An epitope-tagged reporter to detect MMP activation in vivo: Mmp2 activation patterns reveal Mmp14-independent regulation in zebrafish embryos

Abstract

Matrix metalloproteinases (MMPs) are secreted proteases that remodel the extracellular matrix (ECM) during development, disease, and other physiological processes. The ECM provides support for tissues and regulates the activity of surrounding cells. To prevent inappropriate activity, MMPs are synthesized as inactive enzymes. In vitro, MMP-14 activates MMP-2 by proteolytically removing MMP-2’s auto-inhibitory propeptide; however, investigating MMP activation within tissues requires a novel approach. I developed the Epitope-Mediated MMP Activation (EMMA) assay to detect and quantify MMP activation in vivo using immunofluorescence and immunoblotting. EMMAedMmp2 is activated in ECM-rich regions and patterns similar to endogenous protein expression. To investigate the underlying mechanisms of EMMAedMmp2 activation, I analyzed Mmp14α/β sequences and expression patterns. Differences between the two suggest unique roles for each of these paralogues in vivo. Furthermore, using EMMAedMmp2 with pharmacological MMP inhibitors reveals the presence of additional Mmp2 activation mechanisms in developing zebrafish embryos. I also generated a transgenic line of zebrafish expressing EMMAedMmp2 that can be used to investigate MMP activation mechanisms more consistently without the limitations of transient expression. The EMMA Assay is a versatile tool that will improve our understanding of MMP regulation in ECM remodelling and its implications in development and disease.