title: Differential subcellular localization renders HAI-2 a matriptase inhibitor in breast cancer cells but not in mammary epithelial cells.
abstract: The type 2 transmembrane serine protease matriptase is under tight control primarily by the actions of the integral membrane Kunitz-type serine protease inhibitor HAI-1. Growing evidence indicates that HAI-2 might also be involved in matriptase inhibition in some contexts. Here we showed that matriptase inhibition by HAI-2 depends on the subcellular localizations of HAI-2, and is observed in breast cancer cells but not in mammary epithelial cells. HAI-2 is co-expressed with matriptase in 21 out of 26 human epithelial and carcinoma cells examined. HAI-2 is also a potent matriptase inhibitor in solution, but in spite of this, HAI-2 inhibition of matriptase is not observed in all contexts where HAI-2 is expressed, unlike what is seen for HAI-1. Induction of matriptase zymogen activation in mammary epithelial cells results in the formation of matriptase-HAI-1 complexes, but matriptase-HAI-2 complexes are not observed. In breast cancer cells, however, in addition to the appearance of matriptase-HAI-1 complex, three different matriptase-HAI-2 complexes, are formed following the induction of matriptase activation. Immunofluorescent staining reveals that activated matriptase is focused at the cell-cell junctions upon the induction of matriptase zymogen activation in both mammary epithelial cells and breast cancer cells. HAI-2, in contrast, remains localized in vesicle/granule-like structures during matriptase zymogen activation in human mammary epithelial cells. In breast cancer cells, however, a proportion of the HAI-2 reaches the cell surface where it can gain access to and inhibit active matriptase. Collectively, these data suggest that matriptase inhibition by HAI-2 requires the translocation of HAI-2 to the cell surface, a process which is observed in some breast cancer cells but not in mammary epithelial cells.
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University Washington, DC, 20057, United States of America; Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan, ROC.
authors.forename: Hsiang-Hua D
authors.initials: HH
authors.lastname: Chang
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University Washington, DC, 20057, United States of America.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University Washington, DC, 20057, United States of America.
authors.forename: Hongyu
authors.initials: H
authors.lastname: Lai
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University Washington, DC, 20057, United States of America.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Yang
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University Washington, DC, 20057, United States of America; Department of Biology, Carleton College, Northfield, MN, 55057, United States of America.
authors.forename: Chun-Che
authors.initials: CC
authors.lastname: Tseng
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University Washington, DC, 20057, United States of America.
authors.forename: Ying-Jung J
authors.initials: YJ
authors.lastname: Lai
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University Washington, DC, 20057, United States of America.
authors.forename: Yu
authors.initials: Y
authors.lastname: Pan
authors.affiliation: Thomas Jefferson High School for Science and Technology, Alexandria, VA, 22046, United States of America.
authors.forename: Emily
authors.initials: E
authors.lastname: Zhou
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University Washington, DC, 20057, United States of America.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Johnson
authors.affiliation: Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan, ROC.
authors.forename: Jehng-Kang
authors.initials: JK
authors.lastname: Wang
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University Washington, DC, 20057, United States of America.
authors.forename: Chen-Yong
authors.initials: CY
authors.lastname: Lin
mesh_terms: D002460:Cell Line; D045744:Cell Line, Tumor; D003594:Cytoplasmic Granules / Q000737:chemistry / Q000378:metabolism; D004790:Enzyme Induction; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000201:enzymology* / Q000473:pathology; D015870:Gene Expression; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007365:Intercellular Junctions / Q000378:metabolism; D042361:Mammary Glands, Human / Q000201:enzymology* / Q000473:pathology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009928:Organ Specificity; D011485:Protein Binding; D021381:Protein Transport; D053491:Proteinase Inhibitory Proteins, Secretory / Q000235:genetics / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D004792:Enzyme Precursors; D008562:Membrane Glycoproteins; D053491:Proteinase Inhibitory Proteins, Secretory; C109149:SPINT1 protein, human; C109148:SPINT2 protein, human; D012697:Serine Endopeptidases; C485596:ST14 protein, human