SDF-1 and PDGF enhance [alpha]v[beta]5-mediated ERK activation and adhesion-independent growth of human pre-B cell lines

CD23 acts through the [alpha]v[beta]5 integrin to promote growth of human pre-B cell lines in an adhesion-independent manner. [alpha]v[beta]5 is expressed on normal B-cell precursors in the bone marrow. Soluble CD23 (sCD23), short CD23-derived peptides containing the arg-lys-cys (RKC) motif recognized by [alpha]v[beta]5 and anti-[alpha]v[beta]5 monoclonal antibodies (MAbs) all sustain growth of pre-B cell lines. The chemokine stromal cell-derived factor-1 (SDF-1) regulates key processes during B-cell development. SDF-1 enhanced the growth-sustaining effect driven by ligation of [alpha]v[beta]5 with anti-[alpha]v[beta]5 MAb 15F-11, sCD23 or CD23-derived RKC-containing peptides. This effect was restricted to B-cell precursors and was specific to SDF-1. The enhancement in growth was associated with the activation of extracellular signal-regulated kinase (ERK) and both these responses were attenuated by the MEK inhibitor U0126. Finally, platelet-derived growth factor also enhanced both [alpha]v[beta]5-mediated cell growth and ERK activation. The data suggest that adhesion-independent growth-promoting signals delivered to B-cell precursors through the [alpha]v[beta]5 integrin can be modulated by cross-talk with receptors linked to both G-protein and tyrosine kinase-coupled signalling pathways

Hsp90 and associated co-chaperones of the Malaria parasite

Heat shock protein 90 (Hsp90) is one of the major guardians of cellular protein homeostasis, through its specialized molecular chaperone properties. While Hsp90 has been extensively studied in many prokaryotic and higher eukaryotic model organisms, its structural, functional, and biological properties in parasitic protozoans are less well defined. Hsp90 collaborates with a wide range of co-chaperones that fine-tune its protein folding pathway. Co-chaperones play many roles in the regulation of Hsp90, including selective targeting of client proteins, and the modulation of its ATPase activity, conformational changes, and post-translational modifications. Plasmodium falciparum is responsible for the most lethal form of human malaria. The survival of the malaria parasite inside the host and the vector depends on the action of molecular chaperones. The major cytosolic P. falciparum Hsp90 (PfHsp90) is known to play an essential role in the development of the parasite, particularly during the intra-erythrocytic stage in the human host. Although PfHsp90 shares significant sequence and structural similarity with human Hsp90, it has several major structural and functional differences. Furthermore, its co-chaperone network appears to be substantially different to that of the human host, with the potential absence of a key homolog. Indeed, PfHsp90 and its interface with co-chaperones represent potential drug targets for antimalarial drug discovery. In this review, we critically summarize the current understanding of the properties of Hsp90, and the associated co-chaperones of the malaria parasite

The Electronics and Data Acquisition System of the DarkSide Dark Matter Search

It is generally inferred from astronomical measurements that Dark Matter (DM) comprises approximately 27\% of the energy-density of the universe. If DM is a subatomic particle, a possible candidate is a Weakly Interacting Massive Particle (WIMP), and the DarkSide-50 (DS) experiment is a direct search for evidence of WIMP-nuclear collisions. DS is located underground at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy, and consists of three active, embedded components; an outer water veto (CTF), a liquid scintillator veto (LSV), and a liquid argon (LAr) time projection chamber (TPC). This paper describes the data acquisition and electronic systems of the DS detectors, designed to detect the residual ionization from such collisions

Differential regulation of monocyte cytokine release by αv and β2 integrins that bind CD23

<p>The human soluble CD23 (sCD23) protein displays highly pleiotropic cytokine-like activity. Monocytic cells express the sCD23-binding integrins αvβ3, αvβ5, αMβ2 and αXβ2, but it is unclear which of these four integrins most acutely regulates sCD23-driven cytokine release.</p> <p>The hypothesis that ligation of different sCD23-binding integrins promoted release of distinct subsets of cytokines was tested. Lipopolysaccharide (LPS) and sCD23 promoted release of distinct groups of cytokines from the THP-1 model cell line. The sCD23-driven cytokine release signature was characterised by elevated amounts of RANTES (CCL5) and a striking increase in IL-8 (CXCL8) secretion, but little release of MIP-1β (CCL4.) Antibodies to αvβ3 or αXβ2 both promoted IL-8 release, consistent with the sCD23-driven pattern, but both also evoked strong MIP-1β secretion; simultaneous ligation of these two integrins further increased cytokine secretion but did not alter the pattern of cytokine output. In both model cell lines and primary tissue, integrin-mediated cytokine release was more pronounced in immature monocyte cells than in mature cells.</p> <p>The capacity of anti-integrin MAbs to elicit a cytokine release response is epitope-dependent and also reflects the differentiation state of the cell. Although a pattern of cytokine release identical to that provoked by sCD23 could not be elicited with any individual anti-integrin MAb, αXβ2 and αvβ3 appear to regulate IL-8 release, a hallmark feature of sCD23-driven cytokine secretion, more acutely than αMβ2 or αvβ5.</p&gt

Analysis of the CD23-αv integrin interaction: a study with model peptides

The human CD23 protein binds to αvβ3 and αvβ5 integrins. The integrins recognize a short tripeptide motif of arg-lys-cys (RKC) in CD23, and peptides containing this motif inhibit the binding of CD23 to B cells and monocytes; neither fibronectin, nor vitronectin, which contain arg-gly-asp motifs, inhibit binding of RKC-containing peptides to cells. RKC-containing peptides derived from CD23 show dose-dependent, biphasic binding profiles to both αvβ3 and αvβ5 that are cation-independent but sensitive to high chloride ion concentrations. Substitution of one basic residue in the RKC motif with alanine reduces but does not abolish integrin binding or the ability of peptides to stimulate pre-B cell growth or cytokine release by monocytes. Substitution of both basic residues abolishes both integrin binding and biological activity of CD23-derived peptides. These features indicate that binding of RKC-containing peptides to αv integrins has clearly distinct characteristics to those for binding of RGD-containing ligands

The DarkSide program at LNGS

(The DarkSide Collaboration) The DarkSide program at Laboratori Nazionali del Gran Sasso aims to perform background-free WIMP searches using double phase liquid argon time projection chambers, with the ultimate goal of covering all parameters down to the so-called neutrino floor. One of the distinct features of the program is the use of underground argon with has a reduced content of the $radioactive^{39}$ Ar compared to atmospheric argon. The DarkSide Collaboration is currently operating the DarkSide-50 experiment, the first such WIMP detector using underground argon, resulting in the best WIMP limits obtained with argon. The results obtained with DarkSide-50 and the plans for the next steps of the DarkSide program, the 20 t fiducial mass DarkSide-20k detector and the 200 t fiducial Argo, are reviewed in this proceedings