Myosin Ii Facilitates Ligand Discrimination During T Cell Activation

The importance of T cell receptor (TCR) mechano-transduction in T cell signaling is highlighted by recent studies showing that T cells can sense and generate force through the interaction between the TCR and peptide major histocompatibility complex (pMHC). In this study, we investigate the multifaceted role of non-muscle myosin II in TCR mechano-transduction, focusing on ligand discrimination. Using structure illumination microscopy (SIM), we analyze actomyosin arc structures at the immunological synapse with surfaces coated with either strong agonist OVA:H2Kb or weak agonist G4:H2Kb for OT1 T cells. We find that stimulation of T cells with weak agonist resulted disorganized actomyosin arcs, while strong agonist coated stimulation resulted in highly organized actomyosin arcs. As expected, this ligand-dependent actomyosin arc organization is disrupted upon inhibition of myosin II using para-nitro-blebbistatin. Consistent with previous studies, the frequencies of T-APC conjugation as well as the phosphorylation level of early signaling molecules like Src, Zap-70, and LAT are attenuated upon myosin II inhibition. These data highlight the importance of actomyosin activity in T cell activation triggered by a highly potent ligand. Together, our results suggest an important role for myosin II in TCR mechano-transduction in ligand discrimination which highlights the biophysical connection between intracellular to membrane-associated cellular components.