TY - JOUR

T1 - Molecular determinants of receptor binding and signaling by the CX3C chemokine fractalkine

AU - Mizoue, L S

AU - Sullivan, S K

AU - King, D S

AU - Kledal, T N

AU - Schwartz, T W

AU - Bacon, K B

AU - Handel, T M

N1 - Keywords: Amino Acid Sequence; Animals; Arginine; COS Cells; Calcium; Cell Line; Cells, Cultured; Chemokine CX3CL1; Chemokines, CX3C; Chemotaxis; Dose-Response Relationship, Drug; Epitopes; Escherichia coli; Humans; Kinetics; Ligands; Lysine; Magnetic Resonance Spectroscopy; Membrane Proteins; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Mutation; Neuroglia; Phenylalanine; Protein Binding; Protein Structure, Tertiary; Signal Transduction; Spectrometry, Fluorescence; Time Factors; Transfection

PY - 2001

Y1 - 2001

N2 - Fractalkine/CX3CL1 is a membrane-tethered chemokine that functions as a chemoattractant and adhesion protein by interacting with the receptor CX3CR1. To understand the molecular basis for the interaction, an extensive mutagenesis study of fractalkine's chemokine domain was undertaken. The results reveal a cluster of basic residues (Lys-8, Lys-15, Lys-37, Arg-45, and Arg-48) and one aromatic (Phe-50) that are critical for binding and/or signaling. The mutant R48A could bind but not induce chemotaxis, demonstrating that Arg-48 is a signaling trigger. This result also shows that signaling residues are not confined to chemokine N termini, as generally thought. F50A showed no detectable binding, underscoring its importance to the stability of the complex. K15A displayed unique signaling characteristics, eliciting a wild-type calcium flux but minimal chemotaxis, suggesting that this mutant can activate some, but not all, pathways required for migration. Fractalkine also binds the human cytomegalovirus receptor US28, and analysis of the mutants indicates that US28 recognizes many of the same epitopes of fractalkine as CX3CR1. Comparison of the binding surfaces of fractalkine and the CC chemokine MCP-1 reveals structural details that may account for their dual recognition by US28 and their selective recognition by host receptors.

AB - Fractalkine/CX3CL1 is a membrane-tethered chemokine that functions as a chemoattractant and adhesion protein by interacting with the receptor CX3CR1. To understand the molecular basis for the interaction, an extensive mutagenesis study of fractalkine's chemokine domain was undertaken. The results reveal a cluster of basic residues (Lys-8, Lys-15, Lys-37, Arg-45, and Arg-48) and one aromatic (Phe-50) that are critical for binding and/or signaling. The mutant R48A could bind but not induce chemotaxis, demonstrating that Arg-48 is a signaling trigger. This result also shows that signaling residues are not confined to chemokine N termini, as generally thought. F50A showed no detectable binding, underscoring its importance to the stability of the complex. K15A displayed unique signaling characteristics, eliciting a wild-type calcium flux but minimal chemotaxis, suggesting that this mutant can activate some, but not all, pathways required for migration. Fractalkine also binds the human cytomegalovirus receptor US28, and analysis of the mutants indicates that US28 recognizes many of the same epitopes of fractalkine as CX3CR1. Comparison of the binding surfaces of fractalkine and the CC chemokine MCP-1 reveals structural details that may account for their dual recognition by US28 and their selective recognition by host receptors.

U2 - 10.1074/jbc.M101348200

DO - 10.1074/jbc.M101348200

M3 - Journal article

C2 - 11432858

VL - 276

SP - 33906

EP - 33914

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 36

ER -