S1P induces proliferation of pulmonary artery smooth muscle cell by promoting YAP-induced Notch3 expression and activation.

Sphingosine-1-phosphate (S1P), a natural multifunctional phospholipid, is highly increased in plasma from patients with pulmonary arterial hypertension (PAH) and mediates proliferation of pulmonary artery smooth muscle cell (PASMC) by activating Notch3 signaling pathway. However, the mechanisms underpinning S1P-mediated induction of PASMC proliferation remain unclear. In this study, using biochemical and molecular biology approaches, RNA-interference and gene expression analyses, 5'-Ethynyl-2'-deoxyuridine (EdU) incorporation assay and 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, we demonstrated that S1P promoted the activation of STAT3 through sphingosine-1-phosphate receptor 2 (S1PR2), and subsequently upregulated the expression of the microRNA miR-135b, which further reduced the expression of E3 ubiquitin ligase β-transduction repeat-containing protein (β-TrCP) and led to a reduction in YAP ubiquitinated degradation in PASMC. YAP is the core effector of Hippo pathway and mediates the expression of particular genes. The accumulation of YAP further increased the expression and activation of Notch3, and ultimately promoted the proliferation of PASMC. In addition, we showed that pre-blocking S1PR2, prior silencing STAT3, miR-135b or YAP, and prior inhibition of Notch3 all attenuated S1P-induced PASMC proliferation. Taken together, our study indicates that S1P stimulates PASMC proliferation by activation of S1PR2/STAT3/miR-135b/β-TrCP/YAP/Notch3 pathway, and our data suggest that targeting this cascade might have potential value in ameliorating PASMC hyperproliferation and benefit PAH.