260 research outputs found
RIP Links TLR4 to Akt and Is Essential for Cell Survival in Response to LPS Stimulation
Receptor-interacting protein (RIP) has been reported to associate with tumor necrosisâassociated factor (TRAF)2 and TRAF6. Since TRAF2 and TRAF6 play important roles in CD40 signaling and TRAF6 plays an important role in TLR4 signaling, we examined the role of RIP in signaling via CD40 and TLR4. Splenocytes from RIPâ/â mice proliferated and underwent isotype switching normally in response to anti-CD40âIL-4 but completely failed to do so in response to LPSâIL-4. However, they normally up-regulated TNF-α and IL-6 gene expression and CD54 and CD86 surface expression after LPS stimulation. RIPâ/â splenocytes exhibited increased apoptosis and impaired Akt phosphorylation after LPS stimulation. These results suggest that RIP is essential for cell survival after TLR4 signaling and links TLR4 to the phosphatidylinositol 3 kinaseâAkt pathway
Defective nuclear translocation of nuclear factor of activated T cells and extracellular signal-regulated kinase underlies deficient IL-2 gene expression in Wiskott-Aldrich syndrome
ProducciĂłn CientĂficaBackground: Proliferation and IL-2 production in response to
T-cell receptor ligation are impaired in patients with Wiskott-
Aldrich syndrome (WAS). The transcription factors nuclear
factor-kB (NF-kB), nuclear factor of activated T cells (NF-AT),
and activating protein-1 (AP-1) play a critical role in IL-2 gene
expression.
Objective: To investigate the mechanisms of impaired IL-2
production after T-cell receptor ligation in T cells deficient in
WAS protein (WASP).
Methods: T cells from WASP2/2 mice were stimulated with
anti-CD3 and anti-CD28. Nuclear NF-kB, NF-AT, and AP-1
DNA-binding activity was examined by electroshift mobility
assay. NF-ATp dephosphorylation and nuclear localization
were examined by Western blot and indirect immunofluorescence.
Phosphorylation of the mitogen-activated protein
kinases Erk and Jnk, and of their nuclear substrates Elk-1 and
c-Jun, was examined by Western blot. Expression of mRNA for
IL-2 and the NF-kBâdependent gene A20 and of the AP-1
components c-fos and c-Jun was examined by quantitative
RT-PCR.
Results: Nuclear translocation and activity of NF-kB were
normal in T cells from WASP2/2 mice. In contrast, NF-ATp
dephosphorylation and nuclear localization, nuclear AP-1
binding activity, and expression of c-fos, but not c-Jun, were all
impaired. Phosphorylation of Jnk, c-Jun, and Erk were normal.
However, nuclear translocation of phosphorylated
Erk and phosphorylation of its nuclear substrate Elk1,
which activates the c-fos promoter, were impaired.
Conclusion: These results suggest that WASP is essential for
NF-ATp activation, and for nuclear translocation of p-Erk,
Elk1 phosphorylation, and c-fos gene expression in T cells.
These defects underlie defective IL-2 expression and T-cell
proliferation in WAS
Characterization of antifungal C-type lectin receptor expression on murine epithelial and endothelial cells in mucosal tissues
Funding Information: We thank P. Asamaphan, A. Clark, and B. Kerscher for providing NIH overexpression cell lines, S. Yamasaki for the antiâMincle antibody, the staff of the University of Aberdeen animal facility for the care for our animals, and the Iain Fraser Cytometry Centre at the University of Aberdeen for their assistance. This work was supported by funding from the Wellcome Trust (102705, 217163), the Medical Research Council Centre for Medical Mycology, and the University of Exeter (MR/N006364/2).Peer reviewedPublisher PD
WIP and WASP play complementary roles in T cell homing and chemotaxis to SDF-1a
ProducciĂłn CientĂficaHoming of lymphocytes to tissues is a biologically important multistep process that involves selectindependent
rolling, integrin-dependent adhesion and chemokine-directed chemotaxis. The actin
cytoskeleton plays a central role in lymphocyte adhesion and motility. WiskottâAldrich syndrome
protein (WASP), the product of the gene mutated in WiskottâAldrich syndrome, and its partner,
the WiskottâAldrich syndrome protein-interacting protein (WIP), play important roles in actin
re-organization in T lymphocytes. We used mice with disruption of the WASP and WIP genes to
examine the role of WASP and WIP in T cell homing. T cell homing to spleen and lymph nodes in vivo
was deficient in WASP / and WIP / mice and severely impaired in WASP / WIP / double knockout
