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Updated: Jul 24, 2026
Growth Assays to Assess Polyglutamine Toxicity in Yeast
Published on: March 5, 2012
Androgen receptors containing expanded polyglutamine tracts exhibit progressive toxicity when stably expressed in the
D M Avila1, D R Allman, J-M Gallo
1Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
Abstract:
The pathogenesis of X-linked spinal and bulbar muscular atrophy (SBMA) has been traced to an expansion of repeated glutamine (Gln) residues within the amino terminus of the human androgen receptor (AR). To examine the mechanisms by which these expanded repeat ARs (Exp-ARs) are toxic to neurons, we have established and characterized a cell culture model by stably transfecting SH-SY 5Y neuroblastoma cells with cDNAs containing either normal AR (81 series; 23 Glns) or Exp-AR (902 series; 56 Glns). At a low passage number, no differences in cell morphology, growth properties, or susceptibility to toxic insults were observed between clones expressing normal AR or Exp-AR. Initially, both types of cultures were found to express similar levels of specific hormone binding in monolayer binding assays. Immunohistochemical studies demonstrated the vast majority of both the normal AR and Exp-AR were localized to the nucleus in the absence and presence of androgen. As the 902 series of clones were propagated, the Exp-AR content in the cells appeared to decline progressively. However, this decrease actually reflects a gradual disappearance of the Exp-AR cell population. No such selection occurred during the propagation of cells expressing the normal AR. This selection against cells expressing physiological levels of Exp-AR occurs in the absence of intracellular aggregates and suggests that mechanisms other than those involving the formation of aggregates underlie the observed toxicity of Exp-ARs.
Insights
X-linked spinal and bulbar muscular atrophy (SBMA) is linked to expanded repeat androgen receptors (Exp-ARs). A cell model shows Exp-ARs cause neuronal toxicity through mechanisms independent of intracellular aggregates.
Area of Science:
- Neuroscience
- Genetics
- Molecular Biology
Background:
- X-linked spinal and bulbar muscular atrophy (SBMA) pathogenesis involves expanded glutamine repeats in the androgen receptor (AR).
- Understanding the toxicity mechanisms of expanded repeat ARs (Exp-ARs) in neurons is crucial for SBMA research.
Purpose of the Study:
- To establish and characterize a cell culture model for investigating Exp-AR toxicity in neurons.
- To explore the mechanisms underlying Exp-AR neurotoxicity, particularly in relation to intracellular aggregates.
Main Methods:
- Stable transfection of SH-SY5Y neuroblastoma cells with normal AR and Exp-AR cDNAs.
- Cell morphology, growth, hormone binding, and nuclear localization assessments.
- Long-term propagation of transfected cell lines to observe Exp-AR population dynamics.
Main Results:
- No initial differences in cell properties or hormone binding between normal AR and Exp-AR expressing cells.
- Exp-ARs were primarily localized in the nucleus, similar to normal AR.
- A progressive decline in Exp-AR cell population occurred during propagation, indicating selection against Exp-AR expression, independent of aggregate formation.
Conclusions:
- Exp-ARs exert toxicity in a neuronal cell model through mechanisms not dependent on intracellular aggregate formation.
- A selection process actively removes cells expressing physiological levels of Exp-AR.
- Further research is needed to elucidate the precise non-aggregate-dependent mechanisms of Exp-AR neurotoxicity in SBMA.
