Regulation of Membrane-Type Matrix Metalloproteinase-1 Expression by Growth Factors and Phorbol 12-Myristate 13-Acetate

Authors


  • Note. The novel nucleotide sequence reported here is available at the EMBL Data Bank under accession number X90925.

J. Keski-Oja, Dept. of Virology, University of Helsinki, Haartmaninkatu 3, FIN-00290 Helsinki, Finland
Fax:+358 0 434 6491.

Abstract

Overexpression of membrane-type matrix metalloproteinase (MT-MMP-1) results in the activation of both endogenous and exogenous 72-kDa gelatinase. To understand the effects of MT-MMP-1 on 72-kDa gelatinase activation, we analyzed its expression in human fibroblasts and HT-1080 fibrosarcoma cells. Both cell types expressed the MT-MMP-1 mRNA constitutively at a considerable level and treatment of cells with PMA enhanced the expression about 2–3-fold. Concanavalin A treatment increased MT-MMP-1 mRNA levels in fibroblasts about 4-fold. Induction of MT-MMP-1 by phorbol 12-myristate 13-acetate (PMA) required protein synthesis as shown by cycloheximide inhibition. The induction was also inhibited by dexamethasone. Analysis of MT-MMP-1 mRNA stability using actinomycin D indicated that the half-life was rather long and not affected by PMA, suggesting transcriptional regulation. Only HT-1080 cells had significant 72-kDa gelatinase processing activity after treatment with PMA or concanavalin A, while fibroblasts were virtually negative. Immunoblotting analysis of fibroblast lysates indicated that MT-MMP-1 was present mainly in a 60-kDa form. PMA and concanavalin A caused 2–4-fold increases in its protein levels, while in HT-1080 cells PMA, concanavalin A, or overexpression of MT-MMP-1 did not significantly enhance the level of the 60-kDa protein. Instead, an immunoreactive, proteolytically processed 43-kDa form was observed, and its appearance correlated to 72-kDa gelatinase processing activity. Thus 72-kDa gelatinase activation, while enhanced by MT-MMP-1 expression, needs additional co-operating factors.

Abbreviations
bFGF

basic fibroblast groth factor

ConA

concanavalin A

EGF

epidermal growth factor

IL-1β

interleukin-1β

MT-MMP-1

membrane-type matrix metalloproteinase-1

PMA

phorbol 12-myristate 13-acetate

TGF-β

transforming growth factor-β

TTMP-2

tissue inhibitor of metalloproteinases type 2

TNF-α

tumor necrosis factor-α

uPA

urokinase type of plasminogen activator

Ancillary

Advertisement