Membrane-type 5 matrix metalloproteinase is expressed in differentiated neurons and regulates axonal growth

Expression of membrane-type (MT) 5 matrix metalloproteinase (MMP) in the mo use brain was examined. MT5-MMP was expressed in the cerebrum in embryos, b ut it declined after birth. In contrast, expression in the cerebellum start ed to increase postnatally and continued thereafter. The cells expressing M T5-MMP were postmitotic neurons that showed gelatinolytic activities. Speci fic expression of MT5-MMP was observed in the neurons but not in the glial cells when embryonal mouse carcinoma P19 cells were differentiated in vitro by retinoic acid treatment. Neurons isolated from dorsal root ganglia also expressed MT5-MMP, and it was localized at the edge of growth cone. Proteo glycans inhibit neurite extension and regulate synaptogenesis. The inhibito ry effect of the proteoglycans on neurite extension of dorsal root ganglia neurons was effectively eliminated by recombinant MT5-MMP. Thus, MT5-MMP ex pressed in neurons may play a role in axonal growth that contributes to the regulation of neural network formation.