Delayed identification of compound heterozygous (Phe508del/Arg117His) cystic fibrosis variants in a patient awaiting liver transplantation.

A man in his 60s undergoing liver transplant assessment was referred to the respiratory team after a thoracic CT scan revealed diffuse tree-in-bud changes. He had a history of infertility, chronic pancreatitis and liver cirrhosis with portal hypertension. Broncho-alveolar lavage was positive for Pseudomonas aeruginosa Genetic screening found two cystic fibrosis transmembrane conductance regulator variants: Phe508del and Arg117His-7T. The patient was referred to the regional cystic fibrosis (CF) centre for follow-up but died from hepatobiliary complications. The atypical presentation with relatively late onset of pulmonary disease and hepatobiliary disease predominance created a diagnostic challenge. This case is a reminder that while CF is a monogenic disorder, its manifestation, natural history and extent can be highly variable. Taking a thorough medical history of any chronic illness is essential, and patients with the appropriate clinical presentation, regardless of age, should be investigated for CF.

Idiopathic pulmonary fibrosis: airway volume measurement identifies progressive disease on computed tomography scans.

Airways tell a tale: measuring change in airway volume using functional respiratory imaging can differentiate between stable and progressive idiopathic pulmonary fibrosis on CT scans #imagebiomarkers #ipf http://bit.ly/2M8KVLl.

Cryo-EM structures of the human glutamine transporter SLC1A5 (ASCT2) in the outward-facing conformation.

Alanine-serine-cysteine transporter 2 (ASCT2, SLC1A5) is the primary transporter of glutamine in cancer cells and regulates the mTORC1 signaling pathway. The SLC1A5 function involves finely tuned orchestration of two domain movements that include the substrate-binding transport domain and the scaffold domain. Here, we present cryo-EM structures of human SLC1A5 and its complex with the substrate, L-glutamine in an outward-facing conformation. These structures reveal insights into the conformation of the critical ECL2a loop which connects the two domains, thus allowing rigid body movement of the transport domain throughout the transport cycle. Furthermore, the structures provide new insights into substrate recognition, which involves conformational changes in the HP2 loop. A putative cholesterol binding site was observed near the domain interface in the outward-facing state. Comparison with the previously determined inward-facing structure of SCL1A5 provides a basis for a more integrated understanding of substrate recognition and transport mechanism in the SLC1 family.

Receptor-Mediated Delivery of CRISPR-Cas9 Endonuclease for Cell-Type-Specific Gene Editing.

CRISPR-Cas RNA-guided endonucleases hold great promise for disrupting or correcting genomic sequences through site-specific DNA cleavage and repair. However, the lack of methods for cell- and tissue-selective delivery currently limits both research and clinical uses of these enzymes. We report the design and in vitro evaluation of S. pyogenes Cas9 proteins harboring asialoglycoprotein receptor ligands (ASGPrL). In particular, we demonstrate that the resulting ribonucleoproteins (Cas9-ASGPrL RNP) can be engineered to be preferentially internalized into cells expressing the corresponding receptor on their surface. Uptake of such fluorescently labeled proteins in liver-derived cell lines HEPG2 (ASGPr+) and SKHEP (control; diminished ASGPr) was studied by live cell imaging and demonstrates increased accumulation of Cas9-ASGPrL RNP in HEPG2 cells as a result of effective ASGPr-mediated endocytosis. When uptake occurred in the presence of a peptide with endosomolytic properties, we observed receptor-facilitated and cell-type specific gene editing that did not rely on electroporation or the use of transfection reagents. Overall, these in vitro results validate the receptor-mediated delivery of genome-editing enzymes as an approach for cell-selective gene editing and provide a framework for future potential applications to hepatoselective gene editing in vivo.

Conundrum in an asthma exacerbation.

A 66-year-old man, an asthmatic, presented with symptoms suggestive of an acute exacerbation of asthma. His arterial blood gas revealed type 1 respiratory failure (PaO2 <8 kPa or 60 mm Hg with normal or low PaCO2) with a compensated lactic acidosis. He was treated for an asthma exacerbation and sepsis. Despite treatment, his respiratory rate remained elevated although his hypoxaemia improved. There was progressive worsening of the lactic acidosis. Treatment for sepsis was augmented. Peak flow measurements were not used to assess the severity of his exacerbation nor his response to treatment. An alternate diagnosis of acute coronary syndrome with acute pulmonary oedema was made and his asthma treatment was stopped. This coincided with a decline in his serum lactate. A diagnosis of salbutamol-induced lactic acidosis (SILA) was made. SILA is a relatively common complication of salbutamol therapy in moderate/severe asthma exacerbations. It is caused by a mechanism different from the lactataemia that is associated with septic shock and life-threatening asthma.

Engineered stabilization and structural analysis of the autoinhibited conformation of PDE4.

