Studies to elucidate the effects of iron (III) on recognition of hyaluronate by the cell surface receptor CD44

Studies to elucidate the effects of iron (III) on recognition of hyaluronate by the cell surface receptor CD44

Carbohydrates -- Metabolism

Iron -- Metabolism

Rheumatoid arthritis -- Etiology

Bintz, Brittania Jane

2006

Summers, Jack

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Iron and the poly-anionic carbohydrate, hyaluronate (HA), have both been implicated as possible contributors to rheumatoid arthritis (RA), an autoimmune disease of unknown etiology. In this work, we hypothesized that in RA patients, iron is bound by HA in such a way as to affect HA binding by the cell surface glycoprotein CD44, a known HA receptor. To test this hypothesis, we developed cell based assays to determine the effects of iron binding to HA on HA binding by CD44. As part of this effort, we prepared biotinylated HA and biotinylated Fe complexed HA. Mesothelioma cells expressing CD44 were treated with each of these conjugates, and the resulting materials were treated with avidin-fluorescein and the bound fluorescein was measured using a fluorescence microtiter plate reader. We found that Fe (III) decreases the apparent affinity of CD44 receptors on Mesothelioma cells for HA (Observed fluorescence intensity decreased by a factor of -2). In competition experiments, addition of non-biotinylated Fe complexed HA did not inhibit binding of biotinylated HA. Addition of nonbiotinylated HA, however, appeared to increase the uptake of biotinylated Fe complexed HA. These results suggest that iron (III) may crosslink HA molecules, leading to a greater uptake of HA. This crosslinking may influence receptor clustering which is believed to be important to intra-cellular signaling.

2014-07-22

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