Faculty Opinions recommendation of Rapid and unidirectional perforin pore delivery at the cytotoxic immune synapse.

Our current quantitative knowledge of the kinetics of antibody-mediated immunity is partly based on idealized experiments throughout the last decades. However, new experimental techniques often render contradictory quantitative outcomes that shake previously uncontroversial assumptions. This has been the case in the field of T-cell receptors, where recent techniques for measuring the 2-dimensional rate constants of T-cell receptor–ligand interactions exposed results contradictory to those obtained with techniques measuring 3-dimensional interactions. Recently, we have developed a mathematical framework to rationalize those discrepancies, focusing on the proper fine-grained description of the underlying kinetic steps involved in the immune synapse. In this perspective article, we apply this approach to unveil potential blind spots in the case of B-cell receptors (BCR) and to rethink the interactions between B cells and follicular dendritic cells (FDC) during the germinal center (GC) reaction. Also, we elaborate on the concept of “catch bonds” and on the recent observations that B-cell synapses retract and pull antigen generating a “retracting force”, and propose some testable predictions that can lead to future research.

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Ca2+/Calmodulin-Dependent Protein Kinase II Is a Modulator of CARMA1-Mediated NF-κB Activation

Molecular and Cellular Biology ◽

10.1128/mcb.02469-05 ◽

2006 ◽

Vol 26 (14) ◽

pp. 5497-5508 ◽

Cited By ~ 72

Author(s):

Kazuhiro Ishiguro ◽

Todd Green ◽

Joseph Rapley ◽

Heather Wachtel ◽

Cosmas Giallourakis ◽

...

Keyword(s):

T Cell ◽

Protein Kinase ◽

T Cell Activation ◽

Cell Activation ◽

Cell Receptor ◽

Tcr Signaling ◽

Dependent Protein Kinase ◽

Immune Synapse ◽

Protein Kinase Ii ◽

Dependent Protein

ABSTRACT CARMA1 is a central regulator of NF-κB activation in lymphocytes. CARMA1 and Bcl10 functionally interact and control NF-κB signaling downstream of the T-cell receptor (TCR). Computational analysis of expression neighborhoods of CARMA1-Bcl10MALT 1 for enrichment in kinases identified calmodulin-dependent protein kinase II (CaMKII) as an important component of this pathway. Here we report that Ca2+/CaMKII is redistributed to the immune synapse following T-cell activation and that CaMKII is critical for NF-κB activation induced by TCR stimulation. Furthermore, CaMKII enhances CARMA1-induced NF-κB activation. Moreover, we have shown that CaMKII phosphorylates CARMA1 on Ser109 and that the phosphorylation facilitates the interaction between CARMA1 and Bcl10. These results provide a novel function for CaMKII in TCR signaling and CARMA1-induced NF-κB activation.

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Synaptic Clusters of MHC Class II Molecules Induced on DCs by Adhesion Molecule–mediated Initial T-Cell Scanning

Molecular Biology of the Cell ◽

10.1091/mbc.e05-01-0005 ◽

2005 ◽

Vol 16 (7) ◽

pp. 3314-3322 ◽

Cited By ~ 54

Author(s):

Hortensia de la Fuente ◽

María Mittelbrunn ◽

Lorena Sánchez-Martín ◽

Miguel Vicente-Manzanares ◽

Amalia Lamana ◽

...

Keyword(s):

T Cells ◽

Mhc Class Ii ◽

Class Ii ◽

Regulatory Pathway ◽

Immune Synapse ◽

Mhc Ii ◽

Cytoskeleton Reorganization ◽

Adhesive Contacts ◽

Enhance Antigen Presentation ◽

Mhc Class Ii Molecules

Initial adhesive contacts between T lymphocytes and dendritic cells (DCs) facilitate recognition of peptide-MHC complexes by the TCR. In this report, we studied the dynamic behavior of adhesion and Ag receptors on DCs during initial contacts with T-cells. Adhesion molecules LFA-1- and ICAM-1,3-GFP as well as MHC class II-GFP molecules were very rapidly concentrated at the DC contact area. Binding of ICAM-3, and ICAM-1 to a lesser extent, to LFA-1 expressed by mature but not immature DC, induced MHC-II clustering into the immune synapse. Also, ICAM-3 binding to DC induced the activation of the Vav1-Rac1 axis, a regulatory pathway involved in actin cytoskeleton reorganization, which was essential for MHC-II clustering on DCs. Our results support a model in which ICAM-mediated MHC-II clustering on DC constitutes a priming mechanism to enhance antigen presentation to T-cells.

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Removal of C-Terminal Src Kinase from the Immune Synapse by a New Binding Protein

Molecular and Cellular Biology ◽

10.1128/mcb.25.6.2227-2241.2005 ◽

2005 ◽

Vol 25 (6) ◽

pp. 2227-2241 ◽

Cited By ~ 27

Author(s):

Souad Rahmouni ◽

Torkel Vang ◽

Andres Alonso ◽

Scott Williams ◽

Marianne van Stipdonk ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

T Cell Activation ◽

Interleukin 2 ◽

Antigen Receptor ◽

T Cell Antigen Receptor ◽

Intracellular Location ◽

Immune Synapse ◽

Cell Antigen Receptor ◽

Cell Antigen

ABSTRACT The Csk tyrosine kinase negatively regulates the Src family kinases Lck and Fyn in T cells. Engagement of the T-cell antigen receptor results in a removal of Csk from the lipid raft-associated transmembrane protein PAG/Cbp. Instead, Csk becomes associated with an ∼72-kDa tyrosine-phosphorylated protein, which we identify here as G3BP, a phosphoprotein reported to bind the SH3 domain of Ras GTPase-activating protein. G3BP reduced the ability of Csk to phosphorylate Lck at Y505 by decreasing the amount of Csk in lipid rafts. As a consequence, G3BP augmented T-cell activation as measured by interleukin-2 gene activation. Conversely, elimination of endogenous G3BP by RNA interference increased Lck Y505 phosphorylation and reduced TCR signaling. In antigen-specific T cells, endogenous G3BP moved into a intracellular location adjacent to the immune synapse, but deeper inside the cell, upon antigen recognition. Csk colocalization with G3BP occurred in this “parasynaptic” location. We conclude that G3BP is a new player in T-cell-antigen receptor signaling and acts to reduce the amount of Csk in the immune synapse.

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