Circadian oscillator proteins across the kingdoms of life : Structural aspects 06 Biological Sciences 0601 Biochemistry and Cell Biology

Circadian oscillators are networks of biochemical feedback loops that generate 24-hour rhythms and control numerous biological processes in a range of organisms. These periodic rhythms are the result of a complex interplay of interactions among clock components. These components are specific to the organism but share molecular mechanisms that are similar across kingdoms. The elucidation of clock mechanisms in different kingdoms has recently started to attain the level of structural interpretation. A full understanding of these molecular processes requires detailed knowledge, not only of the biochemical and biophysical properties of clock proteins and their interactions, but also the three-dimensional structure of clockwork components. Posttranslational modifications (such as phosphorylation) and protein-protein interactions, have become a central focus of recent research, in particular the complex interactions mediated by the phosphorylation of clock proteins and the formation of multimeric protein complexes that regulate clock genes at transcriptional and translational levels. The three-dimensional structures for the cyanobacterial clock components are well understood, and progress is underway to comprehend the mechanistic details. However, structural recognition of the eukaryotic clock has just begun. This review serves as a primer as the clock communities move towards the exciting realm of structural biology

Properties of the sodium current in rat chromaffin cells exposed to nerve growth factor in vitro

1. This paper examines the electrophysiological properties of cultured rat adrenal chromaffin cells at different stages of neuron-like morphological differentiation in response to nerve growth factor (NGF). 2. Chromaffin cells display a large variability in the morphological changes after exposure to NGF. However, a marked tendency to neuronal phenotypic transformation prevails after two weeks in culture. 3. The voltage dependence of the macroscopic Na currents, judged by the current to voltage relationship, did not change significantly as a result of NGF treatment. Moreover, when kinetics, half-activation, and half-inactivation parameters of Na currents were compared between control and NGF-treated cells, no significant differences were observed. 4. Peak Na currents in control cells remained &lt; 1 nA throughout the 17 d of observation, whereas currents &gt; 1 nA became more frequent after the first week of NGF exposure. Cells with Na currents &gt; 2 nA were found routinely in cultures exposed to NGF for &gt; or = 15 d, but inadequate voltage control and neurite spiking prevented a thorough examination. Sodium current density in the population of NGF-treated chromaffin cells increased progressively over time, until an apparent plateau (3.5-fold increase) was reached by the end of the second week. No significant changes were observed in control, untreated cells. 5. The increase in Na channel density induced by NGF in chromaffin cells in compatible with the acquisition of the neuronal phenotype. Interestingly, the increase in Na channel expression occurs in slower time scale than in their neoplastic correlate, the PC12 cells. Na channels newly expressed by chromaffin cells after NGF treatment are functionally indistinguishable from those already present before treatment. </jats:p

Effects of the fatty acid amide hydrolase inhibitor URB597 on the sleep-wake cycle, c-Fos expression and dopamine levels of the rat

Our group has described previously that the endogenous cannabinoid anandamide induces sleep. The hydrolysis of this lipid involves the activity of the fatty acid amide hydrolase (FAAH), which additionally catalyzes the degradation of the satiety factor oleoylethanolamide and the analgesic-inducing lipid palmitoylethanolamide. It has been demonstrated that the inhibition of the FAAH by URB597 increases levels of anandamide, oleoylethanolamide and palmitoylethanolamide in the brain of rats. In order to determinate the physiological properties of the FAAH inhibition on the sleep modulation, we report the pharmacological effects on the sleep-wake cycle of the rat after i.c.v. administrations of URB597, oleoylethanolamide or palmitoylethanolamide (10, 20 mu g/5 mu l). Separate unilateral i.c.v. injections of 3 compounds during the lights-on period, increased wakefulness and decreased slow wave (SW) sleep in rats in a dose-dependent fashion. We additionally found out that, compared to controls, c-Fos immunoreactivity in hypothalamus and dorsal raphe nucleus was increased in rats that received URB597, oleoylethanolamide or palmitoylethanolamide (10, 20 mu g/5 mu l, i.c.v.). Next, we found that after an injection of the compounds, levels of dopamine were increased whereas extracellular levels of levodopa (L-DOPA) were decreased. These findings indicate that that inhibition of the FAAH, via URB597, modulates waking. These effects were mimicked separately by the administration of oleoylethanolamide or palmitoylethanolamide. The alertness induced by the compounds tested here activated wake-promoting brain regions and they also induced the release of dopamine. Our results suggest that FAAH activity as well as two molecules that are catalyzed by this enzyme, oleoylethanolamide and palmitoylethanolamide, participate in the regulation of the waking state. Alternative approaches to treat sleep disorders such as excessive somnolence might consider the use of the URB597, oleoylethanolamide or palmitoylethanolamide since all compounds enhance waking. (c) 2007 Elsevier B.V. All rights reserved

Dyskinesia in Parkinson's disease: mechanisms and current non-pharmacological interventions

Dopamine replacement therapy in Parkinson's disease is associated with several unwanted effects, of which dyskinesia is the most disabling. The development of new therapeutic interventions to reduce the impact of dyskinesia in Parkinson's disease is therefore a priority need. This review summarizes the key molecular mechanisms that underlie dyskinesia. The role of dopamine receptors and their associated signaling mechanisms including dopamine-cAMP-regulated neuronal phosphoprotein, extracellular signal-regulated kinase, mammalian target of rapamycin, mitogen and stress-activated kinase-1 and Histone H3 are summarized, along with an evaluation of the role of cannabinoid and nicotinic acetylcholine receptors. The role of synaptic plasticity and animal behavioral results on dyskinesia are also evaluated. The most recent therapeutic advances to treat Parkinson's disease are discussed, with emphasis on the possibilities and limitations of non-pharmacological interventions such as physical activity, deep brain stimulation, transcranial magnetic field stimulation and cell replacement therapy. The review suggests new prospects for the management of Parkinson's disease-associated motor symptoms, especially the development of dyskinesia