SLP‐76 is recruited to CD22 and dephosphorylated by SHP‐1, thereby regulating B cell receptor‐induced c‐Jun N‐terminal kinase activation

Abstract

Despite the important role in the development and activation of T cells, NK cells, mast cells, and macrophages, the expression and function of SLP-76 in B cells have been largely unknown. Here we demonstrate that SLP-76 is expressed in all mouse B cell lines tested and in normal splenic B cells, and serves as an SHP-1 substrate. Dephosphorylation of SLP-76 by SHP-1 inhibits its association with Nck, down-regulating cJun N-terminal kinase (JNK) activation and exerting a positive effect on apoptosis. Knockdown of SLP-76 in WEHI-231 cells by small interfering RNA attenuated JNK activation, but showed little effects on extracellular signal-regulated kinase (ERK) or p38 activation. Although WEHI-231 does not express linker for activation of T cells (LAT), SLP-76 localizes in membrane fraction, which increases following B cell receptor (BCR) cross-linking. Further analyses revealed that SLP-76 complexed with Gads is associated with tyrosine-phosphorylated CD22 through the SH2 domains of SLP-76 and Gads. Given that SHP-1 binds to CD22 upon BCR ligation, our findings suggest that dephosphorylation of SLP-76 recruited to CD22 by SHP-1 inhibits BCR-induced JNK activation, dictating apoptosis.

Positive and Negative Regulation of High Affinity IgE Receptor Signaling by Src Homology Region 2 Domain-Containing Phosphatase 1

“…Secondly, Syk activity was comparable between WT-and me-BMMC. Direct dephosphorylation of SLP-76 (39,43) and LAT (44) by SHP-1 demonstrated in other cell types may support our conclusion. Fc RI-induced Lyn activation leads to tyrosine phosphorylation and activation of SHP-1, which results in the dephosphorylation and inactivation of SHP-1 itself (36).…”

“…The cells were washed twice with PBS-VE and lysed in TNE buffer (1% Nonidet P-40, 10 mM Tris-HCl (pH 7.5), 150 mM NaCl, 2 mM Na3VO4, and 2 mM EDTA). Subcelular fractionation to obtain cytoplasmic and membrane fractions was performed as described (39). The total cell lysates (TCL), cytoplasmic, or membrane fraction thus prepared were subjected to immunoprecipitation and Western blot analysis as described (37).…”

“…SPE-7-sensitized WT-BMMC were stimulated with 50 ng/ml DNP-HSA for 2 and 5 min. After solubilizing cells with hypotonic buffer, cytosolic, and membrane fractions were separated by ultracentrifugation as previously described (39). The samples thus obtained were subjected to immunoblots with anti-SHP-1 Ab (top) or anti-Lyn Ab (bottom).…”

Lack of the leukocyte-associated Ig-like receptor-1 expression in high-risk chronic lymphocytic leukaemia results in the absence of a negative signal regulating kinase activation and cell division

“…17,18 Leukocyte-associated Ig-like receptor-1 is expressed also on B lymphocytes where it downregulates B-cell receptor (BCR)-mediated calcium mobilization; 19 interestingly, recruitment of SHP-1 has been shown to regulate ERK, p38 MAPK and JNK activation in chicken and murine B-cell lines. [20][21][22][23] In turn, a link between p38 MAPK, JNK or ERK activation and NF-kB nuclear translocation has been described in a murine B lymphoma cell line. 24 In this paper, we show that: (i) LAIR-1 is mostly absent in highrisk (HR) CLL and differentially expressed in intermediate-risk (IR) and low-risk (LR) CLL and the intensity of expression relates to the stage of disease: (ii) constitutive and BCR-mediated activation of p38 and JNK is inhibited by LAIR-1 through an ITIM-dependent signal that is missing in HR CLL; (iii) when the molecule is expressed, engagement of LAIR-1 blocks Akt and NF-kB activation and prevents CLL division.…”

The Phosphatase Src Homology Region 2 Domain-Containing Phosphatase-1 Is an Intrinsic Central Regulator of Dendritic Cell Function

“…In addition, in lymphocytes, NK cells, and macrophages, SHP-1 can regulate pathways such as PI3K/AKT, JAK/STAT, chemokine receptor signaling, and NF-kB activation (7,14), all of which are functionally important in DCs. Furthermore, SHP-1 can modulate MAPK signaling, both positively and negatively, depending on the cell type (15)(16)(17). These observations have led us to hypothesize that SHP-1 may be a key DC-intrinsic regulator and thereby may control downstream T cell responses.…”