CALCIUM IONOPHORES DECREASE PERICELLULAR GELATINOLYTIC ACTIVITY VIA INHIBITION OF 92-KDA GELATINASE EXPRESSION AND DECREASE OF 72-KDA GELATINASE ACTIVATION
J. Lohi et J. Keskioja, CALCIUM IONOPHORES DECREASE PERICELLULAR GELATINOLYTIC ACTIVITY VIA INHIBITION OF 92-KDA GELATINASE EXPRESSION AND DECREASE OF 72-KDA GELATINASE ACTIVATION, The Journal of biological chemistry, 270(29), 1995, pp. 17602-17609
To understand the roles of intracellular calcium levels on gelatinase/
type IV collagenase expression, we analyzed the effects of calcium ion
ophores on the expression of 92- and 72-kDa gelatinases (MMP-9 and MMP
-2) in human fibrosarcoma cells (HT-1080). Calcium ionophores ionomyci
n 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 de
gradation of radiolabeled gelatin. Gelatin zymography and immunoblotti
ng 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 gelatin
ase mRNA and protein. The decrease of 99-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 conv
ersion of 72-kDa gelatinase proenzyme to its presumed 64- and 62-kDa a
ctive forms as determined by gelatin zymography and immunoblotting. Si
multaneous treatment with the ionophores or thapsigarin resulted in in
hibition of PMA-induced gelatinase activation. The expression of membr
ane-type matrix metalloproteinase, a potential activator of 72-kDa gel
atinase, was not affected by ionophores. The results indicate that cal
cium ionophores decrease gelatinolysis by repressing both the expressi
on of 92-kDa gelatinase and the activation of the 72-kDa gelatinase.