Targeting TMED4 enhances CD8+ T cell function and CAR T cell efficacy in solid tumors through the IRE1α-autophagy axis.

Endoplasmic reticulum stress (ERS) and autophagy regulate tumor-infiltrating T cell function and exhaustion, but the underlying mechanisms remain unclear. Here, we identified the ERS-related transmembrane protein TMED4 (transmembrane emp24 domain-containing 4) as a critical regulator of CD8+ T cell antitumor immunity. Tmed4 deletion in T cells enhanced antitumor responses by promoting CD8+ T proliferation, infiltration, and killing capacity, while reducing terminal exhaustion. Mechanistically, Tmed4 deficiency hyperactivated the inositol-requiring enzyme 1α (IRE1α)-X-box binding protein 1 (XBP1) axis and induced autophagy flux in an IRE1α-dependent manner. Genetic deletion of Ern1 (IRE1α) or Becn1 (Beclin1) impaired the antitumor effects of Tmed4 deficiency, underscoring the role of ERS and autophagy in CD8+ T cell function. Moreover, Tmed4-deficient chimeric antigen receptor T cells (CAR T cells) displayed improved antitumor immunity. Pharmacological inhibition of Tmed4 using antisense oligonucleotide also enhanced CD8+ T cell-mediated tumor control. In summary, our study reveals that TMED4 governs CD8+ T cell effector function and limits terminal exhaustion through IRE1α-driven autophagy, establishing TMED4 as a promising immunotherapeutic target for improving CAR T cell efficacy.