Monomer-dimer equilibria of interleukin-8 and neutrophil-activating peptide 2. Evidence for IL-8 binding as a dimer and oligomer to IL-8 receptor B.
By chemical cross-linking experiments we show that at physiologically relevant concentrations IL-8 and NAP-2 monomers are in an equilibrium with dimers and even oligomers (KD approximately 300-800 nM). Oligomerization seems to be more prevalent for IL-8 than for NAP-2. The form in which IL-8 and NAP-2 bind to their specific receptors was analyzed in binding experiments with COS-1 cells expressing IL-8 receptor A or B in recombinant forms. Both receptors were cloned from the human myeloid leukemic cell line AML-193. Type A receptor had high affinity for IL-8 (KD approximately 4 nM) and low affinity for NAP-2 (KD > or = 700 nM), whereas the type B receptor was of equally high affinity (KD approximately 2 nM) for both IL-8 and NAP-2. However, IL-8 receptor B could bind specifically three to four times more IL-8 than NAP-2, and NAP-2 was a weak competitor for IL-8 binding to the same receptor. In addition, IL-8, but not NAP-2, could be cross-linked to dimers when bound to IL-8 receptor B. We suggest from these findings that IL-8, but not NAP-2, binds as a dimer and oligomer to IL-8 receptor.
Schnitzel
W
W
Sandoz Forschungsinstitut, Vienna, Austria.
Monschein
U
U
Besemer
J
J
D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D016209:Interleukin-8 / Q000302:isolation & purification / Q000378:metabolism*; D007457:Iodine Radioisotopes; D007700:Kinetics; D007951:Leukemia, Myeloid; D046911:Macromolecular Substances; D010455:Peptides / Q000302:isolation & purification / Q000378:metabolism*; D018123:Receptors, Interleukin / Q000096:biosynthesis / Q000378:metabolism*; D023062:Receptors, Interleukin-8A; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured; D001620:beta-Thromboglobulin
D003432:Cross-Linking Reagents; D016209:Interleukin-8; D007457:Iodine Radioisotopes; D046911:Macromolecular Substances; C061615:PPBP protein, human; D010455:Peptides; D018123:Receptors, Interleukin; D023062:Receptors, Interleukin-8A; D011994:Recombinant Proteins; D001620:beta-Thromboglobulin; C009862:connective tissue-activating peptide