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Glutamate is the most abundant excitatory neurotransmitter in the central nervous system, and its precise control is vital to maintain normal brain function and to prevent excitotoxicity.sup.1. The removal of extracellular glutamate is achieved by plasma-membrane-bound transporters, which couple glutamate transport to sodium, potassium and pH gradients using an elevator mechanism.sup.2-5. Glutamate transporters also conduct chloride ions by means of a channel-like process that is thermodynamically uncoupled from transport.sup.6-8. However, the molecular mechanisms that enable these dual-function transporters to carry out two seemingly contradictory roles are unknown. Here we report the cryo-electron microscopy structure of a glutamate transporter homologue in an open-channel state, which reveals an aqueous cavity that is formed during the glutamate transport cycle. The functional properties of this cavity, combined with molecular dynamics simulations, reveal it to be an aqueous-accessible chloride permeation pathway that is gated by two hydrophobic regions and is conserved across mammalian and archaeal glutamate transporters. Our findings provide insight into the mechanism by which glutamate transporters support their dual function, and add information that will assist in mapping the complete transport cycle shared by the solute carrier 1A transporter family. Glutamate transporters conduct chloride ions through an aqueous channel with hydrophobic gates that forms during the glutamate transport cycle., Author(s): Ichia Chen [sup.1] , Shashank Pant [sup.2] [sup.3] [sup.4] , Qianyi Wu [sup.1] , Rosemary J. Cater [sup.1] [sup.7] , Meghna Sobti [sup.5] [sup.6] , Robert J. Vandenberg [sup.1] [...]

The long noncoding RNA (lncRNA) GAS5 has been found to act as a decoy for the glucocorticoid receptor (GR), thus implicating GAS5 as a potential regulator of glucocorticoid sensitivity and resistance. Airway smooth muscle (ASM) cells and airway epithelial cells (AEC) play an important role in the pathogenesis and persistence of asthma and other chronic airways diseases. These airway structural cell types are also important cellular targets of the anti- inflammatory actions of glucocorticoids. In this study, we sought to examine the relevance of GAS5 to glucocorticoid sensitivity and resistance in ASM and AEC. We provide the first evidence that pro-inflammatory mediators up-regulate GAS5 levels in both airway epithelial and smooth muscle cells, and that decreasing GAS5 levels can enhance glucocorticoid action in AEC. Key words: glucocorticoid, steroid resistance, non-coding RNA, lncRNA, airway inflammation. Le long ARN non codant (ARNnc) GAS5 s'est avere agir comme leurre du recepteur des glucocorticoides (GR), l'impliquant ainsi comme regulateur potentiel de la sensibilite et de la resistance aux glucocorticoides. Les cellules de muscle lisse respiratoire (MLR) et les cellules epitheliales respiratoires (CER) jouent un role important dans la pathogenese et la persistance de l'asthme et d'autres maladies respiratoires chroniques. Les types de cellules structurales des voies respiratoires constituent aussi des cibles importantes de l'action anti-inflammatoire des glucocorticoides. Dans cette etude, les auteurs cherchaient a examiner la pertinence de GAS5 dans la sensibilite et la resistance aux glucocorticoides chez les MLR et les CER. Ils fournissent les premieres indications que des mediateurs pro-inflammatoires regulent a la hausse les niveaux de GAS5 tant dans les cellules epitheliales respiratoires que dans les cellules de muscle lisse, et que la diminution des niveaux de GAS5 peut accroitre l'action des glucocorticoides dans les CER. [Traduit par la Redaction] Mots-cles: glucocorticoide, resistance aux steroides, ARN non codant, ARNnc, inflammatoire des voies respiratoires., Introduction Long noncoding RNAs (lncRNAs) are now known to be important regulators of gene expression and cellular function and can perform diverse functions, from tethering transcription factors to DNA, to [...]

F1Fo ATP synthase functions as a biological generator and makes a major contribution to cellular energy production. Proton flow generates rotation in the Fo motor that is transferred to the F1 motor to catalyze ATP production, with flexible F1/Fo coupling required for efficient catalysis. F1Fo ATP synthase can also operate in reverse, hydrolyzing ATP and pumping protons, and in bacteria this function can be regulated by an inhibitory ε subunit. Here we present cryo-EM data showing E. coli F1Fo ATP synthase in different rotational and inhibited sub-states, observed following incubation with 10 mM MgATP. Our structures demonstrate how structural transitions within the inhibitory ε subunit induce torsional movement in the central stalk, thereby enabling its rotation within the Fο motor. This highlights the importance of the central rotor for flexible coupling of the F1 and Fo motors and provides further insight into the regulatory mechanism mediated by subunit ε. Cryo-EM structures of E. coli F1Fo ATP synthase highlight the role of the inhibitory ε subunit in regulating the torsional movement of the central stalk within the Fo motor and central stalk flexibility in coupling the F1 and Fo motors. [ABSTRACT FROM AUTHOR]

Airway wall remodeling comprises a broad range of structural changes including increases in the volume of airway smooth muscle (ASM) and fibrillar collagen. The impact of fibrillar collagen remodeling on ASM proliferation was investigated. Human ASM cultured on type I fibrillar collagen remodeled the collagen substrate by both degradation (collagenolysis) and formation of networks comprised of thicker reticular collagen fibrils (fibrillogenesis). In cultures maintained on fibrillar collagen, the levels of matrix metalloproteases (MMPs) -1 and -14 mRNA and active MMP-2 were higher than in cultures maintained on nonfibrillar type I collagen (gelatin) or plastic. Although there was no apparent increase in cytotoxicity or apoptosis, the number of ASM was lower on fibrillar collagen than on gelatin or plastic for control conditions. Furthermore, maintenance on fibrillar collagen attenuated basic fibroblast growth factor-stimulated increases in cell number and the percentage of cells entering S-phase. In cultures maintained on fibrillar collagen, the MMP inhibitor ilomastat (2.5 [micro]M) 1) attenuated collagenolysis, 2) enhanced fibrillogenesis, and 3) inhibited proliferation. In contrast, knockdown of the [beta]1-integrin gene in ASM maintained on fibrillar collagen led to an increase in proliferation and reduced MMP-1 and -14 expression. Thus, ASM remodel the pericellular environment by degrading collagen fibrils and spinning them into larger collagen assemblies. Moreover, the collagen fibrils limit proliferation and activate autocrine MMPs in a [beta]-integrin-dependent manner, suggesting a potential negative feedback on modeling executed through fibrillar collagen activation of [beta]-integrins. asthma; extracellular matrix; integrin; matrix metalloprotease; proliferation doi:10.1152/ajplung.00312.2009

Abstract: Bleomycin-induced lung fibrosis in mice reproduces some key features of pulmonary fibrosis in humans including alveolar inflammation, myofibroblast proliferation, and collagen deposition. Glucocorticoids have been used as first-line therapy [...]