Lubricin/Proteoglycan 4 Binding to CD44 Receptor: A Mechanism of the Suppression of Proinflammatory Cytokine-Induced Synoviocyte Proliferation by Lubricin

Arthritis Rheumatol. 2015 Jun;67(6):1503-13. doi: 10.1002/art.39087.


Objective: To evaluate the binding of recombinant human proteoglycan 4 (rhPRG4) to CD44 receptor and its consequences on cytokine-induced synoviocyte proliferation.

Methods: The binding of rhPRG4 to CD44 and competition with high molecular weight (HMW) hyaluronic acid (HA) was evaluated using a direct enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance. Sialidase A and O-glycosidase digestion of rhPRG4 was performed, and CD44 binding was evaluated using ELISA. Rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) were stimulated with interleukin-1β (IL-1β) or tumor necrosis factor α (TNFα) for 48 hours in the presence or absence of rhPRG4 or HMW HA at 20, 40, and 80 μg/ml, and cell proliferation was measured. The contribution of CD44 was assessed by coincubation with a CD44 antibody (IM7). The antiproliferative effect of rhPRG4 was investigated following treatment of PRG4(-/-) mouse synoviocytes with IL-1β or TNFα in the presence or absence of IM7.

Results: Recombinant human PRG4 bound CD44 and interfered with the binding of HMW HA to CD44. Removal of sialic acid and O-glycosylations significantly increased CD44 binding by rhPRG4 (P < 0.001). Both rhPRG4 and HMW HA at 40 and 80 μg/ml significantly suppressed IL-1β-induced proliferation of RA FLS (P < 0.05). Recombinant human PRG4 at 20, 40, and 80 μg/ml significantly suppressed TNFα-induced RA FLS proliferation (P < 0.05). CD44 neutralization reversed the effect of rhPRG4 on IL-1β- and TNFα-stimulated RA FLS and the effect of HMW HA on IL-1β-stimulated RA FLS. Recombinant human PRG4 inhibited cytokine-induced proliferation of PRG4(-/-) synoviocytes, which could be prevented by blocking CD44.

Conclusion: PRG4 (lubricin) is a novel putative ligand for CD44 and may control synoviocyte overgrowth in inflammatory arthropathies via a CD44-mediated mechanism.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Arthritis, Rheumatoid / metabolism*
  • Cell Proliferation / drug effects
  • Cell Proliferation / physiology*
  • Enzyme-Linked Immunosorbent Assay
  • Fibroblasts / drug effects
  • Fibroblasts / metabolism*
  • Humans
  • Hyaluronan Receptors / metabolism*
  • Hyaluronic Acid / metabolism*
  • Interleukin-1beta / pharmacology
  • Mice
  • Mice, Knockout
  • Proteoglycans / genetics*
  • Proteoglycans / metabolism*
  • Surface Plasmon Resonance
  • Synovial Membrane / cytology*
  • Tumor Necrosis Factor-alpha / pharmacology


  • CD44 protein, human
  • Cd44 protein, mouse
  • Hyaluronan Receptors
  • Interleukin-1beta
  • PRG4 protein, human
  • Prg4 protein, mouse
  • Proteoglycans
  • Tumor Necrosis Factor-alpha
  • Hyaluronic Acid