title: ADAMTS-5 deficiency does not block aggrecanolysis at preferred cleavage sites in the chondroitin sulfate-rich region of aggrecan.
abstract: In the mouse, proteolysis in the aggrecan interglobular domain is driven by ADAMTS-5, and mice deficient in ADAMTS-5 catalytic activity are protected against aggrecan loss and cartilage damage in experimental models of arthritis. Here we show that despite ablation of ADAMTS-5 activity, aggrecanolysis can still occur at two preferred sites in the chondroitin sulfate-rich region. Retinoic acid was more effective than interleukin-1alpha (IL) in promoting cleavage at these sites in ADAMTS-5-deficient cartilage. These results suggest that cleavage at preferred sites in the chondroitin sulfate-rich region is mediated by ADAMTS-4 or an aggrecanase other than ADAMTS-5. Following retinoic acid or IL-1alpha stimulation of cartilage explants, aggrecan fragments in medium and extracts contained SELE(1279) or FREEE(1467) C-terminal sequences. Some SELE(1279) and FREEE(1467) fragments were retained in the cartilage, with intact G1 domains. Other SELE(1279) fragments were released into the medium and co-migrated with the (374)ALGS neoepitope, indicating they were aggrecanase-derived fragments. In contrast none of the FREEE(1467) fragments released into the medium co-migrated with the (374)ALGS neoepitope, suggesting that, despite their size, these fragments were not products of aggrecanase cleavage in the interglobular domain. ADAMTS-5, but not ADAMTS-1, -4, or -9, was up-regulated 8-fold by retinoic acid and 17-fold by IL-1alpha treatment. The data show that whereas ADAMTS-5 is entirely responsible for cleavage in the interglobular domain, cleavage in the chondroitin sulfate-rich region is driven either by ADAMTS-4, which compensates for loss of ADAMTS-5 in this experimental system, or possibly by another aggrecanase. The data show that there are differential aggrecanase activities with preferences for separate regions of the core protein.
authors.affiliation: Department of Paediatrics & Murdoch Childrens Research Institute, University of Melbourne, Royal Children's Hospital, Parkville 3052, Australia.
authors.forename: Charlotte J
authors.initials: CJ
authors.lastname: East
authors.forename: Heather
authors.initials: H
authors.lastname: Stanton
authors.forename: Suzanne B
authors.initials: SB
authors.lastname: Golub
authors.forename: Fraser M
authors.initials: FM
authors.lastname: Rogerson
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Fosang
mesh_terms: D051722:ADAM Proteins / Q000172:deficiency / Q000235:genetics* / Q000502:physiology*; D000071121:ADAMTS4 Protein; D000071116:ADAMTS5 Protein; D053674:Aggrecans / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D002356:Cartilage / Q000378:metabolism; D019902:Chondrocytes / Q000378:metabolism; D002809:Chondroitin Sulfates / Q000737:chemistry*; D000939:Epitopes / Q000737:chemistry; D053582:Interleukin-1alpha / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D011348:Procollagen N-Endopeptidase / Q000502:physiology; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D053674:Aggrecans; D000939:Epitopes; D053582:Interleukin-1alpha; D002809:Chondroitin Sulfates; D051722:ADAM Proteins; D000071116:ADAMTS5 Protein; C498489:Adamts5 protein, mouse; D011348:Procollagen N-Endopeptidase; D000071121:ADAMTS4 Protein; C000603919:Adamts4 protein, mouse