Studies using this micro-system demonstrated significant morphological differences between alveolar epithelial cells (transformed human alveolar epithelial cell line, A549 and primary murine alveolar epithelial cells, AECs) exposed to combination of solid mechanical and surface-tension stresses (cyclic propagation of air-liquid interface and wall stretch) compared to cell populations exposed solely to cyclic stretch. We have also measured significant differences in both cell death and cell detachment rates in cell monolayers experiencing combination of stresses. This research describes new tools for studying the combined effects of fluid mechanical and solid mechanical stress on alveolar cells. It also highlights the role that surface tension forces may play in the development of clinical pathology, especially under conditions of surfactant dysfunction. The results support the need for further research and improved understanding on techniques to reduce and eliminate fluid stresses in clinical settings.

In Bacteroidetes, one of the dominant phyla of the mammalian gut, active uptake of large nutrients across the outer membrane is mediated by SusCD protein complexes via a “pedal bin” transport mechanism. However, many features of SusCD function in glycan uptake remain unclear, including ligand binding, the role of the SusD lid and the size limit for substrate transport. Here we characterise the β2,6 fructo-oligosaccharide (FOS) importing SusCD from Bacteroides thetaiotaomicron (Bt1762-Bt1763) to shed light on SusCD function. Co-crystal structures reveal residues involved in glycan recognition and suggest that the large binding cavity can accommodate several substrate molecules, each up to ~2.5 kDa in size, a finding supported by native mass spectrometry and isothermal titration calorimetry. Mutational studies in vivo provide functional insights into the key structural features of the SusCD apparatus and cryo-EM of the intact dimeric SusCD complex reveals several distinct states of the transporter, directly visualising the dynamics of the pedal bin transport mechanism.

Fibrosis of the lungs and other organs is characterized by the accumulation of myofibroblasts, effectors of wound-repair that are responsible for the deposition and organization of new extracellular matrix (ECM) in response to tissue injury. During the resolution phase of normal wound repair, myofibroblast apoptosis limits the continued deposition of ECM. Mounting evidence suggests that myofibroblasts from fibrotic wounds acquire resistance to apoptosis, but the mechanisms regulating this resistance have not been fully elucidated. Endothelin-1 (ET-1), a soluble peptide strongly associated with fibrogenesis, decreases myofibroblast susceptibility to apoptosis through activation of phosphatidylinositol 3′-OH kinase (PI3K)/AKT. Focal adhesion kinase (FAK) also promotes myofibroblast resistance to apoptosis through PI3K/AKT-dependent and – independent mechanisms, although the role of FAK in ET-1 mediated resistance to apoptosis has not been explored. The goal of this study was to investigate whether FAK contributes to ET-1 mediated myofibroblast resistance to apoptosis and to examine potential mechanisms downstream of FAK and PI3K/AKT by which ET-1 regulates myofibroblast survival. Here, we show that ET-1 regulates myofibroblast survival by Rho/ROCK-dependent activation of FAK. The anti-apoptotic actions of FAK are, in turn, dependent on activation of PI3K/AKT and the subsequent increased expression of Survivin, a member of the inhibitor of apoptosis protein (IAP) family. Collectively, these studies define a novel mechanism by which ET-1 promotes myofibroblast resistance to apoptosis through upregulation of Survivin.

Extended Data Fig. 2 RagAB binds a wide range of oligopeptides EDFig2.tiff a-c, LC-MS/MS analysis of peptides bound to RagAB W83 KRAB, showing length distribution (a), total charge (b) and pI (c). d-f, Analysis of peptides bound to RagAB W83 wild-type, showing length distribution (d), total charge (e) and pI (f). For charge calculations, the pH was assumed to be 7.0 and contributions of any His residues were ignored. g, Amino acid frequency of RagAB-bound peptides (KRAB and wild-type combined; black) vs. the amino acid composition in the P. gingivalis proteome (gray), showing a substantial enrichment of Ala, Glu, Lys, Thr and Val. By contrast, aromatics (Phe, Trp) and bulky hydrophobics (Leu) appear to be underrepresented. The peptides bound to RagAB from W83 KRAB vary in length from 7 to 29 residues, with a broad maximum of around 13 residues that fits well with the peptide density observed in the structures. Assuming equal abundance of each detected peptide, there is a slight preference for neutral to slightly acidic peptides, and the pI distribution has a bimodal shape, with maxima for acidic and slightly basic peptides. Analysis of the smaller RagAB-bound peptide set from wild-type W83 (d-f) yields a slightly wider size range from 5-36 residues, but overall there are no dramatic differences in the collective length, net charge and pI of the RagAB-bound peptide populations from W83 KRAB and wild-type strains. Extended Data Fig. 3 Molecular dynamics simulations of RagAB show lid opening EDFig3.tiff a, C α-rmsd values of RagB lids in apo-RagAB (red) and peptide-bound RagAB (green) with reference to the starting crystal structure in the closed conformation. The C α-rmsd values of the RagB lids in RagA 2 B 2 are shown in blue with reference to the OO EM state. Each point indicates an average of 50 ns simulation trajectory. b, Comparison of the RagA 2 B 2 open conformation from EM (magenta) Data description i.e.