Disrupting SUMOylation enhances transcriptional function and ameliorates polyglutamine androgen receptor–mediated disease
Jason P. Chua, Satya L. Reddy, Zhigang Yu, Elisa Giorgetti, Heather L. Montie, Sarmistha Mukherjee, Jake Higgins, Richard C. McEachin, Diane M. Robins, Diane E. Merry, Jorge A. Iñiguez-Lluhí, Andrew P. Lieberman
Jason P. Chua, Satya L. Reddy, Zhigang Yu, Elisa Giorgetti, Heather L. Montie, Sarmistha Mukherjee, Jake Higgins, Richard C. McEachin, Diane M. Robins, Diane E. Merry, Jorge A. Iñiguez-Lluhí, Andrew P. Lieberman
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Research Article

Disrupting SUMOylation enhances transcriptional function and ameliorates polyglutamine androgen receptor–mediated disease

Abstract

Expansion of the polyglutamine (polyQ) tract within the androgen receptor (AR) causes neuromuscular degeneration in individuals with spinobulbar muscular atrophy (SBMA). PolyQ AR has diminished transcriptional function and exhibits ligand-dependent proteotoxicity, features that have both been implicated in SBMA; however, the extent to which altered AR transcriptional function contributes to pathogenesis remains controversial. Here, we sought to dissociate effects of diminished AR function from polyQ-mediated proteotoxicity by enhancing the transcriptional activity of polyQ AR. To accomplish this, we bypassed the inhibitory effect of AR SUMOylation (where SUMO indicates small ubiquitin-like modifier) by mutating conserved lysines in the polyQ AR that are sites of SUMOylation. We determined that replacement of these residues by arginine enhances polyQ AR activity as a hormone-dependent transcriptional regulator. In a murine model, disruption of polyQ AR SUMOylation rescued exercise endurance and type I muscle fiber atrophy; it also prolonged survival. These changes occurred without overt alterations in polyQ AR expression or aggregation, revealing the favorable trophic support exerted by the ligand-activated receptor. Our findings demonstrate beneficial effects of enhancing the transcriptional function of the ligand-activated polyQ AR and indicate that the SUMOylation pathway may be a potential target for therapeutic intervention in SBMA.

Authors

Jason P. Chua, Satya L. Reddy, Zhigang Yu, Elisa Giorgetti, Heather L. Montie, Sarmistha Mukherjee, Jake Higgins, Richard C. McEachin, Diane M. Robins, Diane E. Merry, Jorge A. Iñiguez-Lluhí, Andrew P. Lieberman

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Figure 1

A cellular model expressing non-SUMOylatable polyQ AR.

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A cellular model expressing non-SUMOylatable polyQ AR. (A) AR10Q, AR112Q...
(A) AR10Q, AR112Q, or AR111Q-KRKR were induced to express AR in the presence of 10 nM R1881 for 24 hours, then analyzed by Western blot. Dox, doxycycline. (B and C) AR10Q, AR112Q, and AR111Q-KRKR cells were induced to express AR for 24 hours, then treated with R1881 for varying times and immunostained for AR (red). Nuclei were stained by DAPI. (B) Cytoplasmic (score 0) to nuclear (score 4) translocation was determined at indicated times. Data are mean ± SEM. n = 3 replicate experiments. (C) Arrows indicate nuclei containing aggregates after 24 hours of treatment with 10 nM R1881. Scale bar: 2 μm. (D) AR112Q- and AR111Q-KRKR–expressing cells were transfected with HA-SUMO3 and treated with 10 nM R1881 for 24 hours. Whole-cell lysates (left panel) were immunoprecipitated for AR and blotted for HA or AR (right panel). (E) AR112Q or AR111Q-KRKR cells were transfected with HA-ubiquitin and hCHIP, and treated with YM-1, as indicated. Following incubation with 10 mM MG132, lysates were collected and analyzed for AR ubiquitination. Whole-cell lysates (left panel) were immunoprecipitated for AR and blotted for AR and HA (middle and right panels).