Search

Aim Traffic between the plasma membrane and the endomembrane compartments is an essential feature of eukaryotic cells. The secretory pathway sends cargoes from biosynthetic compartments to the plasma membrane. This is counterbalanced by a retrograde endocytic route and is essential for cell homoeostasis. Cells need to adapt rapidly to environmental challenges such as the reduction of pO2 which, however, has not been analysed in relation to membrane trafficking in detail. Therefore, we determined changes in the plasma membrane trafficking in normoxia, hypoxia, and after reoxygenation. Methods Membrane trafficking was analysed by using the bulk membrane endocytosis marker FM 1-43, the newly developed membrane probe mCLING, wheat germ agglutinin as well as fluorescently labelled cholera toxin subunit B. Additionally, the uptake of specific membrane proteins was determined. In parallel, a non-biased SILAC screen was performed to analyse the abundance of membrane proteins in normoxia and hypoxia. Results Membrane trafficking was increased in hypoxia and quickly reversed upon reoxygenation. This effect was independent of the hypoxia-inducible factor ( HIF) system. Using SILAC technology, we identified that the actin-bundling protein T-plastin is recruited to the plasma membrane in hypoxia. By the use of T-plastin knockdown cells, we could show that T-plastin mediates the hypoxia-induced membrane trafficking, which was associated with an increased actin density in the cells as determined by electron microscopy. Conclusion Membrane trafficking is highly dynamic upon hypoxia. This phenotype is quickly reversible upon reoxygenation, which suggests that this mechanism participates in the cellular adaptation to hypoxia. [ABSTRACT FROM AUTHOR]

Phosphoinositides are key regulators of synaptic vesicle cycling and endocytic traffic; the actin cytoskeleton also seems to be involved in modulating these processes. We investigated the effects of perturbing phosphoinositide signalling and actin dynamics on vesicle cycling in frog motor nerve terminals, using fluorescence and electron microscopy, and electrophysiology. Antibody staining for Β-actin revealed that actin surrounds but does not overlap with synaptic vesicle clusters. Latrunculin A, which disrupts actin filaments by binding actin monomers, and wortmannin, an inhibitor of phosphatidyl inositol-3-kinase (PI3-kinase), each disrupted the pattern of presynaptic actin staining, but not vesicle clusters in resting terminals. Latrunculin A, but not wortmannin, also reduced vesicle mobilization and exocytosis. Both drugs inhibited the stimulation-induced uptake of the styryl dye FM 1-43 and blocked vesicle reformation from internalized membrane objects after tetanic stimulation. These results are consistent with a role of PI3-kinase and the actin cytoskeleton in the slow pathway of vesicle endocytosis, used primarily by reserve pool vesicles. [ABSTRACT FROM AUTHOR]

Kazakhstan is undergoing a rapid modernization process, which carries the risk of an epidemic of obesity and cardiovascular disease. We enrolled a sample of about 50 children for every combination of gender, environment (urban vs. rural), ethnic group (Kazakh vs. Russian), and age group from 7 to 18 years, for a total of 4,808 children. Anthropometry and blood pressure were measured on all children while fasting blood cholesterol and glucose were measured only in 2,616 children aged > or =12 years. The prevalence of overweight and risk of overweight ranged from 2.8 (rural male Kazakhs) to 9.1% (urban male Russians). The prevalence of prehypertension and hypertension ranged from 8.3 (urban females) to 15.9% (rural females); that of hypercholesterolemia from 11.5 (male rural Russians) to 26.5% (female rural Kazakhs); and the overall prevalence of impaired fasting glucose was 0.1%. We conclude that overweight and cardiovascular risk factors are less prevalent in children living in Kazakhstan than in those living in Western countries. However, these figures are not negligible and suggest that preventive measures are needed to contain the epidemic of overweight and cardiovascular disease that will most likely accompany the modernization of Kazakhstan in the next years., (Copyright 2007 Wiley-Liss, Inc.)