Overexpression of a 123-kDa anion transport inhibitor binding protein and two cytoskeleton proteins in Drosophila Kc cell variants resistant to disulfonic stilbenes

Drugs of the disulfonic stilbene class, which inhibit anion transport in the cell membrane in many cell types, have been found to inhibit anion transport and cell growth in Drosophila Kc cells. Cell variants selected by a stepwise selection protocol for the ability to grow in the presence of the disulfonic stilbenes are severalfold resistant to growth inhibition by the drugs. Both the resistant populations and a cloned cell line show dramatic overexpression of three polypeptides. The most highly overproduced protein is a 123-kDa plasma membrane protein which binds the reversible anion transport inhibitor, flufenamic acid, in a protection biotinylation experiment. The 123-kDa putative anion transport protein copurifies with, and immunologically cross-reacts with, two detergent-insoluble cytoskeleton proteins of 46- and 62-kDa molecular weight, which are each overexpressed more than 8-fold in the variants. Resistance to growth inhibition by the disulfonic stilbenes and amplified expression of the 123-, 62-, and 46-kDa proteins are simultaneously lost over a period of 30 weeks in the absence of selective conditions, suggesting that the function of the overproduced polypeptides is related to growth control in Drosophila cells.     

A dynamic metabolite valve for the control of central carbon metabolism

Successful redirection of endogenous resources into heterologous pathways is a central tenet in the creation of efficient microbial cell factories. This redirection, however, may come at a price of poor biomass accumulation, reduced cofactor regeneration and low recombinant enzyme expression. In this study, we propose a metabolite valve to mitigate these issues by dynamically tuning endogenous processes to balance the demands of cell health and pathway efficiency. A control node of glucose utilization, glucokinase (Glk), was exogenously manipulated through either engineered antisense RNA or an inverting gene circuit. Using these techniques, we were able to directly control glycolytic flux, reducing the specific growth rate of engineered Escherichia coli by up to 50% without altering final biomass accumulation. This modulation was accompanied by successful redirection of glucose into a model pathway leading to an increase in the pathway yield and reduced carbon waste to acetate. This work represents one of the first examples of the dynamic redirection of glucose away from central carbon metabolism and enables the creation of novel, efficient intracellular pathways with glucose used directly as a substrate.     

Dietary Docosahexaenoic Acid Supplementation Modulates Hippocampal Development in the Pemt?/? Mouse

The development of fetal brain is influenced by nutrients such as docosahexaenoic acid (DHA, 22:6) and choline. Phosphatidylethanolamine-N-methyltransferase (PEMT) catalyzes the biosynthesis of phosphatidylcholine from phosphatidylethanolamine enriched in DHA and many humans have functional genetic polymorphisms in the PEMT gene. Previously, it was reported that Pemt^−/− mice have altered hippocampal development. The present study explores whether abnormal phosphatidylcholine biosynthesis causes altered incorporation of DHA into membranes, thereby influencing brain development, and determines whether supplemental dietary DHA can reverse some of these changes. Pregnant C57BL/6 wild type (WT) and Pemt^−/− mice were fed a control diet, or a diet supplemented with 3 g/kg of DHA, from gestational day 11 to 17. Brains from embryonic day 17 fetuses derived from Pemt^−/− dams fed the control diet had 25–50% less phospholipid-DHA as compared with WT (p < 0.05). Also, they had 60% more neural progenitor cell proliferation (p < 0.05), 60% more neuronal apoptosis (p < 0.01), and 30% less calretinin expression (p < 0.05; a marker of neuronal differentiation) in the hippocampus compared with WT. The DHA-supplemented diet increased fetal brain Pemt^−/− phospholipid-DHA to WT levels, and abrogated the neural progenitor cell proliferation and apoptosis differences. Although this diet did not change proliferation in the WT group, it halved the rate of apoptosis (p < 0.05). In both genotypes, the DHA-supplemented diet increased calretinin expression 2-fold (p < 0.05). These results suggest that the changes in hippocampal development in the Pemt^−/− mouse could be mediated by altered DHA incorporation into membrane phospholipids, and that maternal dietary DHA can influence fetal brain development.