The N-Terminal, Polybasic Region Is Critical for Prion Protein Neuroprotective Activity

Several lines of evidence suggest that the normal form of the prion protein, PrPC, exerts a neuroprotective activity against cellular stress or toxicity. One of the clearest examples of such activity is the ability of wild-type PrPC to suppress the spontaneous neurodegenerative phenotype of transgenic mice expressing a deleted form of PrP (Δ32–134, called F35). To define domains of PrP involved in its neuroprotective activity, we have analyzed the ability of several deletion mutants of PrP (Δ23–31, Δ23–111, and Δ23–134) to rescue the phenotype of Tg(F35) mice. Surprisingly, all of these mutants displayed greatly diminished rescue activity, although Δ23–31 PrP partially suppressed neuronal loss when expressed at very high levels. Our results pinpoint the N-terminal, polybasic domain as a critical determinant of PrPC neuroprotective activity, and suggest that identification of molecules interacting with this region will provide important clues regarding the normal function of the protein. Small molecule ligands targeting this region may also represent useful therapeutic agents for treatment of prion diseases

Remarkable Reduction of MAP2 in the Brains of Scrapie-Infected Rodents and Human Prion Disease Possibly Correlated with the Increase of Calpain

Microtubule-associated protein 2 (MAP2) belongs to the family of heat stable MAPs, which takes part in neuronal morphogenesis, maintenance of cellular architecture and internal organization, cell division and cellular processes. To obtain insight into the possible alteration and the role of MAP2 in transmissible spongiform encephalopathies (TSEs), the MAP2 levels in the brain tissues of agent 263K-infected hamsters and human prion diseases were evaluated. Western blots and IHC revealed that at the terminal stages of the diseases, MAP2 levels in the brain tissues of scrapie infected hamsters, a patient with genetic Creutzfeldt-Jakob disease (G114V gCJD) and a patient with fatal familial insomnia (FFI) were almost undetectable. The decline of MAP2 was closely related with prolonged incubation time. Exposure of SK-N-SH neuroblastoma cell line to cytotoxic PrP106-126 peptide significantly down-regulated the cellular MAP2 level and remarkably disrupted the microtubule structure, but did not alter the level of tubulin. Moreover, the levels of calpain, which mediated the degradation of a broad of cytoskeletal proteins, were significantly increased in both PrP106-126 treated SK-N-SH cells and brain tissues of 263K prion-infected hamsters. Our data indicate that the decline of MAP2 is a common phenomenon in TSEs, which seems to occur at an early stage of incubation period. Markedly increased calpain level might contribute to the reduction of MAP2

Relation between nuclear DNA content and rate of cell growth during interphase in four species of Angiospermae

Among four species of Angiospermae with known nuclear DNA content (Cucurbita pepo - 2.6 pg, Helianthus annuus - 12.0 pg, Vicia faba — 38.0 pg, and Tulipa kaufmanniana - 93.7 pg) the cell growth in the intermitotic period of the cell cycle has been observed to be the fastest in Vicia faba, slower in Helianthus annuus and the slowest in Cucurbita pepo and Tulipa kaufmanniana

Resistance to Phytophthora infestans in diploid and tetraploid potato families. 1. Resistance in detached leaflets

Potato families, segregating for resistance to Phytophthora infestans, were tested repeatedly to evaluate the distribution of resistance to P. infestans, the repeatability of testing results and correlation between resistance and some other characters. Four diploid and four tetraploid families were evaluated together with their parents and with potato cultivars used as standard. For all inoculations a virulent fungus isolate MP 245 was used. Leaflets were collected from plants growing in the field (summer tests) or in a glasshouse (autumn and spring tests). Segregation of major genes determining resistance was detectable in most families. In families originating from mating a resistant parent with a susceptible partner some progeny genotypes with resistance level of the resistant parent could be identified. In families originating from two parents showing only some resistance, a transgression of resistance could be found in the progeny. The expression of resistance depended on testing conditions. Some genotypes were consistently superior or inferior in resistance under all testing conditions, but often repeated evaluations of genotypes did not provide consistent results and significant interactions genotypes x tests were detectable

Resistance to Phytophthora infestans in diploid and tetraploid potato families. 3. Correlations between characters

In four diploid and four tetraploid families correlations were evaluated between resistance to Phytophthora infestans of leaflets, tuber slices and whole tubers as well as correlations between three aspects of resistance and maturity or tuber shape regularity. A virulent P. infestans isolate was used for inoculations. Only in the family D4 a significant positive correlation was found between all the three aspects of resistance. Genotypes with susceptible leaflets and resistant tuber slices were not identified in any family. In some families genotypes with resistant whole tubers and susceptible tuber slices were found; the family D5 was found to have genotypes in which resistance of leaflets was associated with susceptibility of tuber slices. The resistance to P. infestans of leaflets or tuber slices tended to be negatively correlated with both early maturity and regularity of tuber shape

Tau inhibits tubulin oligomerization induced by prion protein

AbstractIn previous studies we have demonstrated that prion protein (PrP) interacts with tubulin and disrupts microtubular cytoskeleton by inducing tubulin oligomerization. These observations may explain the molecular mechanism of toxicity of cytoplasmic PrP in transmissible spongiform encephalopathies (TSEs). Here, we check whether microtubule associated proteins (MAPs) that regulate microtubule stability, influence the PrP-induced oligomerization of tubulin. We show that tubulin preparations depleted of MAPs are more prone to oligomerization by PrP than those containing traces of MAPs. Tau protein, a major neuronal member of the MAPs family, reduces the effect of PrP. Importantly, phosphorylation of Tau abolishes its ability to affect the PrP-induced oligomerization of tubulin. We propose that the binding of Tau stabilizes tubulin in a conformation less susceptible to oligomerization by PrP. Since elevated phosphorylation of Tau leading to a loss of its function is observed in Alzheimer disease and related tauopathies, our results point at a possible molecular link between these neurodegenerative disorders and TSEs