Abstract
Abs or their recombinant fragments against surface receptors of the Ig superfamily can induce or block the receptors' native function depending on whether they induce or prevent the assembly of signalosomes on their cytoplasmic tails. In this study, we introduce a novel paradigm based on the observation that a bispecific tandem single-chain variable region fragment ligand of CTLA-4 by itself converts this inhibitory receptor into an activating receptor for primary human T lymphocytes. This reversal of function results from increased recruitment of the serine/threonine phosphatase 2A to the cytoplasmic tail of CTLA-4, consistent with a role of this phosphatase in the regulation of CTLA-4 function, and assembly of a distinct signalosome that activates an lck-dependent signaling cascade and induces IL-2 production. Our data demonstrate that the cytoplasmic domain of CTLA-4 has an inherent plasticity for signaling that can be exploited therapeutically with recombinant ligands for this receptor.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Abatacept
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Adjuvants, Immunologic / metabolism
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Adjuvants, Immunologic / physiology*
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Antibodies, Bispecific / metabolism*
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Antibodies, Bispecific / pharmacology
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Antigens, CD
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Antigens, Differentiation / immunology
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Antigens, Differentiation / metabolism
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Antigens, Differentiation / physiology*
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Binding Sites, Antibody
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CD28 Antigens / pharmacology
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CTLA-4 Antigen
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Enzyme Activation / immunology
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Humans
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Immunoconjugates / metabolism*
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Immunoglobulin Fragments / metabolism*
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Jurkat Cells
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Ligands
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Lymphocyte Activation / immunology*
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Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / metabolism
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Phosphoprotein Phosphatases / metabolism
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Protein Phosphatase 2
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Receptor-CD3 Complex, Antigen, T-Cell / biosynthesis
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Receptor-CD3 Complex, Antigen, T-Cell / physiology
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Signal Transduction / immunology
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Suppressor Factors, Immunologic / immunology
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Suppressor Factors, Immunologic / metabolism
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Suppressor Factors, Immunologic / physiology*
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T-Lymphocyte Subsets / enzymology
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T-Lymphocyte Subsets / immunology*
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T-Lymphocyte Subsets / metabolism*
Substances
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Adjuvants, Immunologic
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Antibodies, Bispecific
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Antigens, CD
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Antigens, Differentiation
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CD28 Antigens
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CTLA-4 Antigen
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CTLA4 protein, human
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Immunoconjugates
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Immunoglobulin Fragments
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Ligands
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Receptor-CD3 Complex, Antigen, T-Cell
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Suppressor Factors, Immunologic
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immunoglobulin Fv
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Abatacept
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Lymphocyte Specific Protein Tyrosine Kinase p56(lck)
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Phosphoprotein Phosphatases
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Protein Phosphatase 2