(DKO) mice. Deficiency of WASP, WIP or both did not interfere with selectin-dependent rolling or
integrin-dependent adhesion of T cells in vitro. Chemotaxis to stromal cell-derived factor-1a (SDF-1a)
in vitro was mildly reduced in T cells from WASP / mice. In contrast, it was significantly impaired in
T cells from WIP / mice and severely reduced in T cells from DKO mice. Cellular F-actin increase
following SDF-1a stimulation was normal in WASP / and WIP / T cells, but severely reduced in
T cells from DKO mice. Actin re-organization and polarization in response to SDF-1a was abnormal in
T cells from all knockout mice. Early biochemical events following SDF-1a stimulation that are
important for chemotaxis and that included phosphorylation of Lck, cofilin, PAK1 and extracellular
regulated kinase (Erk) and GTP loading of Rac-1 were examined in T cells from DKO mice and found to
be normal. These results suggest that WASP and WIP are not essential for T lymphocyte rolling and
adhesion, but play important and partially redundant roles in T cell chemotaxis in vitro and homing
in vivo and function downstream of small GTPases
Mechanism of recruitment of WASP to the immunological synapse and of its activation following TCR ligation
ProducciĂłn CientĂficaF-actin polymerization following engagement of the T cell receptor (TCR) is dependent on WASP and is critical for T cell activation. The link between TCR and WASP is not fully understood. In resting cells, WASP exists in a complex with WIP, which inhibits its activation by Cdc42. We show that the adaptor protein CrkL binds directly to WIP. Further, TCR ligation results in the formation of a ZAP-70-CrkL-WIP-WASP complex, which is recruited to lipid rafts and the immunological synapse. TCR engagement also causes PKCtheta-dependent phosphorylation of WIP, causing the disengagement of WASP from the WIP-WASP complex, thereby releasing it from WIP inhibition. These results suggest that the ZAP-70-CrkL-WIP pathway and PKCtheta link TCR to WASP activation
"Acute pseudo-pericardial tamponade": the compression of the thoracal inferior vena cava â a case report
We describe a case of 68-year-old woman which was admitted to our hospital for mitral valve replacement (MVR), in whom acute compresion of the vena cava inferior developed after repair of lacerated atrio-caval junction with hemostatic tissue sealant, biologic glue (BioGlue, Cryolife, ınc, Kennesaw, Ga). Removal of the BioGlue relieved the unexpected problem
Targeted Inactivation of the IL-4 Receptor α Chain I4R Motif Promotes Allergic Airway Inflammation
The insulin/interleukin-4 (IL-4) receptor (I4R) motif mediates the association of insulin receptor substrate (IRS)-2 with the interleukin-4 (IL-4)Rα chain and transduces mitogenic signals in response to IL-4. Its physiological functions were analyzed in mice with a germline point mutation that changed the motif's effector tyrosine residue into phenylalanine (Y500F). The Y500F mutation abrogated IRS-2 phosphorylation and impaired IL-4âinduced CD4+ T lymphocyte proliferation but left unperturbed Stat6 activation, up-regulation of IL-4-responsive gene products, and Th cell differentiation under Th2 polarizing conditions. However, in vivo the Y500F mutation was associated with increased allergen-induced IgE production, airway responsiveness, tissue eosinophilia, and mucus production. These results define an important role for the I4R motif in regulating allergic inflammation
WIP deficiency reveals a differential role for WIP and the actin cytoskeleton in T and B cell activation
ProducciĂłn CientĂficaWIP stabilizes actin filaments and is important for filopodium formation. To define the role of WIP in immunity, we generated WIP-deficient mice. WIP(minus sign/minus sign) mice have normal lymphocyte development, but their T cells fail to proliferate, secrete IL-2, increase their F-actin content, polarize and extend protrusions following T cell receptor ligation, and are deficient in conjugate formation with superantigen-presenting B cells and anti-CD3 bilayers. In contrast, WIP-deficient B lymphocytes have enhanced proliferation and CD69 expression following B cell receptor ligation and mount normal antibody responses to T-independent antigens. Both WIP-deficient T and B cells show a profound defect in their subcortical actin filament networks. These results suggest that WIP is important for immunologic synapse formation and T cell activation
- âŠ