Specificity and regulation of casein kinase-mediated phosphorylation of alpha-synuclein.
alpha-Synuclein (alpha-syn) is the major component of pathologic inclusions that characterize neurodegenerative disorders such as Parkinson disease, dementia with Lewy body disease, and multiple system atrophy. The present study uses novel phospho-specific antibodies to assess the presence and regulation of phosphorylated Ser87 and Ser129 in alpha-syn in human brain samples and in a transgenic mouse model of alpha-synucleinopathies. By immunohistochemistry, alpha-syn phosphorylated at Ser129, but not at Ser87, was abundant in alpha-syn inclusions. Under normal conditions, Ser129 phosphorylation, but not Ser87 phosphorylation, was detected at low levels in the soluble biochemical fractions in human alpha-syn transgenic mice and stably transfected cultured cells. Therefore, a role for Ser87 phosphorylation in alpha-synucleinopathies is unlikely, and in vitro assays showed that phosphorylation at this site would inhibit polymerization. In vitro studies also indicated that hyperphosphorylation of Ser129 alpha-syn in pathologic inclusions may be due in part to the intrinsic properties of aggregated alpha-syn to act as substrates for kinases but not phosphatases. Further studies in transgenic mice and cultured cells suggest that cellular toxicity, including proteasomal dysfunction, increases casein kinase 2 activity, which results in elevated Ser129 alpha-syn phosphorylation. These data provide novel explanations for the presence of hyperphosphorylated Ser129 alpha-syn in pathologic inclusions.
Waxman
Elisa A
EA
Department of Pharmacology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6084, USA.
Giasson
Benoit I
BI
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D047390:Casein Kinase II / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D002479:Inclusion Bodies / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008875:Middle Aged; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D012694:Serine / Q000737:chemistry / Q000378:metabolism; D013378:Substantia Nigra / Q000378:metabolism* / Q000473:pathology; D013379:Substrate Specificity; D015854:Up-Regulation; D051844:alpha-Synuclein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D051844:alpha-Synuclein; D012694:Serine; D047390:Casein Kinase II; D046988:Proteasome Endopeptidase Complex