Advances in Brief Tyrosine Phosphorylation Mediates ConA-induced Membrane Type 1-Matrix Metalloproteinase Expression and Matrix Metalloproteinase-2 Activation in MDA-MB-231 Human Breast Carcinoma Cells 1

ConA-induced cell surface activation ofpro-matrix metalloprotelnase-2 (pro-MMP.2) by MDA-MB-231 human breast cancer cells Is apparently mediated by up-regulation of membrane type 1 MMP (MT1-MMP) through transcriptional and posttranscriptlonal mechanisms. Here, we have explored the respective roles of cell surface Clustering and protein tyrosine phosphorylation in the ConA-lnductlon effects. Treatment with succinyl-ConA, a variant lacking significant clusterabifity, partially sUm idated MT1-MMP mRNA and protein levels but did not Induce MMP-2 activation, suggesting that clustering contributes to the transcriptional regulation by ConA but appears to be CrItICalfor the nontranscriptional component. We further found that genistein, an inhibitor of tyrosine phosphorylatlon, blocked ConA-Induced pro-MMP-2 activation and ConA-Induced MT1-MMP mRNA level in a dose-dependent manner, Implicating tyrosine phosphorylation In the transcriptional aspect. This was confirmed by the dose-dependent promotion of pro-MMP-2 activa ton by sodium orthovanadate In the presence of suboptimal concentra tons of ConA (7.5 @ag/ml), with optimal effects seen at 25 @ag/ml or thovanadate. Genistein did not inhibit the ConA potentlation of MMP-2 activation In MCF-7 ceUs,In which transfected MT1-MMP Is driven by a heterologous promoter, supporting the major Implication of phosphoty rosine In the transcriptional component of ConA regulation. These data describe a major signaling event upstream of MT1-MMP Induction by ConA and set the stage for further analysis of the nontranscriptional component.