title: Extracellular and Luminal pH Regulation by Vacuolar H+-ATPase Isoform Expression and Targeting to the Plasma Membrane and Endosomes.
abstract: Plasma membrane vacuolar H(+)-ATPase (V-ATPase) activity of tumor cells is a major factor in control of cytoplasmic and extracellular pH and metastatic potential, but the isoforms involved and the factors governing plasma membrane recruitment remain uncertain. Here, we examined expression, distribution, and activity of V-ATPase isoforms in invasive prostate adenocarcinoma (PC-3) cells. Isoforms 1 and 3 were the most highly expressed forms of membrane subunit a, with a1 and a3 the dominant plasma membrane isoforms. Correlation between plasma membrane V-ATPase activity and invasiveness was limited, but RNAi knockdown of either a isoform did slow cell proliferation and inhibit invasion in vitro Isoform a1 was recruited to the cell surface from the early endosome-recycling complex pathway, its knockdown arresting transferrin receptor recycling. Isoform a3 was associated with the late endosomal/lysosomal compartment. Both a isoforms associated with accessory protein Ac45, knockdown of which stalled transit of a1 and transferrin-transferrin receptor, decreased proton efflux, and reduced cell growth and invasiveness; this latter effect was at least partly due to decreased delivery of the membrane-bound matrix metalloproteinase MMP-14 to the plasma membrane. These data indicate that in prostatic carcinoma cells, a1 and a3 isoform populations predominate in different compartments where they maintain different luminal pH. Ac45 plays a central role in navigating the V-ATPase to the plasma membrane, and hence it is an important factor in expression of the invasive phenotype.
authors.affiliation: From the Endothelial Cell Biology Unit, School of Molecular and Cellular Biology and.
authors.forename: Gina A
authors.initials: GA
authors.lastname: Smith
authors.affiliation: From the Endothelial Cell Biology Unit, School of Molecular and Cellular Biology and.
authors.forename: Gareth J
authors.initials: GJ
authors.lastname: Howell
authors.affiliation: School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Clair
authors.initials: C
authors.lastname: Phillips
authors.affiliation: School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Muench
authors.affiliation: From the Endothelial Cell Biology Unit, School of Molecular and Cellular Biology and.
authors.forename: Sreenivasan
authors.initials: S
authors.lastname: Ponnambalam
authors.affiliation: School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom m.a.harrison@leeds.ac.uk.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Harrison
mesh_terms: D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000201:enzymology* / Q000235:genetics; D011992:Endosomes / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D053511:Matrix Metalloproteinase 14 / Q000235:genetics / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*
chemical_list: C089598:ATP6AP1 protein, human; D007527:Isoenzymes; C507086:MMP14 protein, human; D053511:Matrix Metalloproteinase 14; D025262:Vacuolar Proton-Translocating ATPases
keywords: endocytosis; membrane trafficking; receptor internalization; receptor recycling; vacuolar ATPase