N-terminal polyglutamine-containing fragments inhibit androgen receptor transactivation function.
Abstract Several neurodegenerative diseases, including Kennedy's disease (KD), are associated with misfolding and aggregation of polyglutamine (polyQ)-expansion proteins. KD is caused by a polyQ-expansion in the androgen receptor (AR), a key player in male sexual differentiation. Interestingly, KD patients often show signs of mild-to-moderate androgen insensitivity syndrome (AIS) resulting from AR dysfunction. Here, we used the yeast Saccharomyces cerevisiae to investigate the molecular mechanism behind AIS in KD. Upon expression in yeast, polyQ-expanded N-terminal fragments of AR lacking the hormone binding domain caused a polyQ length-dependent growth defect. Interestingly, while AR fragments with 67 Q formed large, SDS-resistant inclusions, the most pronounced toxicity was observed upon expression of 102 Q fragments which accumulated exclusively as soluble oligomers in the 100-600 kDa range. Analysis using a hormone-dependent luciferase reporter revealed that full-length polyQ-expanded AR is fully functional in transactivation, but becomes inactivated in the presence of the corresponding polyQ-expanded N-terminal fragment. Furthermore, the greatest impairment of AR activity was observed upon interaction of full-length AR with soluble AR fragments. Taken together, our results suggest that soluble polyQ-containing fragments bind to full-length AR and inactivate it, thus providing insight into the mechanism behind AIS in KD and possibly other polyglutamine diseases, such as Huntington's disease.
Schiffer
Niclas W
NW
Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, D-82152 Martinsried, Germany.
Céraline
Jocelyn
J
Hartl
F Ulrich
FU
Broadley
Sarah A
SA
D015153:Blotting, Western; D055534:Bulbo-Spinal Atrophy, X-Linked / Q000235:genetics / Q000378:metabolism; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D047468:Immunoprecipitation; D007202:Indicators and Reagents; D008156:Luciferases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000378:metabolism* / Q000633:toxicity; D010957:Plasmids / Q000235:genetics; D011944:Receptors, Androgen / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D013347:Subcellular Fractions / Q000378:metabolism; D015533:Transcriptional Activation / Q000235:genetics*; D014238:Trichloroacetic Acid
D007202:Indicators and Reagents; D010446:Peptide Fragments; D010455:Peptides; D011944:Receptors, Androgen; C097188:polyglutamine; D014238:Trichloroacetic Acid; D008156:Luciferases