Biomedical subjects

Shin-ichiro Kubo

Publications and source records attributed to Shin-ichiro Kubo.

5 recordsLinked to original sources

PubMed2006

Up-regulation of hMUTYH, a DNA repair enzyme, in the mitochondria of substantia nigra in Parkinson's disease.

There is ample evidence for the involvement of oxidative stress in mitochondrial DNA damage and repair mechanisms in Parkinson's disease (PD). The human MutY homolog (hMUTYH) which removes misincorporated adenine opposite 8-oxoG in DNA functions in post-replication, and is localized in the nuclei and mitochondria. We hypothesized that hMUTYH is involved in the disease process of PD. To test our hypothesis, we performed immunohistochemical and biochemical studies on brains of patients with PD and those of control patients. Our results showed up-regulation of hMUTYH in the mitochondria of the SN of PD patients. Western blot analysis also revealed high hMUTYH levels in PD patients and expression of a 47-kDa molecule in the brains as the major isoform. This molecule was localized within the mitochondria as confirmed by double staining with a mitochondrial marker. To confirm the presence of this molecule, we examined the mRNAs of isoforms that translate to the 47-kDa molecule. Based on the amount of mRNAs, the major molecule was alpha4. Interestingly, this molecule lacks the mitochondria targeting sequence. Our results suggest that hMUTYH might be a useful marker of oxidative stress and that oxidative stress and genomic instability are important in the PD disease process.

Aged↗

PubMed2006

Recessive Parkinson's disease.

Parkinson's disease (PD) is a progressive neurodegenerative disease caused by loss of dopaminergic neurons in the substantia nigra pars compacta. Although the etiology of PD remains unclear, it is now clear that genetic factors contribute to the pathogenesis of the disease. Recently, several causative genes have been identified in monogenic forms of PD. Accumulating evidence indicates that their gene products play important roles in mitochondrial function, oxidative stress response, and the ubiquitin-proteasome system, which are also implicated in sporadic PD, suggesting that these gene products share a common pathway to nigral degeneration in both familial and sporadic PD. Here, we review recent advances in knowledge about genes associated with recessive PD, including parkin, PINK1, and DJ-1.

Dopamine↗

PubMed2005

A combinatorial code for the interaction of alpha-synuclein with membranes.

Considerable genetic and pathological evidence has implicated the small, soluble protein alpha-synuclein in the pathogenesis of familial and sporadic forms of Parkinsons disease (PD). However, the precise role of alpha-synuclein in the disease process as well as its normal function remain poorly understood. We recently found that an interaction with lipid rafts is crucial for the normal, pre-synaptic localization of alpha-synuclein. To understand how alpha-synuclein interacts with lipid rafts, we have now developed an in vitro binding assay to rafts purified from native membranes. Recapitulating the specificity observed in vivo, recombinant wild type but not PD-associated A30P mutant alpha-synuclein binds to lipid rafts isolated from cultured cells and purified synaptic vesicles. Proteolytic digestion of the rafts does not disrupt the binding of alpha-synuclein, indicating an interaction with lipid rather than protein components of these membranes. We have also found that alpha-synuclein binds directly to artificial membranes whose lipid composition mimics that of lipid rafts. The binding of alpha-synuclein to these raft-like liposomes requires acidic phospholipids, with a preference for phosphatidylserine (PS). Interestingly, a variety of synthetic PS with defined acyl chains do not support binding when used individually. Rather, the interaction with alpha-synuclein requires a combination of PS with oleic (18:1) and polyunsaturated (either 20:4 or 22:6) fatty acyl chains, suggesting a role for phase separation within the membrane. Furthermore, alpha-synuclein binds with higher affinity to artificial membranes with the PS head group on the polyunsaturated fatty acyl chain rather than on the oleoyl side chain, indicating a stringent combinatorial code for the interaction of alpha-synuclein with membranes.

Amino Acid Substitution↗

PubMed2004

Expression of 8-oxoguanine DNA glycosylase (OGG1) in Parkinson's disease and related neurodegenerative disorders.

Oxidative stress including DNA oxidation is implicated in Parkinson's disease (PD). We postulated that DNA repair enzymes such as 8-oxoguanosine DNA glycosylase (OGG1) are involved in the PD process. We performed immunohistochemical and biochemical studies on brains of patients with PD and those of patients with progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) as disease controls, and control subjects. We found higher expression levels of mitochondrial isoforms of OGG1 enzymes in the substantia nigra (SN) in cases of PD. Furthermore, Western blot analysis revealed high OGG1 levels in the SN of the patients with PD. Our results indicate the importance of oxidative stress within the susceptible lesions in the pathogenesis of PD.

Adult↗

PubMed2004

Lipid rafts mediate the synaptic localization of alpha-synuclein.

Alpha-synuclein contributes to the pathogenesis of Parkinson's disease (PD), but its precise role in the disorder and its normal function remain poorly understood. Consistent with a presumed role in neurotransmitter release and its prominent deposition in the dystrophic neurites of PD, alpha-synuclein localizes almost exclusively to the nerve terminal. In brain extracts, however, alpha-synuclein behaves as a soluble, monomeric protein. Using a binding assay to characterize the association of alpha-synuclein with cell membranes, we find that alpha-synuclein binds saturably and with high affinity to characteristic intracellular structures that double label for components of lipid rafts. Biochemical analysis demonstrates the interaction of alpha-synuclein with detergent-resistant membranes and reveals a shift in electrophoretic mobility of the raft-associated protein. In addition, the A30P mutation associated with PD disrupts the interaction of alpha-synuclein with lipid rafts. Furthermore, we find that both the A30P mutation and raft disruption redistribute alpha-synuclein away from synapses, indicating an important role for raft association in the normal function of alpha-synuclein and its role in the pathogenesis of PD.

Amino Acid Substitution↗