Activity of innate antimicrobial peptides and ivacaftor against clinical cystic fibrosis respiratory pathogens.

Int J Antimicrob Agents. 2017 Jun 27;:

Authors: Payne JE, Dubois AV, Ingram RJ, Weldon S, Taggart CC, Elborn JS, Tunney MM

Abstract
There is a clear need for new antimicrobials to improve current treatment of chronic lung infection in people with cystic fibrosis (CF). This study determined the activity of antimicrobial peptides (AMPs) and ivacaftor, a novel CF transmembrane regulator potentiator for treatment of CF. Antimicrobial activity of AMPs (LL37, Human β-Defensins [HβD] 1-4 and SLPI) and ivacaftor against clinical respiratory isolates (Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus spp., Achromobacter spp. and Stenotrophomonas maltophilia) were determined using radial diffusion and time-kills assays, respectively. Synergy of LL37 and ivacaftor with tobramycin was determined by time-kill with in vivo activity of ivacaftor and tobramycin compared using a murine infection model. LL37 and HβD3 were the most active AMPs tested with MICs for genera ranging from 1.1-51.9 mg/L and 1-35.4 mg/L, respectively, with the exception of Achromobacter which was resistant. HβD1 and SLPI demonstrated no antimicrobial activity. LL37 demonstrated synergy with tobramycin against 4/5 S. aureus and 2/5 Streptococcus spp. isolates. Ivacaftor demonstrated bactericidal activity against Streptococcus spp. (mean log10 decrease 3.31 CFU/ml), bacteriostatic activity against S. aureus (mean log10 change 0.13 CFU/ml) but no activity against other genera. Moreover, ivacaftor demonstrated synergy with tobramycin with a mean log10 decrease of 5.72 CFU/ml and 5.53 CFU/ml at 24 hours for S. aureus and Streptococcus spp., respectively. Ivacaftor demonstrated immunomodulatory but no antimicrobial activity in a P. aeruginosa in vivo murine infection model. Following further modulation to enhance activity, AMPs and ivacaftor offer real potential as therapeutics to augment antibiotic therapy of respiratory infection in CF.

PMID: 28666755 [PubMed - as supplied by publisher]

The metabolic footprint of the airway bacterial community in cystic fibrosis.

Microbiome. 2017 Jun 30;5(1):67

Authors: Narayanamurthy V, Sweetnam JM, Denner DR, Chen LW, Naureckas ET, Laxman B, White SR

Abstract
BACKGROUND: Progressive, chronic bacterial infection of the airways is a leading cause of death in cystic fibrosis (CF). Culture-independent methods based on sequencing of the bacterial 16S rRNA gene describe a distinct microbial community that decreases in richness and diversity with disease progression. Understanding the functional characteristics of the microbial community may aid in identifying potential therapies and may assist in management, but current methods are cumbersome. Here, we demonstrate the use of an oxidative metabolic assay as a complement to sequencing methods to describe the microbiome in the airways of patients with CF.
METHODS: Expectorated sputum was collected from 16 CF subjects and 8 control subjects. The Biolog Gen III Microplate was used in a community-level physiological profiling (CLPP)-based assay to examine oxidative metabolic activity. 16S rRNA V4 amplicon sequencing was used to characterize the taxonomy and diversity of the samples. Correlations were then identified among the oxidative activity and taxonomy data. In an additional paired analysis, sputum from seven CF subjects were collected at two separate clinic visits and compared for oxidative activity, taxonomy, and diversity.
RESULTS: Significant differences in oxidative metabolic activity, microbial taxonomy, and diversity were found between the CF and control sputum samples. Oxidative activity correlated positively with total genera but not with other measures of diversity or taxonomy, demonstrating that the metabolic assay complements the structural aspects of the microbiome. As expected, Pseudomonas was significantly enriched in CF samples, while Streptococcus and Prevotella were similarly abundant in both CF and control samples. Paired analysis of CF samples at separate clinic visits revealed comparable oxidative activity that correlated with similar stability in taxonomy and diversity.
CONCLUSIONS: The CLPP assay used in this study complements existing sequencing methods to delineate the oxidative metabolic footprint of the CF airway bacterial community. This method may be useful to study the CF microbial community over time and with changes in disease state.

PMID: 28666467 [PubMed - in process]

The PAPI-1 pathogenicity island-encoded small RNA PesA influences Pseudomonas aeruginosa virulence and modulates pyocin S3 production.

