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Brittsan, AG; Ginsburg, KS; Chu, G; Yatani, A; Wolska, BM; Schmidt, AG; Asahi, M; MacLennan, DH; Bers, DM; Kranias, EG.
Chronic SR Ca2+-ATPase inhibition causes adaptive changes in cellular Ca2+ transport.
Circ Res. 2003; 92(7): 769-776. Doi: 10.1161/01.RES.0000066661.49920.59 [OPEN ACCESS]
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Schmidt Albrecht

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Phospholamban, the critical regulator of the cardiac SERCA2a Ca2+ affinity, is phosphorylated at Ser16 and Thr17 during beta-adrenergic stimulation (eg, isoproterenol). To assess the impact of nonphosphorylatable phospholamban, a S16A, T17A double-mutant (DM) was introduced into phospholamban knockout mouse hearts. Transgenic lines expressing DM phospholamban at levels similar to wild types (WT) were identified. In vitro phosphorylation confirmed that DM phospholamban could not be phosphorylated, but produced the same shift in EC50 of SERCA2a for Ca2+ as unphosphorylated WT phospholamban. Rates of basal twitch [Ca2+]i decline were not different in DM versus WT cardiomyocytes. Isoproterenol increased the rates of twitch [Ca2+]i decline in WT, but not DM myocytes, confirming the prominent role of phospholamban phosphorylation in this response. Increased L-type Ca2+ current (ICa) density, with unaltered characteristics, was the major compensation in DM myocytes. Consequently, the normal beta-adrenergic-induced increase in ICa caused larger dynamic changes in absolute ICa density. Isoproterenol increased Ca2+ transients to a comparable amplitude in DM and WT. There were no changes in myofilament Ca2+ sensitivity, or the expression levels and Ca2+ removal activities of other Ca2+-handling proteins. Nor was there evidence of cardiac remodeling up to 10 months of age. Thus, chronic inhibition of SERCA2a by ablation of phospholamban phosphorylation (abolishing its adrenergic regulation) results in a unique cellular adaptation involving greater dynamic ICa modulation. This ICa modulation may partly compensate for the loss in SERCA2a responsiveness and thereby partially normalize beta-adrenergic inotropy in DM phospholamban mice.
Find related publications in this database (using NLM MeSH Indexing)
Adaptation, Physiological - drug effects
Animals -
Biological Transport - drug effects
Blotting, Western -
Calcium - metabolism
Calcium Channels - physiology
Calcium-Binding Proteins - genetics Calcium-Binding Proteins - metabolism
Calcium-Transporting ATPases - genetics Calcium-Transporting ATPases - metabolism
Cell Line -
Echocardiography -
Female -
Heart Ventricles - cytology Heart Ventricles - drug effects
Humans -
Isoproterenol - pharmacology
Male -
Membrane Potentials - drug effects
Mice -
Mice, Inbred Strains -
Mice, Knockout -
Mice, Transgenic -
Microsomes - metabolism
Mutation -
Myocytes, Cardiac - cytology Myocytes, Cardiac - drug effects Myocytes, Cardiac - physiology
Patch-Clamp Techniques -
Phosphorylation - drug effects
Rabbits -
Sarcoplasmic Reticulum - metabolism
Sarcoplasmic Reticulum Calcium-Transporting ATPases -
Transfection -
Ventricular Function -

Find related publications in this database (Keywords)
sarcoplasmic reticulum
SR Ca(2+-)ATPase
transgenic mice
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