Hypoxia-induced TPC2 transcription and glycosylation aggravates pulmonary arterial hypertension by blocking autophagy flux.

Pulmonary arterial hypertension (PAH) is a serious medical condition that causes a failure in the right heart. Two-pore channel 2 (TPC2) is upregulated in PAH, but its roles in PAH remain largely unknown. Our investigation aims at the mechanisms by which TPC2 regulates PAH development. We established an experimental PAH rat model via monocrotaline administration. Human and rat pulmonary arterial smooth muscle cells (PASMCs) were treated hypoxia as in vitro cell PAH models. The thickness of pulmonary arterial wall and obstructive arteriopathy in rats were examined. Autophagy was detected through TEM, and Ca measurement and mRFP-GFP-LC3 transfection. The expression of α-SMA, LC3, p62, TPC2, HIF1α and STT3B were analyzed by qRT-PCR, western blot or IHC staining. The binding of HIF1α to TPC2 promoter was determined by ChIP-qPCR and EMSA assays. TPC2 glycosylation was evaluated by western blot. Transwell assay was applied to analyze cell migration. TPC2 expression was promoted and autophagy was inhibited in PAH rats and hypoxia-treated PASMCs. HIF1α directly bound to the promoter of TPC2, thus transcriptionally activating its expression in PAH rats and hypoxic PASMCs. Knockdown of TPC2 facilitated autophagic flux and repressed PASMC migration. STT3B enhanced TPC2 glycosylation in hypoxic PASMCs. Furthermore, Overexpression of TPC2 suppressed autophagic flux and promoted PASMC migration, but these effects were abrogated by STT3B knockdown or PNGase F, an eraser of N-linked glycans. Suppression of TPC2 enhanced autophagy and alleviated PAH in vivo. HIF1α-induced TPC2 transcription and subsequent STT3B-dependent TPC2 glycosylation inhibit autophagic flux and aggravate PAH. Our study suggests TCP2 as a potential therapeutic target for PAH.