Cross-species genetic screens identify transglutaminase 5 as a regulator of polyglutamine-expanded ataxin-1
Won-Seok Lee, … , Juan Botas, Huda Y. Zoghbi
Won-Seok Lee, … , Juan Botas, Huda Y. Zoghbi
Published May 2, 2022
Citation Information: J Clin Invest. 2022;132(9):e156616. https://doi.org/10.1172/JCI156616.
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Research Article Genetics Neuroscience

Cross-species genetic screens identify transglutaminase 5 as a regulator of polyglutamine-expanded ataxin-1

Abstract

Many neurodegenerative disorders are caused by abnormal accumulation of misfolded proteins. In spinocerebellar ataxia type 1 (SCA1), accumulation of polyglutamine-expanded (polyQ-expanded) ataxin-1 (ATXN1) causes neuronal toxicity. Lowering total ATXN1, especially the polyQ-expanded form, alleviates disease phenotypes in mice, but the molecular mechanism by which the mutant ATXN1 is specifically modulated is not understood. Here, we identified 22 mutant ATXN1 regulators by performing a cross-species screen of 7787 and 2144 genes in human cells and Drosophila eyes, respectively. Among them, transglutaminase 5 (TG5) preferentially regulated mutant ATXN1 over the WT protein. TG enzymes catalyzed cross-linking of ATXN1 in a polyQ-length–dependent manner, thereby preferentially modulating mutant ATXN1 stability and oligomerization. Perturbing Tg in Drosophila SCA1 models modulated mutant ATXN1 toxicity. Moreover, TG5 was enriched in the nuclei of SCA1-affected neurons and colocalized with nuclear ATXN1 inclusions in brain tissue from patients with SCA1. Our work provides a molecular insight into SCA1 pathogenesis and an opportunity for allele-specific targeting for neurodegenerative disorders.

Authors

Won-Seok Lee, Ismael Al-Ramahi, Hyun-Hwan Jeong, Youjin Jang, Tao Lin, Carolyn J. Adamski, Laura A. Lavery, Smruti Rath, Ronald Richman, Vitaliy V. Bondar, Elizabeth Alcala, Jean-Pierre Revelli, Harry T. Orr, Zhandong Liu, Juan Botas, Huda Y. Zoghbi

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Figure 3

Validation of TGM5, IRAK1, SRPK3, and STK16 in SCA1 animal models.

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Validation of TGM5, IRAK1, SRPK3, and STK16 in SCA1 animal models. (A) S...
(A) Scanning electron microscopy images of Drosophila eyes expressing human ATXN1[82Q] with knockdown of Drosophila homologs of TGM5, IRAK1, SRPK3, or STK16. Scale bar: 100 μm in the top images; 10 μm in the bottom images. (B) Effect of TGM5 or STK16 knockdown on the motor performance of Drosophila SCA1 model expressing ATXN1[82Q] in the CNS. Data shown as mean ± SEM, *P < 0.05, linear mixed-effect model ANOVA. (C) Schematic representation for stereotaxic injection of adeno-associated virus serotype 9 (AAV9) carrying shRNAs into the cerebella of adult SCA1 mice (left), and representative fluorescence brain images with or without bright field taken after 4 weeks of the injection (right). Scale bar: 2 mm. (D) Western blot analysis of WT and mutant ATXN1 in the cerebella of SCA1 mice after the knockdown of Stk16, Tgm5, Irak1, or Srpk3 using 3 different shRNAs. Data shown as mean ± SD, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001; 1-way ANOVA was performed in ATXN1[2Q] and ATXN1[154Q] separately. Post hoc Dunnett’s test; 2-tailed t test was used for comparing ATXN1[2Q] and ATXN1[154Q]. (E) qRT-PCR data of the mRNA levels of the 4 genes knocked down in D. Data shown as mean ± SD, **P < 0.01, ***P < 0.001, ****P < 0.0001, 1-way ANOVA, post hoc Tukey’s test.