Reduced Ca2+-sensitivity of SERCA 2a in failing human myocardium due to reduced serin-16 phospholamban phosphorylation

Item Type:	Article
Title:	Reduced Ca2+-sensitivity of SERCA 2a in failing human myocardium due to reduced serin-16 phospholamban phosphorylation
Creators Name:	Schwinger, R.H.G. and Muench, G. and Boelck, B. and Karczewski, P. and Krause, E.G. and Erdmann, E.
Abstract:	It is still a matter of debate, whether decreased protein expression of SERCA 2a and phospholamban (PLB), or alterations in the phosphorylation state of PLB are responsible for the reduced SERCA 2a function in failing human myocardium. Thus, in membrane preparations from patients with terminal heart failure due to idiopathic dilated cardiomyopathy (NYHA IV. heart transplants) and control hearts (NF), SERCA 2a activity was measured with an NADH coupled assay with as well as without stimulation with protein kinase A (PKA). The protein expression of SERCA 2a, PLB and calsequestrin as well as the phosphorylation status of PLB (Back-phosphorylation technique: Serine-16-PLB specific antibody) were analysed using Western blotting technique and specific antibodies. In NF, the maximal activity (Vmax) and the Ca(2+)-sensitivity of SERCA 2a activity were significantly higher compared to NYHA IV. Protein expression of SERCA 2a, PLB and calsequestrin were unchanged, whereas both, the phosphorylation status of PLB as well as serine-16-PLB-phosphorylation, were significantly reduced in NYHA IV. After stimulation with PKA only the Ca(2+)-sensitivity, but not Vmax increased concentration-dependently. Therefore, in human myocardium, the Ca(2+)-sensitivity but not the Vmax of SERCA 2a is regulated by cAMP-dependent phosphorylation of phospholamban at position serine-16. Threonine-17-PLB-phosphorylation or direct phosphorylation of SERCA 2a may be candidates for regulation of maximal SERCA 2a activity in human myocardium.
Keywords:	Sarcoplasmic Reticulum, Heart Failure, Ca2+-Transporting ATPase, Phospholamban, Human Myocardium, Force-Frequency-Relationship
Source:	Journal of Molecular and Cellular Cardiology
ISSN:	0022-2828
Publisher:	Elsevier
Volume:	31
Number:	3
Page Range:	479-491
Date:	1 March 1999
Official Publication:	https://doi.org/10.1006/jmcc.1998.0897
PubMed:	View item in PubMed

Repository Staff Only: item control page