Abstract 11241: RAS-Association Domain Family Protein 1a (RASSF1A) is a Main Regulator for TNF-a Signaling in Cardiomyocytes
Tumor necrosis factor-α (TNF-α) plays a key role in the pathogenesis of heart failure. Although cardiomyocytes are known to express the TNF-α receptors (TNFR) the mechanism of TNF-α signal transmission is incompletely understood. In this study we aim to investigate whether the tumor suppressor Ras-association domain family protein 1 isoform A (RASSF1A) modulates TNF-α signaling in cardiomyocytes.
We used RASSF1A knockout (RASSF1A-/-) mice and wild type (WT) littermates in this study. Acute stimulation for 30 minutes with low-dose of TNF-α (10μg/kg i.v.) increased cardiac contractility and intracellular calcium transient amplitude in WT mice. In contrast, RASSF1A-/- mice showed a blunted contractile response. Mechanistically, we found that RASSF1A formed a molecular complex with the TNF-α receptor 1 in cardiomyocytes and this interaction was essential to the recruitment of TRADD and TRAF2, the major downstream effectors of TNF-α signaling. By mapping the interaction domain, we found that the C-terminal region of RASSF1A was responsible for the interaction with TRADD and TRAF2. RASSF1A was essential in regulating calcium transients and contractility in cardiomyocytes downstream of TNF-α signaling through regulation of cytoplasmic phospholipase A2 (cPLA2) and phosphorylation of calcium handling molecules. In addition, using adenoviral-mediated NF-κB luciferase reporter, we found a significantly lower NF-κB-luciferase activation in cardiomyocytes lacking RASSF1A following TNF-α treatment. Importantly, overexpressing human RASSF1A in cells lacking this molecule rescued the NF-κB luciferase activation to the same level as control cells. Furthermore, in an in vivo model of systemic endotoxaemia by bolus lipopolysaccharide (LPS) injection, we found that RASSF1A-/- mice displayed a significantly lower contractility compared to wild type despite a comparable level of serum TNF-α.
In conclusion, our present work contributes a novel effector pathway via RASSF1A which transmits the positive inotropic effect of TNF-α and should therefore be preserved or even stimulated in the treatment of heart failure. In addition, enhancement of RASSF1A function/expression might well benefit patients with heart failure.
- © 2013 by American Heart Association, Inc.