Temporary halt sites in the « Vallon de la Chaume » (Lacoste) from Late Neolithic to Iron Age

Une campagne de sondages archéologiques a été engagée sur la rive gauche du vallon de la Chaume dans l’abri de la Trémie et à quelques mètres en amont, dans la grotte Adrian afin de vérifier l’existence d’une occupation funéraire du vallon. En effet, dans le cadre de la prospection du massif du Luberon l’association GREC Luberon a découvert en 2013 sur les deux sites plusieurs ossements humains ainsi que des tessons en céramique attribuable au Néolithique. Cette campagne a permis d’attester que le porche de la grotte Adrian et l’abri de la Trémie ont été des lieux de passage et probablement des refuges occasionnels depuis le Néolithique final. L’inhumation primaire découverte lors de la désobstruction de l’abri de la Trémie révèle qu’il a également servi à des fins mortuaires à l’âge du Fer. Cette intervention documente l’occupation humaine sur le petit Luberon à la fin de la Préhistoire et aux âges des métaux.An archaeological campaign was conducted on the left bank of the small valley called “La Chaume” in the rock shelter “la Trémie” and few meters uphill in the cave “Adrian”. The aim was to check if those places were used for funerary purposes as human bones associated with neolithic potteries were discovered during an exploration lead by the association G.R.E.C Luberon in 2013. The porch of the Adrian cave and “La Trémie” rock-shelter were used as temporary halt site from the Late Neolithic. The primary burial discovered during the removal of obstruction date actually from the Iron age. The archaeological campaign gives some elements on the human occupation of the “Petit Luberon” from the end of Prehistory to the metal ages

Natural processes involved in the formation of Pleistocene bone assemblages in continental South-East Asian caves : the case of the cave of the monk (Chiang Dao Wildlife Sanctuary, Thailand).

A large paleontological assemblage typical of Ailuropoda-Stegodon fauna was discovered in the Cave of the Monk, in northern Thailand. Geological and taphonomic approaches were conducted in order to determine site formation processes. A sedimentological study indicated that the fossiliferous layer resulted from mediumsize burrowing animals occupying the cave. Bone surface analysis confirmed that Porcupine was the main, if not exclusive, bone accumulator. A bone accumulation rate was calculated. The assemblage appears to have formed over an average period of one to several tens of thousand of years. This time frame means that the assemblage can not be considered as a homogeneous reference for palaeoenvironmental reconstruction as may have been assumed without the present analysis

Role of lipid rafts in E-cadherin– and HGF-R/Met–mediated entry of Listeria monocytogenes into host cells

Listeria monocytogenes uptake by nonphagocytic cells is promoted by the bacterial invasion proteins internalin and InlB, which bind to their host receptors E-cadherin and hepatocyte growth factor receptor (HGF-R)/Met, respectively. Here, we present evidence that plasma membrane organization in lipid domains is critical for Listeria uptake. Cholesterol depletion by methyl-β-cyclodextrin reversibly inhibited Listeria entry. Lipid raft markers, such as glycosylphosphatidylinositol-linked proteins, a myristoylated and palmitoylated peptide and the ganglioside GM1 were recruited at the bacterial entry site. We analyzed which molecular events require membrane cholesterol and found that the presence of E-cadherin in lipid domains was necessary for initial interaction with internalin to promote bacterial entry. In contrast, the initial interaction of InlB with HGF-R did not require membrane cholesterol, whereas downstream signaling leading to F-actin polymerization was cholesterol dependent. Our work, in addition to documenting for the first time the role of lipid rafts in Listeria entry, provides the first evidence that E-cadherin and HGF-R require lipid domain integrity for their full activity

A Pseudo-tRNA Modulates Antibiotic Resistance in \u3cem\u3eBacillus cereus\u3c/em\u3e

