CD8 Binding of MHC-Peptide Complexes in cis or trans Regulates CD8+ T-cell Responses.
Liu YLudwig Institute for Cancer Research, University of Lausanne, and Department of Oncology, University Hospital of Lausanne, 1009, Lausanne, Switzerland.
Cuendet MALudwig Institute for Cancer Research, University of Lausanne, and Department of Oncology, University Hospital of Lausanne, 1009, Lausanne, Switzerland; Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland; Department of Physiology and Biophysics, Weill Cornell Medicine, New York, USA.
Goffin LLudwig Institute for Cancer Research, University of Lausanne, and Department of Oncology, University Hospital of Lausanne, 1009, Lausanne, Switzerland.
Šachl RDepartment of Biophysical Chemistry, J. Heyrovsky Institute of Physical Chemistry of the Czech Academy of Sciences, 18223 Prague, Czech Republic.
Cebecauer MDepartment of Biophysical Chemistry, J. Heyrovsky Institute of Physical Chemistry of the Czech Academy of Sciences, 18223 Prague, Czech Republic.
Cariolato LLudwig Institute for Cancer Research, University of Lausanne, and Department of Oncology, University Hospital of Lausanne, 1009, Lausanne, Switzerland.
Guillaume PLudwig Institute for Cancer Research, University of Lausanne, and Department of Oncology, University Hospital of Lausanne, 1009, Lausanne, Switzerland.
Reichenbach PLudwig Institute for Cancer Research, University of Lausanne, and Department of Oncology, University Hospital of Lausanne, 1009, Lausanne, Switzerland.
Irving MLudwig Institute for Cancer Research, University of Lausanne, and Department of Oncology, University Hospital of Lausanne, 1009, Lausanne, Switzerland.
Coukos GLudwig Institute for Cancer Research, University of Lausanne, and Department of Oncology, University Hospital of Lausanne, 1009, Lausanne, Switzerland.
Luescher IFLudwig Institute for Cancer Research, University of Lausanne, and Department of Oncology, University Hospital of Lausanne, 1009, Lausanne, Switzerland. Electronic address: immanuel.luescher@unil.ch.
English
The coreceptor CD8αβ can greatly promote activation of T cells by strengthening T-cell receptor (TCR) binding to cognate peptide-MHC complexes (pMHC) on antigen presenting cells and by bringing p56Lck to TCR/CD3. Here, we demonstrate that CD8 can also bind to pMHC on the T cell (in cis) and that this inhibits their activation. Using molecular modeling, fluorescence resonance energy transfer experiments on living cells, biochemical and mutational analysis, we show that CD8 binding to pMHC in cis involves a different docking mode and is regulated by posttranslational modifications including a membrane-distal interchain disulfide bond and negatively charged O-linked glycans near positively charged sequences on the CD8β stalk. These modifications distort the stalk, thus favoring CD8 binding to pMHC in cis. Differential binding of CD8 to pMHC in cis or trans is a means to regulate CD8+ T-cell responses and provides new translational opportunities.