A mutation in a CD44 variant of inflammatory cells enhances the mitogenic interaction of FGF with its receptor
Shlomo Nedvetzki, … , Avner Yayon, David Naor
Shlomo Nedvetzki, … , Avner Yayon, David Naor
Published April 15, 2003
Citation Information: J Clin Invest. 2003;111(8):1211-1220. https://doi.org/10.1172/JCI17100.
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Article Autoimmunity

A mutation in a CD44 variant of inflammatory cells enhances the mitogenic interaction of FGF with its receptor

Abstract

Synovial fluid cells from joints of rheumatoid arthritis (RA) patients express a novel variant of CD44 (designated CD44vRA), encoding an extra trinucleotide (CAG) transcribed from intronic sequences flanking a variant exon. The CD44vRA mutant was detected in 23 out of 30 RA patients. CD44-negative Namalwa cells transfected with CD44vRA cDNA or with CD44v3-v10 (CD44vRA wild type) cDNA bound FGF-2 to an equal extent via their associated heparan sulfate chains. However, Namalwa cells, immobilizing FGF-2 via their cell surface CD44vRA, bound substantially more soluble FGF receptor-1 (FGFR-1) than did Namalwa cells immobilizing the same amount of FGF-2 via their cell surface CD44v3-v10. The former cells stimulated the proliferation of BaF-32 cells, bearing FGFR-1, more efficiently than did the latter cells. Finally, isolated primary synovial fluid cells from RA patients expressing CD44vRA bound more soluble FGFR-1 to their cell surface–associated FGF-2 than did corresponding synovial cells expressing CD44v3-v10 or synovial cells from osteoarthritis patients. The binding of soluble FGFR-1 to RA synovial cells could be specifically reduced by their preincubation with Ab’s against the v3 exon product of CD44. Hence, FGF-2 attached to the heparan sulfate moiety expressed by the novel CD44 variant of RA synovium cells exhibits an augmented ability to stimulate FGFR-1–mediated activities. A similar mechanism may foster the destructive inflammatory cascade not only in RA, but also in other autoimmune diseases.

Authors

Shlomo Nedvetzki, Itshak Golan, Nathalie Assayag, Erez Gonen, Dan Caspi, Micha Gladnikoff, Avner Yayon, David Naor

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Synovial fluid cells from RA patients bind soluble FGFR-1 in a CD44v-dep...
Synovial fluid cells from RA patients bind soluble FGFR-1 in a CD44v-dependent manner. (a) Binding of soluble FGFR-1 to synovial fluid cells of RA patients is CD44v3 associated. Synovial fluid cells from three RA patients (RA6, RA8, RA11) were incubated with soluble FGFR-1 conjugated to AP in the presence of medium (bar 1) isotype-matched control immunoglobulin (bar 2), or 1 μg (bar 3), 300 ng (bar 4), 30 ng (bar 5), and 1 ng (bar 6) anti-CD44v3 mAb. The interaction of FGFR-1 with FGF-2, bound to the joint cells, was analyzed as indicated in Figure 5b. Anti-CD44v3 mAb reduced the binding of soluble FGFR-1 to the synovial fluid cells in a dose-dependent manner. The highest concentration (1 μg) of anti-CD44v3 mAb reduced FGFR-1 binding to synovial fluid cells from additional four RA patients (not shown). (b) Anti-CD44v3 mAb, but not anti–pan-CD44mAb (F-10-44-2), directed against a constant epitope inhibits the binding of soluble FGFR-1 to synovial fluid cells of RA patients. Synovial fluid cells from three RA patients (RA2, RA3, RA6) were incubated with soluble FGFR-1 conjugated to AP in the presence of medium (bar 1), isotype matched control immunoglobulin (bar 2), 1 μg anti-CD44v3 mAb (bar 3), and 1 μg anti–pan CD44mAb (bar 4). The interaction of the FGFR-1 with FGF-2 bound to the joint cells, was analyzed as described in Figure 5b.