Bacterial genomic islands are often flanked by tRNA genes, which act as sites for the integration of foreign DNA into the host chromosome. For example, Bacillus cereus ATCC14579 contains a pathogenicity island flanked by a predicted pseudo-tRNA, tRNAOther, which does not function in translation. Deletion of tRNAOther led to significant changes in cell wall morphology and antibiotic resistance and was accompanied by changes in the expression of numerous genes involved in oxidative stress responses, several of which contain significant complementarities to sequences surrounding tRNAOther. This suggested that tRNAOther might be expressed as part of a larger RNA, and RACE analysis subsequently confirmed the existence of several RNA species that significantly extend both the 3′ and 5′-ends of tRNAOther. tRNAOther expression levels were found to be responsive to changes in extracellular iron concentration, consistent with the presence of three putative ferric uptake regulator (Fur) binding sites in the 5′ leader region of one of these larger RNAs. Taken together with previous data, this study now suggests that tRNAOther may function by providing a tRNA-like structural element within a larger regulatory RNA. These findings illustrate that while integration of genomic islands often leaves tRNA genes intact and functional, in other instances inactivation may generate tRNA-like elements that are then recruited to other functions in the cell

A FRET analysis to unravel the role of cholesterol in Rac1 and PI 3-kinase activation in the InlB/Met signalling pathway

The signalling pathway for the hepatocyte growth factor receptor, Met/HGF-R, is hijacked by the bacterial surface protein InlB to induce Listeria monocytogenes entry into non-phagocytic cells. We previously showed that Listeria invades host cells by interacting with specialized microdomains of the host plasma membrane called lipid rafts. In this study, we analysed in living cells signalling events that are crucial for Listeria entry using a fluorescence resonance energy transfer-based microscopic method. Phosphoinositide (PI) 3-kinase activity and Rac1 signalling induced by Listeria interacting with epithelial cells were monitored as well as signalling induced by soluble InlB and the Met natural ligand HGF. We found that InlB and HGF induced similar kinetics of PI 3-kinase and Rac1 activation. PI 3-kinase activation was upstream and independent of Rac1 activation. Cholesterol-depletion experiments were performed to address the role of lipid rafts in Met signalling. The amount of 3′-phosphoinositides produced by PI 3-kinase was not affected by cholesterol depletion, while their membrane dynamic was cholesterol-dependent. Rac1 activation, downstream from PI 3-kinase, was cholesterol-dependent suggesting that the spatial distribution of 3′-phosphoinositides within membrane microdomains is critical for Rac1 activation and consequently for F-actin assembly at bacterial entry site.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74959/1/j.1462-5822.2006.00832.x.pd

A Pseudo-tRNA Modulates Antibiotic Resistance in Bacillus cereus

Bacterial genomic islands are often flanked by tRNA genes, which act as sites for the integration of foreign DNA into the host chromosome. For example, Bacillus cereus ATCC14579 contains a pathogenicity island flanked by a predicted pseudo-tRNA, tRNA(Other), which does not function in translation. Deletion of tRNA(Other) led to significant changes in cell wall morphology and antibiotic resistance and was accompanied by changes in the expression of numerous genes involved in oxidative stress responses, several of which contain significant complementarities to sequences surrounding tRNA(Other). This suggested that tRNA(Other) might be expressed as part of a larger RNA, and RACE analysis subsequently confirmed the existence of several RNA species that significantly extend both the 39 and 5\u27-ends of tRNA(Other). tRNA(Other) expression levels were found to be responsive to changes in extracellular iron concentration, consistent with the presence of three putative ferric uptake regulator (Fur) binding sites in the 59 leader region of one of these larger RNAs. Taken together with previous data, this study now suggests that tRNA(Other) may function by providing a tRNA-like structural element within a larger regulatory RNA. These findings illustrate that while integration of genomic islands often leaves tRNA genes intact and functional, in other instances inactivation may generate tRNA-like elements that are then recruited to other functions in the cell

Live cell fluorescence microscopy to study microbial pathogenesis

Advances in microscopy and fluorescent probes provide new insight into the nanometer-scale biochemistry governing the interactions between eukaryotic cells and pathogens. When combined with mathematical modelling, these new technologies hold the promise of qualitative, quantitative and predictive descriptions of these pathways. Using the light microscope to study the spatial and temporal relationships between pathogens, host cells and their respective biochemical machinery requires an appreciation for how fluorescent probes and imaging devices function. This review summarizes how live cell fluorescence microscopy with common instruments can provide quantitative insight into the cellular and molecular functions of hosts and pathogens.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72689/1/j.1462-5822.2009.01283.x.pd