PLoS One. 2017;12(6):e0180386

Authors: Ferrara S, Falcone M, Macchi R, Bragonzi A, Girelli D, Cariani L, Cigana C, Bertoni G

Abstract
Small non-coding RNAs (sRNAs) are post-transcriptional regulators of gene expression that have been recognized as key contributors to bacterial virulence and pathogenic mechanisms. In this study, we characterized the sRNA PesA of the opportunistic human pathogen Pseudomonas aeruginosa. We show that PesA, which is transcribed within the pathogenicity island PAPI-1 of P. aeruginosa strain PA14, contributes to P. aeruginosa PA14 virulence. In fact, pesA gene deletion resulted in a less pathogenic strain, showing higher survival of cystic fibrosis human bronchial epithelial cells after infection. Moreover, we show that PesA influences positively the expression of pyocin S3 whose genetic locus comprises two structural genes, pyoS3A and pyoS3I, encoding the killing S3A and the immunity S3I proteins, respectively. Interestingly, the deletion of pesA gene results in increased sensitivity to UV irradiation and to the fluoroquinolone antibiotic ciprofloxacin. The degree of UV sensitivity displayed by the PA14 strain lacking PesA is comparable to that of a strain deleted for pyoS3A-I. These results suggest an involvement of pyocin S3 in DNA damage repair and a regulatory role of PesA on this function.

PMID: 28665976 [PubMed - in process]

Primary Ciliary Dyskinesia Diagnosis. Is Color Better Than Black and White?

Am J Respir Crit Care Med. 2017 Jul 01;196(1):9-10

Authors: Knowles MR, Leigh MW

PMID: 28665204 [PubMed - in process]

A semiquantitative MRI-Score can predict loss of lung function in patients with cystic fibrosis: Preliminary results.

Eur Radiol. 2017 Jun 29;:

Authors: Schaefer JF, Hector A, Schmidt K, Teufel M, Fleischer S, Graepler-Mainka U, Riethmueller J, Gatidis S, Schaefer S, Nikolaou K, Hartl D, Tsiflikas I

Abstract
OBJECTIVES: To evaluate the applicability of a semiquantitative MRI scoring system (MR-CF-S) as a prognostic marker for clinical course of cystic fibrosis (CF) lung disease.
METHODS: This observational study of a single-centre CF cohort included a group of 61 patients (mean age 12.9 ± 4.7 years) receiving morphological and functional pulmonary MRI, pulmonary function testing (PFT) and follow-up of 2 years. MRI was analysed by three raters using MR-CF-S. The inter-rater agreement, correlation of score categories with forced expiratory volume in 1 s (FEV1) at baseline, and the predictive value of clinical parameters, and score categories was assessed for the whole cohort and a subgroup of 40 patients with moderately impaired lung function.
RESULTS: The inter-rater agreement of MR-CF-S was sufficient (mean intraclass correlation coefficient 0.92). MR-CF-S (-0.62; p < 0.05) and most of the categories significantly correlated with FEV1. Differences between patients with relevant loss of FEV1 (>3%/year) and normal course were only significant for MR-CF-S (p < 0.05) but not for clinical parameters. Centrilobular opacity (CO) was the most promising score category for prediction of a decline of FEV1 (area under curve: whole cohort 0.69; subgroup 0.86).
CONCLUSIONS: MR-CF-S is promising to predict a loss of lung function. CO seems to be a particular finding in CF patients with an abnormal course.
KEY POINTS: • Lung imaging is essential in the diagnostic work-up of CF patients • MRI serves as a powerful, radiation-free modality in paediatric CF patients • Observational single-centre study showed significant correlation of MR-CF score and FEV 1 • MR-CF score is promising in predicting a loss of lung function.

PMID: 28664245 [PubMed - as supplied by publisher]

Bacteraemia and fungaemia in cystic fibrosis patients with febrile pulmonary exacerbation: a prospective observational study.

