The role of G-protein-coupled receptor kinase 5 in pathogenesis of sporadic Parkinson's disease.

Sporadic Parkinson's disease (sPD) is a common neurodegenerative disorder, characterized by selective degeneration of dopaminergic neurons in the substantia nigra. Although the pathogenesis of the disease remains undetermined, phosphorylation of alpha-synuclein and its oligomer formation seem to play a key role. However, the protein kinase(s) involved in the phosphorylation in the pathogenesis of sPD has not been identified. Here, we found that G-protein-coupled receptor kinase 5 (GRK5) accumulated in Lewy bodies and colocalized with alpha-synuclein in the pathological structures of the brains of sPD patients. In cotransfected cells, GRK5 phosphorylated Ser-129 of alpha-synuclein at the plasma membrane and induced translocation of phosphorylated alpha-synuclein to the perikaryal area. GRK5-catalyzed phosphorylation also promoted the formation of soluble oligomers and aggregates of alpha-synuclein. Genetic association study revealed haplotypic association of the GRK5 gene with susceptibility to sPD. The haplotype contained two functional single-nucleotide polymorphisms, m22.1 and m24, in introns of the GRK5 gene, which bound to YY1 (Yin Yang-1) and CREB-1 (cAMP response element-binding protein 1), respectively, and increased transcriptional activity of the reporter gene. The results suggest that phosphorylation of alpha-synuclein by GRK5 plays a crucial role in the pathogenesis of sPD.

Pseudo-autosomal dominant inheritance of PARK2: two families with parkin gene mutations.

We report two families (Family S and Family N) with early-onset parkinsonism in two generations. The mode of inheritance appeared to be autosomal dominant, however, haplotye analysis suggested linkage to chromosome 6q25.2-27, the PARK2 locus, and all affected members were homozygotes in their haplotypes. In Family S, the affected father was married to unaffected mother, who carried one disease-linked haplotype at chromosome 6q25.2-27. In Family N, the unaffected mother carried one disease-linked haplotype. Quantitative PCR amplification analysis revealed exon 3 deletion in Family S and exon 5 deletion in Family N. The age of onset was from 18 to 22 years in Family S and 25 to 42 years in Family N. In both of their hometowns, most people lived in the same districts for many generations and consanguineous marriages had been common. Thus, the carrier state of the parkin gene might have been high in those communities, and marriage of a patient and a carrier is expected to result in autosomal dominant like inheritance. We conclude that PARK2 cannot be excluded even if the mode of inheritance appears as autosomal dominant, when the affected patients are young.

Large-scale search of SNPs for type 2 DM susceptibility genes in a Japanese population.

The etiology of type 2 diabetes (DM) is polygenic. We investigated here genes and polymorphisms that associate with DM in the Japanese population. Single-nucleotide polymorphisms (SNPs) of 398 derived from 120 candidate genes were examined for association with DM in a population-based case-control study. The study group consisted of 148 cases and 227 controls recruited from Funagata, Japan. No evident subpopulation structure was detected for the tested population. The association tests were conducted with standard allele positivity tables (chi(2) tests) between SNP genotype frequency and case-control status. The independent association of the SNPs from serum triglyceride levels and body mass index was examined by multiple logistic regression analysis. A value of P<0.01 was accepted as statistically significant. Six genes (met proto-oncogene, ATP-binding cassette transporter A1, fatty acid binding protein 2, LDL receptor defect C complementing, aldolase B, and sulfonylurea receptor) were shown to be associated with DM.