Recycling cell surface glycoproteins undergo limited oligosaccharide reprocessing in LEC1 mutant Chinese hamster ovary cells

The ability of particular cell surface glycoproteins to recycle and become exposed to individual Golgi enzymes has been demonstrated. This study was designed to determine whether endocytic trafficking includes significant reentry into the overall oligosaccharide processing pathway. The Lec1 mutant of Chinese hamster ovary (CHO) cells lack N - acetylglucosaminyltransferase I (GlcNAc-TI) activity resulting in surface expression of incompletely processed Man5GlcNAc2 N -linked oligosaccharides. An oligosaccharide tracer was created by exoglycosylation of cell surface glycoproteins with purified porcine GlcNAc-TI and UDP-[3H]GlcNAc. Upon reculturing, all cell surface glycoproteins that acquired [3H]GlcNAc were acted upon by intracellular mannosidase II, the next enzyme in the Golgi processing pathway of complex N -linked oligosaccharides (t1/2= 3-4 h). That all radiolabeled cell surface glycoproteins were included in this endocytic pathway indicates a common intracellular compartment into which endocytosed cell surface glycoproteins return. Significantly, no evidence was found for continued oligosaccharide processing consistent with transit through the latter cisternae of the Golgi apparatus. These data indicate that, although recycling plasma membrane glycoproteins can be reexposed to individual Golgi-derived enzymes, significant reentry into the overall contiguous processing pathway is not evident.      

Immediate baroreflex-neuroendocrine interactions in humans during graded water immersion

Healthy male subjects underwent graded water immersion for a study of arterial baroreceptors and neuroendocrine responses. Blood samples were studied for plasma renin activity, aldosterone, arginine vasopressin, norepinephrine and epinephrine. Results showed that ten minutes of immersion was enough to suppress the release of arginine vasopressin, renin, and norepinephrine. The role of baroreceptors in the release of these substances is discussed.     

Corticosterone and time-activity budget: an experiment with Black-legged kittiwakes

In vertebrates, the well established increase in plasma corticosterone in response to food shortage is thought to mediate adjustments of foraging behavior and energy allocation to environmental conditions. However, investigating the functional role of corticosterone is often constrained by the difficulty to track time-activity budget of free-ranging animals. To examine how an experimental increase in corticosterone affects the activity budget of male Black-legged kittiwakes (Rissa tridactyla), we used miniaturized activity loggers to record flying/foraging, presence on the sea surface and nest attendance. To investigate how corticosterone affects allocation processes between self-foraging and foraging devoted to the brood, we monitored body mass change of males from capture (day 0) to recapture (day 3). Among control birds, males in poor condition at day 0 spent significantly more time flying/foraging and less time attending the nest site than did males in good condition. Corticosterone treatment affected time spent flying/foraging in interaction with body condition at day 0: corticosterone-implanted males in good condition spent more time flying/foraging than control ones; this was not observed in poor condition males. In control birds, change in body mass was negatively correlated with body condition at day 0. This was reinforced by corticosterone treatment and, on average, corticosterone-implanted males gained much more mass than controls. These results suggest that in Black-legged kittiwakes, body condition and corticosterone levels can interact to mediate foraging decisions and possibly energy allocation: when facing stressful environmental conditions, birds in good body condition may afford to increase the time spent foraging probably to maintain brood provisioning, whereas poor body condition birds seemed rather to redirect available energy from reproduction to self-maintenance.     

Non-random distribution of the Ty1 elements within nuclear DNA of Saccharomyces cerevisiae

Ty1 homologous sequences appear to be non-randomly distributed among different density classes of nuclear yeast DNA. Characteristic patterns of Ty1 containing EcoRI fragments can be generated from the various DNA fractions. The sequences are particularly enriched in the A + T rich part of the main nuclear DNA fraction, while the frequency in the rDNA containing heavy satellite DNA is low. The transposon however, seems to be present in this dense fraction, at least for some strains.     

How to choose templates for modeling of protein complexes: Insights from benchmarking template-based docking

Comparative docking is based on experimentally determined structures of protein-protein complexes (templates), following the paradigm that proteins with similar sequences and/or structures form similar complexes. Modeling utilizing structure similarity of target monomers to template complexes significantly expands structural coverage of the interactome. Template-based docking by structure alignment can be performed for the entire structures or by aligning targets to the bound interfaces of the experimentally determined complexes. Systematic benchmarking of docking protocols based on full and interface structure alignment showed that both protocols perform similarly, with top 1 docking success rate 26%. However, in terms of the models' quality, the interface-based docking performed marginally better. The interface-based docking is preferable when one would suspect a significant conformational change in the full protein structure upon binding, for example, a rearrangement of the domains in multidomain proteins. Importantly, if the same structure is selected as the top template by both full and interface alignment, the docking success rate increases 2-fold for both top 1 and top 10 predictions. Matching structural annotations of the target and template proteins for template detection, as a computationally less expensive alternative to structural alignment, did not improve the docking performance. Sophisticated remote sequence homology detection added templates to the pool of those identified by structure-based alignment, suggesting that for practical docking, the combination of the structure alignment protocols and the remote sequence homology detection may be useful in order to avoid potential flaws in generation of the structural templates library.