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The αβ T Cell Receptor Is an Anisotropic Mechanosensor

2009; Elsevier BV; Volume: 284; Issue: 45 Linguagem: Inglês

10.1074/jbc.m109.052712

1083-351X

Sun Taek Kim, Koh Takeuchi, Zhenyu Sun, Maki Touma, Carlos E. Castro, Amr Fahmy, Matthew J. Lang, Gerhard Wagner, Ellis L. Reinherz,

Immune Cell Function and Interaction

Thymus-derived lymphocytes protect mammalian hosts against virus- or cancer-related cellular alterations through immune surveillance, eliminating diseased cells. In this process, T cell receptors (TCRs) mediate both recognition and T cell activation via their dimeric αβ, CD3ϵγ, CD3ϵδ, and CD3ζζ subunits using an unknown structural mechanism. Here, site-specific binding topology of anti-CD3 monoclonal antibodies (mAbs) and dynamic TCR quaternary change provide key clues. Agonist mAbs footprint to the membrane distal CD3ϵ lobe that they approach diagonally, adjacent to the lever-like Cβ FG loop that facilitates antigen (pMHC)-triggered activation. In contrast, a non-agonist mAb binds to the cleft between CD3ϵ and CD3γ in a perpendicular mode and is stimulatory only subsequent to an external tangential but not a normal force (∼50 piconewtons) applied via optical tweezers. Specific pMHC but not irrelevant pMHC activates a T cell upon application of a similar force. These findings suggest that the TCR is an anisotropic mechanosensor, converting mechanical energy into a biochemical signal upon specific pMHC ligation during immune surveillance. Activating anti-CD3 mAbs mimic this force via their intrinsic binding mode. A common TCR quaternary change rather than conformational alterations can better facilitate structural signal initiation, given the vast array of TCRs and their specific pMHC ligands. Thymus-derived lymphocytes protect mammalian hosts against virus- or cancer-related cellular alterations through immune surveillance, eliminating diseased cells. In this process, T cell receptors (TCRs) mediate both recognition and T cell activation via their dimeric αβ, CD3ϵγ, CD3ϵδ, and CD3ζζ subunits using an unknown structural mechanism. Here, site-specific binding topology of anti-CD3 monoclonal antibodies (mAbs) and dynamic TCR quaternary change provide key clues. Agonist mAbs footprint to the membrane distal CD3ϵ lobe that they approach diagonally, adjacent to the lever-like Cβ FG loop that facilitates antigen (pMHC)-triggered activation. In contrast, a non-agonist mAb binds to the cleft between CD3ϵ and CD3γ in a perpendicular mode and is stimulatory only subsequent to an external tangential but not a normal force (∼50 piconewtons) applied via optical tweezers. Specific pMHC but not irrelevant pMHC activates a T cell upon application of a similar force. These findings suggest that the TCR is an anisotropic mechanosensor, converting mechanical energy into a biochemical signal upon specific pMHC ligation during immune surveillance. Activating anti-CD3 mAbs mimic this force via their intrinsic binding mode. A common TCR quaternary change rather than conformational alterations can better facilitate structural signal initiation, given the vast array of TCRs and their specific pMHC ligands.