ABSTRACT
Cardiac hypertrophy is one of the major risk factors for chronic heart failure. The role of endophilinA2 (EndoA2) in clathrin-mediated endocytosis and clathrin-independent endocytosis is well documented. In the present study, we tested the hypothesis that EndoA2 protects against angiotensin II (Ang II)-induced cardiac hypertrophy by mediating intracellular angiotensin II type 1 receptor (AT1-R) trafficking in neonatal rat cardiomyocytes (NRCMs). Cardiac hypertrophy was evaluated by using cell surface area and quantitative RT-PCR (qPCR) analyses. For the first time, we found that EndoA2 attenuated cardiac hypertrophy and fibrosis induced by Ang II. Moreover, EndoA2 inhibited apoptosis induced by excessive endoplasmic reticulum stress (ERS), which accounted for the beneficial effects of EndoA2 on cardiac hypertrophy. We further revealed that there was an interaction between EndoA2 and AT1-R.The expression levels of EndoA2, which inhibits AT1-R transport from the cytoplasm to the membrane, and the interaction between EndoA2 and AT1-R were obviously decreased after Ang II treatment. Furthermore, Ang II inhibited the co-localization of AT1-R with GRP-78, which was reversed by EndoA2 overexpression. In conclusion, our results suggested that EndoA2 plays a role in protecting against cardiac hypertrophy induced by Ang II, possibly by inhibiting AT1-R transport from the cytoplasm to the membrane to suppress signal transduction.
Subject(s)
Acyltransferases/genetics , Angiotensin II/genetics , Cardiomegaly/prevention & control , Myocytes, Cardiac/metabolism , Receptor, Angiotensin, Type 1/genetics , Acyltransferases/antagonists & inhibitors , Acyltransferases/metabolism , Adenoviridae/genetics , Adenoviridae/metabolism , Angiotensin II/metabolism , Angiotensin II/pharmacology , Animals , Animals, Newborn , Apoptosis/genetics , Cardiomegaly/chemically induced , Cardiomegaly/genetics , Cardiomegaly/physiopathology , Endoplasmic Reticulum Stress/genetics , Gene Expression Regulation , Genetic Vectors/chemistry , Genetic Vectors/metabolism , Heat-Shock Proteins/genetics , Heat-Shock Proteins/metabolism , Myocytes, Cardiac/cytology , Myocytes, Cardiac/drug effects , Primary Cell Culture , Protein Transport , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , Rats , Rats, Sprague-Dawley , Receptor, Angiotensin, Type 1/metabolism , Signal Transduction , TransfectionABSTRACT
Apoptosis plays a critical role in normal embryonic development and tissue homeostasis regulation. EndophilinA2 (EndoA2) is widely reported to regulate endocytosis. Additionally, EndoA2 has been demonstrated to be involved in tumor metastasis, neuroregulation and vascular function. In this study, we used siRNA and Ad-EndoA2 transfection strategy to investigate whether EndoA2 provides a protective effect against apoptosis induced by H2O2 in H9C2 cardiomyocytes and the underlying mechanisms. We found that EndoA2 siRNA knockdown promoted H2O2-induced apoptosis in H9C2 cardiomyocytes, evidenced by decreased cell number, increased apoptotic cells, and activation of caspase-3. In contrast, EndoA2 overexpression showed the opposite effects and inhibited H2O2-induced apoptosis in H9C2 cardiomyocytes. Further studies revealed that EndoA2 overexpression strengthened autophagy, evidenced by the increased LC3 II/I ratio and P62 degradation, whereas EndoA2 siRNA knockdown produced the opposite effects. Furthermore, we revealed that there was an interaction between Bif-1 and Beclin-1. Upon H2O2 treatment, the association of Bif-1 and Beclin-1 remarkably increased. EndoA2 overexpression further promoted the binding of Bif-1 with Beclin-1, whereas EndoA2 siRNA knockdown reduced this association. These data strongly suggested that EndoA2 inhibited H2O2-induced apoptosis in H9C2 cardiomyocytes, possibly by promoting Bif-1 to form a complex with Beclin-1 and strengthening autophagy. This study provides a novel target for heart diseases.
