EXPRESSION OF CALCIUM-BINDING PROTEINS MRP8 AND MRP14 IS ASSOCIATED WITH DISTINCT MONOCYTIC DIFFERENTIATION PATHWAYS IN HL-60 CELLS

MRP8 and MRP14 are two calcium-binding proteins of the S-100 family which are expressed during distinct stages of monocytic maturation. To further investigate their regulation the human leukemic cell line HL-60 which can be induced to differentiate to monocytes/macrophages by 12-O- tetradecanoylphorbol 13-acetate (TPA), 1, 25-(OH)2 Vitamin D3 (VD3), tumor necrosis factor-α (TNF-α) and interferon-g (IFN-g) were analyzed for expression of MRP8/MRP14. Employing Northern blotting, a sandwich enzyme- linked immunosorbent assay and immunocytochemical analysis we determined MRP8/MRP14 mRNA and protein levels, which were found to be elevated after VD3 and reduced after TPA treatment. TNF-α and IFN-g did not affect MRP8/MRP14 levels. Western blot analysis revealed that formation of MRP8/MRP14 to biologically active complexes which has previously been shown to be a calcium-mediated process is not dependent on the differentiation stages of HL-60 cells. Restriction of MRP8/MRP14 expression to only distinct pathways of monocytic differentiation in HL-60 cells may thus reflect different functional phenotypes of monocytes/macrophages in vivo. © 1993 Academic Press, Inc.