Structural features discriminate androgen receptor N/C terminal and coactivator interactions

Laboratories for Reproductive Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599-7500, USA.
Molecular and Cellular Endocrinology (Impact Factor: 4.41). 06/2011; 348(2):403-10. DOI: 10.1016/j.mce.2011.03.026
Source: PubMed


Human androgen receptor (AR) transcriptional activity involves interdomain and coactivator interactions with the agonist-bound AR ligand binding domain (LBD). Structural determinants of the AR NH(2)- and carboxyl-terminal interaction between the AR NH(2)-terminal FXXLF motif and activation function 2 (AF2) in the LBD were shown previously by crystallography. In this report, we provide evidence for a region in AR LBD helix 12 outside the AF2 binding cleft that facilitates interactions with the FXXLF and LXXLL motifs. Mutagenesis of glutamine 902 to alanine in AR LBD helix 12 (Q902A) disrupted AR FXXLF motif binding to AF2, but enhanced coactivator LXXLL motif binding. Functional compensation for defective FXXLF motif binding by AR-Q902A was suggested by the slower dissociation rate of bound androgen. Functional importance of glutamine 902 was indicated by the charged residue germline mutation Q902R that caused partial androgen insensitivity, and a similar somatic mutation Q902K reported in prostate cancer, both of which increased the androgen dissociation rate and decreased AR transcriptional activity. High affinity equilibrium androgen binding was retained by alanine substitution mutations at Tyr-739 in AR LBD helix 5 or Lys-905 in helix 12 structurally adjacent to AF2, whereas transcriptional activity decreased and the androgen dissociation increased. Deleterious effects of these loss of function mutations were rescued by the helix stabilizing AR prostate cancer somatic mutation H874Y. Sequence NH(2)-terminal to the AR FXXLF motif contributed to the AR NH(2)- and carboxyl-terminal interaction based on greater AR-2-30 FXXLF motif peptide binding to the agonist-bound AR LBD than a shorter AR-20-30 FXXLF motif peptide. We conclude that helix 12 residues outside the AF2 binding cleft modulate AR transcriptional activity by providing flexibility to accommodate FXXLF or LXXLL motif binding.

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    • "The androgen receptor (AR) is a nuclear hormone receptor that is activated by binding to androgenic hormones, such as testosterone and dihydrotestosterone (DHT), in the cytoplasm and translocation into the nucleus 2, 3. AR binds to androgen via its COOH-terminal ligand binding domain (LBD). The NH2-terminal of AR contains the transcriptional activation domain, and this activity is modified by a number of cofactors 4. Androgens, via the AR, are essential for the growth and survival of androgen-dependent PCa cells 5. Androgen ablation therapies, which involve surgical or chemical castration and/or androgen antagonists, have been the mainstay of treatment for advanced androgen-dependent PCa since 1941 6, 7. "
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    ABSTRACT: Androgens and the androgen receptor (AR) are essential for growth and differentiation of the normal prostate gland as well as proliferation and survival of prostate cancer (PCa). Increasing evidence suggests that reactivation of the AR plays a pivotal role in disease progression to castration-resistant PCa (CRPC). Forkhead box (FOX) factors exert two distinct effects on AR function in PCa. The A-class of FOX proteins, especially FOXA1, functions as a pioneer factor to facilitate AR transactivation and PCa growth. In contrast, the O-class of FOX proteins such as FOXO1 and FOXO3, which are downstream effectors of the PTEN tumor suppressor, inhibit the transcriptional activity of either full-length AR or constitutively active splice variants of AR in a direct or indirect manner in PCa. FOXO1 also contributes to taxane-mediated inhibition of the AR and CRPC growth. Therefore, FOX family members not only have a tight relationship with AR, but also represent a pivotal group of proteins to be targeted for PCa therapy. The present review focuses primarily on recent advances in the epigenetic, mechanistic and clinical relevant aspects of regulation of the AR by FOXA1 and FOXO1 factors in PCa.
    International journal of biological sciences 06/2014; 10(6):614-619. DOI:10.7150/ijbs.8389 · 4.51 Impact Factor
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    • "Given the importance of inter-domain interactions, it is possible that AR 50–250 within NTD could influence the activity of NL1 in the DNA-binding domain and Hinge region via inter-domain interactions. In addition, AR 50–250 may influence the activity of LBD via interactions between N-and C-terminal regions of AR [30]. These interactions could potentially be regulated by other cellular factors and the integration of these interactions will ultimately determine the localization and function of AR. "
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    ABSTRACT: Nucleocytoplasmic trafficking of the androgen receptor (AR) represents an essential step in androgen action. To determine whether the amino-terminal domain (NTD) contains potential nuclear import and/or export signals, deletion mutants of the NTD tagged with green fluorescent protein (GFP) were generated and tested for their intracellular localization in both AR-negative and AR-positive cell lines. Subcellular localization analysis suggested a role of the NTD in regulating AR subcellular localization and revealed that the region of a.a. 50-250 of the NTD of AR (AR(50-250)) could promote cytoplasmic localization. Leptomycin B inhibited the activity of AR(50-250), suggesting that AR(50-250) export is mediated through exportin 1, either directly or indirectly. These observations argue for an important role of the NTD in regulating AR nucleocytoplasmic trafficking and will facilitate further investigation of interactions among different signals in regulating AR nucleocytoplasmic trafficking, which may lead to new approaches to inhibit AR nuclear localization.
    The Journal of Steroid Biochemistry and Molecular Biology 10/2013; DOI:10.1016/j.jsbmb.2013.09.013 · 3.63 Impact Factor
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    • "However, the H874Y mutation stabilizes the LBD core structure so that T is as effective as DHT in promoting transcriptional activity [29]. The structure stabilizing effects of H874Y are sufficient to overcome the detrimental effects of loss of function mutations that cause androgen insensitivity [40]. The equivalent potency of T and DHT with AR-H874Y suggests that intracrine synthesis of T would promote LacZ-transduced CWR-R1 tumor growth. "
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    ABSTRACT: Prostate cancer (CaP) is the second leading cause of cancer death in American men. Androgen deprivation therapy is initially effective in CaP treatment, but CaP recurs despite castrate levels of circulating androgen. Continued expression of the androgen receptor (AR) and its ligands has been linked to castration-recurrent CaP growth. In this report, the ligand-dependent dominant-negative ARΔ142-337 (ARΔTR) was expressed in castration-recurrent CWR-R1 cell and tumor models to elucidate the role of AR signaling. Expression of ARΔTR decreased CWR-R1 tumor growth in the presence and absence of exogenous testosterone (T) and improved survival in the presence of exogenous T. There was evidence for negative selection of ARΔTR transgene in T-treated mice. Mass spectrometry revealed castration-recurrent CaP dihydrotestosterone (DHT) levels sufficient to activate AR and ARΔTR. In the absence of exogenous testosterone, CWR-R1-ARΔTR and control cells exhibited altered androgen profiles that implicated epithelial CaP cells as a source of intratumoral AR ligands. The study provides in vivo evidence that activation of AR signaling by intratumoral AR ligands is required for castration-recurrent CaP growth and that epithelial CaP cells produce sufficient active androgens for CaP recurrence during androgen deprivation therapy. Targeting intracrine T and DHT synthesis should provide a mechanism to inhibit AR and growth of castration-recurrent CaP.
    PLoS ONE 01/2012; 7(1):e30192. DOI:10.1371/journal.pone.0030192 · 3.23 Impact Factor
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