Neutral trehalase 1 (Nth1) from Saccharomyces cerevisiae
catalyzes disaccharide trehalose hydrolysis and helps yeast to
survive adverse conditions, such as heat shock, starvation or
oxidative stress. 14-3-3 proteins, master regulators of hundreds
of partner proteins, participate in many key cellular processes.
Nth1 is activated by phosphorylation followed by 14-3-3 protein
(Bmh) binding. The activation mechanism is also potentiated by
Ca2+ binding within the EF-hand-like motif. This review
summarizes the current knowledge about trehalases and the
molecular and structural basis of Nth1 activation. The crystal
structure of fully active Nth1 bound to 14-3-3 protein provided
the first high-resolution view of a trehalase from a eukaryotic
organism and showed 14-3-3 proteins as structural modulators
and allosteric effectors of multi-domain binding partners.
Uni-quantal endplate currents (EPC) were recorded at mouse diaphragm neuromuscular synapse by extracellular microelectrode during motor nerve stimulation. The probability of release expressed as quantal content mo, and variability of synaptic latencies expressed as P90
were estimated in the presence of extracellular calcium ([Ca2+]o)
varying between 0.2 and 0.6 mM in the bathing solution. At 0.2 mM [Ca2+]o, mo was low (0.10) and many of long-latency EPCs were present during the late phase of the release (P90 = 2.44 ms). No change in mo was found when [Ca2+]o was 0.3 mM, but P90
decreased by 39 %. For latency shortening, saturating concentration of [Ca2+]o was 0.4 mM, when P90 was 1.49 ms and latencies did not further change at 0.5 and 0.6 mM [Ca2+]o. In the latter concentrations, however, an increase of mo was still observed. It can be concluded that the early phase of the secretion did not significantly change when [Ca2+]o was raised and that only the late phase of the release depends on extracellular
calcium up to 0.4 mM.
Young Wistar rats (aged 12, 25 and 35 days) were exposed to short-term (60 min) hypobaric hypoxia of 41 kPa. Cortical afterdischarges (ADs) were evoked by repeated direct stimulation of the sensorimotor cortex and the duration of ADs was monitored to examine the influence of magnesium sulphate injection (0.3 g/kg b.w.). In 12-day-old hypoxia-exposed rats, an increase of the mean duration of ADs after the repeated
stimulation appeared. This effect was prevented by magnesium administration. In 25- and 35-day-old rats exposed to hypoxia a shortening of ADs was registered but no specific effect of magnesium sulphate pretreatment was observed. The brain susceptibility and ability
to terminate evoked seizures is discussed.
PI4K IIα is a critical enzyme for the maintenance of Golgi and is also known to function in the synaptic vesicles. The product of its catalytical function, phosphatidylinositol 4-phosphate (PI4P), is an important lipid molecule because it is a hallmark of the Golgi and TGN, is directly recognized by many proteins and also serves as a precursor molecule for synthesis of higher phosphoinositides. Here, we report crystal structures of PI4K IIα
enzyme in the apo-state and inhibited by calcium. The apo-
structure reveals a surprising rigidity of the active site residues important for catalytic activity. The structure of calcium inhibited kinase reveals how calcium locks ATP in the active site.
The present study was aimed to evaluate the mechanisms involved in the vasorelaxant effects of red wine polyphenol compounds (RWPC) in small mesenteric rat arteries. RWPC produce relaxation in small mesenteric arteries. This relaxant effect was abolished by endothelial denudation, NO-synthase blockade with L-NAME and partial depolarization with KCl or L-NAME plus KCl. Incubation with the reactive oxygen species scavenger, superoxide dismutase (SOD) plus catalase, or inhibition of NAD(P)H-dependent oxidoreductases with diphenyleneiodonium also inhibited RWPC induced vascular relaxation. Application of RWPC elicited a transient increase in intracellular calcium concentration ([Ca2+]i) in bovine aortic endothelial cells (BAEC), which was attenuated by a mixture of SOD and catalase. Incubation of BAEC with RWPC increased the SOD inhibitable production of O2-. These results suggest the involvement of O2- in the [Ca2+]i increase evoked by RWPC, leading to the activation of enzymes involved in the release of endothelial relaxant factors and subsequent vasodilatation of resistance arteries.