Deubiquitinase USP7 contributes to the pathogenicity of spinal and bulbar muscular atrophy
Anna Pluciennik, … , Sokol V. Todi, Diane E. Merry
Anna Pluciennik, … , Sokol V. Todi, Diane E. Merry
Published November 10, 2020
Citation Information: J Clin Invest. 2021;131(1):e134565. https://doi.org/10.1172/JCI134565.
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Research Article Neuroscience

Deubiquitinase USP7 contributes to the pathogenicity of spinal and bulbar muscular atrophy

Abstract

Polyglutamine (polyQ) diseases are devastating, slowly progressing neurodegenerative conditions caused by expansion of polyQ-encoding CAG repeats within the coding regions of distinct, unrelated genes. In spinal and bulbar muscular atrophy (SBMA), polyQ expansion within the androgen receptor (AR) causes progressive neuromuscular toxicity, the molecular basis of which is unclear. Using quantitative proteomics, we identified changes in the AR interactome caused by polyQ expansion. We found that the deubiquitinase USP7 preferentially interacts with polyQ-expanded AR and that lowering USP7 levels reduced mutant AR aggregation and cytotoxicity in cell models of SBMA. Moreover, USP7 knockdown suppressed disease phenotypes in SBMA and spinocerebellar ataxia type 3 (SCA3) fly models, and monoallelic knockout of Usp7 ameliorated several motor deficiencies in transgenic SBMA mice. USP7 overexpression resulted in reduced AR ubiquitination, indicating the direct action of USP7 on AR. Using quantitative proteomics, we identified the ubiquitinated lysine residues on mutant AR that are regulated by USP7. Finally, we found that USP7 also differentially interacts with mutant Huntingtin (HTT) protein in striatum and frontal cortex of a knockin mouse model of Huntington’s disease. Taken together, our findings reveal a critical role for USP7 in the pathophysiology of SBMA and suggest a similar role in SCA3 and Huntington’s disease.

Authors

Anna Pluciennik, Yuhong Liu, Elana Molotsky, Gregory B. Marsh, Bedri Ranxhi, Frederick J. Arnold, Sophie St.-Cyr, Beverly Davidson, Naemeh Pourshafie, Andrew P. Lieberman, Wei Gu, Sokol V. Todi, Diane E. Merry

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Figure 1

Unbiased quantitative interaction screen for WT and polyQ-expanded AR.

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Unbiased quantitative interaction screen for WT and polyQ-expanded AR. T...
Three independent SILAC experiments were performed. Experiment 1: PC12 cells expressing AR 112Q or AR10Q were grown in heavy or light SILAC medium, respectively (shown in pink). Anti-AR (A) or 3B5H10 antibody (B) was used for IP. Experiment 2 (label swap): AR112Q- or AR10Q-expressing cells were grown in light or heavy SILAC medium, respectively (shown in yellow). Anti-AR (A) or 3B5H10 antibody (B) was used for IP. Experiment 3: cells expressing AR 112Q or AR10Q were grown in heavy or light SILAC medium, respectively (shown in gray). 3B5H10 antibody (B) was used for IP. Cells were induced with doxycycline to express AR and treated with DHT for 48 hours. (A) Left: Venn diagram comparison of common proteins pulled down with anti-AR antibody in 2 experiments. Right: common proteins that were enriched either with AR112Q or AR10Q by 1.5-fold or more. Fold enrichment is shown in Supplemental Tables 1 and 2. (B) Left: Venn diagram comparison of common proteins pulled down with 3B5H10 antibody in 3 independent experiments. Right: common proteins enriched with AR112Q by 1.5-fold or more in at least 2 experiments. Fold enrichment is shown in Supplemental Table 1.