Overexpression of synphilin-1 promotes clearance of soluble and misfolded alpha-synuclein without restoring the motor phenotype in aged A30P transgenic mice.
Lewy bodies and neurites are the pathological hallmark of Parkinson's disease. These structures are composed of fibrillized and ubiquitinated alpha-synuclein suggesting that impaired protein clearance is an important event in aggregate formation. The A30P mutation is known for its fast oligomerization, but slow fibrillization rate. Despite its toxicity to neurons, mechanisms involved in either clearance or conversion of A30P alpha-synuclein from its soluble state into insoluble fibrils and their effects in vivo are poorly understood. Synphilin-1 is present in Lewy bodies, interacting with alpha-synuclein in vivo and in vitro and promotes its sequestration into aggresomes, which are thought to act as cytoprotective agents facilitating protein degradation. We therefore crossed animals overexpressing A30P alpha-synuclein with synphilin-1 transgenic mice to analyze its impact on aggregation, protein clearance and phenotype progression. We observed that co-expression of synphilin-1 mildly delayed the motor phenotype caused by A30P alpha-synuclein. Additionally, the presence of N- and C-terminal truncated alpha-synuclein species and fibrils were strongly reduced in double-transgenic mice when compared with single-transgenic A30P mice. Insolubility of mutant A30P and formation of aggresomes was still detectable in aged double-transgenic mice, paralleled by an increase of ubiquitinated proteins and high autophagic activity. Hence, this study supports the notion that co-expression of synphilin-1 promotes formation of autophagic-susceptible aggresomes and consecutively the degradation of human A30P alpha-synuclein. Notably, although synphilin-1 overexpression significantly reduced formation of fibrils and astrogliosis in aged animals, a similar phenotype is present in single- and double-transgenic mice suggesting additional neurotoxic processes in disease progression.
Institute of Medical Genetics and Applied Genomics, University Tübingen, Tübingen, Germany.
Nicolas
N
Casadei
Anne-Maria
AM
Pöhler
Cristina
C
Tomás-Zapico
Jesús
J
Torres-Peraza
Ivo
I
Schwedhelm
Annemarie
A
Witz
Irina
I
Zamolo
Raymond
R
De Heer
Berry
B
Spruijt
Lucas P J J
LP
Noldus
Jochen
J
Klucken
José J
JJ
Lucas
Philipp J
PJ
Kahle
Rejko
R
Krüger
Olaf
O
Riess
Silke
S
Nuber
D000375:Aging; D000818:Animals; D001343:Autophagy / Q000502:physiology; D052160:Benzothiazoles; D001921:Brain / Q000378:metabolism / Q000473:pathology; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D010300:Parkinson Disease / Q000235:genetics; D017510:Protein Folding; D012995:Solubility; D013844:Thiazoles / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D051844:alpha-Synuclein / Q000235:genetics* / Q000378:metabolism*
D052160:Benzothiazoles; D002352:Carrier Proteins; D009419:Nerve Tissue Proteins; C497604:SNCA protein, human; C118958:SNCAIP protein, human; D013844:Thiazoles; D025801:Ubiquitin; D051844:alpha-Synuclein; C009462:thioflavin T