Regulation of trophoblast fusion dysfunction in preeclampsia by the NCK1/EIF3D/PPARG axis

Background: Abnormal syncytialization of cytotrophoblast (CTB) cells is known to be associated with preeclampsia (PE), however, the underlying molecular mechanisms remain elusive. Results: In this study, proteomic analysis of placental tissues was performed to identify proteins involved in PE pathogenesis. NCK Adaptor Protein 1 (NCK1) was found to be downregulated in placental tissues from patients with early-onset PE. In vitro functional assays revealed that NCK1 was markedly increased during spontaneous syncytialization of CTB cells. NCK1 overexpression alleviated hypoxia-induced defects in CTB cell fusion. Mechanistically, NCK1 upregulated both the expression and stability of Peroxisome Proliferator-Activated Receptor Gamma (PPARG), accompanied by increased m6A modification of its mRNA. Overexpression of PPARG significantly rescued hypoxia-induced syncytialization impairment, whereas PPARG deficiency abolished the promotive effects of NCK1 on CTB syncytialization. Additionally, phosphorylation of Eukaryotic Translation Initiation Factor 3 Subunit (EIF3D) was significantly increased during spontaneous syncytialization, and NCK1 overexpression partially reversed hypoxia-induced suppression of EIF3D phosphorylation. EIF3D knockdown significantly reduced m6A levels on PPARG mRNA, likely due to impaired NCK1-mediated suppression of Alpha-Ketoglutarate-Dependent Homolog 5 (ALKBH5), an m6A demethylase. Furthermore, NCK1 enhanced EIF3D phosphorylation by inhibiting its O-GlcNAcylation. Conclusions: Our findings demonstrate that NCK1 stabilizes PPARG by modulating the crosstalk between O-GlcNAcylation and phosphorylation of EIF3D, thereby restoring hypoxia-impaired syncytialization in CTB cells. This study identifies the NCK1/EIF3D/PPARG axis as a molecular pathway potentially relevant to trophoblast fusion dysfunction in PE.