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  • Title: IFN-gamma up-regulates the human C5a receptor (CD88) in myeloblastic U937 cells and related cell lines.
    Author: Burg M, Martin U, Rheinheimer C, Köhl J, Bautsch W, Böttger EC, Klos A.
    Journal: J Immunol; 1995 Nov 01; 155(9):4419-26. PubMed ID: 7594603.
    Abstract:
    On human mature monocytes the immunomodulator IFN-gamma has been shown to down-regulate the receptor for the anaphylatoxic peptide C5a (CD88, C5aR). In this study, we show that in immature myelo-/monoblastic U937, HL60, and MonoMac6 cells, IFN-gamma induces C5aR-ligand binding activity. In U937 cells, this induction cannot be blocked by the protein kinase C inhibitor staurosporine. An increase in free cytosolic Ca2+ upon ligand binding indicates functional coupling of this receptor in U937 and HL-60 cells. G-Proteins involved in this C5a responsiveness after IFN-gamma induction are completely pertussis toxin sensitive. Our data suggest that an additional pertussis toxin-resistant pathway exists in U937 cells after induction by dibutyryl cAMP. However, this is not due to changes in the mRNA level of the pertussis toxin-insensitive G-protein subunit G alpha 16. Induction by dibutyryl cAMP, but not that by IFN-gamma, resulted in C5a-dependent release of N-acetyl-beta-D-glucosaminidase, further highlighting functional differences in the effects of the inducers. Our data show an IFN-gamma-dependent increase in C5aR expression and suggest a maturation-related change in signaling of the C5aR, presumably at the level of receptor coupling.
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