A bacterial effector counteracts host autophagy by promoting degradation of an autophagy component

Beyond its role in cellular homeostasis, autophagy plays anti‐ and promicrobial roles in host–microbe interactions, both in animals and plants. One prominent role of antimicrobial autophagy is to degrade intracellular pathogens or microbial molecules, in a process termed xenophagy. Consequently, microbes evolved mechanisms to hijack or modulate autophagy to escape elimination. Although well‐described in animals, the extent to which xenophagy contributes to plant–bacteria interactions remains unknown. Here, we provide evidence that Xanthomonas campestris pv. vesicatoria (Xcv) suppresses host autophagy by utilizing type‐III effector XopL. XopL interacts with and degrades the autophagy component SH3P2 via its E3 ligase activity to promote infection. Intriguingly, XopL is targeted for degradation by defense‐related selective autophagy mediated by NBR1/Joka2, revealing a complex antagonistic interplay between XopL and the host autophagy machinery. Our results implicate plant antimicrobial autophagy in the depletion of a bacterial virulence factor and unravel an unprecedented pathogen strategy to counteract defense‐related autophagy in plant–bacteria interactions.     

Species specificity and intraspecific variation in the chemical profiles of Heliconius butterflies across a large geographic range

In many animals, mate choice is important for the maintenance of reproductive isolation between species. Traits important for mate choice and behavioral isolation are predicted to be under strong stabilizing selection within species; however, such traits can also exhibit variation at the population level driven by neutral and adaptive evolutionary processes. Here, we describe patterns of divergence among androconial and genital chemical profiles at inter‐ and intraspecific levels in mimetic Heliconius butterflies. Most variation in chemical bouquets was found between species, but there were also quantitative differences at the population level. We found a strong correlation between interspecific chemical and genetic divergence, but this correlation varied in intraspecific comparisons. We identified “indicator” compounds characteristic of particular species that included compounds already known to elicit a behavioral response, suggesting an approach for identification of candidate compounds for future behavioral studies in novel systems. Overall, the strong signal of species identity suggests a role for these compounds in species recognition, but with additional potentially neutral variation at the population level.     

Nuclear localization of TRK-A in liver cells

The liver represents a site of expression of neurotrophins and their receptors. We have characterized the expression and intracellular localization of the nerve growth factor (NGF) receptor, Trk-A, in liver cells in vivo and in vitro. In both normal and fibrotic liver tissue, Trk-A immunostaining was present in different cell types, including parenchymal cells and cells of the inflammatory infiltrate. In hepatocytes and activated stellate cells (HSC), Trk-A showed a predominant nuclear localization, both in the presence and absence of injury. In cultured HSC, Trk-A was found to be functional, because exposure of the cells to recombinant NGF resulted in stimulation of cell migration and activation of intracellular signaling pathways, including Ras-ERK and PI3K/Akt. Remarkably, in cultured HSC, Trk-A staining was found constitutively in the nucleus. In these cells, Trk-A could be stained only by antibodies directed against the intracellular domain but not by those recognizing the extracellular portion of Trk-A suggesting that the intracellular portion of the receptor is the major determinant of nuclear Trk-A staining. In contrast to HSC, freshly isolated hepatocytes did not show any nuclear localization of the intracellular portion of Trk-A. In pheocromocytoma cells, nuclear staining for Trk-A was not present in conditions of serum deprivation, but could be induced by exposure to NGF or to a mixture of soluble mediators. We conclude that nuclear localization of the intracellular domain of Trk-A is observed constitutively in liver cells such as HSC, while in other cell types it could be induced in response to soluble factors.     

