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.
Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, D-82152 Martinsried, Germany.
Niclas W
NW
Schiffer
Jocelyn
J
Céraline
F Ulrich
FU
Hartl
Sarah A
SA
Broadley
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