Role of Dynamin 2 in mitochondrial fission and cell cycle regulation in pulmonary arterial hypertension: Dysregulation of a miR-124-3p-STAT3-DNM2-DRP1-RGCC pathway links fission and cell proliferation

Background: Mitochondrial fission is mediated by Dynamin-related protein 1 (DRP1). Excessive mitochondrial fission supports rapid cell cycle progression in hyperproliferative cells by synchronizing nuclear and mitochondrial division through a process called mitotic fission. However, DRP1 alone appears insufficient to complete the terminal phase of fission and the mechanism linking fission to cell cycle progression remain unclear. In this study, we propose that Dynamin 2 (DNM2) interacts with DRP1 to regulate mitochondrial fission and cell cycle progression. Here we show that DNM2 is upregulated in pulmonary arterial smooth muscle cells in human and rodent pulmonary arterial hypertension (PAH PASMC), contributing to disease pathophysiology.

Methods: Mitochondrial morphology, protein colocalization and fission were evaluated STED microscopy, protein interactions were examined by immunoprecipitation and transcriptomic changes by RNA-seq. DNM2 expression was measured in PASMC and lungs from PAH patients and rat models of PH-induced by monocrotaline (MCT) or SU5416/hypoxia (Su/Hx). The effects of silencing DNM2 on cell proliferation, cell cycle progression and apoptosis were measured by flow cytometry. Publicly available datasets were analyzed for single-cell RNA-Seq. In vivo siRNA against DNM2 was nebulized to MCT- and Su/Hx-PH rats and therapeutic effects were evaluated by cardiac catheterization and histological analyses.

Results: DNM2 expression is increased PAH PASMC. Mechanistically, DNM2 interacts with DRP1 through its GTPase domain, facilitating Drp1 recruitment to mitochondria and promoting fission. Silencing DNM2 supresses fission and cell proliferation and promotes apoptosis. Additionally, siDNM2 induces G1/G0 cell cycle arrest by decreasing the expression of Regulator of Cell Cycle (RGCC), leading to downstream modulation of CDK4, Cyclin D1 and p27kip1. In contrast, augmenting DNM2 in normal PASMC increases fission and drives proliferation. The elevated DNM2 observed in PAH is mediated by reduced miR-124-3p levels and STAT3 activation. Together these findings suggest a miR-124-3p-STAT3-DNM2-DRP1-RGCC axis that promotes mitotic fission is upregulated in multiple cell types in PAH lungs including PASMC, airway epithelium, endothelial cells, fibroblasts, and macrophages. Nebulized siDNM2 effectively regresses established PAH in rat models of both sexes.

Conclusion: DNM2 functions as a mediator in the terminal steps of DRP1-dependent mitochondrial fission and represents a promising therapeutic target in PAH.