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Examines the role of differentiated megakaryocytes in blood platelets assembly at the ends of proplatelet processes. Features of culture-derived blood platelets; Changes in the microtubule cytoskeleton during proplatelet morphogenesis; Dynamic behavior of proplatelet morphogenesis; Proplatelet model of thrombopoiesis.

Cell-to-cell contact between peripheral blood lymphocytes and transfected human colonic carcinoma cell line HT29 activates transcription of the long terminal repeats (LTR) of human immunodeficiency virus. HIV-1 LTR transcription is controlled by a complex array of virus-encoded and cellular proteins. Using various constructs expressing a lacZ reporter gene under the control of the intact or three deleted forms of HIV-1 LTR, we obtained evidence that the κB regulatory elements located in the U3 region are involved in cell-to-cell activation of HIV-1 LTR. Cell-to-cell contact activates in vitro binding of the nuclear factor κB (NF-κB) p50/p65 heterodimer to an HIV-1 κB oligonucleotide. Cell-to-cell conflict activation of NF-κB was only partially inhibited by 100 μM pyrrolidine dithiocarbamate and was not correlated with a significant decrease of cellular inhibitor κBa. NF-κB nuclear activation was not detectable before 1 h after cell contact and was dependent on protein synthesis. [ABSTRACT FROM AUTHOR]

NOD2 contributes to the innate immune response and to the homeostasis of the intestinal mucosa. In response to its bacterial ligand, NOD2 interacts with RICK and activates the NF-κB and MAPK pathways, inducing gene transcription and synthesis of proteins required to initiate a balanced immune response. Mutations in NOD2 have been associated with an increased risk of Crohn’s Disease (CD), a disabling inflammatory bowel disease (IBD). Because NOD2 signaling plays a key role in CD, it is important to further characterize the network of protein interacting with NOD2. Using yeast two hybrid (Y2H) screens, we identified new NOD2 interacting proteins (NIP). The primary interaction was confirmed by coimmunoprecipitation and/or bioluminescence resonance energy transfer (BRET) experiments for 11 of these proteins (ANKHD1, CHMP5, SDCCAG3, TRIM41, LDOC1, PPP1R12C, DOCK7, VIM, KRT15, PPP2R3B, and C10Orf67). These proteins are involved in diverse functions, including endosomal sorting complexes required for transport (ESCRT), cytoskeletal architecture and signaling regulation. Additionally, we show that the interaction of 8 NIPs is compromised with the 3 main CD associated NOD2 mutants (R702W, G908R and 1007fs). Furthermore, to determine whether these NOD2 protein partners could be encoded by IBD susceptibility genes, a transmission disequilibrium test (TDT) was performed on 101 single nucleotide polymorphisms (SNPs) and the main corresponding haplotypes in genes coding for 15 NIPs using a set of 343 IBD families with 556 patients. Overall this work did not increase the number of IBD susceptibility genes but extends the NOD2 protein interaction network and suggests that NOD2 interactome and signaling depend upon the NOD2 mutation profile in CD. [ABSTRACT FROM AUTHOR]

A key step of epithelial morphogenesis is the creation of the lumen. Luminogenesis by hollowing proceeds through the fusion of apical vesicles at cell--cell contacts. The small nascent lumens grow through extension, coalescence and enlargement, coordinated with cell division, to give rise to a single central lumen. Here, by using MDCK cells grown in 3D-culture, we show that EFA6A (also known as PSD) participates in luminogenesis. EFA6A recruits α-actinin 1 (ACTN1) through direct binding. In polarized cells, ACTN1 was found to be enriched at the tight junction where it acts as a primary effector of EFA6A for normal luminogenesis. Both proteins are essential for the lumen extension and enlargement, where they mediate their effect by regulating the cortical acto-myosin contractility. Finally, ACTN1 was also found to act as an effector for the isoform EFA6B (also known as PSD4) in the human mammary tumoral MCF7 cell line. EFA6B restored the glandular morphology of this tumoral cell line in an ACTN1-dependent manner. Thus, we identified new regulators of cyst luminogenesis essential for the proper maturation of a newlyformed lumen into a single central lumen. [ABSTRACT FROM AUTHOR]

