Endogenous expression of matriptase in neural progenitor cells promotes cell migration and neuron differentiation.

Recent studies show that type II transmembrane serine proteases play important roles in diverse cellular activities and pathological processes. Their expression and functions in the central nervous system, however, are largely unexplored. In this study, we show that the expression of one such member, matriptase (MTP), was cell type-restricted and primarily expressed in neural progenitor (NP) cells and neurons. Blocking MTP expression or MTP activity prevented NP cell traverse of reconstituted basement membrane, whereas overexpression of MTP promoted it. The NP cell mobilization induced by either vascular endothelial growth factor or hepatocyte growth factor was also impaired by knocking down MTP expression. MTP acts upstream of matrix metalloproteinase 2 in promoting NP cell mobility. In embryonic stem cell differentiation to neural cells, MTP knockdown had no effect on entry of embryonic stem cells into the neural lineage. High MTP expression or activity, however, shifts the population dynamics from NP cells toward neurons to favor neuronal differentiation. This is the first report to demonstrate the direct involvement of type II transmembrane serine protease in NP cell function.

Matriptase/epithin participates in mammary epithelial cell growth and morphogenesis through HGF activation.

The epithelial-derived, type II transmembrane serine protease matriptase, the mouse homologue of which is epithin, has been shown to be involved in epidermal differentiation, hair formation, and thymus function. We show in this study that epithin/matriptase (Epi/MTP) plays a significant role in mammary epithelial cell growth and morphogenesis. Epi/MTP is expressed at low level in the mouse mammary epithelium of young animals and it accumulates at the terminal end-bud of the growing ducts. The level of Epi/MTP is elevated in the mammary glands at stages when epithelial proliferation and modeling occur. It is primarily present in the luminal epithelial cells of mouse mammary ducts and lobules. Using an ex vivo three-dimensional culture system for mammary epithelial functional assays, we show that mammary epithelial growth and morphogenesis in the presence of the latent form hepatocyte growth factor (pro-HGF) are blocked either by an inhibitor of the Epi/MTP protease activity or by siRNA knockdown of the Epi/MTP expression. These studies demonstrate that Epi/MTP participates in mammary epithelial growth and modeling through activation of pro-HGF. Our findings reveal an important pathway in normal mammary epithelial morphogenesis which may participate in breast cancer progression.