Contribution of MT1-MMP and of human laminin-5 gamma 2 chain degradation to mammary epithelial cell migration

Membrane-type matrix metalloproteinase 1 (MT1-MMP) is a membrane-anchored m atrix metalloproteinase (MMP) that is frequently associated with processes involving tissue remodelling and cell migration. We have examined MT1-MMP e xpression and subcellular distribution as a function of MCF10A mammary epit helial cell migration using an in vitro outgrowth migration assay. Stronger expression of MT1-MMP was observed at the mRNA and at the protein level in cells at the periphery of the outgrowth. As shown by videomicroscopy, thes e cells were involved in an orientated cell migration, in contrast to stati onary cells distant from the periphery. Furthermore, MT1-MMP was mainly dis tributed in lamellipodia of migratory cells, as well as at their basal surf ace in contact with the substrate. Laminin-5 (Ln-5), a recently described s ubstrate for MT1-MMP, was deposited preferentially in the matrix by migrato ry cells. Fragments of the gamma2 subunit of Ln-5 were also identified in m igratory cultures of MCF10A cells, attesting to its proteolytic degradation . These fragments corresponded in size to those we observed after incubatio n of purified human Ln-5 with the recombinant catalytic domain of human MT1 -MMP. We also show that anti-Ln5 blocking antibodies, MMP inhibitors (BB94 and TIMP-2) and MT1-MMP antisense oligonucleotides significantly decreased MCF10A cell migration. Taken together, these observations demonstrate that MT1-MMP is spatially and temporally regulated during MCF10A cell migration, and suggest that MT1-MMP-mediated pericellular proteolysis of Ln-5 gamma2 chain could contribute to this process.