Mitochondrial localization of St14‐encoding transmembrane serine protease is involved in neural stem/progenitor cell bioenergetics through binding to F0F1–ATP synthase complex

ABSTRACT 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). www.fasebj.org