Cardiac specific expression of threonine 5 to alanine mutant sarcolipin results in structural remodeling and diastolic dysfunction.

Mayilvahanan Shanmugam,Shumin Gao,Lai-Hua Xie,Vikas Shah,Ronald Pachon,Dan Li,Antanina Voit,Gopal J Babu,Nadezhda Fefelova,Ghassan Yehia,Luis Eduardo M Quintas

doi:10.1371/journal.pone.0115822

Abstract

The functional importance of threonine 5 (T5) in modulating the activity of sarcolipin (SLN), a key regulator of sarco/endoplasmic reticulum (SR) Ca2+ ATPase (SERCA) pump was studied using a transgenic mouse model with cardiac specific expression of threonine 5 to alanine mutant SLN (SLNT5A). In these transgenic mice, the SLNT5A protein replaces the endogenous SLN in atria, while maintaining the total SLN content. The cardiac specific expression of SLNT5A results in severe cardiac structural remodeling accompanied by bi-atrial enlargement. Biochemical analyses reveal a selective downregulation of SR Ca2+ handling proteins and a reduced SR Ca2+ uptake both in atria and in the ventricles. Optical mapping analysis shows slower action potential propagation in the transgenic mice atria. Doppler echocardiography and hemodynamic measurements demonstrate a reduced atrial contractility and an impaired diastolic function. Together, these findings suggest that threonine 5 plays an important role in modulating SLN function in the heart. Furthermore, our studies suggest that alteration in SLN function can cause abnormal Ca2+ handling and subsequent cardiac remodeling and dysfunction.

Highlights

Sarcolipin (SLN), a 31 amino acid sarco/endoplasmic reticulum (SR) membrane protein is expressed predominantly in atria and in skeletal muscles and to a very low level in the ventricles [1]
All experiments were performed in accordance with the provision of the animal welfare act, the PHS policy on Human Care and Use of Laboratory Animals, and of AAALAC International and the guidelines and policies approved by the Institute Animal Care and Use Committee (IACUC) in the New Jersey Medical School (NJMS), Rutgers, Newark, NJ
The major goal of this study is to determine the functional importance of threonine 5 in modulating SLN function in the heart in vivo

Summary

Introduction

Sarcolipin (SLN), a 31 amino acid sarco/endoplasmic reticulum (SR) membrane protein is expressed predominantly in atria and in skeletal muscles and to a very low level in the ventricles [1]. The role of SLN as an inhibitor of cardiac SR Ca2+ ATPase (SERCA) is established by overexpressing SLN in the adult rat ventricular myocytes [2] and in mouse hearts by transgenesis [3,4,5]. Results from these studies have demonstrated that increased levels of SLN can inhibit the SERCA function and impair the myocyte contractility.

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