title: Force-dependent transition in the T-cell receptor β-subunit allosterically regulates peptide discrimination and pMHC bond lifetime.
abstract: The αβ T-cell receptor (TCR) on each T lymphocyte mediates exquisite specificity for a particular foreign peptide bound to a major histocompatibility complex molecule (pMHC) displayed on the surface of altered cells. This recognition stimulates protection in the mammalian host against intracellular pathogens, including viruses, and involves piconewton forces that accompany pMHC ligation. Physical forces are generated by T-lymphocyte movement during immune surveillance as well as by cytoskeletal rearrangements at the immunological synapse following cessation of cell migration. The mechanistic explanation for how TCRs distinguish between foreign and self-peptides bound to a given MHC molecule is unclear: peptide residues themselves comprise few of the TCR contacts on the pMHC, and pathogen-derived peptides are scant among myriad self-peptides bound to the same MHC class arrayed on infected cells. Using optical tweezers and DNA tether spacer technology that permit piconewton force application and nanometer scale precision, we have determined how bioforces relate to self versus nonself discrimination. Single-molecule analyses involving isolated αβ-heterodimers as well as complete TCR complexes on T lymphocytes reveal that the FG loop in the β-subunit constant domain allosterically controls both the variable domain module's catch bond lifetime and peptide discrimination via force-driven conformational transition. In contrast to integrins, the TCR interrogates its ligand via a strong force-loaded state with release through a weakened, extended state. Our work defines a key element of TCR mechanotransduction, explaining why the FG loop structure evolved for adaptive immunity in αβ but not γδTCRs or immunoglobulins.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235;
authors.forename: Dibyendu Kumar
authors.initials: DK
authors.lastname: Das
authors.affiliation: Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235;
authors.forename: Yinnian
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115;
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Mallis
authors.affiliation: School of Life Sciences, University of Science and Technology of China, Hefei 230027, People's Republic of China;
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Medical Oncology, Laboratory of Immunobiology, Dana-Farber Cancer Institute, Boston, MA 02115; Department of Medicine, Harvard Medical School, Boston, MA 02115; and.
authors.forename: Derin B
authors.initials: DB
authors.lastname: Keskin
authors.affiliation: Department of Medical Oncology, Laboratory of Immunobiology, Dana-Farber Cancer Institute, Boston, MA 02115;
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Hussey
authors.affiliation: Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235;
authors.forename: Sonia K
authors.initials: SK
authors.lastname: Brady
authors.affiliation: School of Life Sciences, University of Science and Technology of China, Hefei 230027, People's Republic of China; Department of Medical Oncology, Laboratory of Immunobiology, Dana-Farber Cancer Institute, Boston, MA 02115;
authors.forename: Jia-Huai
authors.initials: JH
authors.lastname: Wang
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115; matt.lang@vanderbilt.edu ellis_reinherz@dfci.harvard.edu gerhard_wagner@hms.harvard.edu.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wagner
authors.affiliation: Department of Medical Oncology, Laboratory of Immunobiology, Dana-Farber Cancer Institute, Boston, MA 02115; Department of Medicine, Harvard Medical School, Boston, MA 02115; and matt.lang@vanderbilt.edu ellis_reinherz@dfci.harvard.edu gerhard_wagner@hms.harvard.edu.
authors.forename: Ellis L
authors.initials: EL
authors.lastname: Reinherz
authors.affiliation: Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235; Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37235 matt.lang@vanderbilt.edu ellis_reinherz@dfci.harvard.edu gerhard_wagner@hms.harvard.edu.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Lang
mesh_terms: D000595:Amino Acid Sequence; D008285:Major Histocompatibility Complex; D008958:Models, Molecular; D052898:Optical Tweezers; D010455:Peptides / Q000737:chemistry*; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid
chemical_list: D010455:Peptides; D016693:Receptors, Antigen, T-Cell, alpha-beta
keywords: T-cell receptor; catch bond; mechanosensor; optical tweezers; peptide discrimination