Phosphodiesterase 4 (PDE4) is an essential contributor to intracellular signaling and an important drug target. The four members of this enzyme family (PDE4A to -D) are functional dimers in which each subunit contains two upstream conserved regions (UCR), UCR1 and -2, which precede the C-terminal catalytic domain. Alternative promoters, transcriptional start sites, and mRNA splicing lead to the existence of over 25 variants of PDE4, broadly classified as long, short, and supershort forms. We report the X-ray crystal structure of long form PDE4B containing UCR1, UCR2, and the catalytic domain, crystallized as a dimer in which a disulfide bond cross-links cysteines engineered into UCR2 and the catalytic domain. Biochemical and mass spectrometric analyses showed that the UCR2-catalytic domain interaction occurs in trans, and established that this interaction regulates the catalytic activity of PDE4. By elucidating the key structural determinants of dimerization, we show that only long forms of PDE4 can be regulated by this mechanism. The results also provide a structural basis for the long-standing observation of high- and low-affinity binding sites for the prototypic inhibitor rolipram.

Selectively targeting an inactive conformation of interleukin-2-inducible T-cell kinase by allosteric inhibitors.

ITK (interleukin-2-inducible T-cell kinase) is a critical component of signal transduction in T-cells and has a well-validated role in their proliferation, cytokine release and chemotaxis. ITK is an attractive target for the treatment of T-cell-mediated inflammatory diseases. In the present study we describe the discovery of kinase inhibitors that preferentially bind to an allosteric pocket of ITK. The novel ITK allosteric site was characterized by NMR, surface plasmon resonance, isothermal titration calorimetry, enzymology and X-ray crystallography. Initial screening hits bound to both the allosteric pocket and the ATP site. Successful lead optimization was achieved by improving the contribution of the allosteric component to the overall inhibition. NMR competition experiments demonstrated that the dual-site binders showed higher affinity for the allosteric site compared with the ATP site. Moreover, an optimized inhibitor displayed non-competitive inhibition with respect to ATP as shown by steady-state enzyme kinetics. The activity of the isolated kinase domain and auto-activation of the full-length enzyme were inhibited with similar potency. However, inhibition of the activated full-length enzyme was weaker, presumably because the allosteric site is altered when ITK becomes activated. An optimized lead showed exquisite kinome selectivity and is efficacious in human whole blood and proximal cell-based assays.

N-benzylimidazole carboxamides as potent, orally active stearoylCoA desaturase-1 inhibitors.

A potent, small molecule inhibitor with a favorable pharmacokinetic profile to allow for sustained SCD inhibition in vivo was identified. Starting from a low MW acyl guanidine (5a), identified with a RapidFire High-Throughput Mass Spectrometry (RF-MS) assay, iterative library design was used to rapidly probe the amide and tail regions of the molecule. Singleton synthesis was used to probe core changes. Biological evaluation of a SCD inhibitor (5b) included in vitro potency at SCD-1 and in vivo modulation of the plasma desaturation index (DI) in rats on a low essential fatty acid (LEFA) diet. In addition to dose-dependent decrease in DI, effects on rodent ocular tissue were noted. Therefore, in rat, these SCD inhibitors only recapitulate a portion of phenotype exhibited by the SCD-1 knockout mouse.

A systematic study of 50S ribosomal subunit purification enabling robust crystallization.

A systematic analysis was undertaken to seek correlations between the integrity, purity and activity of 50S ribosomal subunit preparations from Deinococcus radiodurans and their ability to crystallize. Conditions of fermentation, purification and crystallization were varied in a search for crystals that could reliably supply an industrial X-ray crystallography program for the structure-based design of ribosomal antibiotics. A robust protocol was obtained to routinely obtain crystals that gave diffraction patterns extending to 2.9 A resolution and that were large enough to yield a complete data set from a single crystal. To our knowledge, this is the most systematic study of this challenging area so far undertaken. Ribosome crystallization is a complex multi-factorial problem and although a clear correlation of crystallization with subunit properties was not obtained, the search for key factors that potentiate crystallization has been greatly narrowed and promising areas for further inquiry are suggested.

Purification of the large ribosomal subunit via its association with the small subunit.

We have developed an affinity purification of the large ribosomal subunit from Deinococcus radiodurans that exploits its association with FLAG-tagged 30S subunits. Thus, capture is indirect so that no modification of the 50S is required and elution is achieved under mild conditions (low magnesium) that disrupt the association, avoiding the addition of competitor ligands or coelution of common contaminants. Efficient purification of highly pure 50S is achieved, and the chromatography simultaneously sorts the 50S into three classes according to their association status (unassociated, loosely associated, or tightly associated), improving homogeneity.

The availability of web sites offering to sell opioid medications without prescriptions.

OBJECTIVE: This study was designed to determine the availability of web sites offering to sell opioid medications without prescriptions. METHOD: Forty-seven Internet searches were conducted with a variety of opioid medication terms, including "codeine," "no prescription Vicodin," and "OxyContin." Two independent raters examined the links generated in each search and resolved any coding disagreements. The resulting links were coded as "no prescription web sites" (NPWs) if they offered to sell opioid medications without prescriptions. RESULTS: In searches with terms such as "no prescription codeine" and "Vicodin," over 50% of the links obtained were coded as "NPWs." The proportion of links yielding NPWs was greater when the phrase "no prescription" was added to the opioid term. More than 300 opioid NPWs were identified and entered into a database. CONCLUSIONS: Three national drug-use monitoring studies have cited significant increases in prescription opioid use over the past 5 years, particularly among young people. The emergence of NPWs introduces a new vector for unregulated access to opioids. Research is needed to determine the effect of NPWs on prescription opioid use initiation, misuse, and dependence.