Altered patterns of protein phosphorylation in articular chondrocytes treated with interleukin‐1 or synovial cytokines

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Abstract
Cultures of lapine articular chondrocytes were exposed to purified, human, recombinant interleukin‐1 α or partially purified preparations of lapine, synovial, cytokines in the presence of [32P]orthophosphate. After 30 min incubation, phosphoproteins were extracted from the cells, separated by two‐dimensional gel electrophoresis and visualized autoradiographically. Analysis of the autoradiograms revealed that interleukin‐1 and the synovial factors produced marked changes in the pattern of protein phosphorylation. The synovial cytokines induced many of the same changes as interleukin‐1, as well as a number of unique changes. This finding is consistent with the notion that, in addition to interleukin‐1, synoviocytes secrete other cytokines which modulate the metabolism of chondrocytes. These data support the idea that signal transduction in chondrocytes responding to interleukin‐1 involves the activation of one or more protein kinases.