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

Abnormal syncytialization of cytotrophoblast (CTB) cells is known to be associated with preeclampsia (PE), however, the underlying molecular mechanisms remain elusive.

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.

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.