Evidence of a role for a non-matrix-type metalloproteinase activity in the shedding of syndecan-1 from human myeloma cells.
Syndecan-1 is a cell surface proteoglycan that is expressed on human myeloma cells and is thought to act as a co-receptor for certain extracellular matrix proteins and growth factors. The ectodomain of syndecan-1 is thought to be shed from the surface of myeloma cells, although the exact mechanism of release remains unclear. In this study, we used a panel of inhibitors to identify the class of proteinase responsible for shedding the soluble syndecan-1 ectodomain from human myeloma cells. Using enzyme-linked immunosorbent assay, flow cytometry and immunocytochemistry, we demonstrated that myeloma cell lines expressed syndecan-1 on their surface and that this was shed constitutively, but to a varying extent. In addition, phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C, stimulated a marked loss of cell surface syndecan-1 from each of the cell lines and this was associated with a corresponding increase in soluble syndecan-1. Inhibitors of serine and cysteine proteinases, and matrix-type metalloproteinases, did not inhibit constitutive or PMA-stimulated syndecan-1 shedding from JJN3 and RPMI 8226 cells. However, BB-94, a hydroxamate-based, broad-spectrum, metalloproteinase inhibitor, substantially suppressed constitutive and PMA-stimulated syndecan-1 loss from myeloma cells. These data indicate that a non-matrix-type metalloproteinase is responsible for syndecan-1 shedding from the surface of myeloma cells.
Holen
I
I
Division of Genomic Medicine, University of Sheffield Medical School, Sheffield, UK.
Drury
N L
NL
Hargreaves
P G
PG
Croucher
P I
PI
D000911:Antibodies, Monoclonal; D002462:Cell Membrane / Q000737:chemistry; D005434:Flow Cytometry; D019793:Fluorescein; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D017879:Isothiocyanates / Q000276:immunology; D008562:Membrane Glycoproteins / Q000032:analysis / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000378:metabolism*; D009101:Multiple Myeloma / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D011509:Proteoglycans / Q000032:analysis / Q000378:metabolism*; D018709:Statistics, Nonparametric; D013268:Stimulation, Chemical; D053668:Syndecan-1; D053667:Syndecans; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000378:metabolism
D000911:Antibodies, Monoclonal; D017879:Isothiocyanates; D008562:Membrane Glycoproteins; D011509:Proteoglycans; C508241:SDC1 protein, human; D053668:Syndecan-1; D053667:Syndecans; C037152:isothiocyanic acid; D011493:Protein Kinase C; D008666:Metalloendopeptidases; D013755:Tetradecanoylphorbol Acetate; D019793:Fluorescein