Calcium current through voltage-gated calcium channels (VGCC) controls gene expression. Here, we describe a novel signalling pathway in which the VGCC Cacnb4 subunit directly couples neuronal excitability to transcription. Electrical activity induces Cacnb4 association to Ppp2r5d, a regulatory subunit of PP2A phosphatase, followed by (i) nuclear translocation of Cacnb4/Ppp2r5d/PP2A, (ii) association with the tyrosine hydroxylase (TH) gene promoter through the nuclear transcription factor thyroid hormone receptor alpha (TRa), and (iii) histone binding through association of Cacnb4 with HP1c concomitantly with Ser 10 histone H3 dephosphorylation by PP2A. This signalling cascade leads to TH gene repression by Cacnb4 and is controlled by the state of interaction between the SH3 and guanylate kinase (GK) modules of Cacnb4. The human R482X CACNB4 mutation, responsible for a form of juvenile myoclonic epilepsy, prevents association with Ppp2r5 and nuclear targeting of the complex by altering Cacnb4 conformation. These findings demonstrate that an intact VGCC subunit acts as a repressor recruiting platform to control neuronal gene expression.

Our data suggest that preventing and correcting malnutrition using HPN in patients with cancer might have a significant benefit on their well-being. Randomized controlled studies are required to confirm this finding.

Maurocalcine (MCa) is a 33-amino acid residue peptide toxin initially isolated from the scorpion Scorpio maurus maurus. Its structural and functional features make it resembling many Cell Penetrating Peptides. In particular, MCa exhibits a characteristic positively charged face that may interact with membrane lipids. External application of MCa is known to produce Ca2+-release from intracellular stores within seconds. MCa binds directly to the skeletal muscle isoform of the ryanodine receptor, an intracellular channel target of the endoplasmic reticulum, and induces long-lasting channel openings in a mode of smaller conductance. The binding sites for MCa have been mapped within the cytoplasmic domain of the ryanodine receptor. In this manuscript, we further investigated how MCa proceeds to cross biological membranes in order to reach its target. A biotinylated derivative of MCa (MCab) was chemically synthesized, coupled to a fluorescent streptavidin indicator (Cy3 or Cy5) and the cell penetration of the entire complex followed by confocal microscopy and FACS analysis. The data provide evidence that MCa allows the penetration of the macro proteic complex and therefore may be used as a vector for the delivery of proteins in the cytoplasm as well as in the nucleus. Using both FACS and confocal analysis, we show that the cell penetration of the fluorescent complex is observed at concentrations as low as 10 nM, is sensitive to membrane potential and is partly inhibited by heparin. We also show that MCa interacts with the disialoganglioside GD3, the most abundant charged lipid in natural membranes. Despite its action on ryanodine receptor, MCa showed no sign of cell toxicity on HEK293 cells suggesting that it may have a wider application range. These data indicate that MCa may cross the plasma membrane directly by cell translocation and has a promising future as a carrier of various drugs and agents of therapeutic, diagnostic and technological value.

HPN could provide benefit for malnourished patients with gastrointestinal cancer. However, randomized controlled studies are required to confirm this benefit and the safety profile.

Background: Disease stratification, using phenotypic characterization performed either by hypothesis- or data-driven methods, was developed to improve clinical decisions. However, cluster analysis has not been used for allergic rhinitis. Objective: To define clusters in allergic rhinitis and to compare them with ARIA (Allergic Rhinitis and Its Impact on Asthma), a hypothesis-driven approach. Methods: A French observational prospective multicenter study (EVEIL: Echelle visuelle analogique dans la rhinite allergique) was carried out on 990 patients consulting general practitioners for allergic rhinitis and treated as per clinical practice. In this study, changes in symptom scores, visual analogue scales and quality of life were measured at baseline and after 14 days of treatment. A post hoc analysis was performed to identify clusters of patients with allergic rhinitis - using Ward's hierarchical method - and to define their clinical relevance at baseline and after 14 days of treatment. The cluster approach was compared to the ARIA approach. Results: Patients were clustered into 4 phenotypes which partly followed the ARIA classes. These phenotypes differed in their disease severity including symptoms and quality of life. Physicians in real-life practice prescribed medication regardless of the phenotype and severity, with the exception of patients with ocular symptoms. Prescribed treatments were comparable in hypothesis- and data-driven analyses. The prevalence of uncontrolled patients during treatment was similar in the 4 clusters, but was significantly different according to the ARIA classes. Conclusion: Cluster analysis using demographic and clinical parameters only does not appear to add relevant information for disease stratification in allergic rhinitis.

Direct regulation of N-type calcium channels by G-proteins is essential to control neuronal excitability and neurotransmitter release. Binding of the G bg dimer directly onto the channel is characterized by a marked current inhibition ("ON" effect), whereas the pore opening-and time-dependent dissociation of this complex from the channel produce a characteristic set of biophysical modifications ("OFF" effects). Although G-protein dissociation is linked to channel opening, the contribution of channel inactivation to G-protein regulation has been poorly studied. Here, the role of channel inactivation was assessed by examining time-dependent G-protein de-inhibition of Ca v 2.2 channels in the presence of various inactivationaltering β subunit constructs. G-protein activation was produced via μ-opioid receptor activation using the DAMGO agonist. Whereas the "ON" effect of G-protein regulation is independent of the type of β subunit, the "OFF" effects were critically affected by channel inactivation. Channel inactivation acts as a synergistic factor to channel activation for the speed of G-protein dissociation. However, fast inactivating channels also reduce the temporal window of opportunity for G-protein dissociation, resulting in a reduced extent of current recovery, whereas slow inactivating channels undergo a far more complete recovery from inhibition. Taken together, these results provide novel insights on the role of channel inactivation in N-type channel regulation by G-proteins and contribute to the understanding of the physiological consequence of channel inactivation in the modulation of synaptic activity by G-protein coupled receptors.

An increase in intracellular Ca2+ due to voltage-gated Ca2+ (CaV) channel opening represents an important trigger for a number of second-messenger-mediated effects ranging from neurotransmitter release to gene activation. Ca2+ entry occurs through the principal pore-forming protein but several ancillary subunits are known to more precisely tune ion influx. Among them, the CaVbeta subunits are perhaps the most important, given that they largely influence the biophysical and pharmacological properties of the channel. Notably, several functional features may be associated with specific structural regions of the CaVbeta subunits emphasizing the relevance of intramolecular domains in the physiology of these proteins. In the current report, we show that CaVbeta3 contains two PEST motifs and undergoes Ca2+ -dependent degradation which can be prevented by the specific calpain inhibitor calpeptin. Using mutant constructs lacking the PEST motifs, we present evidence that they are necessary for the cleavage of CaVbeta3 by calpain. Furthermore, the deletion of the PEST sequences did not affect the binding of CaVbeta3 to the ion-conducting CaV2.2 subunit and, when expressed in human embryonic kidney-293 cells, the PEST motif-deleted CaVbeta3 significantly increased whole-cell current density and retarded channel inactivation. Consistent with this observation, calpeptin treatment of human embryonic kidney-293 cells expressing wild-type CaVbeta3 resulted in an increase in current amplitude. Together, these findings suggest that calpain-mediated CaVbeta3 proteolysis may be an essential process for Ca2+ channel functional regulation.

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