Remarkably low affinity of CD4/peptide-major histocompatibility complex class II protein interactions
(2016) In Proceedings of the National Academy of Sciences of the United States of America 113(20). p.5682-5687- Abstract
The αβ T-cell coreceptor CD4 enhances immune responses more than 1 million-fold in some assays, and yet the affinity of CD4 for its ligand, peptide-major histocompatibility class II (pMHC II) on antigen-presenting cells, is so weak that it was previously unquantifiable. Here, we report that a soluble form of CD4 failed to bind detectably to pMHC II in surface plasmon resonance-based assays, establishing a new upper limit for the solution affinity at 2.5 mM. However, when presented multivalently on magnetic beads, soluble CD4 bound pMHC II-expressing B cells, confirming that it is active and allowing mapping of the native coreceptor binding site on pMHC II. Whereas binding was undetectable in solution, the affinity of the CD4/pMHC II... (More)
The αβ T-cell coreceptor CD4 enhances immune responses more than 1 million-fold in some assays, and yet the affinity of CD4 for its ligand, peptide-major histocompatibility class II (pMHC II) on antigen-presenting cells, is so weak that it was previously unquantifiable. Here, we report that a soluble form of CD4 failed to bind detectably to pMHC II in surface plasmon resonance-based assays, establishing a new upper limit for the solution affinity at 2.5 mM. However, when presented multivalently on magnetic beads, soluble CD4 bound pMHC II-expressing B cells, confirming that it is active and allowing mapping of the native coreceptor binding site on pMHC II. Whereas binding was undetectable in solution, the affinity of the CD4/pMHC II interaction could be measured in 2D using CD4- and adhesion molecule-functionalized, supported lipid bilayers, yielding a 2D Kd of ∼5,000 molecules/μm2. This value is two to three orders of magnitude higher than previously measured 2D Kd values for interacting leukocyte surface proteins. Calculations indicated, however, that CD4/pMHC II binding would increase rates of T-cell receptor (TCR) complex phosphorylation by threefold via the recruitment of Lck, with only a small, 2-20% increase in the effective affinity of the TCR for pMHC II. The affinity of CD4/pMHC II therefore seems to be set at a value that increases T-cell sensitivity by enhancing phosphorylation, without compromising ligand discrimination.
(Less)
- author
- organization
- publishing date
- 2016-05-17
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Adhesion, Binding equilibrium and kinetics, Protein interactions, T-cell activation, TCR phosphorylation
- in
- Proceedings of the National Academy of Sciences of the United States of America
- volume
- 113
- issue
- 20
- pages
- 6 pages
- publisher
- National Academy of Sciences
- external identifiers
-
- scopus:84969786276
- pmid:27114505
- wos:000375977600057
- ISSN
- 0027-8424
- DOI
- 10.1073/pnas.1513918113
- project
- Intermolecular interactions between molecules on the surface of cells
- language
- English
- LU publication?
- yes
- id
- cb93631a-5054-4a9b-af3b-9edf38f108cf
- date added to LUP
- 2017-01-30 11:17:22
- date last changed
- 2024-05-31 22:24:53
@article{cb93631a-5054-4a9b-af3b-9edf38f108cf,
abstract = {{<p>The αβ T-cell coreceptor CD4 enhances immune responses more than 1 million-fold in some assays, and yet the affinity of CD4 for its ligand, peptide-major histocompatibility class II (pMHC II) on antigen-presenting cells, is so weak that it was previously unquantifiable. Here, we report that a soluble form of CD4 failed to bind detectably to pMHC II in surface plasmon resonance-based assays, establishing a new upper limit for the solution affinity at 2.5 mM. However, when presented multivalently on magnetic beads, soluble CD4 bound pMHC II-expressing B cells, confirming that it is active and allowing mapping of the native coreceptor binding site on pMHC II. Whereas binding was undetectable in solution, the affinity of the CD4/pMHC II interaction could be measured in 2D using CD4- and adhesion molecule-functionalized, supported lipid bilayers, yielding a 2<sub>D</sub> Kd of ∼5,000 molecules/μm<sup>2</sup>. This value is two to three orders of magnitude higher than previously measured 2D K<sub>d</sub> values for interacting leukocyte surface proteins. Calculations indicated, however, that CD4/pMHC II binding would increase rates of T-cell receptor (TCR) complex phosphorylation by threefold via the recruitment of Lck, with only a small, 2-20% increase in the effective affinity of the TCR for pMHC II. The affinity of CD4/pMHC II therefore seems to be set at a value that increases T-cell sensitivity by enhancing phosphorylation, without compromising ligand discrimination.</p>}},
author = {{Jönsson, Peter and Southcombe, Jennifer H. and Mafalda Santos, Ana and Huo, Jiandong and Fernandes, Ricardo A. and McColl, James and Lever, Melissa and Evans, Edward J. and Hudson, Alexander and Chang, Veronica T. and Hanke, Tomáš and Godkin, Andrew and Dunne, Paul D. and Horrocks, Mathew H. and Palayret, Matthieu and Screaton, Gavin R. and Petersen, Jan and Rossjohn, Jamie and Fugger, Lars and Dushek, Omer and Xu, Xiao Ning and Davis, Simon J. and Klenerman, David}},
issn = {{0027-8424}},
keywords = {{Adhesion; Binding equilibrium and kinetics; Protein interactions; T-cell activation; TCR phosphorylation}},
language = {{eng}},
month = {{05}},
number = {{20}},
pages = {{5682--5687}},
publisher = {{National Academy of Sciences}},
series = {{Proceedings of the National Academy of Sciences of the United States of America}},
title = {{Remarkably low affinity of CD4/peptide-major histocompatibility complex class II protein interactions}},
url = {{http://dx.doi.org/10.1073/pnas.1513918113}},
doi = {{10.1073/pnas.1513918113}},
volume = {{113}},
year = {{2016}},
}