This proposal investigates a novel hypertrophic and anti-apoptotic pathway that is mediated by Ras GTPase-activating protein (RasGAP). Our previous results show that nGAP plays a role in cardiac cell hypertrophy by increasing RNA polymerase II (RNA pol II) activity and RNA and protein synthesis through as of yet unknown mechanisms. While investigating this we discovered that RasGAP interacts with Akt and the muscle isoform of the actin-binding protein filamin (FLN2). This proposal will explore the role of these interactions in mediating RasGAP's hypertrophic effects. Our preliminary results show the following: 1. RasGAP binds Akt and filamin simultaneously, through its SH2 and SH3 domains, respectively. 2. RasGAP and filamin concentrations and Akt activity are significantly increased during pressure overload cardiac hypertrophy. 3. When the increase in RasGAP protein is reproduced in tissue culture or a cardiac specific transgenic mouse model, Akt activity and nuclear translocation are enhanced. 4. RasGAP's interaction with the PH domain of Akt mediates its activation via integrin-linked kinase (ILK), which phosphorylates Akt on Ser-473.5. ILK is also upregulated during cardiac hypertrophy. 6. Through activation of Akt, RasGAP is rendered anti-apoptotic, a function that is also dependent on its association with filamin. 7. And most interestingly, Akt mediates RNA pol II phosphorylation. Accordingly our hypothesis is that an increase in free RasGAP concentration during cardiac hypertrophy promotes the formation of a RasGAP/FLN2/Akt complex, which may be further augmented by an increase in FLN2 protein. FLN2, which binds beta-integrins, will recruit this complex to the proximity of ILK (which also binds beta-integrins) and, in turn, will result in phosphorylating Akt on Ser-473. This modification will induce chronic activation and nuclear translocation of Akt, which in turn will mediate mRNA and protein synthesis and protect against apoptosis.
Our aims are: 1. To investigate the mechanism of RasGAP/FLN2-mediated phosphorylation and activation of Akt, 2. To investigate the role of Akt and FLN2 in mediating RasGAP-induced RNA synthesis, protein synthesis, and cell survival. 3. To determine the effect of upregulation of RasGAP and ILK on Akt and related growth and survival pathways in vivo in cardiac specific transgenic mouse models. ? ?

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL057970-07
Application #
6835129
Study Section
Cardiovascular and Pulmonary Research A Study Section (CVA)
Program Officer
Buxton, Denis B
Project Start
1998-01-05
Project End
2007-12-31
Budget Start
2005-01-01
Budget End
2005-12-31
Support Year
7
Fiscal Year
2005
Total Cost
$311,000
Indirect Cost
Name
University of Medicine & Dentistry of NJ
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
623946217
City
Newark
State
NJ
Country
United States
Zip Code
07107
Sayed, Danish; He, Minzhen; Yang, Zhi et al. (2013) Transcriptional regulation patterns revealed by high resolution chromatin immunoprecipitation during cardiac hypertrophy. J Biol Chem 288:2546-58
Han, Mingyue; Yang, Zhi; Sayed, Danish et al. (2012) GATA4 expression is primarily regulated via a miR-26b-dependent post-transcriptional mechanism during cardiac hypertrophy. Cardiovasc Res 93:645-54
Abdellatif, Maha (2012) Sirtuins and pyridine nucleotides. Circ Res 111:642-56
Abdellatif, Maha (2012) Differential expression of microRNAs in different disease states. Circ Res 110:638-50
Han, Mingyue; Toli, Jessica; Abdellatif, Maha (2011) MicroRNAs in the cardiovascular system. Curr Opin Cardiol 26:181-9
Sayed, Danish; He, Minzhen; Hong, Chull et al. (2010) MicroRNA-21 is a downstream effector of AKT that mediates its antiapoptotic effects via suppression of Fas ligand. J Biol Chem 285:20281-90
Abdellatif, Maha (2010) The role of microRNA-133 in cardiac hypertrophy uncovered. Circ Res 106:16-8
Rane, Shweta; He, Minzhen; Sayed, Danish et al. (2010) An antagonism between the AKT and beta-adrenergic signaling pathways mediated through their reciprocal effects on miR-199a-5p. Cell Signal 22:1054-62
Rane, Shweta; He, Minzhen; Sayed, Danish et al. (2009) Downregulation of miR-199a derepresses hypoxia-inducible factor-1alpha and Sirtuin 1 and recapitulates hypoxia preconditioning in cardiac myocytes. Circ Res 104:879-86
Sayed, Danish; Rane, Shweta; Lypowy, Jacqueline et al. (2008) MicroRNA-21 targets Sprouty2 and promotes cellular outgrowths. Mol Biol Cell 19:3272-82

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