title: Vacuolar H+-ATPase is down-regulated by the angiogenesis-inhibitory pigment epithelium-derived factor in metastatic prostate cancer cells.
abstract: The Vacuolar H+-ATPases (V-ATPases), a multi-subunits nanomotor present in all eukaryotic cells resides in the endomembranes of exocytotic and endocytotic pathways. Plasmalemmal V-ATPases have been shown to be involved in tumor cell metastasis. Pigment epithelium-derived factor (PEDF), a potent endogenous inhibitor of angiogenesis, is down-regulated in prostate cancer cells. We hypothesized that the transduction of PEDF in prostate cancer cells will down-regulate V-ATPase function; that in turn will decrease the expression of the V-ATPase accessory protein ATP6ap2 and a-subunit isoforms that target V-ATPase to the cell surface. To test these hypotheses, we used the human androgen-sensitive prostate cancer cells LNCaP, and its castration-refractory-derivative CL1 that were engineered to stably co-express the DsRed Express Fluorescent Protein with or without PEDF. To determine if PEDF down-regulates the function of V-ATPase, we measured the rate of proton fluxes (JH+) of the cytosolic and endosome/lysosome compartments. The mRNA levels for subunit-a isoforms and the ATP6ap2 were measured using quantitative reverse transcription-PCR. The results showed that PEDF expression decreased the rate of JH+ in metastatic CL1 cells without affecting JH+ in non-metastatic LNCaP cells, when studying pH(cyt). Interestingly, PEDF did not affect JH+ in endosomes/lysosomes either in metastatic cells or in non-metastatic cells. We also showed that PEDF significantly decreases the levels of a4 isoform and ATP6ap2 in metastatic CL1 cells, without affecting the levels of a4 isoform in the non-metastatic LNCaP cells. These data identify PEDF as a novel regulator of V-ATPase suggesting a new way by which PEDF may inhibit prostate tumor growth.
authors.affiliation: Texas Tech University Health Sciences Center Department of Cell Physiology & Molecular Biophysics Lubbock USA souad.sennoune&commat;ttuhsc.edu.
authors.forename: S R
authors.initials: SR
authors.lastname: Sennoune
authors.affiliation: Texas Tech University Health Sciences Center Department of Cell Physiology & Molecular Biophysics Lubbock USA.
authors.forename: L E
authors.initials: LE
authors.lastname: Bermudez
authors.affiliation: Texas Tech University Health Sciences Center Department of Cell Physiology & Molecular Biophysics Lubbock USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Lees
authors.affiliation: Texas Tech University Health Sciences Center Department of Urology Lubbock USA.
authors.forename: J
authors.initials: J
authors.lastname: Hirsch
authors.affiliation: Texas Tech University Health Sciences Center Department of Urology Lubbock USA.
authors.forename: S
authors.initials: S
authors.lastname: Filleur
authors.affiliation: Texas Tech University Health Sciences Center Department of Cell Physiology & Molecular Biophysics Lubbock USA.
authors.forename: R
authors.initials: R
authors.lastname: Martínez-Zaguilán
mesh_terms: D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D015536:Down-Regulation; D005136:Eye Proteins / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D008297:Male; D009389:Neovascularization, Pathologic / Q000235:genetics*; D009414:Nerve Growth Factors / Q000378:metabolism / Q000502:physiology*; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020033:Protein Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015843:Serpins / Q000378:metabolism / Q000502:physiology*; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics* / Q000378:metabolism; D000099174:Pigment Epithelium-Derived Factor
chemical_list: D005136:Eye Proteins; D009414:Nerve Growth Factors; D020033:Protein Isoforms; D012333:RNA, Messenger; D015843:Serpins; D025262:Vacuolar Proton-Translocating ATPases; D000099174:Pigment Epithelium-Derived Factor