MMP9 and Alzheimer disease: Recently, a protease cascade, which converts proNGF to mature mNGF and degrades mNGF in the extracellular space by the coordinated activity of plasminogen, tissue plasminogen activator (tPA), neuroserpin, matrix metalloproteinase 9 (MMP-9) and tissue inhibitor of matrix metalloproteinase 1 (TIMP-1) was shown to be defective in AD (Bruno and Cuello, 2006).