title: The scaffolding protein RACK1 interacts with androgen receptor and promotes cross-talk through a protein kinase C signaling pathway.
abstract: The androgen receptor (AR), a member of the nuclear hormone receptor superfamily, functions as a ligand-dependent transcription factor that regulates genes involved in cell proliferation and differentiation. Using a C-terminal region of the human AR in a yeast two-hybrid screen, we have identified RACK1 (receptor for activated C kinase-1) as an AR-interacting protein. In this report we found that RACK1, which was previously shown to be a protein kinase C (PKC)-anchoring protein that determines the localization of activated PKCbetaII isoform, facilitates ligand-independent AR nuclear translocation upon PKC activation by indolactam V. We also observed RACK1 to suppress ligand-dependent and -independent AR transactivation through PKC activation. In chromatin immunoprecipitation assays, we demonstrate a decrease in AR recruitment to the AR-responsive prostate-specific antigen (PSA) promoter following stimulation of PKC. Furthermore, prolonged exposure to indolactam V, a PKC activator, caused a reduction in PSA mRNA expression in prostate cancer LNCaP cells. Finally, we found PKC activation to have a repressive effect on AR and PSA protein expression in androgen-treated LNCaP cells. Our data suggest that RACK1 may function as a scaffold for the association and modification of AR by PKC enabling translocation of AR to the nucleus but rendering AR unable to activate transcription of its target genes.
authors.affiliation: Prostate Research Group, School of Surgical and Reproductive Sciences, University of Newcastle, Framlington Place, Newcastle upon Tyne NE2 4HH, United Kingdom.
authors.forename: Anastasia C
authors.initials: AC
authors.lastname: Rigas
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Ozanne
authors.forename: David E
authors.initials: DE
authors.lastname: Neal
authors.forename: Craig N
authors.initials: CN
authors.lastname: Robson
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002454:Cell Differentiation; D002455:Cell Division; D045744:Cell Line, Tumor; D002843:Chromatin / Q000378:metabolism; D017353:Gene Deletion; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007769:Lactams / Q000494:pharmacology; D008024:Ligands; D008856:Microscopy, Fluorescence; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D000075370:Receptors for Activated C Kinase; D011944:Receptors, Androgen / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D020798:Two-Hybrid System Techniques; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D002843:Chromatin; D007211:Indoles; D007769:Lactams; D008024:Ligands; D010455:Peptides; D020033:Protein Isoforms; D012333:RNA, Messenger; D000075370:Receptors for Activated C Kinase; D011944:Receptors, Androgen; C070301:peptide I; C043969:indolactam V; D011493:Protein Kinase C; D001616:beta-Galactosidase