Ataxin-7 interacts with a Cbl-associated protein that it recruits into neuronal intranuclear inclusions.
Spinocerebellar ataxia 7 (SCA7) is a neurodegenerative disease caused by expansion of a CAG repeat in the coding region of the SCA7 gene. The disease primarily affects the cerebellum and the retina, but also many other central nervous system (CNS) structures as the disease progresses. Ataxin-7, encoded by the SCA7 gene, is a protein of unknown function expressed in many tissues including the CNS. In normal brain, ataxin-7 is found in the cytoplasm and/or nucleus of neurons, but in SCA7 brain ataxin-7 accumulates in intranuclear inclusions. Ataxin-7 is expressed ubiquitously, but mutation leads to neuronal death in only certain areas of the brain. This selective pattern of degeneration might be explained by interaction with a partner that is specifically expressed in vulnerable cells. We used a two-hybrid approach to screen a human retina cDNA library for ataxin-7-binding proteins, and isolated R85, a splice variant of Cbl-associated protein (CAP). R85 and CAP are generated by alternative splicing of the gene SH3P12 which we localized on chromosome 10q23-q24. The interaction between ataxin-7 and the SH3P12 gene products (SH3P12GPs) was confirmed by pull-down and co-immunoprecipitation. SH3P12GPs are expressed in Purkinje cells in the cerebellum. Ataxin-7 colocalizes with full-length R85 (R85FL) in co-transfected Cos-7 cells and with one of the SH3P12GPs in neuronal intranuclear inclusions in brain from a SCA7 patient. We propose that this interaction is part of a physiological pathway related to the function or turnover of ataxin-7. Its role in the pathophysiological process of SCA7 disease is discussed.
Lebre
A S
AS
INSERM U289, Hôpital de la Salpêtrière, 47 boulevard de l'Hôpital, 75651 Paris, Cedex 13, France.
Jamot
L
L
Takahashi
J
J
Spassky
N
N
Leprince
C
C
Ravisé
N
N
Zander
C
C
Fujigasaki
H
H
Kussel-Andermann
P
P
Duyckaerts
C
C
Camonis
J H
JH
Brice
A
A
D017398:Alternative Splicing / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D000067719:Ataxin-7; D015152:Blotting, Northern; D015153:Blotting, Western; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D019556:COS Cells / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D005982:Glutathione Transferase / Q000378:metabolism; D000882:Haplorhini; D006801:Humans; D007124:Immunoenzyme Techniques; D017404:In Situ Hybridization, Fluorescence; D002479:Inclusion Bodies / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000502:physiology*; D011233:Precipitin Tests; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques; D015003:Yeasts / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
C000593829:ATXN7 protein, human; D000067719:Ataxin-7; C000593831:Atxn7 protein, mouse; D003598:Cytoskeletal Proteins; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; C119201:ponsin; D005982:Glutathione Transferase; D001616:beta-Galactosidase