The V 1 domain hydrolyzes ATP and has three catalytic sites located at the interface of alternating subunits A and B. It is composed of eight subunits (A 3B 3CDE 3FG 3H). V 1 is the catalytic domain on the cytosolic side of the membrane. V-ATPase is a multi-subunit complex that has 14 different subunits arranged in two functional domains. V-ATPase is a proton pump located at intracellular compartments of the endomembrane system (e.g., endosomes, lysosomes, Golgi-derived vesicles, clathrin-coated vesicles, secretory vesicles) and the plasma membrane of eukaryotic cells specialized for active proton secretion ). A critical enzyme involved in the process of pH regulation is the vacuolar (H +) – ATPase (V-ATPase). The luminal pH of intracellular compartments is highly controlled. We propose a new V-ATPase-dependent mechanism to inhibit androgen receptor expression in prostate cancer cells involving defective endosomal trafficking of iron and the inhibition of HIF-1 α-subunit turnover. Dimethyloxalylglycine (DMOG), which prevents HIF-1α degradation independently of V-ATPase, also decreased AR levels, supporting our hypothesis that HIF-1α serves as a downstream mediator in the V-ATPase-AR axis. Moreover, iron treatment partially rescued CCA-mediated AR repression. The addition of iron (III) citrate restored HIF-1α hydroxylation and decreased total HIF-1α levels in PCa cells treated with CCA. CCA treatment increased the protein level and nuclear localization of the alpha subunit of the transcription factor HIF-1 (HIF-1α) in PCa cells via decreased hydroxylation and degradation of HIF-1α. V-ATPase-dependent repression of AR expression was linked to defective endo-lysosomal pH regulation and reduced AR expression at the transcriptional level. This treatment decreased PSA mRNA levels, indicative of reduced AR activity. Our studies showed that AR expression was reduced in LAPC4 and LNCaP PCa cell lines treated with nanomolar concentrations of the V-ATPase inhibitor concanamycin A (CCA). Suppression of androgen receptor (AR) expression is a desirable mechanism to manage PCa.
Prostate Cancer (PCa) is the most commonly diagnosed cancer and the third leading cause of death for men in the United States. Received: JanuAccepted: JPublished: June 22, 2018 Keywords: prostate cancer androgen receptor V-ATPase concanamycin HIF-1α
Parra 1ġDepartment of Biochemistry and Molecular Biology, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, 87131, USA Fordyce 1, Summer Raines Hayek 1 and Karlett J.
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