A key step of epithelial morphogenesis is the creation of the lumen. Luminogenesis by hollowing proceeds through the fusion of apical vesicles at cell-cell contact. The small nascent lumens grow through extension, coalescence and enlargement coordinated with cell division to give rise to a single central lumen. Here, using MDCK cells grown in 3D-culture, we show that EFA6A participates in luminogenesis. EFA6A recruits α-actinin 1 (ACTN1) through direct binding. In polarized cells, ACTN1 was found to be enriched at the tight junction where it acts as a primary effector of EFA6A for normal luminogenesis. Both proteins are essential for the lumen extension and enlargement, where they mediate their effect by regulating the cortical acto-myosin contractility. Finally, ACTN1 was also found to act as an effector for the isoform EFA6B in the human mammary tumoral MCF7 cell line. EFA6B restored the glandular morphology of this tumoral cell line in an ACTN1-dependent manner. Thus, we identified new regulators of cyst luminogenesis essential for the proper maturation of a newly-formed lumen into a single central lumen. [ABSTRACT FROM AUTHOR]

Bacterial cyclic glucans are glucose polymers that concentrate within the periplasm of alpha-proteobacteria. These molecules are necessary to maintain the homeostasis of the cell envelope by contributing to the osmolarity of Gram negative bacteria. Here, we demonstrate that Brucella β 1,2 cyclic glucans are potent activators of human and mouse dendritic cells. Dendritic cells activation by Brucella β 1,2 cyclic glucans requires TLR4, MyD88 and TRIF, but not CD14. The Brucella cyclic glucans showed neither toxicity nor immunogenicity compared to LPS and triggered antigen-specific CD8+ T cell responses in vivo. These cyclic glucans also enhanced antigen-specific CD4+ and CD8+ T cell responses including cross-presentation by different human DC subsets. Brucella β 1,2 cyclic glucans increased the memory CD4+ T cell responses of blood mononuclear cells exposed to recombinant fusion proteins composed of anti-CD40 antibody and antigens from both hepatitis C virus and Mycobacterium tuberculosis. Thus cyclic glucans represent a new class of adjuvants, which might contribute to the development of effective antimicrobial therapies. [ABSTRACT FROM AUTHOR]

Abstract: The functions of Src family kinases are tightly regulated through Src homology (SH) domain-mediated protein–protein interactions. We previously reported the biophysical characteristics of the apoptosis-linked gene 2-interacting protein X (Alix) in complex with the haemopoietic cell kinase (Hck) SH3 domain. In the current study, we have combined ITC, NMR, SAXS and molecular modeling to determine a 3D model of the complex. We demonstrate that Hck SH3 recognizes an extended linear proline-rich region of Alix. This particular binding mode enables Hck SH3 to sense a specific non-canonical residue situated in the SH3 RT-loop of the kinase. The resulting model helps clarify the mechanistic insights of Alix–Hck interaction. Structured summary of protein interactions: Hck physically interacts with SAM68 by two hybrid ( View interaction ) FynR96I physically interacts with Alix by two hybrid ( View interaction ) Hck binds to Alix by pull down ( View interaction ) Fyn physically interacts with SAM68 by two hybrid ( View interaction ) Hck and Alix bind by nuclear magnetic resonance ( View interaction ) FynR96I and Alix bind by isothermal titration calorimetry (View Interaction: 1 , 2 ) FynR96I and Alix bind by nuclear magnetic resonance ( View interaction ) FynR96I binds to Alix by pull down ( View interaction ) Hck physically interacts with Alix by two hybrid ( View interaction ) FynR96I and Alix bind by x ray scattering ( View interaction ) Hck physically interacts with NEF by two hybrid ( View interaction ) FynR96I physically interacts with NEF by two hybrid ( View interaction ) [Copyright &y& Elsevier]

Understanding the mechanisms of Salmonella virulence is an important challenge. The capacity of this intracellular bacterial pathogen to cause diseases depends on the expression of virulence factors including the second type III secretion system (TTSS-2), which is used to translocate into the eukaryotic cytosol a set of effector proteins that divert the biology of the host cell and shape the bacterial replicative niche. Yet little is known about the eukaryotic functions affected by individual Salmonella effectors. Here we report that the TFSS-2 effector PipB2 interacts with the kinesin light chain, a subunit of the kinesin-1 motor complex that drives anterograde transport along microtubules. Translocation of PipB2 is both necessary and sufficient for the recruitment of kinesin-1 to the membrane of the Salmonella-containing vacuole. In vivo, PipB2 contributes to the attenuation of Salmonella mutant strains in mice. Taken together, our data indicate that the TrSS-2-mediated fine-tuning of kinesin-1 activity associated with the bacterial vacuole is crucial for the virulence of Salmonella. [ABSTRACT FROM AUTHOR]