No abstract

In eukaryotic cells, autophagy is a highly conserved self-digestion process to promote cell survival in response to nutrient starvation and other metabolic stresses. Autophagy is regulated by cell signalling such as the mTOR (mammalian target of rapamycin) pathway. However, the significance of autophagy in modulation of signal transduction is unclear. Here we show that autophagy negatively regulates Wnt signalling by promoting Dishevelled (Dvl) degradation. Von Hippel-Lindau protein-mediated ubiquitylation is critical for the binding of Dvl2 to p62, which in turn facilitates the aggregation and the LC3-mediated autophagosome recruitment of Dvl2 under starvation; the ubiquitylated Dvl2 aggregates are ultimately degraded through the autophagy-lysosome pathway. Moreover, a reverse correlation between Dvl expression and autophagy is observed in late stages of colon cancer development, indicating that autophagy may contribute to the aberrant activation of Wnt signalling in tumour formation.

Type IV secretion systems mediate the translocation of virulence factors (proteins and/or DNA) from Gramnegative bacteria into eukaryotic cells. A complex of 11 conserved proteins (VirB1-VirB11) spans the inner and the outer membrane and assembles extracellular T-pili in Agrobacterium tumefaciens. Here we report a sequence of protein interactions required for the formation of complexes between VirB2 and VirB5, which precedes their incorporation into pili. The NTPase Walker A active site of the inner membrane protein VirB4 is required for virulence, but an active site VirB4 variant stabilized VirB3 and VirB8 and enabled T-pilus formation. Analysis of VirB protein complexes extracted from the membranes with mild detergent revealed that VirB2-VirB5 complex formation depended on VirB4, which identified a novel T-pilus assembly step. Bicistron expression demonstrated direct interaction of VirB4 with VirB8, and analyses with purified proteins showed that VirB5 bound to VirB8 and VirB10. VirB4 therefore localizes at the basis of a trans-envelope interaction sequence, and by stabilization of VirB8 it mediates the incorporation of VirB5 and VirB2 into extracellular pili.

Background: Apoptosis and autophagy are two closely related systems that induce cell death. Results: X-box-binding protein 1 (XBP1) mRNA splicing regulates BECLIN-1 transcriptional activation, a fundamental player in the initiation of autophagy. Conclusion: XBP1 splicing induces an autophagic response in endothelial cells. Significance: XBP1 could be used as an important pharmacological target that can regulate the autophagic machinery and endothelial cell death.

The refinement of XRD patterns only provides the average structure parameters for the alloying materials because of the symmetric protection. Raman vibrational modes can append the detailed information about the bond length and structure. The refinements of XRD patterns for Bi alloying Cs2AgInCl6 revealed the strong structure distortion with the enlarged octahedron of In­(Bi)­Cl6 and the contracted octahedron of AgCl6 with the increasing Bi. Raman spectra supported the expanded octahedron of InCl6 and the reduced octahedron of AgCl6 but identified the anomalous shortening bond length of Bi–Cl with the increasing Bi. These distorting octahedrons break parity forbidden transition, modify Huang–Rhys factor, and result in the maximum values at 30% Bi alloying and the same variation trend for both photoluminescence and Huang–Rhys factor with the increasing Bi alloying.

Cyclic AMP receptor protein (Crp) is a transcription regulator controlling diverse cellular processes in many bacteria. In Streptomyces coelicolor, it is well established that Crp plays a critical role in spore germination and colony development. Here, we demonstrate that Crp is a key regulator of secondary metabolism and antibiotic production in S. coelicolor and show that it may additionally coordinate precursor flux from primary to secondary metabolism. We found that crp deletion adversely affected the synthesis of three well-characterized antibiotics in S. coelicolor: actinorhodin (Act), undecylprodigiosin (Red), and calcium-dependent antibiotic (CDA). Using chromatin immunoprecipitation-microarray (ChIP-chip) assays, we determined that eight (out of 22) secondary metabolic clusters encoded by S. coelicolor contained Crp-associated sites. We followed the effect of Crp induction using transcription profiling analyses and found secondary metabolic genes to be significantly affected: included in this Crp-dependent group were genes from six of the clusters identified in the ChIP-chip experiments. Overexpressing Crp in a panel of Streptomyces species led to enhanced antibiotic synthesis and new metabolite production, suggesting that Crp control over secondary metabolism is broadly conserved in the streptomycetes and that Crp overexpression could serve as a powerful tool for unlocking the chemical potential of these organisms.

The data reveal corresponding, progressive degenerative changes in articular cartilage and subchondral bone, including striking focal resorptive lesions, in the third carpal bone of racehorses subjected to repetitive, high impact trauma.

Cancer radiotherapy may be immunogenic, but it is unclear why its immunogenic effects are rarely sufficient to prevent tumor recurrence. Here we report a novel Toll receptor-9 (TLR9)-dependent mechanism that initiates tumor regrowth after local radiotherapy. Systemic inhibition of TLR9, but not TLR4, delayed tumor recurrence in mouse models of B16 melanoma, MB49 bladder cancer and CT26 colon cancer after localized high-dose tumor irradiation. Soluble factors in the microenvironment of regressing tumors triggered TLR9 signaling in freshly recruited myeloid cells appearing within four days of radiotherapy. The tumorigenic effects of TLR9 depended on MyD88/NF-κB-mediated upregulation of IL-6 expression, which in turn resulted in downstream activation of Jak/STAT3 signaling in myeloid cells. By comparing global gene expression in wild-type, TLR9- or STAT3-deficient myeloid cells derived from irradiated tumors, we identified a unique set of TLR9/STAT3-regulated genes involved in tumor-promoting inflammation and re-vascularization. Blocking STAT3 function by two myeloid-specific genetic strategies corrected TLR9-mediated cancer recurrence after radiation therapy. Our results suggest that combining localized tumor irradiation with myeloid cell-specific inhibition of TLR9/STAT3 signaling may help eliminate radiation-resistant cancers.