MAPK signaling regulates endothelial cell assembly into networks and expression of MT1-MMP and MMP-2

Microvascular endothelial cells embedded within three-dimensional (3D) type I collagen matrixes assemble into cellular networks, a process that requires the upregulation of membrane type 1 (MT1) matrix metalloproteinase (MMP) and MMP-2. The purpose of this study was to identify the signaling pathways responsible for the transcriptional activation of MT1-MMP and MMP-2 in endothelial cells in 3D collagen lattices. We hypothesized that the 3D type I collagen induction of MT1-MMP and MMP-2 is mediated by the mitogen-activated protein kinase family of enzymes. Here, we show that 3D type I collagen elicits a persistent increase in ERK1/2 and JNK activation and a decrease in p38 activation. Inhibition of ERK1/2 or JNK disrupted endothelial network formation in 3D type I collagen lattices, whereas inhibition of p38 promoted network formation. mRNA levels of both MT1-MMP and MMP-2 were attenuated by ERK1/2 inhibition but unaffected by either JNK or p38 inhibition. By contrast, expression of constitutively active MEK was sufficient to stimulate MMP-2 production in a monolayer of endothelial cells cultured on type I collagen. These results provide evidence that signaling through both ERK1/2 and JNK regulates endothelial assembly into cellular networks but that the ERK1/2 signaling cascade specifically regulates network formation and the production of both MT1-MMP and MMP-2 genes in response to 3D type I collagen.