BMC Pulm Med. 2017 Jun 29;17(1):96

Authors: Grosse-Onnebrink J, Stehling F, Tschiedel E, Olivier M, Mellies U, Schmidt R, Buer J, Rath PM, Steinmann J

Abstract
BACKGROUND: Bloodstream pathogens can be identified by multiplex PCR (SeptiFast (SF)) or blood culture (BC); whether these pathogens are present in cystic fibrosis (CF) patients during febrile pulmonary exacerbations (FPE) has not been sufficiently studied.
METHODS: In this prospective observational study, blood from CF patients experiencing FPE was tested with SF and BC before the initiation of antibiotic treatment.
RESULTS: After contaminants had been excluded, 9 of 72 blood samples tested positive by BC or SF. SF exclusively detected four pathogens; BC, one. Pulmonary pathogen transmission was likely in all cases except for 2 cases of candidaemia, which were believed to be caused by catheter-related infections. For three cases, test results caused us to change the antibiotic regimen. Sensitivity (85.7% vs. 42.9%) and negative predictive value (98.4% vs. 87.0%) tended to be higher for SF than for BC.
CONCLUSIONS: The results of SF and BC show that bacteraemia and fungaemia are present in CF patients during FPE and may affect antibiotic therapy. SF can help rule out catheter-related bloodstream infections.

PMID: 28662657 [PubMed - in process]

Immune Mechanisms in Pulmonary Fibrosis.

Am J Respir Cell Mol Biol. 2016 Sep;55(3):309-22

Authors: Kolahian S, Fernandez IE, Eickelberg O, Hartl D

Abstract
Pulmonary fibrosis, particularly idiopathic pulmonary fibrosis, represents a chronic and progressive disease with high mortality and limited therapeutic options. Excessive deposition of extracellular matrix proteins results in fibrotic remodeling, alveolar destruction, and irreversible loss of lung function. Both innate and adaptive immune mechanisms contribute to fibrogenesis at several cellular and noncellular levels. Here, we summarize and discuss the role of immune cells (T cells, neutrophils, macrophages, and fibrocytes) and soluble mediators (cytokines and chemokines) involved in pulmonary fibrosis, pointing toward novel immune-based therapeutic strategies in the field.

PMID: 27149613 [PubMed - indexed for MEDLINE]

Novel glycopolymer sensitizes Burkholderia cepacia complex isolates from cystic fibrosis patients to tobramycin and meropenem.

PLoS One. 2017;12(6):e0179776

Authors: Narayanaswamy VP, Giatpaiboon S, Baker SM, Wiesmann WP, LiPuma JJ, Townsend SM

Abstract
Burkholderia cepacia complex (Bcc) infection, associated with cystic fibrosis (CF) is intrinsically multidrug resistant to antibiotic treatment making eradication from the CF lung virtually impossible. Infection with Bcc leads to a rapid decline in lung function and is often a contraindication for lung transplant, significantly influencing morbidity and mortality associated with CF disease. Standard treatment frequently involves antibiotic combination therapy. However, no formal strategy has been adopted in clinical practice to guide successful eradication. A new class of direct-acting, large molecule polycationic glycopolymers, derivatives of a natural polysaccharide poly-N-acetyl-glucosamine (PAAG), are in development as an alternative to traditional antibiotic strategies. During treatment, PAAG rapidly targets the anionic structural composition of bacterial outer membranes. PAAG was observed to permeabilize bacterial membranes upon contact to facilitate potentiation of antibiotic activity. Three-dimensional checkerboard synergy analyses were used to test the susceptibility of eight Bcc strains (seven CF clinical isolates) to antibiotic combinations with PAAG or ceftazidime. Potentiation of tobramycin and meropenem activity was observed in combination with 8-128 μg/mL PAAG. Treatment with PAAG reduced the minimum inhibitory concentration (MIC) of tobramycin and meropenem below their clinical sensitivity breakpoints (≤4 μg/mL), demonstrating the ability of PAAG to sensitize antibiotic resistant Bcc clinical isolates. Fractional inhibitory concentration (FIC) calculations showed PAAG was able to significantly potentiate antibacterial synergy with these antibiotics toward all Bcc species tested. These preliminary studies suggest PAAG facilitates a broad synergistic activity that may result in more positive therapeutic outcomes and supports further development of safe, polycationic glycopolymers for inhaled combination antibiotic therapy, particularly for CF-associated Bcc infections.

PMID: 28662114 [PubMed - in process]

Longitudinal Assessment of Children with Mild CF Using Hyperpolarised Gas Lung MRI and LCI.

