M & L Jaargang 2/2

RedactioneelPaul van den Bremt en Regi de Meirsman Een aanzet tot een beheersplan voor een gerangschikt landschap, het staatsbos Berlare-Broek. Luik II: het beheersplan. [Toward a management plan for a protected landscape, the state forest of Berlare-Broek. Part II: the management plan.]Anthony Femey en Edgard Goedleven Vijftig jaar beschermingen in Vlaanderen. [Fifty years of protecting monuments and landscapes in Flanders.]Marijke Hoflack en Herman Stynen (red) De stad: mogelijkheid en noodzaak van ingrijpen. Een gesprek met Geert Bekaert, Bob Cools, Jacques Monsaert en Marcel Smets over het stedelijk beleid in Antwerpen en Gent. [The City: possibilities and necessity of intervention. A conversation with Geert Bekaert, Bob Cools, Jacques Monsaert en Marcel Smets about urban policy in Antwerp and Ghent.]J. Apers Hendrik Beyaert (1823-1894) en het Concert Noble-gebouw. [Hendrik Beyaert (1823-1894) and the Concert Noble building in Brussels.]Groep Planning De hernieuwing van de Concert Noble te Brussel. [The renovation of the Concert Noble in Brussels.]Herman Van den Bossche De redding van de Antwerpse Zoobomen: een dure maar verantwoorde operatie. [Saving the trees of the Antwerp Zoo: an expensive albeit sensible operation.]Errata vorige nummersSummaryM&L Binnenkran

Septin6 and Septin7 GTP binding proteins regulate AP-3- and ESCRT-dependent multivesicular body biogenesis

Septins (SEPTs) form a family of GTP-binding proteins implicated in cytoskeleton and membrane organization, cell division and host/pathogen interactions. The precise function of many family members remains elusive. We show that SEPT6 and SEPT7 complexes bound to F-actin regulate protein sorting during multivesicular body (MVB) biogenesis. These complexes bind AP-3, an adapter complex sorting cargos destined to remain in outer membranes of maturing endosomes, modulate AP-3 membrane interactions and the motility of AP-3-positive endosomes. These SEPT-AP interactions also influence the membrane interaction of ESCRT (endosomal-sorting complex required for transport)-I, which selects ubiquitinated cargos for degradation inside MVBs. Whereas our findings demonstrate that SEPT6 and SEPT7 function in the spatial, temporal organization of AP-3- and ESCRT-coated membrane domains, they uncover an unsuspected coordination of these sorting machineries during MVB biogenesis. This requires the E3 ubiquitin ligase LRSAM1, an AP-3 interactor regulating ESCRT-I sorting activity and whose mutations are linked with Charcot-Marie-Tooth neuropathies

The Bifidobacterium dentium Bd1 Genome Sequence Reflects Its Genetic Adaptation to the Human Oral Cavity

Bifidobacteria, one of the relatively dominant components of the human intestinal microbiota, are considered one of the key groups of beneficial intestinal bacteria (probiotic bacteria). However, in addition to health-promoting taxa, the genus Bifidobacterium also includes Bifidobacterium dentium, an opportunistic cariogenic pathogen. The genetic basis for the ability of B. dentium to survive in the oral cavity and contribute to caries development is not understood. The genome of B. dentium Bd1, a strain isolated from dental caries, was sequenced to completion to uncover a single circular 2,636,368 base pair chromosome with 2,143 predicted open reading frames. Annotation of the genome sequence revealed multiple ways in which B. dentium has adapted to the oral environment through specialized nutrient acquisition, defences against antimicrobials, and gene products that increase fitness and competitiveness within the oral niche. B. dentium Bd1 was shown to metabolize a wide variety of carbohydrates, consistent with genome-based predictions, while colonization and persistence factors implicated in tissue adhesion, acid tolerance, and the metabolism of human saliva-derived compounds were also identified. Global transcriptome analysis demonstrated that many of the genes encoding these predicted traits are highly expressed under relevant physiological conditions. This is the first report to identify, through various genomic approaches, specific genetic adaptations of a Bifidobacterium taxon, Bifidobacterium dentium Bd1, to a lifestyle as a cariogenic microorganism in the oral cavity. In silico analysis and comparative genomic hybridization experiments clearly reveal a high level of genome conservation among various B. dentium strains. The data indicate that the genome of this opportunistic cariogen has evolved through a very limited number of horizontal gene acquisition events, highlighting the narrow boundaries that separate commensals from opportunistic pathogens

Les pressions anthropiques et leurs impacts sur les situations qualitatives et quantitatives de l'eau dans le Bassin versant de la Seine

National audienc

Réflexion prospective régionale: Pays de Loire : esquisse régionale

National audienc

Réflexion prospective régionale: Pays de Loire : esquisse régionale

National audienc

Prospective : l'eau et les milieux aquatiques: Enjeux de sociétés et défis pour la recherche

National audienc

Depletion of SEPT6, SEPT7 affects the dynamic association of ESCRT sub-complexes.

