USP11 promotes endothelial apoptosis-resistance in pulmonary hypertension by deubiquitinating HINT3

ABSTRACT Introduction Pulmonary arterial hypertension (PAH) is a progressive, lethal, and incurable disease of the pulmonary vasculature. Evolving evidence indicates that the ubiquitin-specific proteases (USPs), play an important role in the pathogenesis of PAH by deubiquitinating key proteins involved in cell proliferation, migration, and apoptosis. Our genome-wide association study (GWAS) analysis-paired with transcriptomic profiling indicated that deubiquitinase USP11 and histidine triad nucleotide binding protein 3 (HINT3) are positively correlated and that their expression increased in lungs of PAH patients compared to control (fail donor) group, and inversely correlated with survival. However, mechanisms and function of the USP11/HNT3 axis have not been explored in PAH. Therefore, we aimed to investigate that HINT3 stabilized by USP11 activation links to endothelial apoptosis-resistance in PAH. Methods and Results Expression of USP11 and HINT3 was increased in the lungs of idiopathic PAH (IPAH) patients and Hypoxia/Sugen-treated mice using qRT-PCR and Western blot analyses. USP11 and HINT3 interacted physically as shown by co-immunoprecipitation (co-IP) assay in human pulmonary artery endothelial cells (HPAECs). HINT3 levels were decreased upon transfection of HA-tagged Ubi plasmid into HPAECs. Pretreatment with the potent proteasome inhibitor MG132 prolonged the half-life of HINT3 protein, indicating that HINT3 is degraded by polyubiquitination. HINT3 was stabilized and destabilized by forced overexpression or siRNA knockdown of USP11 respectively. Similarly, treatment with mitoxantrone, a USP11 antagonist, reduced HPAEC HINT3 expression. HINT3 interacted with the antiapoptotic mediator, BCL2. Overexpression of USP11 increased BCL2 content, congruent to elevated lung tissue levels seen in IPAH patients and Hypoxia/Sugen-treated mice. Conversely, knockdown of HINT3 function led to depletion of BCL2. Conclusions The HINT3-USP11 axis contributes to apoptosis-resistance in pulmonary artery endothelial cells, as is potentially a novel and attractive therapeutic target for ubiquitination modulators.