Dataset Information

Discovery Proteomics Identifies a Molecular Link between the Coatomer Protein Complex I and Androgen Receptor-dependent Transcription

ABSTRACT: Aberrant activation of androgen receptor (AR)-dependent transcriptional programs is a hallmark of human prostate cancers. At the molecular level, ligand-mediated AR activation is coordinated through spatial and temporal protein-protein interactions (PPIs) involving AR-interacting proteins, which we designate the “AR-interactome”. Despite many years of research, the ligand-sensitive protein complexes involved in ligand-mediated AR activation in prostate-tumor cells has not been clearly defined. Here, we describe the development, characterization, and utilization of a novel human LNCaP prostate-tumor cell line, N-AR, which stably expresses wild-type AR containing the streptavidin-binding peptide epitope tagged at its N-terminus (SBP-AR). A bioanalytical workflow involving streptavidin-chromatography and label-free quantitative mass spectrometry was used to identify SBP-AR and associated ligand-sensitive proteins/protein complexes functionally linked to AR activation in the cytosol of N-AR cells. Functional studies verified that ligand-sensitive streptavidin-copurified proteins encoded modulators of AR-mediated transcription, suggesting that these novel proteins were putative SBP-AR-interacting proteins in N-AR cells. This was supported by biochemical associations between recombinant SBP-AR and the ligand-sensitive COPI retrograde trafficking complex in vitro. Extensive biochemical and molecular experiments showed that the COPI-retrograde complex regulates ligand-mediated AR transcriptional activation through the mobilization of Golgi-localized ARA160 coactivator into the nuclear compartment of prostate-tumor cells. Collectively, this study provides a bioanalytical strategy to validate the AR-interactome and define novel AR-interacting proteins involved in ligand-mediated AR activation in prostate-tumor cells. Moreover, we describe a cellular system to study how compartment-specific AR-interacting proteins influence AR activation and contribute to aberrant AR-dependent transcription that underlies the majority of human prostate cancers.

INSTRUMENT(S): 6520 Quadrupole Time-of-Flight LC/MS

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Jordy Hsiao

LAB HEAD: Michael Eugene Wright

PROVIDER: PXD002861 | Pride | 2016-07-20

REPOSITORIES: Pride

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Publications

Discovery Proteomics Identifies a Molecular Link between the Coatomer Protein Complex I and Androgen Receptor-dependent Transcription.

Hsiao Jordy J JJ Smits Melinda M MM Ng Brandon H BH Lee Jinhee J Wright Michael E ME

The Journal of biological chemistry 20160630 36

Aberrant androgen receptor (AR)-dependent transcription is a hallmark of human prostate cancers. At the molecular level, ligand-mediated AR activation is coordinated through spatial and temporal protein-protein interactions involving AR-interacting proteins, which we designate the "AR-interactome." Despite many years of research, the ligand-sensitive protein complexes involved in ligand-mediated AR activation in prostate tumor cells have not been clearly defined. Here, we describe the developmen ...[more]

PMID: 27365400

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Project description:Reactivation of androgen receptor (AR) may drive recurrent prostate cancer in castrate patients. Ack1 tyrosine kinase is overexpressed in prostate cancer and promotes castrate resistant xenograft tumor growth and enhances androgen target gene expression and AR recruitment to enhancers. Ack1 phosphorylates AR at Tyr-267 in the N-terminal transactivation domain. In this study, the role of this phosphorylation site was investigated by characterizing the phosphorylation site mutant in the context of full length and truncated AR lacking the ligand-binding domain. The Y267F mutant showed decreased transactivation of reporters. Expression of wild type full length and truncated AR in LNCaP cells increased cell proliferation in androgen-depleted conditions and increased colony formation. However, the Y267F mutant of full length and truncated AR was defective in stimulating cell proliferation. The full length AR Y267F mutant was defective in nuclear translocation induced by androgen or Ack1 kinase. The truncated AR was constitutively localized to the nucleus. Chromatin immunoprecipitation analysis showed that it was recruited to the target enhancers without androgen. The truncated Y267F AR mutant did not exhibit constitutive nuclear localization and androgen enhancer binding activity. Expression of AR responsive genes in cells expressing truncated AR wt and AR-Y267F mutant under androgen deprived conditions was assessed by microarray gene expression analysis. The AR pathway score was increased in cells expressing truncated AR wt and decreased in cells expressing truncated AR-Y267F. These results support the concept that phosphorylation of Tyr-267 is required for AR nuclear translocation and recruitment and DNA binding and transcription of AR responsive genes. Gene expression profiling was performed using RNA samples from LNCaP cells expressing truncated AR-wt and truncated AR-Y267F growing in androgen deprived conditions. The RNA sample from vector control cells were used as reference sample. Two biological replicates were used per each cell line.

Project description:While thousands of long non-coding RNAs (lncRNAs) are expressed in higher eukaryotes, the potential regulatory roles of lncRNAs in regulated gene transcription programs remain rather poorly understood. Here, we report that two lncRNAs highly overexpressed in aggressive prostate cancer, PRNCR1 and PCGEM1, bind successively to the androgen receptor (AR) and strongly enhance both ligand-dependent and ligand-independent AR-mediated gene activation programs and proliferation in prostate cancer cells. Binding of PRNCR1 to the C-terminally acetylated AR on enhancers and its association with DOT1L appear to be required for recruitment of the second lncRNA, PCGEM, to the N-terminally methylated AR. Unexpectedly, recognition of the H3K4me3 promoter mark by the PHD finger-domain of Pygopus2, recruited by PCGEM1, proves to enhance selective looping of AR-bound enhancers to target gene promoters in these cells, revealing a novel aspect of ligand-induced enhancer-promoter interactions. In “resistant” prostate cancer cells, these overexpressed lncRNAs can interact with, and are required for the robust activation of both truncated and full length AR, causing DHT-independent activation of the AR transcriptional program and cell proliferation. Conditionally-expressed short hairpin RNA (shRNA)-mediated targeting of these lncRNAs in these resistant cancer cell lines strongly suppressed xenograft growth in vivo. Together, these results suggest that these overexpressed lncRNAs can potentially serve as a required component of castration-resistance in prostatic tumors. Global Run On (GRO) assay followed by high throughput sequencing (GRO-seq); after knocking down PYGO2 LNCaP cells were grown to 30-50% confluence and siRNA/ASO transfections were carried out using Lipofectamine 2000 (Invitrogen) according to the manufacturer’s instructions. Control samples were transfected with scramble ASO and control siRNA, respectively. On the following day of transfection, the cells were cultured in UltraCULTURE (Phenol red free) + 5% Charcoal Dextran Stripped (CDS) serum for 48 hours. For androgen induction, we treat cells with DHT from a 100 uM stock in 70% ethanol to a final concentration of 100 nM for 1 hour Control siRNA, -DHT Control siRNA, +DHT Pygo2 siRNA, -DHT Pygo2 siRNA, +DHT

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Dataset Information

Discovery Proteomics Identifies a Molecular Link between the Coatomer Protein Complex I and Androgen Receptor-dependent Transcription

Publications

Discovery Proteomics Identifies a Molecular Link between the Coatomer Protein Complex I and Androgen Receptor-dependent Transcription.

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