Am J Respir Crit Care Med. 2017 Jun 29;:

Authors: Smith L, Marshall H, Aldag I, Horn F, Collier G, Hughes D, West N, Horsley A, Taylor CJ, Wild J

PMID: 28661699 [PubMed - as supplied by publisher]

Pulmonary Pseudomonas aeruginosa infection induces autophagy and proteasome proteolytic pathways in skeletal muscles: effects of a pressurized whey protein-based diet in mice.

Food Nutr Res. 2017;61(1):1325309

Authors: Kishta OA, Guo Y, Mofarrahi M, Stana F, Lands LC, Hussain SNA

Abstract
Background: Pulmonary Pseudomonas aeruginosa infection in cystic fibrosis patients is associated with skeletal muscle atrophy. In this study, we investigated the effects of P. aeurginosa infection and a whey protein-rich diet on skeletal muscle proteolytic pathways. Design: An agar bead model of pulmonary P. aeurginosa infection was established in adult C57/Bl6 mice. Protein ubiquitinaiton, lipidation of LC3B protein and expressions of autophagy-related genes and ubiquitin E3 ligases were quantified using immunoblotting and qPCR. The effects of pressure-treated whey protein diet on muscle proteolysis were also evaluated. Results: Pulmonary P. aeurginosa infection reduced diaphragm, tibialis anterior, and soleus muscle weights and increased protein ubiquitination, LC3B protein lipidation, and the expressions of Lc3b, Gabarapl1, Bnip3, Parkin, Atrogin-1, and MuRF1 genes in each muscle. These changes were greater in the tibialis as compared to soleus and diaphragm. Proteolysis indicators increased within one day of infection but were not evident after seven days of infection. A pressurized whey diet attenuated LC3B protein lipidation, expressions of autophagy-related genes (BNIP3), pro-inflammatory cytokines, and protein ubiquitination. Conclusions: We conclude that pulmonary P. aeruginosa infection activates the autophagy, and the proteasome pathways in skeletal muscles and that a pressurized whey protein diet attenuates muscle proteolysis in this model.

PMID: 28659735 [PubMed - in process]

Assessment of acquired mucociliary clearance defects using micro-optical coherence tomography.

Int Forum Allergy Rhinol. 2017 Jun 28;:

Authors: Tipirneni KE, Grayson JW, Zhang S, Cho DY, Skinner DF, Lim DJ, Mackey C, Tearney GJ, Rowe SM, Woodworth BA

Abstract
BACKGROUND: Dehydration of airway surface liquid (ASL) disrupts normal mucociliary clearance (MCC) in sinonasal epithelium, which may lead to chronic rhinosinusitis (CRS). Abnormal chloride (Cl(-) ) transport is one such mechanism that contributes to this disorder and can be acquired secondary to environmental perturbations, such as hypoxia at the tissue surface. The objective of this study was to assess the technological feasibility of the novel micro-optical coherence tomography (μOCT) imaging technique for investigating acquired MCC defects in cultured human sinonasal epithelial (HSNE) cells.
METHODS: Primary HSNE cell cultures were subjected to a 1% oxygen environment for 12 hours to induce acquired cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction. Ion transport characteristics were assessed with pharmacologic manipulation in Ussing chambers. ASL, periciliary fluid (PCL), and ciliary beat frequency (CBF) were evaluated using μOCT.
RESULTS: Amiloride-sensitive transport (ΔISC ) was greater in cultures exposed to hypoxia (hypoxia: -13.2 ± 0.6 μA/cm(2) ; control: -6.5 ± 0.1 μA/cm(2) ; p < 0.01), whereas CFTR-mediated anion transport was significantly diminished (hypoxia: 28.6 ± 0.3 μA/cm(2) ; control: 36.2 ± 1.6 μA/cm(2) ; p < 0.01), consistent with acquired CFTR dysfunction and sodium hyperabsorption. Hypoxia diminished all markers of airway surface function microanatomy as observed with μOCT, including ASL (hypoxia: 5.0 ± 0.4 μm; control: 9.0 ± 0.9 μm; p < 0.01) and PCL depth (hypoxia: 2.5 ± 0.1 μm; control: 4.8 ± 0.3 μm; p < 0.01), and CBF (hypoxia: 8.7 ± 0.3 Hz; control: 10.2 ± 0.3 Hz; p < 0.01).
CONCLUSION: Hypoxia-induced defects in epithelial anion transport in HSNE led to predictable effects on markers of MCC measured with novel μOCT imaging. This imaging method represents a technological leap forward and is feasible for assessing acquired defects impacting the airway surface.

