Regulation of collagenolytic protease secretion through c-Src in osteoclasts

The role of pp60c-src activity in the synthesis and secretion of the collag enolytic cysteine proteases (CCPs), cathepsin K (CAK), cathepsin L (CAL), a nd cathepsin B (CAB), by osteoclasts was investigated. Synthesis and secret ion of CAL were up-regulated by 1 alpha,25-(OH)(2)D-3, but neither those of CAK dominant relative to GAL, nor CAB, barely detectable, levels changed i n the experiments. Though PP1, a pp60(c-sre) inhibitor, had no effect on CC Ps synthesis, suppressed the CAK and CAL secretion. Wortmannin, a phosphati dylinositol 3-kinase (PI3-kinase) inhibitor that works as a second messenge r for pp60(c-src), and cytochalasin B, an inhibitor of actin polymerization , suppressed the secretion of both CAK and CAL without suppressing synthesi s. Hydroxyproline release, an indicator of degradation of type-I collagen, and F-actin ring formation, a structure linked to osteoclastic bone resorpt ion, were suppressed by PP1, cytochalasin B or wortmannin. These results su ggested inhibition of pp60(c-src) activity affected the osteoclastic cytosk eleton, which in turn reflected the suppression of bone resorption. (C) 200 0 Academic Press.