Evidence for cadherin-11 cleavage in the synovium and partial characterization of its mechanism.

Abstract

INTRODUCTION:

Engagement of the homotypic cell-to-cell adhesion molecule cadherin-11 on rheumatoid arthritis (RA) synovial fibroblasts with a chimeric molecule containing the cadherin-11 extracellular binding domain stimulated cytokine, chemokine, and matrix metalloproteinases (MMP) release, implicating cadherin-11 signaling in RA pathogenesis. The objective of this study was to determine if cadherin-11 extracellular domain fragments are found inside the joint and if a physiologic synovial fibroblast cleavage pathway releases those fragments.

METHODS:

Cadherin-11 cleavage fragments were detected by western blot in cell media or lysates. Cleavage was interrupted using chemical inhibitors or short-interfering RNA (siRNA) gene silencing. The amount of cadherin-11 fragments in synovial fluid was measured by western blot and ELISA.

RESULTS:

Soluble cadherin-11 extracellular fragments were detected in human synovial fluid at significantly higher levels in RA samples compared to osteoarthritis (OA) samples. A cadherin-11 N-terminal extracellular binding domain fragment was shed from synovial fibroblasts after ionomycin stimulation, followed by presenilin 1 (PSN1)-dependent regulated intramembrane proteolysis of the retained membrane-bound C-terminal fragments. In addition to ionomycin-induced calcium flux, tumor necrosis factor (TNF)-α also stimulated cleavage in both two- and three-dimensional fibroblast cultures. Although cadherin-11 extracellular domains were shed by a disintegrin and metalloproteinase (ADAM) 10 in several cell types, a novel ADAM- and metalloproteinase-independent activity mediated shedding in primary human fibroblasts.

CONCLUSIONS:

Cadherin-11 undergoes ectodomain shedding followed by regulated intramembrane proteolysis in synovial fibroblasts, triggered by a novel sheddase that generates extracelluar cadherin-11 fragments. Cadherin-11 fragments were enriched in RA synovial fluid, suggesting they may be a marker of synovial burden and may function to modify cadherin-11 interactions between synovial fibroblasts.

• Authors: Erika H Noss, Gerald F M Watts, Davide Zocco, Tracy L Keller, Malcolm Whitman, Carl P Blobel, David M Lee, Michael B Brenner
• Journal: Arthritis research & therapy (Arthritis Res Ther) Vol. 17 Pg. 126 (May 15 2015) ISSN: 1478-6362 [Electronic] England
• PMID: 25975695 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Cadherins
• Peptide Fragments
• RNA, Small Interfering
• osteoblast cadherin

Topics

• Arthritis, Rheumatoid (metabolism)
• Blotting, Western
• Cadherins (metabolism)
• Cells, Cultured
• Enzyme-Linked Immunosorbent Assay
• Fibroblasts (metabolism)
• Humans
• Immunoprecipitation
• Osteoarthritis (metabolism)
• Peptide Fragments (metabolism)
• RNA, Small Interfering
• Synovial Fluid (chemistry, metabolism)
• Synovial Membrane (metabolism)
• Transfection