Gene expression is regulated at multiple levels including the cap-dependent translation of mRNA into proteins. Eukaryotic translation initiation factor4E (eIF4E) binds to the 5'-m7GTP cappresent on all eukaryotic cytoplasmic mRNAs. eIF4E is the central component of the cap-dependent translation initiation complex (eIF4F). The assembly of eIF4F is negatively regulated by 4E-binding proteins (4E-BPs or BPs), which bind eIF4E and block eIF4F assembly to inhibit cap-dependent translation. Three BPs have been identified as BP1, BP2 and BP3 (BP3). We have found that LV BP1 protein expression is greatly increased in advanced congestive heart failure (CHF). We examined the effect of double gene knockout (DKO) of BP1 and BP2 on transverse aortic constriction (TAC) or myocardial infarct induced CHF in mice, and the results demonstrated that BP1/2 DKO profoundly improved the survival rate and LV function in these mice. We also found that BP1/2 DKO increased LV sarcoplasmic reticulum Ca++ ATPase (SERCA2a) protein content ~2.5 fold at the protein level. Based on these preliminary data, the overall goal of this proposal is to determine how enhancing cap-dependent translation initiation by BP1/2 DKO and BP1 KO exert their profound cardiac protective effect against the development of CHF in mice by achieving following research objectives: (i) Determine the consequences of enhancing cap-dependent translational initiation by DKO on stress-induced CHF. Our working hypothesis is that enhancing cap-dependent translation initiation by DKO will protect the heart from TAC or infarct induced CHF;(ii) Identify whether the cardioprotective effect observed in DKO mice is mainly due to loss of function of BP1 or BP2. Our working hypothesis is that the cardiac protective effect is mainly due to the deletion of BP1, and that cardiac myocyte specific BP1 overexpression will cause or exacerbates LV dysfunction;(iii) Identify underlying molecular mechanisms for the cardioprotective effect of enhancing translational initiation by BP1/2 DKO. Our working hypothesis is that BP1/2 DKO will improve the translational efficiency of mRNAs (such as SERCA2a) that have an excessive amount of secondary structure in the 5'-untranslatedregions (5'-UTRs). The project will take advantage of mouse models with targeted disruption of BP1, BP2 and BP1/2, cardiac specific BP1 transgenic mice and of technologies for combined analysis of the transcriptome and translatome. Our research team includes experts in translational control (Dr. Bitterman), molecular cardiology and experimental CHF models (Dr. Chen), polyribosome microarrays (Dr. Bitterman), and membrane protein complexes involved in calcium transport (such as SERCA2a) in cardiac myocytes (Dr. David Thomas). These studies will provide novel insights into the role of cap-dependent translation initiation on the development of CHF. Our preliminary finding indicates that regulation of cap-dependent translation initiation by targeting 4E-binding proteins may be a novel therapeutic approach to treat CHF.
Cardiovascular disease ranks as America's No. 1 killer that accounts for nearly one million deaths each year. 4E binding proteins (4E-BPs) play an important role in regulating the translation of mRNA into proteins. We recently found that 4E-BP1 was significantly increased in the advance heart failure. The purpose of this project is to determine the effect 4E-BP gene deletion on the development of congestive heart failure and to understand how 4E-BPs play a critical role in regulating the development of congestive heart failure. The findings from this project are going to advance our understanding of the development of heart failure and to identify novel new therapeutic targets for treating congestive heart failure.
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