Novel sarco(endo)plasmic reticulum proteins and calcium homeostasis in striated muscles.

he impact of calcium signaling on many cellular functions is reflected by the tight regulation of the intracellular Ca(2+) concentration that is ensured by diverse pumps, channels, transporters and Ca(2+) binding proteins. In this review, we present recently identified novel sarco(endo)plasmic reticulum proteins that may have a potential involvement in the regulation of Ca(2+) homeostasis in striated muscles

Ryanodine receptor 1 mutations, dysregulation of calcium homeostasis and neuromuscular disorders

The skeletal muscle ryanodine receptor is an intracellular calcium release channel which plays a central role in excitation contraction coupling. At least 80 mutations have been identified in the gene encoding the skeletal muscle ryanodine receptor and linked to several neuromuscular disorders, whose common feature appears to be a dysregulation of calcium homeostasis. A decade of research into the functional consequences of how these mutations affect the functional properties of the ryanodine receptor and their impact on disease, have significantly advanced our understanding of Malignant Hyperthermia, Central Core Disease and Multiminicore Disease. This review gives an overview of the important findings in the field of calcium homeostasis in skeletal muscle and describes how mutations in the ryanodine receptor gene might affect the function of this intracellular calcium release channel and lead to neuromuscular disorders

Ryanodine receptor 1 mutations, dysregulation of calcium homeostasis and neuromuscular disorders.

The skeletal muscle ryanodine receptor is an intracellular calcium release channel which plays a central role in excitation contraction coupling. At least 80 mutations have been identified in the gene encoding the skeletal muscle ryanodine receptor and linked to several neuromuscular disorders, whose common feature appears to be a dysregulation of calcium homeostasis. A decade of research into the functional consequences of how these mutations affect the functional properties of the ryanodine receptor and their impact on disease, have significantly advanced our understanding of Malignant Hyperthermia, Central Core Disease and Multiminicore Disease. This review gives an overview of the important findings in the field of calcium homeostasis in skeletal muscle and describes how mutations in the ryanodine receptor gene might affect the function of this intracellular calcium release channel and lead to neuromuscular disorder

SRP-27 is a novel component of the supramolecular signaling complex involved in skeletal muscle excitation-contraction coupling.

SRP-27 is a newly identified integral membrane protein constituent of the skeletal muscle sarcoplasmic reticulum We identified its primary structure from cDNA clones isolated from a mouse skeletal muscle cDNA library. ESTs of SRP-27 were found mainly in cDNA libraries from excitable tissues of mouse. Western blot analysis confirmed the expression of SRP-27 in skeletal muscle and to a lower extent in heart and brain. Mild trypsin proteolysis combined with primary structure prediction analysis, suggest that SRP-27 has 4 transmembrane spanning alfa helices and its COOH-terminal domain faces the cytoplasmic side of the endo(sarco)plasmic reticulum. The expression of SRP-27 is higher in fast twitch skeletal muscles compared to slow twitch muscles and peaks during the first month of post-natal development. High resolution immunohistochemistry and western blot analysis of subcellular fractions indicate that SRP-27 is distributed in both longitudinal tubules and in terminal cisternae of the sarcoplasmic reticulum, as well as in the perinuclear membrane systems and the nuclear envelope of myotubes and adult fibers. SRP-27 co-sediments with the ryanodine receptor macromolecular complex in high salt sucrose gradient centrifugation, is pulled-down by anti-ryanodine receptor antibodies as well as by maurocalcin, a well characterized ryanodine receptor modulator. Our data indicate that SRP-27 is part of a sarcoplasmic reticulum supramolecular complex suggesting the involvement of SRP-27 in the structural organization or function of the molecular machinery underlying excitation-contraction coupling

One-day prevalence of asymptomatic carriage of toxigenic and non-toxigenic Clostridioides difficile in 10 French hospitals

International audienceBackground: Asymptomatic faecal carriage of Clostridioides difficile has been widely evaluated, but its prevalence across a wide range of clinical departments and related risk factors are not well described. The objectives of the PORTADIFF study were to evaluate the prevalence and identifying risk factors leading to asymptomatic carriage of both toxigenic and non-toxigenic C. difficile.Methods: The PORTADIFF study was a 1-day prevalence study carried out in 10 different French hospitals. Adult patients, who agreed to participate, were included in this study and provided a fresh stool sample. C. difficile strains isolated from carriage were characterized by polymerase chain reaction (PCR) detection of tcdA, tcdB, cdtA and cdtB, and PCR ribotyping.Results: In total, 721 patients were included in this study. The median age was 73 years (range 18-101 years) and the male/female ratio was 1.06. C. difficile (either toxigenic or non-toxigenic strains) was isolated from 79 (11%) patients; 42 (5.8%) strains were toxigenic. The prevalence rates of asymptomatic carriage ranged from 5% on surgical wards to 19% on long-term care wards. The main risk factors associated with asymptomatic carriage were antibiotic treatment within the preceding 3 months (81.8% vs 53.7%; P<0.01), hospitalization within the preceding 2 months (55.8% vs 33%; P<0.01), cumulative duration of hospital stay before study inclusion (mean 50.1 vs 34.5 days; P<0.047), and hospitalization on a ward with high global incidence of C. difficile infection.Conclusion: Eleven percent of hospitalized patients were asymptomatic carriers of toxigenic or non-toxigenic C. difficile, and may constitute a potential reservoir of C. difficile strains