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Background <p>Fli-1, a member of the ETS transcription factor family, has been implicated in multiple inflammatory and immune-related disorders, including sepsis, lupus, Alzheimer’s disease, and post-traumatic stress disorder (PTSD). Recent studies further suggest a critical role for Fli-1 in CD4⁺ T cells in graft-versus-host disease, systemic sclerosis, and PTSD; however, its precise function and regulation during inflammatory CD4⁺ T cell responses remain incompletely understood.</p> Methods <p>Wild-type and CD4⁺ T cell–specific Fli-1 knockout mice were administered LPS via intraperitoneal injection. Survival rates and splenic T cell activation were subsequently assessed. In vitro, cultured Jurkat and HEK cells were utilized to investigate the STUB1/Fli-1–related signaling pathway.</p> Results <p>Here, we demonstrate that Fli-1 expression is markedly upregulated in splenic CD4⁺ T cells in a murine model of endotoxemia. CD4⁺ T cell-specific deletion of Fli-1 significantly improves survival and attenuates splenic CD4⁺ T cell activation. Mechanistically, we identify STUB1 as a novel E3 ubiquitin ligase for Fli-1 that promotes K27-linked ubiquitination and proteasomal degradation under basal conditions. Inflammatory stimulation disrupts the STUB1/HSP70 interaction, reducing STUB1-mediated ubiquitination and enhancing Fli-1 protein stability. Consistent with these findings, Fli-1 knockout reduces TNFα, IFNγ, and IL-10 expression, whereas STUB1 knockout enhances their expression in Jurkat cells. Gain- and loss-of-function studies further reveal that Fli-1 modulates NFκB signaling, a key pathway in T cell activation.</p> Conclusions <p>Collectively, our results identify the STUB1/Fli-1 axis as a previously unrecognized regulator of CD4⁺ T cell function and a potential therapeutic target for inflammatory diseases.</p>

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STUB1-mediated ubiquitination regulates Fli-1 stability and CD4⁺T cell activation during inflammation

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月26日

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  • Pengfei Li,
  • Liu Liu,
  • Yan Wu,
  • Meng Liu,
  • Maria Trojanowska,
  • Hongkuan Fan

摘要

Background

Fli-1, a member of the ETS transcription factor family, has been implicated in multiple inflammatory and immune-related disorders, including sepsis, lupus, Alzheimer’s disease, and post-traumatic stress disorder (PTSD). Recent studies further suggest a critical role for Fli-1 in CD4⁺ T cells in graft-versus-host disease, systemic sclerosis, and PTSD; however, its precise function and regulation during inflammatory CD4⁺ T cell responses remain incompletely understood.

Methods

Wild-type and CD4⁺ T cell–specific Fli-1 knockout mice were administered LPS via intraperitoneal injection. Survival rates and splenic T cell activation were subsequently assessed. In vitro, cultured Jurkat and HEK cells were utilized to investigate the STUB1/Fli-1–related signaling pathway.

Results

Here, we demonstrate that Fli-1 expression is markedly upregulated in splenic CD4⁺ T cells in a murine model of endotoxemia. CD4⁺ T cell-specific deletion of Fli-1 significantly improves survival and attenuates splenic CD4⁺ T cell activation. Mechanistically, we identify STUB1 as a novel E3 ubiquitin ligase for Fli-1 that promotes K27-linked ubiquitination and proteasomal degradation under basal conditions. Inflammatory stimulation disrupts the STUB1/HSP70 interaction, reducing STUB1-mediated ubiquitination and enhancing Fli-1 protein stability. Consistent with these findings, Fli-1 knockout reduces TNFα, IFNγ, and IL-10 expression, whereas STUB1 knockout enhances their expression in Jurkat cells. Gain- and loss-of-function studies further reveal that Fli-1 modulates NFκB signaling, a key pathway in T cell activation.

Conclusions

Collectively, our results identify the STUB1/Fli-1 axis as a previously unrecognized regulator of CD4⁺ T cell function and a potential therapeutic target for inflammatory diseases.