Molecular ageing of alpha- and Beta-synucleins: protein damage and repair mechanisms.
PLoS One
; 8(4): e61442, 2013.
Article
em En
| MEDLINE
| ID: mdl-23630590
ABSTRACT
Abnormal α-synuclein aggregates are hallmarks of a number of neurodegenerative diseases. Alpha synuclein and ß-synucleins are susceptible to post-translational modification as isoaspartate protein damage, which is regulated in vivo by the action of the repair enzyme protein L-isoaspartyl O-methyltransferase (PIMT). We aged in vitro native α-synuclein, the α-synuclein familial mutants A30P and A53T that give rise to Parkinsonian phenotypes, and ß-synuclein, at physiological pH and temperature for a time course of up to 20 days. Resolution of native α-synuclein and ß-synuclein by two dimensional techniques showed the accumulation of a number of post-translationally modified forms of both proteins. The levels of isoaspartate formed over the 20 day time course were quantified by exogenous methylation with PIMT using S-Adenosyl-L-[(3)H-methyl]methionine as a methyl donor, and liquid scintillation counting of liberated (3)H-methanol. All α-synuclein proteins accumulated isoaspartate at â¼1% of molecules/day, â¼20 times faster than for ß-synuclein. This disparity between rates of isoaspartate was confirmed by exogenous methylation of synucleins by PIMT, protein resolution by one-dimensional denaturing gel electrophoresis, and visualisation of (3)H-methyl esters by autoradiography. Protein silver staining and autoradiography also revealed that α-synucleins accumulated stable oligomers that were resistant to denaturing conditions, and which also contained isoaspartate. Co-incubation of approximately equimolar ß-synuclein with α-synuclein resulted in a significant reduction of isoaspartate formed in all α-synucleins after 20 days of ageing. Co-incubated α- and ß-synucleins, or α, or ß synucleins alone, were resolved by non-denaturing size exclusion chromatography and all formed oligomers of â¼57.5 kDa; consistent with tetramerization. Direct association of α-synuclein with ß-synuclein in column fractions or from in vitro ageing co-incubations was demonstrated by their co-immunoprecipitation. These results provide an insight into the molecular differences between α- and ß-synucleins during ageing, and highlight the susceptibility of α-synuclein to protein damage, and the potential protective role of ß-synuclein.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Alfa-Sinucleína
/
Beta-Sinucleína
Limite:
Animals
/
Humans
Idioma:
En
Revista:
PLoS One
Assunto da revista:
CIENCIA
/
MEDICINA
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Reino Unido