Abstract
Prostate cancer is an androgen receptor (AR)-driven disease and post-translational modification of AR is critical for AR activation. We previously reported that Arrest-defective protein 1 (ARD1) is an oncoprotein in prostate cancer. It acetylates and activates AR to promote prostate tumorigenesis. However, the ARD1-targeted residue within AR and the mechanisms of the acetylation event in prostate tumorigenesis remained unknown. In this study, we show that ARD1 acetylates AR at lysine 618 (K618) in vitro and in vivo. An AR construct with the charged lysine substitution by arginine (AR-618R) reduces RNA Pol II binding, AR transcriptional activity, prostate cancer cell growth, and xenograft tumor formation due to attenuation of AR nuclear translocation, whereas, construct mimicking neutral polar substitution acetylation at K618 by glutamine (AR-618Q) enhanced these effects beyond that of the wild-type AR. Mechanistically, ARD1 forms a ternary complex with AR and HSP90 in vitro and in vivo. Expression of ARD1 increases levels of AR acetylation and AR-HSP90 dissociation in a dose dependent manner. Moreover, the AR acetylation defective K618R mutant is unable to dissociate from HSP90 while the HSP90-dissociated AR is acetylated following ligand exposure. This work identifies a new mechanism for ligand-induced AR-HSP90 dissociation and AR activation. Targeting ARD1-mediated AR acetylation may be a potent intervention for AR-dependent prostate cancer therapy.
Highlights
Androgen receptor (AR) plays a crucial role in prostate cancer (PCa) [1, 2]
We demonstrated that the DNA binding domain (DBD) of androgen receptor (AR) is strongly acetylated by Arrestdefective protein 1 (ARD1) (Figure 1A)
To determine which lysine in motif II is acetylated by ARD1, we mutated all but one lysine, respectively, within motif II and again subjected each DBD mutant to in vitro acetylation assay (Figure S2C)
Summary
Activation of AR via mutation, amplification, overexpression, or posttranslational modification leads to PCa initiation and progression [3,4,5]. Alternative strategies that inhibit AR activity without contributing to disease progression are needed. AR undergoes a conformational change leading to ARHSP90 dissociation, rapid nuclear translocation, and AR target gene transcription [9]. Unchecked, this process eventually leads to prostate tumorigenesis. New approaches for targeting the interaction of AR and HSP90, as well as the androgen-driven AR nuclear translocation may provide more efficacious therapeutic strategies while avoiding the deleterious effects of ADT
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