PMID: 28658531 [PubMed - as supplied by publisher]

Chasing Zero: Increasing Infection Control Compliance on an Inpatient Cystic Fibrosis Unit.

J Nurs Care Qual. 2017 Jun 23;:

Authors: Johnson S, McNeal M, Mermis J, Polineni D, Burger S

Abstract
Patients with cystic fibrosis have increased risk of pulmonary infections, and reducing spread of microorganisms is critical. To improve hospital-staff adherence to infection control guidelines, we implemented brightly colored Safe Zone floor decals, staff compliance contracts, and an infection control in-service video. Audits of staff adherence conducted pre and postintervention demonstrated an increased and sustainable improvement among each group (P < .05). These effective measures may be implemented to improve infection control compliance elsewhere.

PMID: 28658183 [PubMed - as supplied by publisher]

Adeno-Associated Virus (AAV) gene therapy for cystic fibrosis: current barriers and recent developments.

Expert Opin Biol Ther. 2017 Jun 28;:

Authors: Guggino WB, Cebotaru L

Abstract
INTRODUCTION: Since the cystic fibrosis (CF) gene was discovered in 1989, researchers have worked to develop a gene therapy. One of the most promising and enduring vectors is the AAV, which has been shown to be safe. In particular, several clinical trials have been conducted with AAV serotype 2. All of them detected viral genomes, but identification of mRNA transduction was not consistent; clinical outcomes in Phase II studies were also inconsistent. The lack of a positive outcome has been attributed to a less-than-efficient viral infection by AAV2, a weak transgene promoter and the host immune response to the vector. Areas Covered: Herein, the authors focus on AAV gene therapy for CF, evaluating past experience with this approach and identifying ways forward, based on the progress that has already been made in identifying and overcoming the limitations of AAV gene therapy. Expert opinion: Such progress makes it clear that this is an opportune time to push forward toward the development of a gene therapy for CF. Drugs to treat the basic defect in CF represent a remarkable advance but cannot treat a significant cohort of patients with rare mutations. Thus, there is a critical need to develop a gene therapy for those individuals.

PMID: 28657358 [PubMed - as supplied by publisher]

Molecular Dynamics Flexible Fitting (MDFF) Simulations Identify New Models of Closed State CFTR.

J Chem Inf Model. 2017 Jun 28;:

Authors: Simhaev L, McCarty NA, Ford RC, Senderowitz H

Abstract
Cystic Fibrosis (CF) is a lethal, genetic disease found in particular in humans of European origin which is caused by mutations in the CFTR chloride channel. The search for CF therapies acting by modulating the impaired function of mutant CFTR will be greatly advanced by high resolution structures of CFTR in different states. To date, two medium resolution EM structures of CFTR are available (one of a distant zebrafish (Danio rerio) CFTR ortholog and one of human CFTR). The two models are nearly identical to one another and both correspond to the inward-facing, NBDs separated, closed state of the channel. In addition, lower resolution structural data are available for human CFTR in an alternative conformation which likely features associated NBDs and thus geometrically resembles the conducting state of the channel. Multiple homology models of human CFTR in multiple states have been developed over the years, yet their correspondence to the existing structural information is unexplored. In this work we use molecular dynamics flexible fitting (MDFF) simulations to refine two previously described CFTR models based on the available cryo-EM map of the human protein. This map was recorded in the absence of ATP and consequently represents closed-state CFTR yet its features likely correspond to a NBDs associated conformation of the protein. Accordingly, the resulting models feature dimerized NBDs yet with no membrane traversing pore. Moreover, the open probability of the new models as deduced from the MDFF trajectories is significantly lower than that deduced from control MD trajectories initiated from the starting models. We propose that the new models correspond to a CFTR conformation which to date was largely unexplored yet one that is relevant to the gating cycle of the protein. In particular this conformation may participate in rapid channel opening and closing through small allosteric movements controlled by nucleotide binding and dissociation events. Analyzing the resulting trajectories (and not only the final models as is usually the case), we demonstrate that the refined models have good stereochemical properties and are also in favorable agreement with multiple experimental data. Moreover, despite different starting points, the final models share many common features. Finally, we propose that the combination of high resolution cryo-EM maps which are currently emerging from multiple labs and MDFF simulations will be of value for the development of yet more reliable CFTR models as well as for the identification of binding sites for CFTR modulators.

