title: Involvement of a metalloprotease in spontaneous and phorbol ester-induced release of natural killer cell-associated Fc gamma RIII (CD16-II).
abstract: Two genes encode the CD16 low affinity IgG FcR. CD16-I (Fc gamma RIII-1) is expressed on PMN as a phosphatidylinositol-glycan anchored glycoprotein. CD16-II (Fc gamma RIII-2) is expressed on NK cells and macrophages as a transmembrane glycoprotein associated with CD3 zeta or Fc epsilon RI-gamma. NK cells spontaneously release soluble CD16-II from the cell surface and this is enhanced by activation with phorbol ester. In this study, we demonstrate that a metalloprotease is involved in the spontaneous and PMA-induced release of CD16-II from NK cells. 1,10-phenanthroline, an inhibitor of Zn(2+)-dependent metalloproteases, efficiently inhibits CD16-II release. 1,7-phenanthroline, an inactive analogue that doesn't chelate Zn2+ or other divalent metal cations, and inhibitors of serine proteases do not affect spontaneous or PMA-induced release of CD16-II. Murine P815 mastocytoma cells transfected with human CD16-II cDNA shed membrane CD16, and 1,10-phenanthroline inhibits this process. P815 transfectants expressing CD16-II molecules with truncated cytoplasmic domains also release soluble receptors, indicating that the cytoplasmic segment of CD16-II is not required for interaction with the protease or the cytoskeleton. By contrast, 1,10-phenanthroline does not inhibit PMA-induced release of CD16-I glycoprotein from PMN, indicating a different mechanism of release for this phosphatidylinositol-glycan anchored molecule. Prior studies have demonstrated that NK cells are activated via the inositol phosphate pathway after engagement of CD16-II by immune complexes or Ig-coated tumor cell targets. A membrane metalloprotease with substrate specificity for CD16-II that is activated by PKC stimulation may provide a mechanism for releasing the immune complex or target from the effector cells and halting signal transduction.
authors.affiliation: DNAX Research Institute for Molecular and Cellular Biology, Palo Alto, CA 94304.
authors.forename: D
authors.initials: D
authors.lastname: Harrison
authors.forename: J H
authors.initials: JH
authors.lastname: Phillips
authors.forename: L L
authors.initials: LL
authors.lastname: Lanier
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry / Q000378:metabolism*; D000943:Antigens, Differentiation / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007694:Killer Cells, Natural / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051379:Mice; D009504:Neutrophils / Q000378:metabolism; D010618:Phenanthrolines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011961:Receptors, Fc / Q000737:chemistry / Q000378:metabolism*; D017452:Receptors, IgG; D011994:Recombinant Proteins / Q000378:metabolism; D012995:Solubility; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
chemical_list: D000470:Alkaloids; D015703:Antigens, CD; D000943:Antigens, Differentiation; D010618:Phenanthrolines; D011961:Receptors, Fc; D017452:Receptors, IgG; D011994:Recombinant Proteins; D011493:Protein Kinase C; D008666:Metalloendopeptidases; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate; C025205:1,10-phenanthroline