P II proteins are widespread and highly conserved signal transduction proteins occurring in bacteria, Archaea, and plants and play pivotal roles in controlling nitrogen assimilatory metabolism. This study reports on biochemical properties of the P IIhomologue GlnK (originally termed NrgB) in Bacillus subtilis (BsGlnK). Like other P II proteins, the native BsGlnK protein has a trimeric structure and readily binds ATP in the absence of divalent cations, whereas 2-oxoglutarate is only weakly bound. In contrast to other P II -like proteins, Mg 2؉ severely affects its ATP-binding properties. BsGlnK forms a tight complex with the membrane-bound ammonium transporter AmtB (NrgA), from which it can be relieved by millimolar concentrations of ATP. Immunoprecipitation and co-localization experiments identified a novel interaction between the BsGlnK-AmtB complex and the major transcription factor of nitrogen metabolism, TnrA. In vitro in the absence of ATP, TnrA is completely tethered to membrane (AmtB)-bound GlnK, whereas in extracts from BsGlnK-or AmtB-deficient cells, TnrA is entirely soluble. The presence of 4 mM ATP leads to concomitant solubilization of BsGlnK and TnrA. This ATP-dependent membrane re-localization of TnrA by BsGlnK/AmtB may present a novel mechanism to control the global nitrogen-responsive transcription regulator TnrA in B. subtilis under certain physiological conditions.

Bronchopulmonary dysplasia (BPD) is characterised by impaired alveolarisation, inflammation and aberrant vascular development. Phosphodiesterase (PDE) inhibitors can influence cell proliferation, antagonise inflammation and restore vascular development and homeostasis, suggesting a therapeutic potential in BPD.The aim of the present study was to investigate PDE expression in the lung of hyperoxiaexposed mice, and to assess the viability of PDE4 as a therapeutic target in BPD.Newborn C57BL/6N mice were exposed to normoxia or 85% oxygen for 28 days. Animal growth and dynamic respiratory compliance were reduced in animals exposed to hyperoxia, paralleled by decreased septation, airspace enlargement and increased septal wall thickness. Changes were evident after 14 days and were more pronounced after 28 days of hyperoxic exposure. At the mRNA level, PDE1A and PDE4A were upregulated while PDE5A was downregulated under hyperoxia. Immunoblotting confirmed these trends in PDE4A and PDE5A at the protein expression level. Treatment with cilomilast (PDE4 inhibitor, 5 mg?kg) between days 14 and 28 significantly decreased the mean intra-alveolar distance, septal wall thickness and total airspace area and improved dynamic lung compliance.Pharmacological inhibition of phosphodiesterase improved lung alveolarisation in hyperoxiainduced bronchopulmonary dysplasia, and thus may offer a new therapeutic modality in the clinical management of bronchopulmonary dysplasia.

We conclude that the inhalation of iloprost reverses PAH and vascular structural remodeling in MCT-treated rats. This regimen suggests the possibility of an antiremodeling therapy in PAH.

a b s t r a c tThe Bacillus subtilis glutamine synthetase (GS) plays a dual role in cell metabolism by functioning as catalyst and regulator. GS catalyses the ATP-dependent synthesis of glutamine from glutamate and ammonium. Under nitrogen-rich conditions, GS becomes feedback-inhibited by high intracellular glutamine levels and then binds transcription factors GlnR and TnrA, which control the genes of nitrogen assimilation. While GS-bound TnrA is no longer able to interact with DNA, GlnR-DNA binding is shown to be stimulated by GS complex formation. In this paper we show a new physiological feature of the interaction between glutamine synthetase and TnrA. The transcription factor TnrA inhibits the biosynthetic activity of glutamine synthetase in vivo and in vitro, while the GlnR protein does not affect the activity of the enzyme. Structured summary of protein interactions:GS physically interacts with TnrA by anti bait coimmunoprecipitation (View interaction) TnrA binds to GS by pull down (View interaction) TnrA binds to GS by surface plasmon resonance (View interaction) GlnK physically interacts with TnrA by anti bait coimmunoprecipitation (View interaction) GlnK binds to GS by pull down (View interaction)

We would like to thank C. Méhats and colleagues for their comments regarding our paper on phosphodiesterase (PDE)4 inhibition in hyperoxia-induced bronchopulmonary dysplasia (BPD) [1]. In our article, we stated that inhibition of PDE4 with cilomilast leads to an improved alveolarisation in hyperoxiainduced lung injury in mice [1]. C. Méhats and colleagues raised concerns about our study design and the obtained results. We would like to respond to the issues in question.