LncRNA <i>ZFAS1</i> as a SERCA2a Inhibitor to Cause Intracellular Ca²⁺ Overload and Contractile Dysfunction in a Mouse Model of Myocardial Infarction.

Abstract

Ca²⁺ homeostasis-a critical determinant of cardiac contractile function-is critically regulated by SERCA2a (sarcoplasmic reticulum Ca²⁺-ATPase 2a). Our previous study has identified <i>ZFAS1</i> as a new lncRNA biomarker of acute myocardial infarction (MI). To evaluate the effects of <i>ZFAS1</i> on SERCA2a and the associated Ca²⁺ homeostasis and cardiac contractile function in the setting of MI. <i>ZFAS1</i> expression was robustly increased in cytoplasm and sarcoplasmic reticulum in a mouse model of MI and a cellular model of hypoxia. Knockdown of endogenous <i>ZFAS1</i> by virus-mediated silencing shRNA partially abrogated the ischemia-induced contractile dysfunction. Overexpression of <i>ZFAS1</i> in otherwise normal mice created similar impairment of cardiac function as that observed in MI mice. Moreover, at the cellular level, <i>ZFAS1</i> overexpression weakened the contractility of cardiac muscles. At the subcellular level, <i>ZFAS1</i> deleteriously altered the Ca²⁺ transient leading to intracellular Ca²⁺ overload in cardiomyocytes. At the molecular level, <i>ZFAS1</i> was found to directly bind SERCA2a protein and to limit its activity, as well as to repress its expression. The effects of <i>ZFAS1</i> were readily reversible on knockdown of this lncRNA. Notably, a sequence domain of <i>ZFAS1</i> gene that is conserved across species mimicked the effects of the full-length <i>ZFAS1</i>. Mutation of this domain or application of an antisense fragment to this conserved region efficiently canceled out the deleterious actions of <i>ZFAS1</i>. <i>ZFAS1</i> had no significant effects on other Ca²⁺-handling regulatory proteins. <i>ZFAS1</i> is an endogenous SERCA2a inhibitor, acting by binding to SERCA2a protein to limit its intracellular level and inhibit its activity, and a contributor to the impairment of cardiac contractile function in MI. Therefore, anti-<i>ZFAS1</i> might be considered as a new therapeutic strategy for preserving SERCA2a activity and cardiac function under pathological conditions of the heart.