title: Autophagic degradation of the androgen receptor mediated by increased phosphorylation of p62 suppresses apoptosis in hypoxia.
abstract: Prostate cancer grows under hypoxic conditions. Hypoxia decreases androgen receptor (AR) protein levels. However, the molecular mechanism remains unclear. Here, we report that p62-mediated autophagy degrades AR protein and suppresses apoptosis in prostate cancer LNCaP cells in hypoxia. In LNCaP cells, hypoxia decreased AR at the protein level, but not at the mRNA level. Hypoxia-induced AR degradation was inhibited not only by knockdown of LC3, a key component of the autophagy machinery, but also by knockdown of p62. Depletion of p62 enhanced hypoxia-induced poly(ADP-ribose) polymerase cleavage and caspase-3 cleavage, markers of apoptosis, whereas simultaneous knockdown of p62 and AR suppressed hypoxia-induced apoptosis. Hypoxia increased the formation of a cytosolic p62-AR complex and enhanced sequestration of AR from the nucleus. Formation of this complex was promoted by the increased phosphorylation of serine 403 in the ubiquitin-associated domain of p62 during hypoxia. An antioxidant and an AMP-activated protein kinase (AMPK) inhibitor reduced hypoxia-induced p62 phosphorylation at serine 403 and suppressed hypoxia-induced complex formation between AR and p62. These results demonstrate that hypoxia enhances the complex formation between p62 and AR by promoting phosphorylation of p62 at serine 403, probably through activating AMPK, and that p62-mediated autophagy degrades AR protein for cell survival in hypoxia.
authors.affiliation: Division of Applied Life Sciences, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka 5998531, Japan; Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, Kobe, Hyogo 6578501, Japan.
authors.forename: Takakazu
authors.initials: T
authors.lastname: Mitani
authors.affiliation: Division of Applied Life Sciences, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka 5998531, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Minami
authors.affiliation: Division of Applied Life Sciences, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka 5998531, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Harada
authors.affiliation: Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, Kobe, Hyogo 6578501, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ashida
authors.affiliation: Division of Applied Life Sciences, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka 5998531, Japan. Electronic address: yamaji@biochem.osakafu-u.ac.jp.
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Yamaji
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D017209:Apoptosis; D001343:Autophagy; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D006801:Humans; D010766:Phosphorylation; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D059748:Proteolysis; D017382:Reactive Oxygen Species / Q000378:metabolism; D011944:Receptors, Androgen / Q000378:metabolism*; D000071456:Sequestosome-1 Protein
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D017382:Reactive Oxygen Species; D011944:Receptors, Androgen; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein
keywords: AMP-activated kinase; Androgen receptor; Autophagy; Hypoxia; Prostate cancer; p62