Induction of proinflammatory cytokine release in macrophages by extracellular vesicle-delivered SARS-CoV-2 accessory protein ORF3a
Dr. Sin Yee Fung (Post-doctoral Fellow)
[Supervisor: Professor Dong-Yan Jin]

Although the COVID-19 pandemic has ended, many important questions about SARS-CoV-2 pathogenesis remain to be elucidated. In severe COVID-19, exacerbated proinflammatory cytokine release is often related to acute respiratory distress syndrome and associated with poor prognosis. Macrophages are thought to be major producers of proinflammatory cytokines. However, the relevance of proinflammatory cytokine release from macrophages to the life cycle of SARS-CoV-2 remains to be established. We hypothesized that certain secretory viral factors might be responsible for driving hyperinflammatory response in macrophages. Here, we identified viral ORF3a protein as a key player in proinflammatory cytokine release from macrophages. We identified the existence of ORF3a in extracellular vesicles (EVs) and confirmed its transfer to neighboring cells. Feeding phorbol-12-myristate-13-acetate-differentiated THP-1 cells with ORF3a EVs triggers proinflammatory cytokine release. Our findings highlighted ORF3a as a biomarker for novel diagnostic and therapeutic strategies to mitigate cytokine storm in severe COVID-19.

p38β-mediated BiP phosphorylation drives stemness and chemoresistance by suppressing UPR activation in hepatocellular carcinoma
Dr. Ianto Bosheng Huang (Post-doctoral Fellow)
[Supervisor: Professor Stephanie Ma]

Increasing evidence has demonstrated that tumor-initiating cells (TICs) contribute to tumor initiation and therapy resistance through dysregulation of kinase signaling. However, the intertwined networks of many kinases and their functional downstream targets are yet to be revealed and fully characterized in TICs. In this study, we identified the stress kinase p38β (MAPK11) as a key regulator of TIC maintenance and drug resistance in hepatocellular carcinoma (HCC). A kinome-wide screen in chemotherapy-enriched HCC spheroids revealed p38β as a non-redundant kinase dependency associated with stemness and chemoresistance. High p38β expression correlates with poor prognosis and aggressive clinical features in HCC patients. Mechanistically, p38β promotes phosphorylation of the ER chaperone BiP at threonine 648 (Thr648, T648), enhancing its association with the unfolded protein response (UPR) sensors PERK and IRE1-α. This modification suppresses UPR activation and reduces unfolded protein accumulation, thereby preserving ER proteostasis under chemotherapeutic stress. Functionally, p38β-driven BiP phosphorylation is essential for sustaining TIC phenotypes and conferring cisplatin (CDDP) resistance in vitro and in serial limiting dilution xenograft models. Pharmacological inhibition of BiP using HA15 restores UPR signaling and synergizes with CDDP to suppress patient-derived xenograft (PDX) and organoid (PDO) models. Together, these findings define a previously unrecognized p38β-BiP signaling axis that links ER stress buffering to stemness and chemoresistance, offering a promising therapeutic strategy to overcome treatment failure in HCC.

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