Biochemical and cellular effects of inhibiting Nedd8 conjugation

The conjugation of proteins with the ubiquitin-like protein Nedd8 is an essential cellular process and an important anti-cancer therapeutic target. The major known role of Nedd8 is the attachment to and activation of Cullin RING E3 ubiquitin ligases (CRL). The attachment of Nedd8 to its substrates occurs via a process analogous to ubiquitin transfer, involving a Nedd8 E1 activating enzyme and a Nedd8 E2 conjugating enzyme, Ubc12, which transfers Nedd8 onto lysine residues of target proteins. In this study, we utilize dominant-negative Ubc12 (dnUbc12) and the Nedd8 E1 inhibitor MLN4924 to inhibit cellular neddylation. We demonstrate that dnUbc12 functions by depleting cellular Nedd8 concentrations. Inhibition of cellular neddylation leads to rapid accumulation of CRL substrates and an enlarged and flattened morphology in HEK293 cells. Inhibiting Nedd8 conjugation also causes abnormalities in the actin cytoskeleton. This is likely at least partially mediated via accumulation of the small GTPase RhoA, a recently identified CRL substrate. We indeed found that siRNA mediated knockdown of RhoA can reverse the morphological changes observed upon inhibition of cellular neddylation. In conclusion, the Nedd8 pathway plays an important role in regulating the actin cytoskeleton and cellular morphology. Dysfunction of the actin cytoskeleton may contribute to the anti-cancer effect of Nedd8 inhibition.     

Parathyroid hormone and triglyceride transport: effects on triglyceride secretion rates and adipose tissue lipoprotein lipase in the rat.

In order to determine the effects of parathyroid hormone on triglyceride transport, male Sprague-Dawley rats were injected with parathyroid extract for eight days and triglyceride secretion rates (TGSR) and adipose tissue lipoprotein lipase (LPL) activity were determined. Parathyroid hormone-treated rats demonstrated significantly lower (p less than .005) TGSR in the basal overnight fasted state 15 hours after the previous injection, but this effect on TGSR was not apparent 3 hours after PTE injection when the rats were allowed to eat. In contrast, LPL activity was significantly reduced in the PTH-treated animals at 3 hours and no effect was apparent on this index of triglyceride removal at 15 hours. These findings suggest that parathyroid hormone may exert independent influences on triglyceride production and removal and thus may alter triglyceride homeostasis in conditions in which parathyroid hormone levels are abnormally increased.     

98% identical, 100% wrong: per cent nucleotide identity can lead plant virus epidemiology astray

Short-form publications such as Plant Disease reports serve essential functions: the rapid dissemination of information on the geography of established plant pathogens, incidence and symptomology of pathogens in new hosts, and the discovery of novel pathogens. Many of these sentinel publications include viral sequence data, but most use that information only to confirm the virus'' species. When researchers use the standard technique of per cent nucleotide identity to determine that the new sequence is closely related to another sequence, potentially erroneous conclusions can be drawn from the results. Multiple introductions of the same pathogen into a country are being ignored because researchers know fast-evolving plant viruses can accumulate substantial sequence divergence over time, even from a single introduction. An increased use of phylogenetic methods in short-form publications could speed our understanding of these cryptic second introductions and aid in control of epidemics.     

Synergistic epistasis enhances the co-operativity of mutualistic interspecies interactions

Early evolution of mutualism is characterized by big and predictable adaptive changes, including the specialization of interacting partners, such as through deleterious mutations in genes not required for metabolic cross-feeding. We sought to investigate whether these early mutations improve cooperativity by manifesting in synergistic epistasis between genomes of the mutually interacting species. Specifically, we have characterized evolutionary trajectories of syntrophic interactions of Desulfovibrio vulgaris (Dv) with Methanococcus maripaludis (Mm) by longitudinally monitoring mutations accumulated over 1000 generations of nine independently evolved communities with analysis of the genotypic structure of one community down to the single-cell level. We discovered extensive parallelism across communities despite considerable variance in their evolutionary trajectories and the perseverance within many evolution lines of a rare lineage of Dv that retained sulfate-respiration (SR+) capability, which is not required for metabolic cross-feeding. An in-depth investigation revealed that synergistic epistasis across pairings of Dv and Mm genotypes had enhanced cooperativity within SR− and SR+ assemblages, enabling their coexistence within the same community. Thus, our findings demonstrate that cooperativity of a mutualism can improve through synergistic epistasis between genomes of the interacting species, enabling the coexistence of mutualistic assemblages of generalists and their specialized variants.Subject terms: Microbial ecology, Population genetics, Symbiosis, Population dynamics, Molecular evolution     

Slow clearance of Plasmodium vivax with chloroquine amongst children younger than six months of age in the Brazilian Amazon

Plasmodium vivax is the most widespread parasite causing malaria, being especially prevalent in the Americas and Southeast Asia. Children are one of the most affected populations, especially in highly endemic areas. However, there are few studies evaluating the therapeutic response of infants with vivax malaria. This study retrospectively evaluated the parasitaemia clearance in children diagnosed with vivax malaria during the first five days of exclusive treatment with chloroquine (CQ). Infants aged less than six months old had a significantly slower parasitaemia clearance time compared to the group of infants and children between six months and 12 years old (Kaplan-Meier survival analysis; Wilcoxon test; p = 0.004). The impaired clearance of parasitaemia in younger children with vivax malaria is shown for the first time in Latin America. It is speculated that CQ pharmacokinetics in young children with vivax malaria is distinct, but this specific population may also allow the detection of CQ-resistant parasites during follow-up, due to the lack of previous immunity.