Adapter proteins SLP-76 and BLNK both are expressed by murine macrophages and are linked to signaling via Fcγ receptors I and II/III

168

227

The cytolytic activity of NK cells is tightly regulated by inhibitory receptors specific for MHC class I Ags. We have investigated the composition of signal transduction molecules in the supramolecular activation clusters in the MHC class I-regulated cytolytic and noncytolytic NK cell immune synapses. KIR2DL3-positive NK clones that are specifically inhibited in their cytotoxicity by HLA-Cw*0304 and polyclonal human NK cells were used for conjugate formation with target cells that are either protected or are susceptible to NK cell-mediated cytotoxicity. Polarization of talin, microtubule-organizing center, and lysosomes occurred only during cytolytic interactions. The NK immune synapses were analyzed by three-dimensional immunofluorescence microscopy, which showed two distinctly different synaptic organizations in NK cells during cytolytic and noncytolytic interactions. The center of a cytolytic synapse with MHC class I-deficient target is comprised of a complex of signaling molecules including Src homology (SH)2-containing protein tyrosine phosphatase-1 (SHP-1). Closely related molecules with overlapping functions, such as the Syk kinases, SYK, and ZAP-70, and adaptor molecules, SH2 domain-containing leukocyte protein of 76 kDa and B cell linker protein, are expressed in activated NK cells and are all recruited to the center of the cytolytic synapse. In contrast, the noncytolytic synapse contains SHP-1, but is lacking other components of the central supramolecular activation cluster. These findings indicate a functional role for SHP-1 in both the cytolytic and noncytolytic interactions. We also demonstrate, in three-cell conjugates, that a single NK cell forms a cytolytic synapse with a susceptible target cell in the presence of both susceptible and nonsusceptible target cells.

Section: Discussionsupporting

confidence: 63%

Spatial Organization of Signal Transduction Molecules in the NK Cell Immune Synapses During MHC Class I-Regulated Noncytolytic and Cytolytic Interactions

Vyas

Mehta

Morgan

et al. 2001

168

227

“…Intracellular signals generated upon cross-linking of Fc␥Rs, similar to those initiated by engagement of the Fc⑀R, involve activation of Src family and Syk family tyrosine kinases as well as adapter proteins LAT, Src homology 2 domain-containing leukocyte protein-76, and B cell linker protein, and lead to activation of the PLC␥ pathway (15,25,(73)(74)(75)(76). Among these signal transduction pathway components, Src family kinases, Syk kinase and the adapter protein LAT have all been shown to play critical roles in Fc␥R-regulated phagocytosis (75,(77)(78)(79).…”

Section: Discussionmentioning

confidence: 99%

“…The diacylglycerol activates protein kinase C (PKC), while IP 3 mediates the mobilization of Ca 2ϩ from internal stores, resulting in a transient intracellular Ca 2ϩ ([Ca 2ϩ ]i) flux (19). PLC␥ is activated by Fc⑀R in mast cells (20), by Fc␥RIIIA in NK cells (21)(22)(23), and by Fc␥RI or Fc␥RIIA in neutrophils (24) and monocytes (18,25). The PLC␥/Ca 2ϩ /PKC pathway has been shown to be involved in the activation of all types of mitogenactivated protein kinases (MAPK; ERKs, c-Jun N-terminal kinases (JNKs), and p38 MAPKs) (26 -30), although the PKC-independent Grb2/Sos/Raf1 pathway plays a primary role in the activation of MAPKs (27,(31)(32)(33)(34).…”

mentioning

confidence: 99%

Phospholipase Cγ2 Is Essential for Specific Functions of FcεR and FcγR

Wen

Jou

Chen

et al. 2002

Phospholipase Cγ2 (PLCγ2) plays a critical role in the functions of the B cell receptor in B cells and of the FcRγ chain-containing collagen receptor in platelets. Here we report that PLCγ2 is also expressed in mast cells and monocytes/macrophages and is activated by cross-linking of FcεR and FcγR. Although PLCγ2-deficient mice have normal development and numbers of mast cells and monocytes/macrophages, we demonstrate that PLCγ2 is essential for specific functions of FcεR and FcγR. While PLCγ2-deficient mast cells have normal mitogen-activated protein kinase activation and cytokine production at mRNA levels, the mutant cells have impaired FcεR-mediated Ca2+ flux and inositol 1,4,5-trisphosphate production, degranulation, and cytokine secretion. As a physiological consequence of the effect of PLCγ2 deficiency, the mutant mice are resistant to IgE-mediated cutaneous inflammatory skin reaction. Macrophages from PLCγ2-deficient mice have no detectable FcγR-mediated Ca2+ flux; however, the mutant cells have normal FcγR-mediated phagocytosis. Moreover, PLCγ2 plays a nonredundant role in FcγR-mediated inflammatory skin reaction.

“…Several proteins, including phospholipase Cg, PI3K, and SH2 domain containing leukocyte protein of 76 kDa can interact with Syk to initiate further downstream signaling leading to cytoskeletal changes, ROS, and cytokine production. SH2 domain containing leukocyte protein of 76 kDa is needed for FcgR-mediated ROS production in neutrophils (13), but not in macrophages (14,15), which may be because of differential FcgR expression. Linker for activation of T cells (LAT) and LAT2 can be phosphorylated by Syk and Src kinase Lyn (16,17) and have been shown to be critically involved in myeloid ITAM signaling (18)(19)(20).…”

Section: Fcgri Downstream Signalingmentioning

confidence: 99%

Functional Characteristics of the High Affinity IgG Receptor, FcγRI

Poel¹,

Spaapen

Winkel

et al. 2011

154

114

IgG FcRs are important mediators of immunity and play a key role during Ab-based immunotherapy. Within the leukocyte IgG receptor family, only FcγRI is capable of IgG binding with high affinity. FcγRI exists as a complex of a ligand binding α-chain and an FcR γ-chain. The receptors’ α-chain can, furthermore, elicit several functions independent of the ITAM-bearing FcR γ-chain. Functional implications of high-affinity IgG binding and mechanisms underlying FcR γ-chain–independent signaling remain unclear to this day. In this paper, we provide an overview of past literature on FcγRI and address the implications of recently described interactions between cytosolic proteins and the FcγRI α-chain, as well as cytokine-enhanced FcγRI immune complex binding. Furthermore, an analysis of potential polymorphisms within the FCGR1A gene is provided.