Low-density lipoprotein receptor-related protein 1 (LRP1)-mediated endocytic clearance of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4: Functional differences of non-catalytic domains of ADAMTS-4 and ADAMTS-5 in LRP1 binding [Enzymology]

January 28th, 2014 by Yamamoto, K., Owen, K., Parker, A. E., Scilabra, S. D., Dudhia, J., Strickland, D. K., Troeberg, L., Nagase, H.

Degradation of the cartilage proteoglycan aggrecan is an early event in the development of osteoarthritis (OA), and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5 are considered to be the major aggrecan-degrading enzymes. We have recently found that ADAMTS-5 is rapidly endocytosed via low-density lipoprotein receptor-related protein 1 (LRP1) and degraded by chondrocytes. Here, we report that this regulatory mechanism also applies to ADAMTS-4, although its rate of endocytosis is slower than that of ADAMTS-5. Domain deletion mutagenesis of ADAMTS-4 identified that the cysteine-rich and spacer domains are responsible for binding to LRP1, while the thrombospondin 1 and spacer domains are responsible in ADAMTS-5. The estimated t1/2 value of ADAMTS-4 endocytosis was about 220 min, whereas that of ADAMTS-5 was 100 min. The difference in half-lives between the two enzymes is explained by the 13-fold lower affinity of ADAMTS-4 for LRP1 compared with that of ADAMTS-5. Studies using soluble ligand-binding clusters of LRP1 showed that ADAMTS-4 binds to clusters II and IV with similar KD,app values of 98 nM and 73 nM, respectively, whereas ADAMTS-5 binds to cluster II, III and IV with KD,app values of 3.5 nM, 41 nM and 9 nM, respectively. Thus, ADAMTS-5 competitively inhibits ADAMTS-4 endocytosis, but not vice versa. This study highlights that the affinity between a ligand and LRP1 dictates the rate of internalization and suggests that LRP1 is a major traffic controller of the two aggrecanases, especially under inflammatory conditions, where the protein levels of ADAMTS-4 increase but those of ADAMTS-5 do not.
  • Posted in Journal of Biological Chemistry, Publications
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