Calcium ionophores decrease pericellular gelatinolytic activity via inhibition of 92-kDa gelatinase expression and decrease of 72-kDa gelatinase activation.
To understand the roles of intracellular calcium levels on gelatinase/type IV collagenase expression, we analyzed the effects of calcium ionophores on the expression of 92- and 72-kDa gelatinases (MMP-9 and MMP-2) in human fibrosarcoma cells (HT-1080). Calcium ionophores ionomycin and A23187 reduced the levels of pericellular gelatinolytic activity in both untreated and phorbol 12-myristate 13-acetate (PMA) or tumor necrosis factor-alpha (TNF alpha)-stimulated cells as determined by degradation of radiolabeled gelatin. Gelatin zymography and immunoblotting revealed a dose-dependent decrease in the levels of secreted 92-kDa gelatinase, which was paralleled by a decrease of its mRNA. Treatment of cells with thapsigargin caused similar decreases of 92-kDa gelatinase mRNA and protein. The decrease of 92-kDa gelatinase expression was due to lower transcription rate as determined by transfection assays with 92-kDa gelatinase/luciferase construct. The expression of 72-kDa gelatinase was only slightly decreased by ionophores. Treatment of HT-1080 cells with PMA, TNF alpha, or concanavalin A resulted in the conversion of 72-kDa gelatinase proenzyme to its presumed 64- and 62-kDa active forms as determined by gelatin zymography and immunoblotting. Simultaneous treatment with the ionophores or thapsigargin resulted in inhibition of PMA-induced gelatinase activation. The expression of membrane-type matrix metalloproteinase, a potential activator of 72-kDa gelatinase, was not affected by ionophores. The results indicate that calcium ionophores decrease gelatinolysis by repressing both the expression of 92-kDa gelatinase and the activation of the 72-kDa gelatinase.
Lohi
J
J
Department of Virology, University of Helsinki, Finland.
Keski-Oja
J
J
D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D003208:Concanavalin A / Q000494:pharmacology; D005780:Gelatin / Q000378:metabolism*; D018093:Gelatinases / Q000037:antagonists & inhibitors*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology*; D008970:Molecular Weight; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D007476:Ionophores; D014409:Tumor Necrosis Factor-alpha; D003208:Concanavalin A; D000001:Calcimycin; D015759:Ionomycin; D005780:Gelatin; D018093:Gelatinases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium