The Syk Kinase SmTK4 of Schistosoma mansoni Is Involved in the Regulation of Spermatogenesis and Oogenesis

The signal transduction protein SmTK4 from Schistosoma mansoni belongs to the family of Syk kinases. In vertebrates, Syk kinases are known to play specialized roles in signaling pathways in cells of the hematopoietic system. Although Syk kinases were identified in some invertebrates, their role in this group of animals has not yet been elucidated. Since SmTK4 is the first Syk kinase from a parasitic helminth, shown to be predominantly expressed in the testes and ovary of adult worms, we investigated its function. To unravel signaling cascades in which SmTK4 is involved, yeast two-/three-hybrid library screenings were performed with either the tandem SH2-domain, or with the linker region including the tyrosine kinase domain of SmTK4. Besides the Src kinase SmTK3 we identified a new Src kinase (SmTK6) acting upstream of SmTK4 and a MAPK-activating protein, as well as mapmodulin acting downstream. Their identities and colocalization studies pointed to a role of SmTK4 in a signaling cascade regulating the proliferation and/or differentiation of cells in the gonads of schistosomes. To confirm this decisive role we performed biochemical and molecular approaches to knock down SmTK4 combined with a novel protocol for confocal laser scanning microscopy for morphological analyses. Using the Syk kinase-specific inhibitor Piceatannol or by RNAi treatment of adult schistosomes in vitro, corresponding phenotypes were detected in the testes and ovary. In the Xenopus oocyte system it was finally confirmed that Piceatannol suppressed the activity of the catalytic kinase domain of SmTK4. Our findings demonstrate a pivotal role of SmTK4 in gametogenesis, a new function for Syk kinases in eukaryotes

Dietary restriction would probably not increase longevity in human beings and other species able to leave unsuitable environments.

This article argues that dietary restriction would not increase longevity in species able to leave a place where they are subjected to starvation. Human beings can emigrate when feeding conditions are a threat to survival and thus they would not live longer if subjected to dietary restriction

The 2°c target - a European norm enters the international stage: following the process to adoption in China

“The 2 °C target—a European norm enters the international stage” is an empirical, qualitative study, using the case of China to illustrate the role played by the EU as a leader and forerunner pushing for a 2 °C target using diffusion mechanisms of persuasion and socialization. In order to better understand and evaluate how international and European climate norms enter the global and domestic discourse, the article details the nascent theoretical debate and critically assesses the role of the scientific community as translating medium. In the field of climate change China has been an increasingly important member of the UNFCCC process and a key target of European engagement policies. Process tracing shows that British scientific and political personalities took central roles introducing the discourse about the 2 °C target in China. The article aims to set an example of possible trajectories a norm can follow and will require further testing in the future