Abstract
Both plasminogen (Pg) and urinary-type Pg activator (u-PA), but not tissue-type Pg activator (t-PA), bind to normal and rheumatoid arthritis (RA) human synovial fibroblasts in culture with high affinity and in a dose-dependent manner. Single cell intracellular Ca2+ responses to Pg and u-PA were studied using Fura-2 and digital imaging fluorescence microscopy. Pg activation by u-PA on the surface of RA synovial fibroblasts induces a significant rise in cytosolic free Ca2+ concentration ([Ca2+]i) within 90 s. Pg kringle 4 and the alpha 2,3-linked sialic acid in the carbohydrate chain bound to Thr245 are involved in mediating the increases in [Ca2+]i. This response is not observed in normal synovial fibroblasts, suggesting that RA synovial fibroblasts have altered responses to the binding and activation of Pg on their surfaces.
Highlights
Both plasminogen (Pg) and urinary-type Pg activator The mechanism of Pg activation on the surface of synovial (u-PA), but not tissue-type Pg activator (t-PA), bind to fibroblasts and its physiological effects have not been studied
Normal and rheumatoid arthritis (RA)human synovial Using human synovial fibroblasts in culture, we found that fibroblasts in culture with high affinity and in a dose- rheumatoid synovial cellsbind Pg with a larger capacity than dependentmanner
To obtain [Ca2+li and t-PA bound were calculated after substraction of nonspecific bind- for an individual cell, the mean value of the pixel ratio for the cell was ing measured in the presence of 3 mM unlabeled ligands
Summary
Both plasminogen (Pg) and urinary-type Pg activator The mechanism of Pg activation on the surface of synovial (u-PA), but not tissue-type Pg activator (t-PA), bind to fibroblasts and its physiological effects have not been studied. To obtain [Ca2+li and t-PA bound were calculated after substraction of nonspecific bind- for an individual cell, the mean value of the pixel ratio for the cell was ing measured in the presence of 3 mM unlabeled ligands.
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