Targeted inhibition of Ca2+/calmodulin-dependent protein kinase II in cardiac longitudinal sarcoplasmic reticulum results in decreased phospholamban phosphorylation at threonine 17.
To investigate the role of Ca2+/calmodulin-dependent kinase II in cardiac sarcoplasmic reticulum function, transgenic mice were designed and generated to target the expression of a Ca2+/calmodulin-dependent kinase II inhibitory peptide in cardiac longitudinal sarcoplasmic reticulum using a truncated phospholamban transmembrane domain. The expressed inhibitory peptide was highly concentrated in cardiac sarcoplasmic reticulum. This resulted in a 59.7 and 73.6% decrease in phospholamban phosphorylation at threonine 17 under basal and beta-adrenergic stimulated conditions without changing phospholamban phosphorylation at serine 16. Sarcoplasmic reticulum Ca2+ uptake assays showed that the Vmax was decreased by approximately 30% although the apparent affinity for Ca2+ was unchanged in heterozygous hearts. The in vivo measurement of cardiac function showed no significant reductions in positive and negative dP/dt, but a moderate 18% decrease in dP/dt40, indicative of isovolumic contractility, and a 26.1% increase in the time constant of relaxation (tau) under basal conditions. The changes in these parameters indicate a moderate cardiac dysfunction in transgenic mice. Although the 3 and 4-month-old transgenic mice displayed no overt signs of cardiac disease, when stressed by gestation and parturition, the 7-month-old female mice develop dilated heart failure, suggesting the important role of Ca2+/calmodulin-dependent kinase II pathway in the development of cardiac disease.
Ji
Yong
Y
Department of Genome Science, University of Cincinnati College of Medicine, Ohio 45267-0505, USA.
Li
Bailing
B
Reed
Thomas D
TD
Lorenz
John N
JN
Kaetzel
Marcia A
MA
Dedman
John R
JR
D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors*; D006331:Heart Diseases / Q000201:enzymology / Q000209:etiology; D051379:Mice; D009206:Myocardium / Q000378:metabolism*; D010766:Phosphorylation; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D015398:Signal Transduction; D013912:Threonine; D000099211:Phospholamban
D002135:Calcium-Binding Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D013912:Threonine; D000099211:Phospholamban