB(-/-) mice. The affinity for Ca(2+) of SERCA2 was found to be further increased in these DKO mice. Relative to wild-type and SKO mice, DKO mice were much less spontaneously active and showed a reduced life span. The DKO mice also displayed a severe cardiac phenotype characterized by a more pronounced concentric hypertrophy, diastolic dysfunction and increased ventricular stiffness. Strikingly, beta-adrenergic or forced exercise stress induced acute heart failure and death in DKO mice. Therefore, the increased PLB inhibition represents a compensation for the imposed high Ca(2+)-affinity of SERCA2b in the SKO heart. Limiting SERCA2's affinity for Ca(2+) is physiologically important for normal cardiac function. An improved Ca(2+) transport in the sarcoplasmic reticulum may correct Ca(2+) mishandling in heart failure, but a SERCA pump with a much higher Ca(2+) affinity may be detrimental.
Vangheluwe
Peter
P
Laboratory of Physiology, University of Leuven, Belgium.
Tjwa
Marc
M
Van Den Bergh
An
A
Louch
William E
WE
Beullens
Monique
M
Dode
Leonard
L
Carmeliet
Peter
P
Kranias
Evangelia
E
Herijgers
Paul
P
Sipido
Karin R
KR
Raeymaekers
Luc
L
Wuytack
Frank
F
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000172:deficiency / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000172:deficiency / Q000378:metabolism*; D006332:Cardiomegaly / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D003433:Crosses, Genetic; D006333:Heart Failure / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D017136:Ion Transport / Q000235:genetics; D008136:Longevity / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D010805:Physical Conditioning, Animal / Q000009:adverse effects; D012519:Sarcoplasmic Reticulum / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D013312:Stress, Physiological; D013379:Substrate Specificity / Q000235:genetics; D000099211:Phospholamban
D002118:Calcium; D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000099211:Phospholamban; C506947:Atp2a2 protein, mouse