Metalloprotease-disintegrin MDC9: intracellular maturation and catalytic activity

J Biol Chem. 1999 Feb 5;274(6):3531-40. doi: 10.1074/jbc.274.6.3531.


Metalloprotease disintegrins are a family of membrane-anchored glycoproteins that are known to function in fertilization, myoblast fusion, neurogenesis, and ectodomain shedding of tumor necrosis factor (TNF)-alpha. Here we report the analysis of the intracellular maturation and catalytic activity of the widely expressed metalloprotease disintegrin MDC9. Our results suggest that the pro-domain of MDC9 is removed by a furin-type pro-protein convertase in the secretory pathway before the protein emerges on the cell surface. The soluble metalloprotease domain of MDC9 cleaves the insulin B-chain, a generic protease substrate, providing the first evidence that MDC9 is catalytically active. Soluble MDC9 appears to have distinct specificities for cleaving candidate substrate peptides compared with the TNF-alpha convertase (TACE/ADAM17). The catalytic activity of MDC9 can be inhibited by hydroxamic acid-type metalloprotease inhibitors in the low nanomolar range, in one case with up to 50-fold selectivity for MDC9 versus TACE. Peptides mimicking the predicted cysteine-switch region of MDC9 or TACE inhibit both enzymes in the low micromolar range, providing experimental evidence for regulation of metalloprotease disintegrins via a cysteine-switch mechanism. Finally, MDC9 is shown to become phosphorylated when cells are treated with the phorbol ester phorbol 12-myristate 13-acetate, a known inducer of protein ectodomain shedding. This work implies that removal of the inhibitory pro-domain of MDC9 by a furin-type pro-protein convertase in the secretory pathway is a prerequisite for protease activity. After pro-domain removal, additional steps, such as protein kinase C-dependent phosphorylation, may be involved in regulating the catalytic activity of MDC9, which is likely to target different substrates than the related TNF-alpha-convertase.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • ADAM Proteins
  • ADAM17 Protein
  • Amino Acid Sequence
  • Animals
  • COS Cells
  • Catalysis
  • Cloning, Molecular
  • Collagenases / metabolism
  • Disintegrins*
  • Humans
  • Hydrolysis
  • Hydroxamic Acids / pharmacology
  • Insulin / metabolism
  • Kinetics
  • Matrix Metalloproteinase 1
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Metalloendopeptidases / metabolism
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Phosphorylation
  • Protease Inhibitors / pharmacology
  • Substrate Specificity
  • Tetradecanoylphorbol Acetate / pharmacology


  • Disintegrins
  • Hydroxamic Acids
  • Insulin
  • Membrane Proteins
  • Protease Inhibitors
  • ADAM Proteins
  • ADAM9 protein, human
  • Collagenases
  • Metalloendopeptidases
  • Matrix Metalloproteinase 1
  • ADAM17 Protein
  • ADAM17 protein, human
  • Tetradecanoylphorbol Acetate