Human TLR8 senses UR/URR motifs in bacterial and mitochondrial RNA

Toll‐like receptor (TLR) 13 and TLR2 are the major sensors of Gram‐positive bacteria in mice. TLR13 recognizes Sa19, a specific 23S ribosomal (r) RNA‐derived fragment and bacterial modification of Sa19 ablates binding to TLR13, and to antibiotics such as erythromycin. Similarly, RNase A‐treated Staphylococcus aureus activate human peripheral blood mononuclear cells (PBMCs) only via TLR2, implying single‐stranded (ss) RNA as major stimulant. Here, we identify human TLR8 as functional TLR13 equivalent that promiscuously senses ssRNA. Accordingly, Sa19 and mitochondrial (mt) 16S rRNA sequence‐derived oligoribonucleotides (ORNs) stimulate PBMCs in a MyD88‐dependent manner. These ORNs, as well as S. aureus‐, Escherichia coli‐, and mt‐RNA, also activate differentiated human monocytoid THP‐1 cells, provided they express TLR8. Moreover, Unc93b1 ^−/−‐ and Tlr8 ^−/−‐THP‐1 cells are refractory, while endogenous and ectopically expressed TLR8 confers responsiveness in a UR/URR RNA ligand consensus motif‐dependent manner. If TLR8 function is inhibited by suppression of lysosomal function, antibiotic treatment efficiently blocks bacteria‐driven inflammatory responses in infected human whole blood cultures. Sepsis therapy might thus benefit from interfering with TLR8 function.     

Proteomic profiling of the hypothalamus in two mouse models of narcolepsy

Narcolepsy is a disabling neurological disorder of sleepiness linked to the loss of neurons producing orexin neuropeptides in the hypothalamus. Two well‐characterized phenotypic mouse models of narcolepsy, loss‐of‐function (orexin‐knockout), and progressive loss of orexin (orexin/ataxin‐3) exist. The open question is whether the proteomics signatures of the hypothalamus would be different between the two models. To address this gap, we utilized a label‐free proteomics approach and conducted a hypothalamic proteome analysis by comparing each disease model to that of wild type. Following data processing and statistical analysis, 14 484 peptides mapping to 2282 nonredundant proteins were identified, of which 39 proteins showed significant differences in protein expression across groups. Altered proteins in both models showed commonalties in pathways for mitochondrial dysfunction and neuronal degeneration, as well as altered proteins related to inflammatory demyelination, insulin resistance, metabolic responses, and the dopaminergic and monoaminergic systems. Model‐specific alterations in insulin degraded enzyme (IDE) and synaptosomal‐associated protein‐25 were unique to orexin‐KO and orexin/ataxin‐3, respectively. For both models, proteomics not only identified clinically suspected consequences of orexin loss on energy homeostasis and neurotransmitter systems, but also identified commonalities in inflammation and degeneration despite the entirely different genetic basis of the two mouse models.     

Asymmetric synthesis of the four diastereoisomers of a novel non-steroidal farnesoid X receptor (FXR) agonist: Role of the chirality on the biological activity

An asymmetric synthetic strategy was designed for the preparation of the four possible diastereoisomers of 3,6-dimethyl-1-(2-methylphenyl)-4-(4-phenoxyphenyl)-4,8-dihydro-1H-pyrazolo[3,4-e][1,4]thiazepin-7-one, a non-steroidal FXR agonist, we recently discovered following a virtual screening approach. The results obtained from an AlphaScreen assay clearly demonstrated that only the isomer endowed with 4R,6S absolute configuration is responsible for the biological activity. A deep investigation of the different putative binding modes adopted by these enantiomerically pure ligands using computational modeling studies confirmed the enantioselectivity of FXR towards this class of molecules.     

Effect of CMV-immunoglobulins (cytotect biotest) prophylaxis on CMV pneumonia after lung transplantation

Lung transplant (LT) recipients among solid organ transplant recipients are at high risk for cytomegalovirus (CMV) infections. We evaluated the effect of CMV-Immunoglobulins (CMV-IG) (Cytotect Biotest) on CMV pneumonia diagnosed in 303 follow-up transbronchial biopsies (TBB) of lung transplant recipients. 24 patients (control group, 155 TBB from 1999 to 2002) received acyclovir for 24 months and 33 recipients (study group, 148 TBB from 2003 to 2008) received a combined CMV prophylaxis consisting of CMV-IG (Cytotect Biotest) for 12 months and a short Ganciclovir or Valganciclovir therapy from 21th to 42th postoperative day followed by acyclovir up to 24 months. In our study the percentage of pneumonia at first month TBB was similar in the study group vs the control group, 9.1% (3/33) vs 8.3% (2/24), p=0.9 ns, but after the first month the percentage was significantly lower in the study group in the first year at follow-up TBB, 1% (1/99) vs 6.4% (5/78), p=0.048, and in first two years follow-up TBB, 0.8% (1/122) vs 6.5% 8/124), p=0.018 (Statistical analysis: Chi-square test for proportion differences). Our data suggest a strong efficacy of CMV-IG prophylaxis in reducing CMV pneumonia after first month in lung transplant recipients.