SHP-1 Acts as a Key Regulator of Alloresponses by Modulating LFA-1-Mediated Adhesion in Primary Murine T Cells

Abstract

cThe clinical potential of transplantation is often reduced by T cell-mediated alloresponses that cause graft rejection or graft-versus-host disease. Integrin-mediated adhesion between alloreactive T cells and antigen-presenting cells is essential for allorejection. The identity of the signaling events needed for the activation of integrins such as LFA-1 is poorly understood. Here, we identified a novel role of the protein tyrosine phosphatase SHP-1 in the regulation of murine LFA-1-mediated adhesion in an allograft setting. Upon alloactivation, SHP-1 activity is reduced, resulting in an increase in LFA-1 adhesion compared to that for syngeneically activated T cells. The importance of these differential activation properties was further indicated by small interfering RNA ( R ecipient-derived antigen-presenting cells (APCs) are pivotal for the induction of alloresponses (1). In patients, alloresponses cause significant treatment-related morbidity and mortality, such as graft-versus-host disease (GVHD) or graft rejection. Alloreactive T cells are largely responsible for these detrimental effects (2). In this context, T cell function depends on integrinmediated adhesion and migration.The ␤2 integrins are preferentially expressed among the 12 integrins on lymphocytes. Of these, ␣L␤2 (leukocyte functionassociated antigen 1 [LFA-1], also termed CD11a [␣L chain of LFA-1]-CD18 [␤2 chain of LFA-1]) binds to the ligands ICAM-1, -2, and -3 (intracellular adhesion molecules 1, 2, and 3). The ligands ICAM-1 and -2 are expressed on endothelial cells that line blood vessels on the surface of APCs (3). Following the initial adhesive interaction between potentially alloreactive T cells and allogeneic APCs such as dendritic cells (DCs), LFA-1 facilitates the stable formation of the "immunological synapse," which enhances T cell activation and subsequent effector functions (4, 5). Hence, LFA-1 has emerged as an attractive therapeutic target for the treatment of various inflammatory diseases (6). Immunosuppressive effects induced by LFA-1 antagonists are of substantial interest, since ligation of a T cell receptor (TCR) generates intracellular signals leading to activation of LFA-1-mediated cell adhesion, a process termed "inside-out" signaling. So far, the molecular processes underlying the signaling events between TCR activation and LFA-1 clustering are not fully understood. Adaptor proteins such as ADAP have been identified as key molecules in the TCR "inside-out" pathway (7), and their potential influence in T cell alloreactivity has been discussed (8).Here, we identified the protein tyrosine phosphatase (PTP) SHP-1 as a key regulator of LFA-1-mediated adhesion in primary murine T cells, with particular involvement in alloactivation. We demonstrate for the first time in vitro and in vivo that SHP-1 activity is significantly reduced upon alloactivation, resulting in an increase in the allogeneic activation of T cells and their adhesion to major histocompatibility complex (MHC)-mismatched APCs. Furthermore, we found that SHP-1 ex...

A CD22–Shp1 phosphatase axis controls integrin β7 display and B cell function in mucosal immunity

“…Ptpn6 +/meV CD4 + T cells also localized poorly to PLNs ( Extended Data Fig. 7 ): this may reflect the role of Shp1 in modulating β 2 integrin activity in T cells 11 .…”

“…7). This may reflect the role of Shp1 in modulating β 2 integrin activity in T cells 11 . α 4 β 7 mediates activation-independent tethering and rolling on PP, as well as chemokine/integrin activation-dependent arrest in combination with lymphocyte function-associated antigen 1 (ref.…”

“…Shp1 can be targeted by its binding to phosphorylated immunoreceptor tyrosine-based inhibitory motif (ITIM) sequences in membrane receptors, often acting in conjunction with ITIM-bearing molecules to inhibit signaling pathways, including those involved in integrin activity. In T cells, for example, Shp1 controls deactivation of the lymphocyte function-associated antigen 1 integrin (α L β 2 ) to prevent aberrant adhesion of leukocytes to β 2 integrin ligands or T cell adhesion to antigen-presenting cells 11 . In B cells, upon antigen stimulation, the phosphorylated ITIM sequences of sialic acid-binding Ig-like lectin 2 (CD22; also known as Siglec-2) recruit Shp1 to inhibit downstream components of B cell antigen receptor-induced Ca 2+ signaling 12 .…”

Chimeric antigen receptor–induced BCL11B suppression propagates NK-like cell development

“…Western blotting. Cell lysates of transgene-positive sorted lymphoid progenitors or WT B6 thymocytes were prepared in RIPA buffer as described (46). Equal masses of protein lysates were separated by SDS-PAGE and transferred onto PVDF membranes (Amersham).…”

Runx proteins mediate protective immunity against Leishmania donovani infection by promoting CD40 expression on dendritic cells

“…In addition, we did not detect any significant change in both percentage of LD-infected DCs and intracellular parasite number following SAG treatment for 0.3 h or 1 h (S16 Fig) . The latter finding indicated that the inhibition of LD-induced SHP1 activation, which occurred as early as 0.3 h or 1 h after SAG treatment (Fig 8B ), was not an outcome of SAG-mediated clearance of intracellular LD parasites. Instead, SAG, being a potent inhibitor of SHP-1 [29][30][31][32][33][34][35][36], directly inhibited LD-induced SHP-1 activation at the above-mentioned time points. This conclusion is supported by a report [29] demonstrating that SAG forms stable complexes with SHP-1 and that SAG directly targets the catalytic domain of SHP-1 to inhibit its activity.…”