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Complement 1s is the serine protease that cleaves IGFBP-5 in human osteoarthritic joint fluid

W H Busby1, S A Yocum, M Rowland

  • 1Department of Medicine, University of North Carolina, School of Medicine, Chapel Hill, NC 27599, USA.

Osteoarthritis and Cartilage
|October 22, 2008
PubMed

Insights

Osteoarthritis (OA) joint fluid contains a serine protease, identified as complement 1s (C1s), that degrades insulin-like growth factor-binding protein-5 (IGFBP-5). Inhibiting this protease may enhance IGF-I’s cartilage-protective effects in OA.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Rheumatology

Background:

  • Insulin-like growth factor-I (IGF-I) and IGF binding proteins (IGFBPs) are crucial for cartilage health and chondroprotection in osteoarthritis (OA) models.
  • IGFBP-5 degradation in OA joint fluid can limit the beneficial effects of IGF-I.

Purpose of the Study:

  • To identify the specific protease responsible for degrading IGFBP-5 in human OA joint fluid.

Main Methods:

  • Analysis of OA joint fluid using IGFBP-5 zymography.
  • Immunoblotting and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for protein identification.
  • Testing protease inhibitors to assess activity against IGFBP-5 cleavage.

Main Results:

  • A single proteolytic band cleaving IGFBP-5 was detected in OA joint fluid.
  • This protease was identified as complement 1s (C1s) through immunoblotting and LC-MS/MS.
  • Specific serine protease inhibitors effectively blocked IGFBP-5 cleavage, while matrix metalloproteinase (MMP) inhibitors showed no activity.

Conclusions:

  • Human OA joint fluid contains a serine protease that degrades IGFBP-5.
  • Complement 1s (C1s) is the primary protease responsible for this IGFBP-5 cleavage in OA.
  • Targeting C1s activity could be a therapeutic strategy to enhance IGF-I's chondroprotective effects in OA.
Abstract

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