The kinase LCK and CD4/CD8 co-receptors are crucial components of the T cell antigen receptor (TCR) signaling machinery, leading to key T cell fate decisions. Despite decades of research, the roles of CD4-LCK and CD8-LCK interactions in TCR triggering in vivo remain unknown. In this study, we created animal models expressing endogenous levels of modified LCK to resolve whether and how co-receptor-bound LCK drives TCR signaling. We demonstrated that the role of LCK depends on the co-receptor to which it is bound. The CD8-bound LCK is largely dispensable for antiviral and antitumor activity of cytotoxic T cells in mice; however, it facilitates CD8+ T cell responses to suboptimal antigens in a kinase-dependent manner. By contrast, the CD4-bound LCK is required for efficient development and function of helper T cells via a kinase-independent stabilization of surface CD4. Overall, our findings reveal the role of co-receptor-bound LCK in T cell biology, show that CD4- and CD8-bound LCK drive T cell development and effector immune responses using qualitatively different mechanisms and identify the co-receptor-LCK interactions as promising targets for immunomodulation.

• MeSH
• CD4 Antigens MeSH
• CD8 Antigens metabolism   MeSH
• T-Lymphocytes, Cytotoxic * metabolism   MeSH
• Mice MeSH
• Receptors, Antigen, T-Cell metabolism   MeSH
• Signal Transduction MeSH
• Lymphocyte Specific Protein Tyrosine Kinase p56(lck) * metabolism   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• CD4 Antigens MeSH
• CD8 Antigens MeSH
• Receptors, Antigen, T-Cell MeSH
• Lymphocyte Specific Protein Tyrosine Kinase p56(lck) * MeSH