Analysis of Familial Hemophagocytic Lymphohistiocytosis type 4 (FHL-4) mutant proteins reveals that S-acylation is required for the function of syntaxin 11 in natural killer cells

Natural killer (NK) cell secretory lysosome exocytosis and cytotoxicity are impaired in familial hemophagocytic lymphohistiocytosis type 4 (FHL-4), a disorder caused by mutations in the gene encoding the SNARE protein syntaxin 11. We show that syntaxin 11 binds to SNAP23 in NK cells and that this interaction is reduced by FHL-4 truncation and frameshift mutation proteins that delete all or part of the SNARE domain of syntaxin 11. In contrast the FHL-4 mutant proteins bound to the Sec-1/Munc18-like (SM) protein Munc18-2. We demonstrate that the C-terminal cysteine rich region of syntaxin 11, which is deleted in the FHL-4 mutants, is S-acylated. This posttranslational modification is required for the membrane association of syntaxin 11 and for its polarization to the immunological synapse in NK cells conjugated to target cells. Moreover, we show that Munc18-2 is recruited by syntaxin 11 to intracellular membranes in resting NK cells and to the immunological synapse in activated NK cells. This recruitment of Munc18-2 is abolished by deletion of the C-terminal cysteine rich region of syntaxin 11. These results suggest a pivotal role for S-acylation in the function of syntaxin 11 in NK cells

Modified Particle Repositioning Procedure

Objectives: To evaluate the efficacy of modifications to traditional particle repositioning maneuvers in the treatment of benign paroxysmal positional vertigo. Study Design: Prospective trial of 118 patients with cupolocanalithiasis of the posterior canal treated with three different canal-repositioning techniques. Methods: Results were compared with the maneuvers employed and the statistical importance of rotating patients by 360\ub0 along their longitudinal axis and head shaking on reaching each single position were evaluated. Results: Treatment of patients with our maneuver, which, in comparison with traditional repositioning maneuvers, was modified by breaking the procedure up into seven positions and rotating patients by 360\ub0 along their longitudinal axis, gives a higher, but not statistically significant, number of treatment successes (84.5%) than the traditional Parnes maneuver (60%) (P 5 .154); treatment of a third group of patients with our modified particle repositioning maneuver with the addition of head-shaking on reaching each single position gives a higher (95.6%), statistically significant number of treatment successes than traditional Parnes maneuver (P 5 .00011). Conclusions: The success rates achieved from modified particle repositioning maneuvers are statistically significant. Onset or persistence of dizziness, which patients frequently complain of after liberatory maneuvers, affects only 5.6% of the patients treated. This low incidence is statistically correlated to head-shaking

TRAF2 and p38 are involved in B cells CD40-mediated APE/Ref-1 nuclear translocation: a novel pathway in B cell activation

The interaction between CD40 and its ligand CD40L plays a key role in the regulation of B cell proliferation, activation, isotype switching and the humoral memory response. APE/Ref-1 plays a key role in transcriptional responses during CD40-mediated B cell activation. It is demonstrated that CD40 signaling is mediated principally through TRAF adapter proteins. Different TRAFs exhibit specific biological functions and the role of individual TRAFs in the activation of different CD40-dependent signaling pathways has not yet been defined. To better understand the role of these factors in CD40-mediated B cell activation and how they contribute to APE/Ref-1 activity, we investigated the TRAF molecules and the downstream protein kinases directly activated in the pathways triggered by CD40. Here we show that TRAF2 is involved in CD40-mediated induction of APE/Ref-1 nuclear translocation and that the two proteins physically interact in vitro and in vivo. Moreover, treatment with the p38 inhibitor, SB203580 or site directed mutagenesis of the serine 54 (Ser(54)) in the MAP kinase consensus site present in APE/Ref-1 blocks its nuclear translocation caused by CD40-mediated B cell activation and reveals a potential role of p38 in this pathway. These data together uncovers a new signaling pathway regulating APE/Ref-1 nuclear translocation involving CD40-crosslinking, TRAF2 and p38

Outside inside signalling in CD40-mediated B cell activation

CD40 is a member of the growing tumor necrosis factor receptor (TNF-R) family of molecules, and has been shown to play important roles in T cell-mediated B lymphocyte activation. Ligation of B cell CD40 by CD154 expressed on activated T cells stimulates B cell proliferation, differentiation, isotype switching, upregulation of surface molecules contributing to antigen presentation, development of the germinal center, and the humoral memory response. The present review will summarize recent literature data on the various CD40 signalling pathways, which involve both the TNF-R associated factors (TRAFs) and additional signalling proteins, and lead to activation of kinases and transcription factors. Copyright \ua9 by BIOLIFE, s.a.s