DJ-1 interactions with α-synuclein attenuate aggregation and cellular toxicity in models of Parkinson's disease.

Parkinson's disease (PD) is a devastating neurodegenerative disorder characterized by the loss of neurons in the substantia nigra pars compacta and the presence of Lewy bodies in surviving neurons. These intracellular protein inclusions are primarily composed of misfolded α-synuclein (aSyn), which has also been genetically linked to familial and sporadic forms of PD. DJ-1 is a small ubiquitously expressed protein implicated in several pathways associated with PD pathogenesis. Although mutations in the gene encoding DJ-1 lead to familial early-onset PD, the exact mechanisms responsible for its role in PD pathogenesis are still elusive. Previous work has found that DJ-1--which has protein chaperone-like activity--modulates aSyn aggregation. Here, we investigated possible physical interactions between aSyn and DJ-1 and any consequent functional and pathological relevance. We found that DJ-1 interacts directly with aSyn monomers and oligomers in vitro, and that this also occurs in living cells. Notably, several PD-causing mutations in DJ-1 constrain this interaction. In addition, we found that overexpression of DJ-1 reduces aSyn dimerization, whereas mutant forms of DJ-1 impair this process. Finally, we found that human DJ-1 as well as yeast orthologs of DJ-1 reversed aSyn-dependent cellular toxicity in Saccharomyces cerevisiae. Taken together, these data suggest that direct interactions between DJ-1 and aSyn constitute the basis for a neuroprotective mechanism and that familial mutations in DJ-1 may contribute to PD by disrupting these interactions.

Localization of telomeres and telomere-associated proteins in telomerase-negative Saccharomyces cerevisiae.

Cells lacking telomerase cannot maintain their telomeres and undergo a telomere erosion phase leading to senescence and crisis in which most cells become nonviable. On rare occasions survivors emerge from these cultures that maintain their telomeres in alternative ways. The movement of five marked telomeres in Saccharomyces cerevisiae was followed in wild-type cells and through erosion, senescence/crisis and eventual survival in telomerase-negative (est2::HYG) yeast cells. It was found that during erosion, movements of telomeres in est2::HYG cells were indistinguishable from wild-type telomere movements. At senescence/crisis, however, most cells were in G(2) arrest and the nucleus and telomeres traversed back and forth across the bud neck, presumably until cell death. Type I survivors, using subtelomeric Y' amplification for telomere maintenance, continued to show this aberrant telomere movement. However, Type II survivors, maintaining telomeres by a sudden elongation of the telomere repeats, became indistinguishable from wild-type cells, consistent with growth properties of the two types of survivors. When telomere-associated proteins Sir2p, Sir3p and Rap1p were tagged, the same general trend was seen-Type I survivors retained the senescence/crisis state of protein localization, while Type II survivors were restored to wild type.

Distribution of splicing proteins and putative coiled bodies during pollen development and androgenesis in Brassica napus L.

Small nuclear ribonucleoprotein particles (snRNPs) are subunits of splicing complexes, which show a transcription-dependent localization pattern. We have analyzed the labelling pattern of snRNPs during pollen development and microspore and pollen embryogenesis in Brassica napus with an antibody which recognizes protein D of U1, U2, U4, U5, and U6 snRNPs. It was found that nuclei were labelled almost uniformly for snRNPs in microspores and young bicellular pollen. In the generative nuclei of late-bicellular pollen and in the vegetative nuclei and sperm nuclei of mature pollen no snRNPs could be detected. The snRNP-positive nuclei contained mostly one or two brightly labelled nuclear bodies, most likely coiled bodies, often closely related to the nucleolus. These nuclear bodies increased in size from 0.5 micron in nuclei of young microspores up to 2 microns in nuclei of late microspores and the vegetative nucleus of early-bicellular pollen. Also their number increased during these developmental stages. After induction of embryogenesis the size of the coiled bodies decreased to about 0.5 micron and in several occasions the coiled body was found free in the nucleoplasm, away from the nucleolus. The results support the idea that the size and number of coiled bodies coincide with changes in general nuclear activity. They also indicate that, in nuclei of Brassica napus, at least assembly and disassembly of coiled bodies takes place in the nucleoplasm, whereas mature coiled bodies are located adjacent to the nucleolus.