Could a defective epithelial sodium channel lead to bronchiectasis

Background

Bronchiectasis is defined as a permanent dilation of the airways arising from chronic bronchial inflammation/infection. In 50% of cases, no etiology can be identified. Recently, the role of the epithelial sodium channel ENaC has been pointed out in the pathophysiology of cystic fibrosis, a disease due to mutations in the CFTR gene and causing bronchiectasis in the airways. Moreover, it was found that transgenic mice overexpressing ENaCβ present cystic fibrosis-like lung disease symptoms. Our aim was to evaluate if a defective ENaC protein could be involved in the development of bronchiectasis.

Methods

We extensively analysed ENaCβ and γ genes in 55 patients with idiopathic bronchiectasis and without two mutations in the coding regions of CFTR. Thirty-eight patients presented functional abnormalities suggesting impaired sodium transport (abnormal sweat chloride concentration or nasal potential difference measurement), and 17 had no such evidence.

Results

Sequencing of the exons and flanking introns of the ENaCβ and γ gene identified five different amino-acid changes (p.Ser82Cys, p.Pro369Thr, p.Asn288Ser in ENaCβ ; and p.Gly183Ser, p.Glu197Lys in ENaCγ) in heterozygous state in 8 patients. The p.Ser82Cys amino-acid change was found in 3 unrelated patients who were also heterozygous for a CFTR mutation or variant (1 p.F508del, 1 IVS8-5T, and 1 IVS8-5T:1716G>A (p.E528E)). The other mutations were found in patients without CFTR mutation, the p.Glu197Lys mutation in 2 patients and the other variants in single patients. Among the 8 patients bearing an ENaC mutation, 5 had functional abnormalities suggesting impaired sodium transport.

Conclusion

Our results suggest that several variants in ENaCβ and γ genes might be deleterious for ENaC function and lead to bronchiectasis, especially in patients who are trans-heterozygotes for ENaCβ/CFTR mutations or variants.     

GPR50 is the mammalian ortholog of Mel1c: Evidence of rapid evolution in mammals

Background  

The melatonin receptor subfamily contains three members Mel1a, Mel1b and Mel1c, found in all vertebrates except for Mel1c which is found only in fish, Xenopus species and the chicken. Another receptor, the melatonin related receptor known as GPR50, found exclusively in mammals and later identified as a member of the melatonin receptor subfamily because of its identity to the three melatonin receptors despite its absence of affinity for melatonin. The aim of this study was to describe the evolutionary relationships between GPR50 and the three other members of the melatonin receptor subfamily.     

Identification of a GTP-bound Rho specific scFv molecular sensor by phage display selection

Background  

The Rho GTPases A, B and C proteins, members of the Rho family whose activity is regulated by GDP/GTP cycling, function in many cellular pathways controlling proliferation and have recently been implicated in tumorigenesis. Although overexpression of Rho GTPases has been correlated with tumorigenesis, only their GTP-bound forms are able to activate the signalling pathways implicated in tumorigenesis. Thus, the focus of much recent research has been to identify biological tools capable of quantifying the level of cellular GTP-bound Rho, or determining the subcellular location of activation. However useful, these tools used to study the mechanism of Rho activation still have limitations. The aim of the present work was to employ phage display to identify a conformationally-specific single chain fragment variable (scFv) that recognizes the active, GTP-bound, form of Rho GTPases and is able to discriminate it from the inactive, GDP-bound, Rho in endogenous settings.     

Proteomic characterization of mouse cytosolic and membrane prostate fractions: high levels of free SUMO peptides are androgen-regulated

The prostate is a relatively homogeneous tissue that is highly specialized in synthetic and secretory functions. The frequency of malignant growth explains its great clinical significance. We used here a combination of subcellular fractionation, 1-DE (one-dimensional gel electrophoresis) protein separation and mass spectrometry, to establish a prostate protein expression profile in mice. Analysis of proteins present in cytosolic (C) and membrane (P) prostate fractions led to the identification of 619 distinct proteins. A majority of abundant proteins were found to compose the metabolism and protein synthesis machinery. Those identified also correspond to known endoplasmic reticulum and Golgi residents, chaperones and anterograde cargos. They included a series of proteins involved in exocytic/endocytic trafficking. Among the signaling proteins, we identified the ubiquitin-like peptides smt3. We showed that both free small ubiquitin-related modifier SUMO-2/3 and SUMO-1 levels are subject to tight control by the androgen 5alpha-dihydrotestosterone (DHT). By contrast with SUMO-2/3, free SUMO-1 peptides are particularly abundant in the prostate when compared with other tissues. Therefore, we report prostate protein expression profiles of cytosolic and membrane fractions in mice. Our data suggest that the identified free SUMO peptides play an important role in this secretory tissue.     

Cell-matrix adhesion: the Wech connection

Integrins link the extracellular matrix to the cytoskeleton via a complex of proteins: the integrin-cytoskeleton link. A recent study in Drosophila has uncovered a new component of the link, Wech, and shown that it is essential for integrin-mediated adhesion.     

Combinatorial engineering to enhance thermostability of amylosucrase

Amylosucrase is a transglucosidase that catalyzes amylose-like polymer synthesis from sucrose substrate. About 60,000 amylosucrase variants from two libraries generated by the MutaGen random mutagenesis method were submitted to an in vivo selection procedure leading to the isolation of more than 7000 active variants. These clones were then screened for increased thermostability using an automated screening process. This experiment yielded three improved variants (two double mutants and one single mutant) showing 3.5- to 10-fold increased half-lives at 50 degrees C compared to the wild-type enzyme. Structural analysis revealed that the main differences between wild-type amylosucrase and the most improved variant (R20C/A451T) might reside in the reorganization of salt bridges involving the surface residue R20 and the introduction of a hydrogen-bonding interaction between T451 of the B' domain and D488 of flexible loop 8. This double mutant is the most thermostable amylosucrase known to date and the only one usable at 50 degrees C. At this temperature, amylose synthesis by this variant using high sucrose concentration (600 mM) led to the production of amylose chains twice as long as those obtained by the wild-type enzyme at 30 degrees C.     

Characterization of reproduction-specific genes in a marine bivalve mollusc: influence of maturation stage and sex on mRNA expression

Numerous studies have investigated the reproduction mechanisms in mollusc species at a biochemical and physiological level; few have described these mechanisms at a molecular level, despite great commercial interest in several mollusc species. We investigated genes involved in gonad maturation of the marine scallop Argopecten purpuratus. A cDNA library was made from gonad tissue. After sequence analysis, 418 unique genes were characterized, of these, about 80% were of unknown function. Among the identified sequences, we analyzed the mRNA expression by real-time PCR of 7 genes involved in reproduction mechanisms, either directly: testis-specific serine/threonine-protein kinase (TSSK), vitellogenin (Vg), and spermatogenesis and centriole associated 1 (SCA) or indirectly: calcineurin A (CNA), centrin, RNA-specific adenosine deaminase (ADAR), and cytidine deaminase (CDA). The real-time PCR analyses were conducted on different tissues of mature and immature scallops (testis, ovary, immature gonad, gill, digestive gland and mantle). The genes studied, presented (1) a strong tissue-dependent expression pattern (higher expression in gonad tissues than in all other tissues) and (2) a sex- and maturation-specific expression pattern (except centrin). This is the first time that the expression of specific genes involved in reproduction mechanisms in a marine mollusc has been described at the molecular level.