PMID: 28657312 [PubMed - as supplied by publisher]

The past decade in bench research into pulmonary infectious diseases: What do clinicians need to know?

Respirology. 2017 Jun 28;:

Authors: Finch S, Keir HR, Dicker AJ, Chalmers JD

Abstract
Respiratory infections are primarily treated with antibiotics, drugs that are mostly inexpensive and have been widely available since the 1940s and 1950s. Nevertheless, despite antibiotics, the burden of disease in pneumonia, bronchiectasis, cystic fibrosis, COPD and rare respiratory infections remains exceptionally high. There is an urgent need for translational studies to develop new treatments or new biomarkers to improve outcomes in these conditions. The 'translational gaps' between bench science and clinical practice are particularly challenging in respiratory infections. This is partly due to the poor representativeness of animal models of infection to human disease, and a long-term lack of investment into pulmonary infection research. The revolution in genomics and other omics technologies, however, is beginning to unlock clinically important information about the host response to infection, the behaviour of bacterial communities and the development of new antibiotics. It is not possible to review the extensive progress made in the last decade into the pathophysiology of the different respiratory infections and so here, we focus on major technologies that are now changing respiratory infection research, specifically bacterial whole-genome sequencing, the microbiota, personalized medicine with omics technologies, new antibiotic development and host inflammatory cell biology.

PMID: 28657170 [PubMed - as supplied by publisher]

Corticosteroid-resistant inflammatory signalling in Pseudomonas-infected bronchial cells.

ERJ Open Res. 2017 Apr;3(2):

Authors: Mizutani M, Bérubé J, Ahlgren HG, Bernier J, Matouk E, Nguyen D, Rousseau S

Abstract
Decreasing the inflammatory response that leads to tissue damage during cystic fibrosis (CF) lung disease has been a long-standing goal of CF therapy. While corticosteroids are widely used anti-inflammatory drugs, their efficacy in CF lung disease remains debated. The complex interaction between the colonising bacteria and the host environment may impact corticosteroid responsiveness. In this study, sputum samples from adult CF patients were collected at baseline and during pulmonary exacerbation episodes. Lung function measurements and sputum microbiological analyses were performed. In parallel, the inflammatory response and corticosteroid sensitivity of airway epithelial cells to Pseudomonas-derived exoproducts was investigated. We report that adult CF patients colonised with mucoid Pseudomonas aeruginosa have higher levels of baseline inflammation, more frequent exacerbations and worse lung function compared with patients colonised with nonmucoid P. aeruginosa. Moreover, mucoid P. aeruginosa activates NF-κB via Toll-like receptor (TLR) 2, which acts in an additive manner to TLR5 to drive inflammation in airway epithelial cells. Furthermore, TLR2-mediated intracellular signalling is more resistant to the anti-inflammatory effects of corticosteroid when compared with other TLR signalling pathways. Overall, these results suggest that airway inflammation triggered by mucoid P. aeruginosa is less responsive to the anti-inflammatory action of corticosteroids. Whether this translates into a diminished response of CF patients to corticosteroid therapy should be examined in future clinical studies.

PMID: 28656134 [PubMed - in process]

Stabilization of a nucleotide-binding domain of the cystic fibrosis transmembrane conductance regulator yields insight into disease-causing mutations.

J Biol Chem. 2017 Jun 27;:

Authors: Vernon RM, Chong PA, Lin H, Yang Z, Zhou Q, Aleksandrov AA, Dawson JE, Riordan JR, Brouillette CG, Thibodeau PH, Forman-Kay JD

Abstract
Characterization of the second nucleotide binding domain (NBD2) of the cystic fibrosis transmembrane conductance regulator (CFTR) has lagged behind research into the NBD1 domain, in part because NBD1 contains the F508del mutation which is the dominant cause of cystic fibrosis. Research on NBD2 has also been hampered by the overall instability of the domain and the difficulty of producing reagents. Nonetheless multiple disease-causing mutations reside in NBD2 and the domain is critical to CFTR function, since channel gating involves NBD1:NBD2 dimerization and NBD2 contains the catalytically active ATPase site in CFTR. Recognizing the paucity of structural and biophysical data on NBD2, here, we have defined a bioinformatics-based method for manually identifying stabilizing substitutions in NBD2, and used an iterative process of screening single substitutions against thermal melting points to both produce minimally mutated stable constructs and individually characterize mutations. We present a range of stable constructs with minimal mutations to help inform further research on NBD2. We have used this stabilized background to study the effects of NBD2 mutations identified in CF patients, demonstrating that mutants such as N1303K and G1349D are characterized by lower stability, as previously demonstrated for some NBD1 mutations, suggesting a potential role for NBD2 instability in the pathology of CF.

