Abstract
Cyclophilin A (CyPA), a ubiquitously distributed intracellular protein, is a peptidylprolyl cis-trans-isomerase and the major target of the potent immunosuppressive drug cyclosporin A. Although expressed predominantly as an intracellular molecule, CyPA is secreted by cells in response to inflammatory stimuli and is a potent neutrophil and eosinophil chemoattractant in vitro and in vivo. The mechanisms underlying CyPA-mediated signaling and chemotaxis are unknown. Here, we identified CD147 as a cell surface receptor for CyPA and demonstrated that CD147 is an essential component in the CyPA-initiated signaling cascade that culminates in ERK activation. Both signaling and chemotactic activities of CyPA depended also on the presence of heparans, which served as primary binding sites for CyPA on target cells. The proline 180 and glycine 181 residues in the extracellular domain of CD147 were critical for signaling and chemotactic activities mediated by CD147. Also crucial were active site residues of CyPA, because rotamase-defective CyPA mutants failed to initiate signaling events. These results establish cyclophilins as natural ligands for CD147 and suggest an unusual, rotamase-dependent mechanism of signaling.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Animals
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Antigens, CD*
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Antigens, Neoplasm*
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Antigens, Surface*
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Avian Proteins*
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Basigin
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Binding Sites
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Blood Proteins*
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Blotting, Western
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CHO Cells
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Calcium / metabolism
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Cell Line
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Chemotaxis
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Cloning, Molecular
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Cricetinae
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Cross-Linking Reagents / pharmacology
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Culture Media, Serum-Free / pharmacology
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Cyclophilin A / chemistry*
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Cyclophilin A / metabolism*
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Cyclophilin A / physiology
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Cyclosporine / pharmacology
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Enzyme Activation
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Enzyme Inhibitors / pharmacology
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Flow Cytometry
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Glycine / chemistry
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Heparitin Sulfate / metabolism
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Heparitin Sulfate / physiology
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Humans
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Membrane Glycoproteins / chemistry
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Membrane Glycoproteins / metabolism*
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Molecular Sequence Data
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Mutation
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Plasmids / metabolism
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Proline / chemistry
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Protein Binding
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Protein Structure, Tertiary
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Signal Transduction
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Spectrometry, Fluorescence
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Two-Hybrid System Techniques
Substances
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Antigens, CD
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Antigens, Neoplasm
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Antigens, Surface
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Avian Proteins
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BSG protein, human
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Blood Proteins
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Bsg protein, Gallus gallus
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Bsg protein, rat
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Cross-Linking Reagents
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Culture Media, Serum-Free
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Enzyme Inhibitors
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Membrane Glycoproteins
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Basigin
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Cyclosporine
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Heparitin Sulfate
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Proline
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Cyclophilin A
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Calcium
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Glycine