Phosphorylation of ATXN1 at Ser776 in the cerebellum.
Spinocerebellar ataxia type 1 (SCA1) is one of nine inherited neurodegenerative disorders caused by a mutant protein with an expanded polyglutamine tract. Phosphorylation of ataxin-1 (ATXN1) at serine 776 is implicated in SCA1 pathogenesis. Previous studies, utilizing transfected cell lines and a Drosophila photoreceptor model of SCA1, suggest that phosphorylating ATXN1 at S776 renders it less susceptible to degradation. This work also indicated that oncogene from AKR mouse thymoma (Akt) promotes the phosphorylation of ATXN1 at S776 and severity of neurodegeneration. Here, we examined the phosphorylation of ATXN1 at S776 in cerebellar Purkinje cells, a prominent site of pathology in SCA1. We found that while phosphorylation of S776 is associated with a stabilization of ATXN1 in Purkinje cells, inhibition of Akt either in vivo or in a cerebellar extract-based phosphorylation assay did not decrease the phosphorylation of ATXN1-S776. In contrast, immunodepletion and inhibition of cyclic AMP-dependent protein kinase decreased phosphorylation of ATXN1-S776. These results argue against Akt as the in vivo kinase that phosphorylates S776 of ATXN1 and suggest that cyclic AMP-dependent protein kinase is the active ATXN1-S776 kinase in the cerebellum.
Jorgensen
Nathan D
ND
Institute of Human Genetics, University of Minnesota, Minneapolis, 55455, USA.
Andresen
J Michael
JM
Lagalwar
Sara
S
Armstrong
Ben
B
Stevens
Sam
S
Byam
Courtney E
CE
Duvick
Lisa A
LA
Lai
Shaojuan
S
Jafar-Nejad
Paymaan
P
Zoghbi
Huda Y
HY
Clark
H Brent
HB
Orr
Harry T
HT
D000409:Alanine / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000067696:Ataxin-1; D000067528:Ataxins; D002531:Cerebellum / Q000201:enzymology / Q000378:metabolism*; D004795:Enzyme Stability / Q000235:genetics; D006801:Humans; D051379:Mice; D008806:Mice, Inbred AKR; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017354:Point Mutation; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D011689:Purkinje Cells / Q000201:enzymology / Q000378:metabolism; D012694:Serine / Q000235:genetics / Q000378:metabolism*
C000593749:ATXN1 protein, human; D000067696:Ataxin-1; D000067528:Ataxins; C000593750:Atxn1 protein, mouse; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D012694:Serine; D051057:Proto-Oncogene Proteins c-akt; D000409:Alanine