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 6

Tg modulates mutant ATXN1 and its toxicity in Drosophila SCA1 models.

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Tg modulates mutant ATXN1 and its toxicity in Drosophila SCA1 models. (A...
(A) Western blot and qRT-PCR analyses of ATXN1[82Q] protein and mRNA levels after the knockdown of Tg with 2 different shRNAs in Drosophila eyes expressing ATXN1[82Q]. Knockdown of Tg was confirmed by qRT-PCR (bottom right). Protein lysates were extracted from the pooled 16 fly heads per genotype. Data shown as mean ± SD, *P < 0.05, ***P < 0.001, ****P < 0.0001, 1-way ANOVA, post hoc Dunnett’s test. (B) Western blot and qRT-PCR analyses of ATXN1[82Q] protein and mRNA levels after overexpression of Tg in Drosophila eyes expressing ATXN1[82Q]. Overexpression of Tg was confirmed by qRT-PCR (bottom right). Protein lysates were extracted from the pooled 8 fly heads per genotype. Data shown as mean ± SD, ***P < 0.001, ****P < 0.0001, 1-way ANOVA, post hoc Dunnett’s test. (C) Representative images of Drosophila eyes showing external organization of the ommatidia from negative control and flies expressing ATXN1[82Q] together with Tg or control shRNA. Note the severely degenerated eye with black necrotic patches upon the coexpression of Tg and ATXN1[82Q]. Scale bar: 100 μm in the top images; 50 μm in the bottom images. (D) Effect of Tg knockdown and (E) effect of Tg overexpression 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.