iProXProteomicsBing WuMus Musculushttp://www.iprox.org/page/project.html?id=IPX0014657000bingwu@whu.edu.cnWuhan UniversityiProXfalseRAS P21 Protein Activator 3 constrains Type I Immunity by limiting HCK kinase-mediated STAT4 phosphorylationType I immunity, mediated by IFN-γ, is essential for combating intracellular pathogens but also drives inflammatory diseases. While the IL-12-STAT4 pathway that promotes IFN-γ production is well-established, the intrinsic negative regulators remain poorly defined. We identify RASA3 as a critical negative regulator whose expression is downregulated during Th1 cell differentiation. Its T cell-specific ablation amplified Th1/Tc1 responses, enhancing clearance of Listeria monocytogenes but exacerbating allergic contact dermatitis. Mechanistically, RASA3 constrains IFN-γ production by repressing the translation of the hematopoietic cell kinase (HCK) via ribosomal protein RPL36A. We further identify HCK as a novel direct kinase for STAT4, which binds to and phosphorylates it at Tyr693 residue. Additionally, the RASA3-HCK axis is conserved in human Th1 cells. Our work establishes RASA3 as a fundamental brake on type I immunity and a previously unrecognized role for HCK in STAT4 phosphorylation, presenting new potential targets for modulating Th1/Tc1-driven immune responses.Fri Dec 12 00:00:00 GMT 2025PXD07197810090