title: MPTP treatment of common marmosets impairs proteasomal enzyme activity and decreases expression of structural and regulatory elements of the 26S proteasome.
abstract: Dysfunction of the ubiquitin-proteasome system occurs in the substantia nigra (SN) in Parkinson's disease (PD). However, it is unknown whether this is a primary cause or a secondary consequence of other components of the pathogenic process. We have investigated in nonhuman primates whether initiating cell death through mitochondrial complex I inhibition using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP) altered proteasomal activity or the proteasomal components in the SN. Chymotrypsin-like, trypsin-like and peptidylglutamyl-peptide hydrolase (PGPH) activating of 20S proteasome were decreased in SN homogenates of MPTP-treated marmosets compared to naïve animals. Western blotting revealed a marked decrease in the expression of 20S-alpha subunits, but no change in 20S-beta subunits in the SN of MPTP-treated marmoset compared to naïve animals. There was a marked decrease in the expression of the proteasome activator 700 (PA700) and proteasome activator 28 (PA28) regulatory complexes. The 20S-alpha4 subunit immunoreactivity was decreased in the nucleus of colocalized tyrosine hydroxylase (TH)-positive cells of MPTP-treated animals compared to naïve animals but no difference in the intensity of 20S-beta1i subunit staining. Immunoreactivity for PA700-Rpt5 and PA28-alpha subunits within surviving TH-positive cells of MPTP-treated marmoset was reduced compared to naïve controls. Overall, the changes in proteasomal function and structure occurring follow MPTP-induced destruction of the SN in common marmosets were very similar to those found in PD. This suggests that altered proteasomal function in PD could be a consequence of other pathogenic processes occurring in SN as opposed to initiating cell death as previously suggested.
authors.affiliation: Neurodegenerative Disease Research Group, GKT School of Biomedical and Health Sciences, King's College, London, SE1 1UL, UK.
authors.forename: B-Y
authors.initials: BY
authors.lastname: Zeng
authors.forename: M M
authors.initials: MM
authors.lastname: Iravani
authors.forename: S-T
authors.initials: ST
authors.lastname: Lin
authors.forename: M
authors.initials: M
authors.lastname: Irifune
authors.forename: M
authors.initials: M
authors.lastname: Kuoppamäki
authors.forename: G
authors.initials: G
authors.lastname: Al-Barghouthy
authors.forename: L
authors.initials: L
authors.lastname: Smith
authors.forename: M J
authors.initials: MJ
authors.lastname: Jackson
authors.forename: S
authors.initials: S
authors.lastname: Rose
authors.forename: A D
authors.initials: AD
authors.lastname: Medhurst
authors.forename: P
authors.initials: P
authors.lastname: Jenner
mesh_terms: D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000187:drug effects / Q000201:enzymology; D002144:Callithrix; D007150:Immunohistochemistry; D046988:Proteasome Endopeptidase Complex / Q000096:biosynthesis / Q000378:metabolism*; D021122:Protein Subunits / Q000096:biosynthesis / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D021122:Protein Subunits; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D014446:Tyrosine 3-Monooxygenase; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease