Abstract 301: Cavin-2 Deletion Attenuates Fibroblast Activation and Cardiac Fibrosis via TGF-β Signaling by Interacting With Hsp90

Abstract

Introduction: Heart failure (HF) is a progressive disease associated with high morbidity and mortality. A major cause of HF is the adverse tissue remodeling with interstitial fibrosis. Excessive extracellular matrix (ECM) accumulation is involved in the poor outcome. Transformation to myofibroblasts in resident fibroblasts has an important role for cardiac fibrosis on pressure-overload heart failure. TGF-β signaling is one of the critical pathways in fibroblast activation. Caveolae are major plasma membrane domain defined as 50-100 nm vesicular structures. Caveolins and cavins are known as caveolar-related proteins. TGF-β signaling is tightly connected with caveolae. A previous report shows that induction of Cav-1 expression leads to suppression of TGF-β signaling and an improvement of fibrosis. Although cavin-2/Serum deprivation response protein (SDPR) is also abundant in fibroblasts, the role of cavin-2 in cardiac fibrosis and function remains unknown. Methods and Results: To clarify the role of cavin-2 in cardiac fibroblasts in the pressure-overloaded heart, we performed TAC operation on cavin-2 flox/flox mice and fibroblast-specific cavin-2 knockout (Postin Cre ; SDPR flox/flox ) mice (cavin-2 cKO). Four weeks after TAC, left ventricular fractional shortening (LVFS) was preserved with a significant reduction of cardiac fibrosis in cavin-2 cKO mice. Fibrosis-associated mRNA expression ( Col1a1, Ctgf, Col3 ) and α1 type I collagen deposition were reduced in the hearts of cavin-2-cKO mice after TAC. Transdifferentiation of fibroblasts into activated myofibroblasts is a defining feature of fibrosis. Myofibroblasts express αSMA and secrete ECM proteins via Smad signaling. αSMA-positive cells without showing vascular structure were reduced in cavin-2 cKO after TAC. In mouse embryonic fibroblasts (MEFs), cavin-2 deficiency reduced TGF-β1-induced αSMA production and fibrosis-associated mRNA expression. On the other hand, adenovirus-mediated cavin-2 overexpression significantly increased αSMA production and the fibrosis-associated mRNA expressions. Furthermore, TGF-β1-induced Smad2/3 phosphorylation was attenuated in cavin-2 KO MEFs compared to wild-type (WT) MEFs. A protein-Protein interaction screening using a promiscuous biotin ligase, called BioID, revealed that cavin-2 interacted with Hsp90ab1 and Hsp90b1 which modulate collagen synthesis through regulation of SMA and SMAD pathway. The protein expression level of Hsp90 in cavin-2 KO MEFs significantly decreased compared with that in WT MEFs. Conclusions: Our observations suggest that cavin-2 contributes to the development of cardiac fibrosis through the differentiation from fibroblasts into myofibroblasts via TGF-β/Smad signaling. cavin-2 may be a novel therapeutic target for cardiac fibrosis.