STAP-1-derived peptide suppresses TCR-mediated T cell activation and ameliorates immune diseases by inhibiting STAP-1-LCK binding.

Signal-transducing adaptor protein-1 (STAP-1) is an adaptor protein specifically expressed in immune cells, such as T cells. We previously demonstrated that STAP-1 positively upregulates T cell receptor (TCR)-mediated T cell activation by interacting with LCK and phospholipase C-γ1 and affecting autoimmune demyelination and airway inflammation. In this study, we aimed to generate a new STAP-1-derived peptide, iSP1, to inhibit the STAP-1-LCK interaction. We also analyzed its function in vitro and in vivo. iSP1 successfully interfered with STAP-1-LCK binding and suppressed TCR-mediated signal transduction, interleukin-2 production, and human and murine T cell proliferation. Additionally, iSP1 prevented the progression of experimental autoimmune encephalomyelitis by inhibiting Th1 and Th17 cell infiltration. Our findings suggest iSP1 as a new therapeutic immunomodulatory agent for T cell-mediated autoimmune diseases.