C-terminal phosphorylation of NaV1.5 impairs FGF13-dependent regulation of channel inactivation

International audienceVoltage-gated Na(+) (NaV) channels are key regulators of myocardial excitability, and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII)-dependent alterations in NaV1.5 channel inactivation are emerging as a critical determinant of arrhythmias in heart failure. However, the global native phosphorylation pattern of NaV1.5 subunits associated with these arrhythmogenic disorders and the associated channel regulatory defects remain unknown. Here, we undertook phosphoproteomic analyses to identify and quantify in situ the phosphorylation sites in the NaV1.5 proteins purified from adult WT and failing CaMKIIδc-overexpressing (CaMKIIδc-Tg) mouse ventricles. Of 19 native NaV1.5 phosphorylation sites identified, two C-terminal phosphoserines at positions 1938 and 1989 showed increased phosphorylation in the CaMKIIδc-Tg compared with the WT ventricles. We then tested the hypothesis that phosphorylation at these two sites impairs fibroblast growth factor 13 (FGF13)-dependent regulation of NaV1.5 channel inactivation. Whole-cell voltage-clamp analyses in HEK293 cells demonstrated that FGF13 increases NaV1.5 channel availability and decreases late Na(+) current, two effects that were abrogated with NaV1.5 mutants mimicking phosphorylation at both sites. Additional co-immunoprecipitation experiments revealed that FGF13 potentiates the binding of calmodulin to NaV1.5 and that phosphomimetic mutations at both sites decrease the interaction of FGF13 and, consequently, of calmodulin with NaV1.5. Together, we have identified two novel native phosphorylation sites in the C terminus of NaV1.5 that impair FGF13-dependent regulation of channel inactivation and may contribute to CaMKIIδc-dependent arrhythmogenic disorders in failing hearts

Restoring Rivers One Reach at a Time: Results from a Survey of U.S. River Restoration Practitioners

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72915/1/j.1526-100X.2007.00244.x.pd

Does access to the bluestreak cleaner wrasse Labroides dimidiatus affect indicators of stress and health in resident reef fishes in the Red Sea?

Interactions between the bluestreak cleaner wrasse Labroides dimidiatus and its client reef fish are a textbook example of interspecific mutualism. The fact that clients actively visit cleaners and invite inspection, together with evidence that cleaners eat many client ectoparasites per day, indeed strongly suggests a mutualistic relationship. What remains unknown is how parasite removal affects the physiology of clients and thereby their body condition, health, and immune function. Here we addressed these issues in a field study in Ras Mohammed National Park, Egypt. In our study area, small reef patches are inter-spaced with areas of sandy substrate, thereby preventing many species (i.e., residents, including cleaner wrasses) from travelling between the reef patches. This habitat structure leads to a mosaic of resident clients with and without access to bluestreak cleaner wrasses, further referred to as “cleaner access”, on which we focused our study. We found that residents with cleaner access had higher body condition than residents without cleaner access. However, indicators of stress like variation in cortisol levels corrected for handling time and various immune parameters were apparently unaffected by cleaner access. In fact antibody responses were significantly higher in fishes without cleaner access. This suggests that cleaner access decreases the need for active immunity and that this releases resources that might be allocated to other functions such as somatic growth and reproduction

Human Monkeypox Outbreak Caused by Novel Virus Belonging to Congo Basin Clade, Sudan, 2005

TOC Summary: This virus should be considered endemic to the wetland areas of Bentiu, Unity State, Sudan

Neisseria meningitidis Differentially Controls Host Cell Motility through PilC1 and PilC2 Components of Type IV Pili

Neisseria meningitidis is a strictly human pathogen that has two facets since asymptomatic carriage can unpredictably turn into fulminant forms of infection. Meningococcal pathogenesis relies on the ability of the bacteria to break host epithelial or endothelial cellular barriers. Highly restrictive, yet poorly understood, mechanisms allow meningococcal adhesion to cells of only human origin. Adhesion of encapsulated and virulent meningococci to human cells relies on the expression of bacterial type four pili (T4P) that trigger intense host cell signalling. Among the components of the meningococcal T4P, the concomitantly expressed PilC1 and PilC2 proteins regulate pili exposure at the bacterial surface, and until now, PilC1 was believed to be specifically responsible for T4P-mediated meningococcal adhesion to human cells. Contrary to previous reports, we show that, like PilC1, the meningococcal PilC2 component is capable of mediating adhesion to human ME180 epithelial cells, with cortical plaque formation and F-actin condensation. However, PilC1 and PilC2 promote different effects on infected cells. Cellular tracking analysis revealed that PilC1-expressing meningococci caused a severe reduction in the motility of infected cells, which was not the case when cells were infected with PilC2-expressing strains. The amount of both total and phosphorylated forms of EGFR was dramatically reduced in cells upon PilC1-mediated infection. In contrast, PilC2-mediated infection did not notably affect the EGFR pathway, and these specificities were shared among unrelated meningococcal strains. These results suggest that meningococci have evolved a highly discriminative tool for differential adhesion in specific microenvironments where different cell types are present. Moreover, the fine-tuning of cellular control through the combined action of two concomitantly expressed, but distinctly regulated, T4P-associated variants of the same molecule (i.e. PilC1 and PilC2) brings a new model to light for the analysis of the interplay between pathogenic bacteria and human host cells