Distinct surveillance pathway for immunopathology during acute infection via autophagy and SR-BI

The mechanisms protecting from immunopathology during acute bacterial infections are incompletely known. We found that in response to apoptotic immune cells and live or dead Listeria monocytogenes scavenger receptor BI (SR-BI), an anti-atherogenic lipid exchange mediator, activated internalization mechanisms with characteristics of macropinocytosis and, assisted by Golgi fragmentation, initiated autophagic responses. This was supported by scavenger receptor-induced local increases in membrane cholesterol concentrations which generated lipid domains particularly in cell extensions and the Golgi. SR-BI was a key driver of beclin-1-dependent autophagy during acute bacterial infection of the liver and spleen. Autophagy regulated tissue infiltration of neutrophils, suppressed accumulation of Ly6C(+) (inflammatory) macrophages, and prevented hepatocyte necrosis in the core of infectious foci. Perifocal levels of Ly6C(+) macrophages and Ly6C(-) macrophages were unaffected, indicating predominant regulation of the focus core. SR-BI-triggered autophagy promoted co-elimination of apoptotic immune cells and dead bacteria but barely influenced bacterial sequestration and survival or inflammasome activation, thus exclusively counteracting damage inflicted by immune responses. Hence, SR-BI-and autophagy promote a surveillance pathway that partially responds to products of antimicrobial defenses and selectively prevents immunity-induced damage during acute infection. Our findings suggest that control of infection-associated immunopathology can be based on a unified defense operation

Flotillins Interact with PSGL-1 in Neutrophils and, upon Stimulation, Rapidly Organize into Membrane Domains Subsequently Accumulating in the Uropod

BACKGROUND: Neutrophils polarize and migrate in response to chemokines. Different types of membrane microdomains (rafts) have been postulated to be present in rear and front of polarized leukocytes and disruption of rafts by cholesterol sequestration prevents leukocyte polarization. Reggie/flotillin-1 and -2 are two highly homologous proteins that are ubiquitously enriched in detergent resistant membranes and are thought to shape membrane microdomains by forming homo- and hetero-oligomers. It was the goal of this study to investigate dynamic membrane microdomain reorganization during neutrophil activation. METHODOLOGY/PRINCIPAL FINDINGS: We show now, using immunofluorescence staining and co-immunoprecipitation, that endogenous flotillin-1 and -2 colocalize and associate in resting spherical and polarized primary neutrophils. Flotillins redistribute very early after chemoattractant stimulation, and form distinct caps in more than 90% of the neutrophils. At later time points flotillins accumulate in the uropod of polarized cells. Chemotactic peptide-induced redistribution and capping of flotillins requires integrity and dynamics of the actin cytoskeleton, but does not involve Rho-kinase dependent signaling related to formation of the uropod. Both flotillin isoforms are involved in the formation of this membrane domain, as uropod location of exogenously expressed flotillins is dramatically enhanced by co-overexpression of tagged flotillin-1 and -2 in differentiated HL-60 cells as compared to cells expressing only one tagged isoform. Flotillin-1 and -2 associate with P-selectin glycoprotein ligand 1 (PSGL-1) in resting and in stimulated neutrophils as shown by colocalization and co-immunoprecipitation. Neutrophils isolated from PSGL-1-deficient mice exhibit flotillin caps to the same extent as cells isolated from wild type animals, implying that PSGL-1 is not required for the formation of the flotillin caps. Finally we show that stimulus-dependent redistribution of other uropod-located proteins, CD43 and ezrin/radixin/moesin, occurs much slower than that of flotillins and PSGL-1. CONCLUSIONS/SIGNIFICANCE: These results suggest that flotillin-rich actin-dependent membrane microdomains are importantly involved in neutrophil uropod formation and/or stabilization and organize uropod localization of PSGL-1