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February 6, 2026

TRIB2 promotes pulmonary artery smooth muscle cell proliferation in pulmonary hypertension through SERCA2 ubiquitination

Key Points

To explore how TRIB2 regulates pulmonary artery smooth muscle cell proliferation in the context of pulmonary hypertension.
Utilized PDGF-BB-stimulated human PASMC and various animal models of pulmonary hypertension.
Employed TRIB2 knockdown and overexpression techniques using siRNA and plasmids.
Performed cellular proliferation and migration assays to assess the effects of TRIB2 modulation.
Analyzed protein interactions and ubiquitination via co-immunoprecipitation and immunofluorescence.
TRIB2 was found to be significantly upregulated in pulmonary hypertension models.
Knockdown of TRIB2 led to decreased PASMC proliferation and migration.
TRIB2 was shown to promote SERCA2 ubiquitination, contributing to ER stress and activation of related signaling pathways.
In vivo TRIB2 knockdown improved pulmonary vascular remodeling and hemodynamic issues.

Abstract

Abstract Background Pulmonary hypertension (PH) is a cardiovascular disorder characterized by pulmonary vascular remodeling (PVR) and elevated pulmonary arterial pressure. The hyperproliferation of pulmonary artery smooth muscle cell (PASMC) serves as a pivotal driver in PVR. Tribbles homolog 2 (TRIB2), a pseudokinase protein, primarily regulates cell proliferation through its scaffold or adaptor effect on promoting the degradation of target proteins by E3 ligase-dependent ubiquitination and regulating mitogen-activated protein kinase (MAPK) and protein kinase B (AKT) signaling pathways. However, its role in PH-associated PASMC proliferation remains unclear. Purpose To investigate TRIB2's regulatory mechanism in PASMC proliferation during PH pathogenesis. Methods Platelet-derived growth factor-BB (PDGF-BB)-stimulated human primary PASMC, hypoxia/SU5416-induced PH mice, and monocrotaline-treated PH rats models were employed in this experiment. TRIB2 knockdown and overexpression were modulated using small interfering RNA (siRNA) and plasmid. Ubiquitination and protein interactions were analyzed by co-immunoprecipitation (Co-IP). Cell proliferation was assessed via CCK-8 and EdU assays and cell migration was detected by Transwell and wound healing assays. TRIB2 knockdown in vivo was achieved using AAV-mediated short hairpin RNA (shRNA) delivery. PVR was evaluated through pathological and hemodynamic measurements. Results Transcriptomic analysis identified that TRIB2 was significantly upregulated in pH, and this upregulation was confirmed in both the lung tissues of rodent PH models and PDGF-BB-stimulated PASMC. TRIB2 knockdown attenuated PASMC proliferation and migration. CoIP and immunofluorescence staining revealed that TRIB2 interacted with sarco endoplasmic reticulum calcium adenosine triphosphatase 2 (SERCA2) and colocalized in cells. TRIB2 promoted SERCA2 ubiquitination via Smad ubiquitination regulatory factor 1 (Smurf1). Subsequent SERCA2 degradation induced endoplasmic reticulum (ER) stress and activated associated inositol-requiring enzyme 1α (IRE1α)-X-box binding protein 1s (XBP1s) signaling pathway, while 4-PBA, an ER stress inhibitor, attenuated the pathway activation caused by silencing SERCA2. SERCA2 silencing partially rescued TRIB2 knockdown-induced suppression of PASMC proliferation and migration, while IRE1α-XBP1s pathway inhibitor 4μ8c reversed SERCA2 knockdown-mediated cell proliferation and migration. Additionally, TRIB2 knockdown in vivo ameliorated PVR and pulmonary hemodynamic abnormalities. Conclusion TRIB2 promotes PASMC proliferation through Smurf1-mediated SERCA2 ubiquitination, ultimately leading to PVR. Targeting TRIB2 represents a potential therapeutic strategy for PH.

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