Abstract 19642: A Novel DNA-damage Inducible Interaction between Peroxisome Proliferator Activated Receptor γ and p53 Regulates Pulmonary Arterial Endothelial Cell Homeostasis
Background: Pulmonary arterial (PA) hypertension (PAH) is a life-threatening, vaso-proliferative disorder. Impaired expression and function of the bone morphogenetic protein receptor (BMPR) 2 - peroxisome-proliferator activated receptor (PPAR)γ axis is observed in PAH and associated with PA endothelial cell (EC) apoptosis and dysregulation, smooth muscle cell (SMC) proliferation and neointima formation. Because of its different functions and gene targets in EC and SMC, we hypothesized that the cell specific properties of the BMPR2-PPARγ pathway depend on PPARγ interacting partners.
Methods & Results: An affinity-purification mass spectrometry (AP-MS) screen for novel PPARγ interacting proteins was performed. In addition to known partners (e.g., β-catenin, RXRα), AP-MS analysis of the PPARγ interactome revealed a previously unknown network highly enriched in DNA damage response proteins including p53. New interactions were confirmed by co-immunoprecipitation. In healthy human PAEC, SMC and adventitial fibroblasts, PPARγ/p53 complex formation was induced by the p53 stabilizing agent Nutlin-3 and the DNA-damaging agent, Doxorubicin (Dox). The PPARγ/p53 complex was transcriptionally active. Loss of PPARγ by siRNA suppressed p53 transcriptional activity but not p53 protein levels. Dox treatment of PAEC led to increased expression of PPARγ, p53 and their common target genes GADD45 (DNA repair protein), PGC1α (inducer of mitochondrial biogenesis) and p21 (cell cycle inhibitor). Interestingly, expression of apelin, an EC survival factor and suppressor of SMC proliferation and a known target of PPARγ but not previously related to p53, also increased in PAEC upon treatment with Dox. Whereas Dox induced p21 was reduced by p53 siRNA, PPARγ and p53 siRNAs both significantly suppressed Dox induction of GADD45B, PGC1α and apelin. Nutlin-3, by inducing the PPARγ-p53 complex partially reproduced the effects of Dox. In line with increased apelin expression, PAEC formed significantly more tubes in Matrigel in response to Dox, which was abolished by both PPARγ and p53 siRNAs.
Conclusions: PPARγ and p53 form a novel DNA-damage inducible complex that is transcriptionally active and functions to support PAEC homeostasis and angiogenesis.
Author Disclosures: J.K. Hennigs: None. C.G. Li: None. I. Diebold: None. M. Rabinovitch: None.
- © 2014 by American Heart Association, Inc.