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.

Hepatocyte growth factor (HGF) is a chemoattractant and inducer for neural stem/progenitor (NS/P) cell migration. Although the type II transmembrane serine protease, matriptase (MTP) is an activator of the latent HGF, MTP is indispensable on NS/P cell motility induced by the active form of HGF. This suggests that MTP's action on NS/P cell motility involves mechanisms other than proteolytic activation of HGF. In the present study, we investigate the role of MTP in HGF-stimulated signaling events. Using specific inhibitors of phosphatidylinositol-3-kinase (PI3K), protein kinase B (Akt) or focal adhesion kinase (FAK), we demonstrated that in NS/P cells HGF-activated c-Met induces PI3k-Akt signaling which then leads to FAK activation. This signaling pathway ultimately induces MMP2 expression and NS/P cell motility. Knocking down of MTP in NS/P cells with specific siRNA impaired HGF-stimulation of c-Met, Akt and FAK activation, blocked HGF-induced production of MMP2 and inhibited HGF-stimulated NS/P cell motility. MTP-knockdown NS/P cells cultured in the presence of recombinant protein of MTP protease domain or transfected with the full-length wild-type but not the protease-defected MTP restored HGF-responsive events in NS/P cells. In addition to functioning as HGF activator, our data revealed novel function of MTP on HGF-stimulated c-Met signaling activation.

Knockdown of the suppression of tumorigenicity 14–encoding type II transmembrane serine protease matriptase (MTP) in neural stem/progenitor (NS/P) cells impairs cell mobility, response to chemo‐attractants, and neurovascular niche interaction. In the present study, we showed by Western blot that a portion of MTP can be detected in the mitochondrial fraction of mouse NS/P cells by immunostaining that it is co‐stained with the mitochondrial dye MitoTracker (Thermo Fisher Scientific, Waltham, MA, USA) inside the cells. Co‐immunoprecipitation showed that MTP is bound to the β subunit of mitochondrial F0F1–ATP synthase complex (ATP‐β). Cytoimmunofluorescence staining and an in situ proximity ligation assay further confirmed a physical interaction between MTP and ATP‐β. This interaction relied on the presence of both Cls/Clr urchin embryonic growth factor, bone morphogenic protein 1 and low‐density lipoprotein receptor motifs of MTP. We found that NS/P cell mitochondrial membrane potential is impaired by MTP knockdown, and ATP synthesis and oxygen consumption rate are significantly reduced in MTP‐knockdown NS/P cells. Among the oxidative phosphorylation functions, the greatest effect of MTP knockdown is the reduction by over 50% in the mitochondrial energy reserve capacity. This made MTP‐knockdown NS/P cells unable to overcome hydrogen peroxide stress, which leads to cessation of cell growth. This work identifies 2 previously unknown functions for MTP: first as a binding protein in the mitochondrial F1F0–ATP synthase complex and second as a regulatory mechanism of mitochondrial bioenergetics. Mitochondrial MTP may serve a protective function for NS/P cells in response to stress.—Fang, J.‐D., Tung, H.‐H., Lee, S.‐L. Mitochondrial localization of St14‐encoding transmembrane serine protease is involved in neural stem/progenitor cell bioenergetics through binding to F0F1–ATP synthase complex. FASEB J. 33,4327‐4340 (2019). http://www.fasebj.org

In a rat middle cerebral artery occlusion (MACo) model of ischemic stroke, intracerebroventricular administration of human recombinant hepatocyte growth factor (HGF) mitigated motor impairment and cortical infarction. Recombinant HGF reduced MCAo-induced TNFα and IL1β expression, and alleviated perilesional reactivation of microglia and astrocyte. All of the aforementioned beneficial effects of HGF were antagonized by an inhibitor to the type II transmembrane serine protease matriptase (MTP). MCAo upregulated MTP mRNA and protein