title: Regulation of ADAMTS9 secretion and enzymatic activity by its propeptide.
abstract: ADAMTS9 is a secreted, cell-surface-binding metalloprotease that cleaves the proteoglycans versican and aggrecan. Unlike most precursor proteins, the ADAMTS9 zymogen (pro-ADAMTS9) is resistant to intracellular processing. Instead, pro-ADAMTS9 is processed by furin at the cell surface. Here, we investigated the role of the ADAMTS9 propeptide in regulating its secretion and proteolytic activity. Removal of the propeptide abrogated secretion of the ADAMTS9 catalytic domain, and secretion was inefficiently restored by expression of the propeptide in trans. Substitution of Ala for Asn residues within each of three consensus N-linked glycosylation sites in the propeptide abrogated ADAMTS9 secretion. Thus, the propeptide is an intramolecular chaperone whose glycosylation is critical for secretion of the mature enzyme. In addition to two previously identified furin-processing sites (Arg74 downward arrow and Arg287 downward arrow) the ADAMTS9 propeptide was also furin-processed at Arg209. Substitution of Ala for Arg74, Arg209, and Arg287 resulted in secretion of an unprocessed zymogen. Unexpectedly, versican incubated with cells expressing this pro-ADAMTS9 was processed to a greater extent than when incubated with cells expressing wild-type, furin-processable ADAMTS9. Moreover, cells and medium treated with the proprotein convertase inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethyl ketone had greater versican-cleaving activity than untreated cells. Following furin processing of pro-ADAMTS9, propeptide fragments maintained a non-covalent association with the catalytic domain. Collectively, these observations suggest that, unlike other metalloproteases, furin processing of the ADAMTS9 propeptide reduces its catalytic activity. Thus, the propeptide is a key functional domain of ADAMTS9, mediating an unusual regulatory mechanism that may have evolved to ensure maximal activity of this protease at the cell surface.
authors.affiliation: Department of Biomedical Engineering and Orthopaedic Research Center, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: Bon-Hun
authors.initials: BH
authors.lastname: Koo
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Longpré
authors.forename: Robert P T
authors.initials: RP
authors.lastname: Somerville
authors.forename: J Preston
authors.initials: JP
authors.lastname: Alexander
authors.forename: Richard
authors.initials: R
authors.lastname: Leduc
authors.forename: Suneel S
authors.initials: SS
authors.lastname: Apte
mesh_terms: D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism*; D000071119:ADAMTS9 Protein; D053674:Aggrecans / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology* / Q000235:genetics; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism*; D045683:Furin / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000235:genetics; D053675:Versicans / Q000378:metabolism
chemical_list: D053674:Aggrecans; D004792:Enzyme Precursors; D011498:Protein Precursors; C508322:VCAN protein, human; D053675:Versicans; C468731:FURIN protein, human; D045683:Furin; D051722:ADAM Proteins; D000071119:ADAMTS9 Protein; C412869:ADAMTS9 protein, human