A bidirectional antagonism between aPKC and Yurt regulates epithelial cell polarity

During epithelial cell polarization, Yurt (Yrt) is initially confined to the lateral membrane and supports the stability of this membrane domain by repressing the Crumbs-containing apical machinery. At late stages of embryogenesis, the apical recruitment of Yrt restricts the size of the apical membrane. However, the molecular basis sustaining the spatiotemporal dynamics of Yrt remains undefined. In this paper, we report that atypical protein kinase C (aPKC) phosphorylates Yrt to prevent its premature apical localization. A nonphosphorylatable version of Yrt dominantly dismantles the apical domain, showing that its aPKC-mediated exclusion is crucial for epithelial cell polarity. In return, Yrt counteracts aPKC functions to prevent apicalization of the plasma membrane. The ability of Yrt to bind and restrain aPKC signaling is central for its role in polarity, as removal of the aPKC binding site neutralizes Yrt activity. Thus, Yrt and aPKC are involved in a reciprocal antagonistic regulatory loop that contributes to segregation of distinct and mutually exclusive membrane domains in epithelial cells.     

Docking and molecular dynamics studies of peripheral site ligand–oximes as reactivators of sarin-inhibited human acetylcholinesterase

In the present work, we performed docking and molecular dynamics simulations studies on two groups of long-tailored oximes designed as peripheral site binders of acetylcholinesterase (AChE) and potential penetrators on the blood brain barrier. Our studies permitted to determine how the tails anchor in the peripheral site of sarin-inhibited human AChE, and which aminoacids are important to their stabilization. Also the energy values obtained in the docking studies corroborated quite well with the experimental results obtained before for these oximes.     

ON THE EVOLUTION OF MIGRATION IN HETEROGENEOUS ENVIRONMENTS

Populations often experience variable conditions, both in time and space. Here we develop a novel theoretical framework to study the evolution of migration under the influence of spatially and temporally variable selection and genetic drift. First, we examine when polymorphism is maintained at a locus under heterogeneous selection, as a function of the pattern of spatial heterogeneity and the migration rate. In a second step, we study how levels of migration evolve under the joint action of kin competition and local adaptation at a polymorphic locus. This analysis reveals the existence of evolutionary bistability, whereby a low or a high migration rate may evolve depending on the initial conditions. Last, we relax several assumptions regarding selection heterogeneity commonly made in previous studies and explore the consequences of more complex spatial and temporal patterns of variability in selection on the evolution of migration. We found that small modifications in the pattern of environmental heterogeneity may have dramatic effects on the evolution of migration. This work highlights the importance of considering more general scenarios of environmental heterogeneity when studying the evolution of life‐history traits in ecologically complex settings.     

Microbial Uptake,Toxicity, and Fate of Biofabricated ZnS:Mn Nanocrystals

Despite their importance in nano-environmental health and safety, interactions between engineered nanomaterials and microbial life remain poorly characterized. Here, we used the model organism E. coli to study the penetration requirements, subcellular localization, induction of stress responses, and long-term fate of luminescent Mn-doped ZnS nanocrystals fabricated under “green” processing conditions with a minimized ZnS-binding protein. We find that such protein-coated quantum dots (QDs) are unable to penetrate the envelope of unmodified E. coli but readily translocate to the cytoplasm of cells that have been made competent by chemical treatment. The process is dose-dependent and reminiscent of bacterial transformation. Cells that have internalized up to 0.5 μg/mL of nanocrystals do not experience a significant activation of the unfolded protein or SOS responses but undergo oxidative stress when exposed to high QD doses (2.5 μg/mL). Finally, although they are stable in quiescent cells over temperatures ranging from 4 to 42°C, internalized QDs are rapidly diluted by cell division in a process that does not involve TolC-dependent efflux. Taken together, our results suggest that biomimetic QDs based on low toxicity inorganic cores capped by a protein shell are unlikely to cause significant damage to the microbial ecosystem.