The B-cell surface molecule CD22, when cross-linked, modulates signaling through the IgM (sIgM)-B-cell receptor (BCR) complex. Here we analyzed basis of this interaction between CD22 and human sIgM After lysis B cells or lines in digitonin, coimmunoprecipitated a kinase activity that vitro-phosphorylated two polypeptides 150 130 kDa on tyrosine residues. By immunoblot analysis with rabbit anti-serum specific for synthetic peptide found these proteins to be itself. Furthermore, phosphorylated...

ABSTRACT RLIP76 is a modular protein that was identified as putative effector of Ral, GTPase activated during Ras signaling. To explore further the contribution Ral- pathway to signaling, we have looked for partners RLIP76. μ2, medium chain AP2 complex shown interact with We show also in vivo endogenous and form this interaction independent cells being stimulated by growth factor. Furthermore, differentiates from AP1 μ2 μ1 vitro two hybrid assays. Ral interferes both tranferrin receptor...

Engagement of the B cell Ag receptor can induce a suicide pathway in various types. Earlier studies showed that anti-IgM mAb treatment triggers apoptotic death Burkitt lymphoma-derived line, Ramos. We show two surface molecules, CD19 and CD22, which have been reported to interact either functionally or structurally with receptor, also stimulate when sufficiently aggregated, both Ramos EBV-infected AW lines. In conditions lower cross-linking, molecules enhance response induced by suboptimal...

Thymic cell populations from 12 patients displaying myasthenia gravis were submitted to a phenotypic and functional study. Immunofluorescence analysis of thymic sections revealed the presence in germinal centers B lymphocytes expressing markers--CD19, CD21, IgD, or IgM. After T macrophage depletion single suspensions, cell-enriched isolated. Enriched cells expressed at variable levels activation markers such as CD71, 4F2, CD23, B8.7, indicating that marked proportion them are activated....

With the aim of interrupting growth factor-stimulated Ras signaling pathway at level Grb2–Sos interaction, a peptidimer, made two identical proline-rich sequences from Sos linked by lysine spacer, was designed using structural data Grb2 and peptide complexed with its SH3 domains. The peptidimer affinity for is 40 nM whereas that monomer 16 μM, supporting dual recognition both domains dimer. At 50 nM, blocks selectively complexation in ER 22 (CCL 39 fibroblasts overexpressing epidermal factor...

Src homology 3 (SH3) domains are conserved modules which participate in protein interaction by recognizing proline-rich motifs on target molecules. To identify new SH3-containing proteins, we performed a two-hybrid screen with region of human SOS-1. One the specific SOS-1 interacting clones that were isolated from mouse brain cDNA library defines was named amphiphysin 2 because its to previously reported amphiphysin. Amphiphysin is expressed number tissues through multiple RNA transcripts....

Endocytosis is a regulated physiological process by which membrane receptors and their extracellular ligands are internalized. After internalization, they enter the endosomal trafficking pathway for sorting processing. Amphiphysins consist of family proteins conserved throughout evolution that crucial elements endocytosis machinery in mammalian cells. They act as adaptors series important endocytic process, such dynamin. In order to improve our knowledge amphiphysin function, we performed...

To characterize the signal transduction through antigen receptor (AgR) on human B lymphocytes, we analyzed its association with other molecular components. The surface IgM (sIgM) complex isolated in digitonin contains two expressed polypeptides--the previously described Ig alpha and beta proteins--covalently linked to each a 48/39-kDa heterodimer. We show herein that sIgM from Burkitt's lymphoma cell line, Ramos, or dense tonsillar cells additional molecules--160 kDa 75 size--and enzymatic...

Atopic dermatitis (AD), the most common inflammatory skin disorder, is a multifactorial disease characterized by genetic predisposition, epidermal barrier disruption, strong T helper (Th) type 2 immune reaction to environmental antigens and an altered cutaneous microbiome. Microbial dysbiosis prevalence of Staphylococcus aureus (S. aureus) has been shown exacerbate AD. In recent years, in vitro models AD have developed, but none them reproduce all pathophysiological features. To better mimic...

Abstract Studies in Bim-deficient mice have shown that the proapoptotic molecule Bim plays a key role control of B cell homeostasis and activation. However, human lymphocyte apoptosis is unknown. We show this study that, depending on degree cross-linking, receptors can mediate both Bim-dependent apparent Bim-independent apoptotic pathways. Cross-linked anti-μ Ab-mediated activation induces an original pathway governing expression various isoforms. This new involves following three sequential...

Within the Ras superfamily, Gem is a small GTP-binding protein that plays role in regulating Ca2+ channels and cytoskeletal remodeling interphase cells. Here, we report for first time spindle-associated required proper mitotic progression. Functionally, loss of leads to misaligned chromosomes prometaphase delay. On basis different experimental approaches, demonstrate by RNA interference induces spindle elongation, while its enforced expression results shortening. The length phenotype...

The role of paf-acether (paf), a phospholipid cytokine, in the modulation human B cell function was investigated. Paf, from 1 x 10(-5) M to 10(-6) M, decreased proliferation induced by both phorbol myristate acetate (PMA) and anti-IgM antibodies (anti-IgM Ab). By contrast, 10(-7) 10(-9) paf enhanced PMA triggered, but not triggered proliferation. modulated between 24 72 hr culture indicating that effect did merely reflect shift kinetics. Interestingly, also spontaneous Burkitt...

Gem is a small guanosine triphosphate (GTP)-binding protein within the Ras superfamily, involved in regulation of voltage-gated calcium channel activity and cytoskeleton reorganization. overexpression leads to stress fiber disruption, actin cell shape remodeling neurite elongation interphase cells. In this study, we show that plays crucial role cortical undergoes active during mitosis. Ectopic expression disruption spindle mispositioning metaphase. The positioning by involves its downstream...

This work was focused on the responsiveness of B cells from blood and tonsils to typical cell growth factors (BCGF) in absence anti-mu antibody. direct not observed with small dense either organ. Large tonsillar but large did respond directly a high m.w. BCGF (m.w. 50,000 BCGF), whereas both organs responded low 20,000 BCGF). The responsive express 4F2 marker thus belong population vivo-preactivated cells. Moreover, this is localized Leu-1+ Leu-1- subsets do differ their upon costimulation...

A novel monoclonal antibody (anti-B8.7) is reported which recognizes an epitope expressed either on in vitro activated B cells or a fraction of fresh large (putatively vivo preactivated). B8.7 antigen also present two out eight cell lines tested and characterized as membrane component displaying approximate molecular weight 55,000 to 60,000. By contrast, absent from resting cells, monocytes, T the non-B tested. After activation, appears later than transferrin receptor its expression...

Abstract Among human peripheral blood B cells we localized the precursors of two interleukin‐dependent cell activation processes: specific response to a particulate antigen, trinitrophenylated polyacrylamide beads (TNP‐PAA) and polyclonally induced pokeweed mitogen. In both cases belong OKB7 + , sIgD − mouse red subpopulation. However, they differ when density, reflecting stage reached by in blood, is considered. Only intermediate density respond TNP‐PAA, whereas optimal mitogen obtained...