Lactate-associated regulation of PTPN1 modulates TCR and IL-2 signaling to suppress T cell functions

The Warburg effect in cancer contributes to lactate accumulation and acidification of the tumor microenvironment, which suppresses T cell effector functions. While the suppressive effects of lactate-induced acidification are well-recognized, the specific molecular “sensors” that transduce this extracellular acidic stress into intracellular signaling failure remain inadequately defined. This study aims to identify the genetic regulators and biochemical mechanisms that preserve T cell function under lactate-rich conditions. We performed a genome-wide CRISPR knockout screen in human Jurkat T cells using the Brunello pooled library to identify genes required for maintaining T cell activation marker CD25 expression under lactate stress. Following the identification of PTPN1 (Protein Tyrosine Phosphatase Non-Receptor Type 1), we assessed oxidized PTP active-site signals by flow cytometry. To elucidate the molecular mechanism, we employed site-directed mutagenesis (C215A) to evaluate the contribution of PTPN1 to TCR-proximal and cytokine-mediated signaling under lactate stress. Our unbiased screen identified PTPN1 as a primary negative regulator of CD25 in response to lactate. Lactate exposure reduced oxidized PTP active-site signals and was associated with changes in intracellular redox balance, while PTPN1 depletion and reconstitution experiments implicated PTPN1 and its Cys215 residue in this redox-associated response. PTPN1 depletion preserved phosphorylation of key TCR-proximal and IL-2/STAT5 signaling components, including Lck, ZAP70, and STAT5, under lactate stress. Consistently, lactate suppressed TCR-mediated activation and IL-2/STAT5 responsiveness. Notably, reconstitution with PTPN1 C215A mutant or pharmacological inhibition of PTPN1 successfully restored signaling transduction and effector functions in T cells despite severe acidic stress. Our study identify PTPN1 as an important regulator of T-cell signaling under lactate stress and implicate Cys215 in the stress-associated redox response. These findings link lactate-associated changes in cellular redox balance to PTPN1-dependent regulation of TCR–IL-2/STAT5 signaling and nominate PTPN1 as a potential therapeutic target for preserving T-cell function in lactate-rich tumor microenvironments.