The goal of this proposal is to demonstrate that genetic deletion of PHLPP1 and PHLPP2, newly discovered phosphatases that selectively remove a phosphate from Ser473 on Akt, will modulate cardiac hypertrophy and survival through Akt dependent and independent mechanisms. Proposed work will examine the hypothesis that PHLPP1 and PHLPP2 have non-overlapping functions in cardiomyocytes and that global or cardiac- specific removal of distinct PHLPP isoforms will augment cardiac hypertrophy and failure. We have demonstrated for the first time that PHLPP1 and PHLPP2 are expressed in the heart and that decreasing PHLPP1 in cardiomyocytes or the heart increases Akt activity. The effect of PHLPP isoform removal in vitro and in vivo on cardiac signaling and development of hypertrophy following injury has not been investigated. Preliminary data suggests that removal of PHLPP2 in cardiomyocytes has no effect on Akt phosphorylation, however, increases cardiomyocyte size at baseline as well as following hypertrophic stimulation. To delineate the role of PHLPP1 and PHLPP2 in cardiomyocytes and the heart, the first aim will characterize the effect of PHLPP1 and PHLPP2 on cardiomyocyte signaling, hypertrophy and survival in vitro. Proposed experiments will use neonatal rat cardiomyocytes with gain and loss of PHLPP1 and PHLPP2 and adult cardiac myocytes from the PHLPP gene-target mice.
The aim will investigate Akt as well as other signaling pathways that may be regulated by the PHLPP isoforms. This line of inquiry will be important for interpreting the cardiac phenotype of the PHLPP gene-targeted mice.
The second aim will determine whether PHLPP1 and PHLPP2 gene-targeted mice show differences in the development of cardiac hypertrophy and failure in vivo. The cardiac phenotype of the PHLPP isoform gene-targeted mice will be examined at baseline and following pressure overload or agonist induced hypertrophy. The ability of the PHLPP isoforms to effect the transition from hypertrophy to failure will all be examined. Lastly, the third aim is to elucidate the mechanism of action of PHLPP1 isoforms in cardiomyocyte hypertrophy and in particular their ability to regulate phosphorylation and translocation of HDAC5 and GRK5. This proposal intends to discover new targets of PHLPP that may be helpful in providing innovative avenues for therapeutic strategies to treat heart disease.

Public Health Relevance

Cardiovascular disease and development of heart failure are amongst the primary causes of death in the United States and worldwide. We have found that a newly discovered phosphatase, PHLPP, negatively regulates Akt activity and survival in the heart. Here we seek to further understand through removal of PHLPP, its isoform specificity for Akt and target substrates following cardiac hypertrophy and failure and determine the potential for PHLPP as a target for therapeutic strategies to improve cardiac function.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Cardiac Contractility, Hypertrophy, and Failure Study Section (CCHF)
Program Officer
Adhikari, Bishow B
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of California San Diego
Schools of Medicine
La Jolla
United States
Zip Code
Yeh, Szu-Tsen; Zambrano, Cristina M; Koch, Walter J et al. (2018) PH domain leucine-rich repeat protein phosphatase 2 (PHLPP2) regulates G-protein-coupled receptor kinase 5 (GRK5)-induced cardiac hypertrophy in vitro. J Biol Chem 293:8056-8064
Castaldi, Alessandra; Dodia, Ramsinh Mansinh; Orogo, Amabel M et al. (2017) Decline in cellular function of aged mouse c-kit+ cardiac progenitor cells. J Physiol 595:6249-6262
Dusaban, Stephanie S; Chun, Jerold; Rosen, Hugh et al. (2017) Sphingosine 1-phosphate receptor 3 and RhoA signaling mediate inflammatory gene expression in astrocytes. J Neuroinflammation 14:111
Yung, Bryan S; Brand, Cameron S; Xiang, Sunny Y et al. (2017) Selective coupling of the S1P3 receptor subtype to S1P-mediated RhoA activation and cardioprotection. J Mol Cell Cardiol 103:1-10
Castaldi, Alessandra; Chesini, Gino P; Taylor, Amy E et al. (2016) Sphingosine 1-phosphate elicits RhoA-dependent proliferation and MRTF-A mediated gene induction in CPCs. Cell Signal 28:871-9
Kim, KyeongJin; Qiang, Li; Hayden, Matthew S et al. (2016) mTORC1-independent Raptor prevents hepatic steatosis by stabilizing PHLPP2. Nat Commun 7:10255
Moc, Courtney; Taylor, Amy E; Chesini, Gino P et al. (2015) Physiological activation of Akt by PHLPP1 deletion protects against pathological hypertrophy. Cardiovasc Res 105:160-70