ABSTRACT
OBJECTIVE: To determine whether mutations in the genes for alpha-synuclein or beta-synuclein are responsible for dementia with Lewy bodies (DLB), a disorder closely related to Parkinson disease (PD). METHODS: The authors ascertained 33 sporadic cases of DLB and 10 kindreds segregating DLB. DNA samples from the 43 index cases were screened for alterations in the genes for alpha-synuclein and beta-synuclein, as alpha-synuclein alterations cause PD and beta-synuclein may modulate alpha-synuclein aggregation and neurotoxicity. RESULTS: Two amino acid alterations were identified in unrelated DLB index cases: a valine to methionine substitution at codon 70 (V70M) and a proline to histidine substitution at codon 123 (P123H), both in the beta-synuclein gene. These amino acid substitutions occur at conserved residues in highly conserved regions of the beta-synuclein protein. Screening of at least 660 chromosomes from control subjects matched to the patients' population groups failed to identify another V70M or P123H allele. Cosegregation analysis of an extended pedigree segregating the P123H beta-synuclein alteration suggested that it is a dominant trait with reduced penetrance or a risk factor polymorphism. Histopathology and immunohistochemistry analysis of index case brain sections revealed widespread Lewy body pathology and alpha-synuclein aggregation without evidence of beta-synuclein aggregation. CONCLUSION: Mutations in the beta-synuclein gene may predispose to DLB.
Subject(s)
Amino Acid Substitution , Lewy Body Disease/genetics , Mutation, Missense , Nerve Tissue Proteins/genetics , Point Mutation , Aged , Aged, 80 and over , Amino Acid Sequence , Animals , Brain Chemistry , Cattle , Codon/genetics , Cystic Fibrosis/genetics , DNA Mutational Analysis , Disease Progression , Female , Genetic Predisposition to Disease , Humans , Japan/epidemiology , Lewy Body Disease/epidemiology , Lewy Body Disease/pathology , Male , Mice , Middle Aged , Molecular Sequence Data , Parkinson Disease/genetics , Parkinson Disease/pathology , Pedigree , Rats , Sequence Alignment , Sequence Homology, Amino Acid , Species Specificity , Synucleins , Thrombophilia/genetics , Washington/epidemiology , alpha-Synuclein , beta-SynucleinABSTRACT
Neuronal and oligodendrocytic aggregates of fibrillar alpha-synuclein define several diseases of the nervous system. It is likely that these inclusions impair vital metabolic processes and compromise viability of affected cells. Here, we report that a 12-amino acid stretch ((71)VTGVTAVAQKTV(82)) in the middle of the hydrophobic domain of human alpha-synuclein is necessary and sufficient for its fibrillization based on the following observations: 1) human beta-synuclein is highly homologous to alpha-synuclein but lacks these 12 residues, and it does not assemble into filaments in vitro; 2) the rate of alpha-synuclein polymerization in vitro decreases after the introduction of a single charged amino acid within these 12 residues, and a deletion within this region abrogates assembly; 3) this stretch of 12 amino acids appears to form the core of alpha-synuclein filaments, because it is resistant to proteolytic digestion in alpha-synuclein filaments; and 4) synthetic peptides corresponding to this 12-amino acid stretch self-polymerize to form filaments, and these peptides promote fibrillization of full-length human alpha-synuclein in vitro. Thus, we have identified key sequence elements necessary for the assembly of human alpha-synuclein into filaments, and these elements may be exploited as targets for the design of drugs that inhibit alpha-synuclein fibrillization and might arrest disease progression.
Subject(s)
Nerve Tissue Proteins/metabolism , Amino Acid Sequence , Humans , Molecular Sequence Data , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/ultrastructure , Nervous System Diseases/drug therapy , Peptide Fragments/metabolism , Protein Binding , Protein Conformation , Recombinant Proteins/metabolism , Recombinant Proteins/ultrastructure , Synucleins , alpha-Synuclein , beta-SynucleinABSTRACT
Aggregated alpha-synuclein proteins form brain lesions that are hallmarks of neurodegenerative synucleinopathies, and oxidative stress has been implicated in the pathogenesis of some of these disorders. Using antibodies to specific nitrated tyrosine residues in alpha-synuclein, we demonstrate extensive and widespread accumulations of nitrated alpha-synuclein in the signature inclusions of Parkinson's disease, dementia with Lewy bodies, the Lewy body variant of Alzheimer's disease, and multiple system atrophy brains. We also show that nitrated alpha-synuclein is present in the major filamentous building blocks of these inclusions, as well as in the insoluble fractions of affected brain regions of synucleinopathies. The selective and specific nitration of alpha-synuclein in these disorders provides evidence to directly link oxidative and nitrative damage to the onset and progression of neurodegenerative synucleinopathies.
