Tunicamycin treated fibroblasts secrete a cathepsin B-like protease |
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Authors: | J Brian Parent Hans C Bauer Kenneth Olden |
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Institution: | 1. Department of Oncology, Howard University Cancer Center Washington, D.C. 20060 USA;2. Laboratory of Molecular Biology, National Cancer Institute, Bethesda, MD. 20205 USA |
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Abstract: | We have investigated the effect of tunicamycin on the localization of lysosomal hydrolases in chicken embryo fibroblast cultures. We showed that treatment with tunicamycin (0.05 μg/ml) resulted in a 7–10 fold increase in the cathepsin B-like activity in the culture medium compared to untreated cultures. The protease activity was identified as cathepsin B-like based on 1) substrate specificity (benzoylpro-phe-arg14C]anilide is rapidly hydrolyzed), 2) the pH optimum for activity of 5.5, 3) inhibition by thiol reactive compounds, 4) inhibition of the activity by leupeptin but not by pepstatin or phenylmethylsulfonyl fluoride, and 5) by the demonstration of a protease with similar properties in the lysosomal fraction of untreated cultures. The secretion of the cathepsin B-like protease was specific and not due to leakage from damaged cells. |
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Keywords: | TM tunicamycin PMSF phenylmethylsulfonyl fluoride |
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