DDIT3 Promotes Starvation-Induced Autophagy via ER Stress in Vero Cells

Vero cells in high-density vaccine cultures often face nutrient starvation, especially in suspension-adapted Vero cells. Previous studies showed that serum starvation dramatically enhances autophagy and mitophagy in suspension-adapted Vero cells. Transcriptomic profiling also revealed significant upregulation of DDIT3, a marker of endoplasmic reticulum stress (ERS), in suspension-adapted Vero cells compared to adherent cells. To investigate the functional role of DDIT3, an Earle's Balanced Salt Solution (EBSS)-induced starvation model was established in adherent Vero cells, recapitulating key autophagy and ER stress responses observed under suspension conditions. The genetic silencing of DDIT3 by shRNA attenuated autophagy, as evidenced by a reduced LC3-II/LC3-I ratio and impaired autophagosome-lysosome activity. Notably, DDIT3 knockdown enhanced cell proliferation and increased the yield of H1N1 influenza virus under nutrient-deprived conditions. Collectively, these results suggest that DDIT3 may serve as a critical regulator linking ER stress to autophagy in Vero cells, and that the suppression of DDIT3 may represent a promising strategy for developing autophagy-resistant Vero cell lines suitable for high-density suspension culture in vaccine production.