Abstract 10900: Implication of the Post-Translational Formation of Hypusine in Eif5a in Pulmonary Arterial Hypertension

Abstract

Pulmonary Arterial Hypertension (PAH) is characterized by progressive pulmonary arteries (PAs) obstruction leading to heart failure and death. PA smooth muscle cells (PASMCs) of PAH patients display a “cancer-like” phenotype that contributes to PA remodeling. Eukaryotic translation initiation factor 5A (eIF5A) was shown to provide cancer cells with a competitive advantage by increasing translation of mRNAs with oncogenic proprieties, many of them containing proline/glycine-rich patterns. Strikingly, eIF5A is the only protein containing the unique, polyamine-derived amino acid hypusine, which is required for its function. Hypusine formation is catalyzed by the sequential actions of deoxyhypusine synthase (DHPS) and deoxyhypusine hydrolase (DOHH). We hypothesized that increased eiF5A Hyp in PAH-PASMCs is required to promote translational efficiency of a set of factors conferring a higher survival and fibroproliferative capacity, leading to pulmonary vascular remodeling. Data derived from a comparative proteomic analysis (LC-MSMS) between normal and PAH-PASMCs and confirmed by Western blot indicate that DHPS and DOHH are overexpressed in PAH-PASMCs compared to controls (p<0.05). Consistently, both total and hypusinated forms of eIF5A were found up-regulated in dissected PAs and PASMCs from PAH patients and animal models (MCT and Su/Hx rats, p<0.05). In vitro , inhibition of DHPS and DOHH, using GC7 and ciclopirox, respectively, significantly attenuates PAH-PASMCs survival and proliferation, (Annexin V; Ki67 labeling and EdU incorporation, p<0.01). These effects were confirmed by a reduced expression eiF5A Hyp , MCM2, PCNA and Survivin (p<0.01) and a downregulation of BRD4, EP300 and COL1, three factors implicated in PAH containing proline/glycine-rich patterns. In vivo , inhibition of DHPS using GC7 in MCT rats with established PAH improves hemodynamics (RVSP, mPAP, CO, p<0.05) and vascular remodeling (EVG, p<0.05). Furthermore, preliminary data indicate that smooth muscle cells-targeted inactivation of one allele of Dhps tends to confer protection against Su/Hx-induced PAH in mice. We showed for the first time that hypusine signaling is implicated in PAH development and represents a new promising therapeutic target.