ATAXIN-1 interacts with the repressor Capicua in its native complex to cause SCA1 neuropathology.
Spinocerebellar ataxia type 1 (SCA1) is one of several neurodegenerative diseases caused by expansion of a polyglutamine tract in the disease protein, in this case, ATAXIN-1 (ATXN1). A key question in the field is whether neurotoxicity is mediated by aberrant, novel interactions with the expanded protein or whether its wild-type functions are augmented to a deleterious degree. We examined soluble protein complexes from mouse cerebellum and found that the majority of wild-type and expanded ATXN1 assembles into large stable complexes containing the transcriptional repressor Capicua. ATXN1 directly binds Capicua and modulates Capicua repressor activity in Drosophila and mammalian cells, and its loss decreases the steady-state level of Capicua. Interestingly, the S776A mutation, which abrogates the neurotoxicity of expanded ATXN1, substantially reduces the association of mutant ATXN1 with Capicua in vivo. These data provide insight into the function of ATXN1 and suggest that SCA1 neuropathology depends on native, not novel, protein interactions.
Lam
Yung C
YC
Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA.
Bowman
Aaron B
AB
Jafar-Nejad
Paymaan
P
Lim
Janghoo
J
Richman
Ronald
R
Fryer
John D
JD
Hyun
Eric D
ED
Duvick
Lisa A
LA
Orr
Harry T
HT
Botas
Juan
J
Zoghbi
Huda Y
HY
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D000067696:Ataxin-1; D000067528:Ataxins; D001921:Brain / Q000378:metabolism; D002531:Cerebellum / Q000378:metabolism*; D017124:Conserved Sequence; D004330:Drosophila / Q000196:embryology / Q000502:physiology*; D005124:Eye Abnormalities / Q000209:etiology; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D020754:Spinocerebellar Ataxias / Q000209:etiology* / Q000235:genetics; D014158:Transcription, Genetic; D014921:Wings, Animal / Q000002:abnormalities
C000593749:ATXN1 protein, human; D000067696:Ataxin-1; D000067528:Ataxins; C000593750:Atxn1 protein, mouse; C498611:Cic protein, mouse; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D012097:Repressor Proteins; C097188:polyglutamine