<p>(<b>A</b>) Cell surface receptor-bound Alexa-EGF was endocytosed for the indicated periods of time in HeLa cells treated with the indicated siRNAs. Cells were then stained with anti Hrs antibodies. Extent of colocalization between Alexa-EGF and Hrs was quantified. (<b>B</b>) Similarly treated cells were stained with anti CHMP2B (Vps 2), an ESCRT-III subunit. Extent of colocalization between Alexa-EGF and ESCRTIII was determined. (<b>C</b>) Control and siRNA treated HeLa cells were stained with antibodies against Hrs and Tsg101. (<b>D</b>) The extent of colocalization between Hrs and Tsg101 was quantified. (<b>E</b>) Co-localization of LRSAM1 with Tsg101 and AP-3 and quantification (<b>G</b>). (<b>F</b>) AP-3 was immunuprecipitated from HeLa cell extracts with anti AP-3δ antibodies. The immunoprecipitates were probed by western blotting using antibodies against AP-3d and LRSAM1. The values are means ± SD of at least 3 independent experiments.</p

Depletion of SEPT6, SEPT7 affects the motility of endosomes and the dynamic association of AP-3.

<p>(<b>A</b>) Time-lapse video microscopy of HeLa cells stably expressing GFP-AP-3d and transiently expressing Cherry-SEPT6, Cherry-SEPT7 or mRFP-Lifeact (acquisition: 200 ms/frame, intervals between frames: 475 ms) (Bar 5 µm). (<b>B</b>) HeLa cells stably expressing GFP-AP-3δ were depleted or not from SEPT6 or SEPT7 and observed by video-microscopy. The upper panels shows examples of trajectories of GFP-AP-3δ-positive objects (300 objects per condition). Cell surface receptor-bound Alexa-EGF was endocytosed for 5 min. in control and SEPT6- or SEPT7-depleted Hela cells and Alexa-EGF-positive objects were observed by video-microscopy. The lower panels show examples of trajectories (300 objects per condition). (<b>C</b>) Cell surface bound Alexa-EGF was internalized in GFP-AP-3δ expressing HeLa cells depleted or not from SEPT6 or SEPT7 and followed by videomicrosopy. The extend of colocalization between GFP-AP-3 and Alexa-EGF was estimated. (<b>D</b>) The interaction of GFP-AP-3 with individual Alexa-EGF-positive structures was recorded and quantified (25 structures per condition) (<b>E</b>). The values are means ± SD of 3 independent experiments.</p

Depletion of SEPT6, SEPT7, BORG4, AP-3μ and Rab7 affect transport from early to late endosomes.

<p>(<b>A</b>) Hela expressing Gag-GFP cells were transfected with indicated siRNAs. Culture supernatants (VLP) and cell lysates prepared as described in Materials and Methods were probed by western blotting with anti GFP and anti LAMP1 antibodies and then quantified (<b>B</b>). Values were normalized to tubulin. The secreted GAP-GFP represented 59±4, 46±1, 14±7, 5.7±3, 9.8±4.5, 8.2±5, 11±5.8, 21.8±7, 10.8±7.6, 15±8.9, 14±6.5% of the total GAG-GFP. (<b>C</b>) Cell surface receptor bound Alexa 564-transferrin was endocytosed for the indicated period of time in HeLa cells treated with the indicated siRNAs. Fluorescence intensities were then quantified. (<b>D</b>) Anti GFP antibodies pre-bound to the cell surface GFP-MPR of GFP-MPR expressing cells treated with the indicated siRNAs were endocytosed for indicated periods of time as indicated in Materials and Methods. Co-localization between the endocytosed anti GFP antibody and GFP-MPR was quantified. (<b>E</b>) Cell surface receptor bound Alexa-EGF (green) was endocytosed for the indicated periods of time in HeLa cells treated with the indicated siRNAs as indicated in Materials and Methods. Fluorescence intensities were quantified. (<b>F</b>) Similarly treated cells were stained with antibodies against EEA1 and the extent of co-localization of Alexa-EGF with EEA1 was calculated. (<b>G</b>) Cell surface receptor bound EGF was endocytosed for the indicated periods of time in siRNA-treated HeLa cells. The cells were stained with antibodies against the activated EGF receptor phosphorylated on Tyr1068 (pEGFR) and EEA1. The fluorescence associated with the pEGFR was quantified. (<b>H</b>) Lysates from similarly treated cells were probed by western blotting using antibodies against the pEGFR or the total EGF receptor. The values are means ± SD of 3 independent experiments.</p