PMID: 28655774 [PubMed - as supplied by publisher]

Diabetes of the exocrine pancreas: American Diabetes Association-compliant lexicon.

Pancreatology. 2017 Jun 19;:

Authors: Petrov MS

Abstract
Multidisciplinary teams, including gastroenterologists, endocrinologists, surgeons, dietitians, primary care physicians, and other health professionals, are involved in management of individuals with diabetes of the exocrine pancreas (DEP). This necessitates introduction of a uniform terminology to ensure proper communication and reporting. Because DEP is a form of secondary diabetes mellitus, it makes sense to align the evolving DEP lexicon with nomenclature and diagnostic standards advocated by a world leading professional body in the field of diabetes such as the American Diabetes Association. This Editorial offers a historical excursus on the terms used and proposes a new concise nomenclature and diagnostic criteria. This new taxonomy of DEP, compliant with the American Diabetes Association standards of diagnosis and care for patients with diabetes mellitus, will ensure standardisation of reporting in future clinical studies on DEP and enable a dynamic incorporation of glucose dysregulation mechanisms related specifically to diseases of the exocrine pancreas as new evidence emerges.

PMID: 28655595 [PubMed - as supplied by publisher]

A Model for the Transient Subdiffusive Behavior of Particles in Mucus.

Biophys J. 2017 Jan 10;112(1):172-179

Authors: Ernst M, John T, Guenther M, Wagner C, Schaefer UF, Lehr CM

Abstract
In this study we have applied a model to explain the reported subdiffusion of particles in mucus, based on the measured mean squared displacements (MSD). The model considers Brownian diffusion of particles in a confined geometry, made from permeable membranes. The applied model predicts a normal diffusive behavior at very short and long time lags, as observed in several experiments. In between these timescales, we find that the "subdiffusive" regime is only a transient effect, MSD∝τ(α),α<1. The only parameters in the model are the diffusion-coefficients at the limits of very short and long times, and the distance between the permeable membranes L. Our numerical results are in agreement with published experimental data for realistic assumptions of these parameters. Finally, we show that only particles with a diameter less than 40 nm are able to pass through a mucus layer by passive Brownian motion.

PMID: 28076809 [PubMed - indexed for MEDLINE]

The ciliopathy-associated CPLANE proteins direct basal body recruitment of intraflagellar transport machinery.

Nat Genet. 2016 Jun;48(6):648-56

Authors: Toriyama M, Lee C, Taylor SP, Duran I, Cohn DH, Bruel AL, Tabler JM, Drew K, Kelly MR, Kim S, Park TJ, Braun DA, Pierquin G, Biver A, Wagner K, Malfroot A, Panigrahi I, Franco B, Al-Lami HA, Yeung Y, Choi YJ, University of Washington Center for Mendelian Genomics, Duffourd Y, Faivre L, Rivière JB, Chen J, Liu KJ, Marcotte EM, Hildebrandt F, Thauvin-Robinet C, Krakow D, Jackson PK, Wallingford JB

Abstract
Cilia use microtubule-based intraflagellar transport (IFT) to organize intercellular signaling. Ciliopathies are a spectrum of human diseases resulting from defects in cilia structure or function. The mechanisms regulating the assembly of ciliary multiprotein complexes and the transport of these complexes to the base of cilia remain largely unknown. Combining proteomics, in vivo imaging and genetic analysis of proteins linked to planar cell polarity (Inturned, Fuzzy and Wdpcp), we identified and characterized a new genetic module, which we term CPLANE (ciliogenesis and planar polarity effector), and an extensive associated protein network. CPLANE proteins physically and functionally interact with the poorly understood ciliopathy-associated protein Jbts17 at basal bodies, where they act to recruit a specific subset of IFT-A proteins. In the absence of CPLANE, defective IFT-A particles enter the axoneme and IFT-B trafficking is severely perturbed. Accordingly, mutation of CPLANE genes elicits specific ciliopathy phenotypes in mouse models and is associated with ciliopathies in human patients.

PMID: 27158779 [PubMed - indexed for MEDLINE]