Identifying the functional part of heparin-binding protein (HBP) as a monocyte stimulator and the novel role of monocytes as HBP producers.
Heparin-binding protein (HBP), an evolutionary ancient and biologically highly important molecule in inflammation, is an inactive serine protease due to mutations in the catalytic triad. The histidine (position 41) in the conserved sequence TAAHC is mutated to serine and this sequence (TAASC) plays a crucial role when HBP binds to monocytes. We synthesized a 20-44 HBP peptide, cyclicized by a sulphur bridge, which encompasses this amino acid and functions as full-length HBP. Using a human monocyte cell line, we have shown that lipopolysaccharide (LPS)-triggered secretion of IL-6 is enhanced up to 10-fold when full-length HBP or the peptide are present in low-to-moderate concentrations. A monoclonal antibody neutralizing HBP also neutralizes the peptide, indicating that the ligand for the HBP receptor is located near serine in position 41 on the HBP surface. A 'back mutated' 20-44 peptide (serine→histidine) has some, but not significant, stimulatory effect on monocytes. Normally, HBP production and release is ascribed to neutrophil granulocytes, but here we find that also monocytes secrete HBP when stimulated with LPS. Furthermore, a small amount of HBP can be demonstrated when monocytes are incubated in medium alone. Our efforts to identify a suggested HBP receptor on monocytes has failed so far.
Schou
Morten
M
Bartholin Instituttet XPU, Biocenter Copenhagen, Rigshospitalet, Blegdamsvej 9, Copenhagen Ø, Denmark. morten.schou@rh.regionh.dk
Djurup
René
R
Norris
Kjeld
K
Flodgaard
Hans
H
D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology*; D001769:Blood / Q000187:drug effects / Q000378:metabolism; D001798:Blood Proteins / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology*; D018821:CD18 Antigens / Q000276:immunology; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology*; D002460:Cell Line; D003470:Culture Media / Q000494:pharmacology; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology*; D010457:Peptidoglycan / Q000494:pharmacology; D054730:Protein Interaction Domains and Motifs / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D013267:Stilbenes / Q000494:pharmacology; D000072377:Syk Kinase
C062991:AZU1 protein, human; D000911:Antibodies, Monoclonal; D023181:Antimicrobial Cationic Peptides; D001798:Blood Proteins; D018821:CD18 Antigens; D002352:Carrier Proteins; D003470:Culture Media; C508600:IL6 protein, human; D015850:Interleukin-6; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D010446:Peptide Fragments; D010457:Peptidoglycan; D013267:Stilbenes; C041525:3,3',4,5'-tetrahydroxystilbene; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase