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Cox Terhorst

Publications and source records attributed to Cox Terhorst.

36 records · Page 2Linked to original sources
PubMed2004

SAP increases FynT kinase activity and is required for phosphorylation of SLAM and Ly9.

The free Src homology 2 (SH2) domain protein SAP, encoded by the X-linked lymphoproliferative disease gene SH2D1A, controls signal transduction initiated by engagement of the SLAM-related receptors in T and NK cells. Here we demonstrate that SAP is required for phosphorylation of both SLAM and Ly9 in thymocytes and peripheral T cells. Furthermore, in vitro protein interaction studies and yeast two-hybrid analyses indicated that SAP binds directly to FynT and Lck. While SAP bound to both the SH3 domain and to the kinase domain of FynT, SAP bound solely to the kinase domain of Lck. The existence of a strong interaction between SAP and the SH3 domain of FynT prompted us to study the role of SAP in modulating the activity of FynT. In vitro addition of SAP to the autoinhibited form of FynT caused a large increase in FynT catalytic activity. By contrast, the SAP mutant R78E, which is unable to bind to the FynT SH3 domain, did not increase FynT activity and also displayed a reduced adaptor function upon transfection into T cells. Our results demonstrate that SAP is an adaptor that bridges SLAM and Ly9 with Src-like protein tyrosine kinases (PTKs), and has the ability to activate FynT.

Animals↗
PubMed2004

Expression of the SH2D1A gene is regulated by a combination of transcriptional and post-transcriptional mechanisms.

The SH2D1A gene, which is altered or deleted in patients with X-linked lymphoproliferative disease, encodes the small protein SAP (for SLAM-associated protein) that is expressed in T and NK cells. A 22-bp fragment in close proximity to an initiator-like site was defined as the basal promoter of mouse SH2D1A, and a highly homologous 33-bp segment was defined as the human basal promoter. When an Ets consensus site was mutated, no reporter activity was detectable. Gel mobility supershift assays revealed that the two transcription factors Ets-1 and Ets-2 bind to the human and mouse sequences. The involvement of Ets-1 and Ets-2 in expression of SH2D1A was functionally confirmed by overexpression studies of their dominant-negative forms. We also found that SH2D1A mRNA decays very rapidly in mouse T cells, and its 3' untranslated region (UTR) has RNA-destabilizing activity in transfection studies with reporter/3' UTR constructs. As judged by RNA-gel mobility shift assays, this rapid degradation of SH2D1A mRNA was due to a balance in binding of the factors AUF1 and HuR to its 3' UTR. Although the SH2D1A mRNA level decreased upon triggering of the T cell receptor (TCR), the RNA degradation rate itself was not altered by TCR engagement.

3' Untranslated Regions↗
PubMed2004

Induced reactivity of intestinal CD4(+) T cells with an epithelial cell lectin, galectin-4, contributes to exacerbation of intestinal inflammation.

Inflammatory bowel disease is an immune-mediated intestinal inflammatory condition that is associated with an increase in autoantibodies that bind to epithelial cells. However, it is unknown whether the epithelial cell-derived products that are recognized by such autoantibodies are involved in the pathogenic process. Through a combined antigen-screening approach utilizing humoral and cellular immune responses, we identify herein an epithelial lectin, galectin-4, that specifically stimulates IL-6 production by CD4(+) T cells. Interestingly, the reactivity of CD4(+) T cells to galectin-4 is precisely elicited under intestinal inflammatory conditions. The galectin-4-mediated production of IL-6 is MHC class II independent and induced by PKCtheta-associated pathway through the immunological synapse. The galectin-4-mediated stimulation of CD4(+) T cells is shown to exacerbate chronic colitis and delay the recovery from acute intestinal injury. These studies identify the presence of an immunogenic, endogenous lectin in the intestine and dissect the biological role of lectin/CD4(+) T cell interactions under inflammatory conditions.

Animals↗
PubMed2004

Colitis is associated with thymic destruction attenuating CD4+25+ regulatory T cells in the periphery.

BACKGROUND & AIMS: Syngeneic bone marrow transplantation into the adult tgepsilon26 mouse results in severe wasting disease and colitis. On transplantation, the rudimentary thymus of the adult tgepsilon26 mouse repopulates briefly but quickly regresses in temporal association with the onset of colitis. The aim of this study is to test the hypothesis that treatment of colitis restores thymic capability to generate regulatory T cells (CD4+25+ T(R) cells). METHODS: Colitis was induced by bone marrow transplantation into adult irradiated tgepsilon26 mice. Colitis was prevented by 3 distinct modalities. CD4+25+ T cells were collected from both the thymus and spleen and studied for regulatory function by an in vitro suppression assay. RESULTS: CD4+25+ T(R) cells do not develop efficiently in the thymus of bone marrow transplanted adult tgepsilon26 mice, which have a developmental arrest affecting thymic epithelium. By contrast, the thymic epithelium of neonatal tgepsilon26 mice supports development of T(R) cells. Consequently, colitis develops only in adult transplanted mice but not in the neonatally transplanted mice. Treatment of colitis prevents destruction of the thymus of adult transplanted tgepsilon26 mice and T(R) cells are produced. CONCLUSIONS: The negative impact of colitis on T(R) development in the thymus, which was confirmed in a second model of colitis, has profound implications for the pathogenesis and treatment of human inflammatory bowel disease.

Animals↗
PubMed2004

Blocking inducible co-stimulator in the absence of CD28 impairs Th1 and CD25+ regulatory T cells in murine colitis.

Several autoimmune disease models depend on an imbalance in the activation of aggressor T(h)1 and CD4(+)CD25(+) regulatory T (T(reg)) cells. Here we compare the requirement for signals through the co-stimulatory molecules CD28 and inducible co-stimulator (ICOS) in chronic murine colitis, a model for inflammatory bowel disease. We used a colitis model in which disease-causing CD45RB(hi) T cells alone or in combination with CD4(+)CD25(+) T cells from either CD28-deficient or wild-type donors were transferred into T cell-deficient animals, half of which were treated with ICOS-blocking reagents. Blocking ICOS on the surface of CD28-deficient T(h)1 cells abrogated development of colitis, whereas blocking CD28 or ICOS alone had little to no effect on disease induction. In contrast to T(h)1 cells, regulatory T cell functioning depended mostly on CD28 signaling with only a minor contribution for ICOS. We conclude that CD28 and ICOS collaborate to development of murine colitis by aggressor T(h)1 cells, and that CD28 is required for T(reg) cells, which should caution against the use of CD28-blocking reagents in inflammatory bowel disease.

Animals↗
PubMed2003

SAP couples Fyn to SLAM immune receptors.

SAP (SLAM-associated protein) is a small lymphocyte-specific signalling molecule that is defective or absent in patients with X-linked lymphoproliferative syndrome (XLP). Consistent with its single src homology 2 (SH2) domain architecture and unusually high affinity for SLAM (also called CD150), SAP has been suggested to function by blocking binding of SHP-2 or other SH2-containing signalling proteins to SLAM receptors. Additionally, SAP has recently been shown to be required for recruitment and activation of the Src-family kinase FynT after SLAM ligation. This signalling 'adaptor' function has been difficult to conceptualize, because unlike typical SH2-adaptor proteins, SAP contains only a single SH2 domain and lacks other recognized protein interaction domains or motifs. Here, we show that the SAP SH2 domain binds to the SH3 domain of FynT and directly couples FynT to SLAM. The crystal structure of a ternary SLAM-SAP-Fyn-SH3 complex reveals that SAP binds the FynT SH3 domain through a surface-surface interaction that does not involve canonical SH3 or SH2 binding interactions. The observed mode of binding to the Fyn-SH3 domain is expected to preclude the auto-inhibited conformation of Fyn, thereby promoting activation of the kinase after recruitment. These findings broaden our understanding of the functional repertoire of SH3 and SH2 domains.

Amino Acid Sequence↗
PubMed2003

The SAP and SLAM families in immune responses and X-linked lymphoproliferative disease.

SAP (signalling lymphocytic activation molecule (SLAM)-associated protein) is a T- and natural killer (NK)-cell-specific protein containing a single SH2 domain encoded by a gene that is defective or absent in patients with X-linked lymphoproliferative syndrome (XLP). The SH2 domain of SAP binds with high affinity to the cytoplasmic tail of the haematopoietic cell-surface glycoprotein SLAM and five related receptors. SAP regulates signal transduction of the SLAM-family receptors by recruiting SRC kinases. Similarly, the SAP-related proteins EAT2A and EAT2B are thought to control signal transduction that is initiated by SLAM-related receptors in professional antigen-presenting cells. In this review, we discuss recent findings on the structure and function of proteins of the SAP and SLAM families.

Animals↗
PubMed2003

Role of the CD5 molecule on TCR gammadelta T cell-mediated immune functions: development of germinal centers and chronic intestinal inflammation.

Although CD4(+) T cells form a major subset of TCRalphabeta T cells, only a small number of TCRgammadelta T cells express CD4. Factors contributing to the down-regulation of CD4(+) TCRgammadelta T cells have not been identified. The CD5 molecule is expressed on most TCRgammadelta T cells in the spleen, whereas only a few intestinal intraepithelial TCRgammadelta T cells express this molecule in wild-type mice and TCRbeta mutant (beta(-/-)) mice. Unexpectedly, in the present studies, the lack of CD5 led to a remarkable increase of a CD4(+) TCRgammadelta T cell subset in CD5(-/-)beta(-/-) mice. The CD4(+) TCRgammadelta T cells were also detectable in MHC II(-/-)CD5(-/-)beta(-/-) triple-mutant mice. This CD4(+) TCRgammadelta T cell subset provided help in Mycobacterium-induced germinal center (GC) formation and showed a T(h)-like cytokine profile. In contrast, CD5(+) TCRgammadelta T cells suppressed the CD4(+) TCRgammadelta T cell-mediated GC formation, presumably by eliminating this CD4(+) subset. Unlike intraepithelial gammadelta T cells, >30% of TCRgammadelta T cells in the colonic lamina propria (LP) expressed CD5. The lack of CD5 also led to increased numbers of CD4(+) TCRgammadelta T cells in the colonic LP and increased susceptibility to development of chronic colitis in beta(-/-) mice. Cell transfer studies suggest that CD5(+) TCRgammadelta T cells are capable of selectively eliminating CD4(+) TCRgammadelta T cells in the intestine. The CD4(+) TCRgammadelta T cells possess immune functions similar to CD4(+) TCRalphabeta T cells.

Animals↗
PubMed2002

The role of SAP in murine CD150 (SLAM)-mediated T-cell proliferation and interferon gamma production.

CD150 (signaling lymphocyte activation molecule [SLAM]) is a self-ligand cell surface glycoprotein expressed on T cells, B cells, macrophages, and dendritic cells. To further explore the role of CD150 signaling in costimulation and T(H)1 priming we have generated a panel of rat antimouse CD150 monoclonal antibodies. CD150 cell surface expression is up-regulated with rapid kinetics in activated T cells and lipopolysaccharide/interferon gamma (IFN-gamma)-activated macrophages. Anti-CD150 triggering induces strong costimulation of T cells triggered through CD3. DNA synthesis of murine T cells induced by anti-CD150 is not dependent on SLAM-associated protein (SAP, SH2D1A), because anti-CD150 induces similar levels of DNA synthesis in SAP(-/-) T cells. Antibodies to CD150 also enhance IFN-gamma production both in wild-type and SAP(-/-) T cells during primary stimulation. The level of IFN-gamma production is higher in SAP(-/-) T cells than in wild-type T cells. Anti-CD150 antibodies also synergize with interleukin 12 (IL-12) treatment in up-regulation of IL-12 receptor beta(2) mRNA during T(H)1 priming, and inhibit primary T(H)2 polarization in an IFN-gamma-dependent fashion. Cross-linking CD150 on CD4 T cells induces rapid serine phosphorylation of Akt/PKB. We speculate that this is an important pathway contributing to CD150-mediated T-cell proliferation.

Animals↗
PubMed2002

T cell-specific expression of the murine CD3delta promoter.

T cell-specific expression of human and mouse CD3delta is known to be governed by an enhancer element immediately downstream from the gene. Here we demonstrate by transgenic and in vitro studies that the murine CD3delta (mCD3delta) promoter prefers to be expressed in cells of the T lineage. Deletion analyses of a promoter segment (-401/+48 bp) followed by transient transfections indicate that upstream elements between -149 and -112 bp contribute to full expression of the gene. Furthermore, a core promoter region -37/+29 appears to contribute to a T cell specificity. Using substitution mutant scanning, four positive and one negative regulatory elements were found within the mCD3delta core promoter. The first two positive elements comprise two classical initiator-like sites, which recruit TFII-I, whereas a third contains a functional Ets binding site. Immediately adjacent to the observed transcription start site is a negative element that utilizes the transcription regulator YY1. The last positive regulatory element contains a potentially functional CREB binding site and the minor transcriptional start site. Because NERF-2, Elf-1, and Ets-1 are expressed preferentially in lymphocytes and because, in addition, YY1 represses the promoter activity strongly in non-T cells, we conclude that the combination of these transcription factors contributes to the T cell-specific expression pattern of mouse CD3delta.

Animals↗
PubMed2002

Mouse novel Ly9: a new member of the expanding CD150 (SLAM) family of leukocyte cell-surface receptors.

Human CS1, also known as novel Ly9, 19A24, or CRACC, is a member of the immunoglobulin gene superfamily (IgSF) expressed on natural killer cells and other leukocytes. Here we describe the cloning of the mouse homologue of this gene. The mouse novel Ly9 gene is shown to encode a transmembrane protein composed of two extracellular immunoglobulin-like domains, a transmembrane region and an 88-amino acid cytoplasmic domain. Mouse novel Ly9 is structurally similar to the extracellular domains of CD84 and CD229 (Ly9). Both mouse and human novel Ly9 genes mapped close to the CD229gene in a region where other members of the CD150 family have also been mapped, and analysis of their genomic sequences showed that they have an identical intron/exon organization. Northern blot analysis revealed that the expression of mouse and human novel Ly9 was predominantly restricted to hematopoietic tissues, with the exception of testis. Here we show that SAP (SH2D1A), an adapter protein responsible for the X-linked lymphoproliferative disease, binds to the phosphorylated cytoplasmic tail of human but not mouse novel Ly9. Taken together, these data indicate that mouse novel Ly9 is a new member of the expanding CD150 family of cell surface receptors.

Amino Acid Sequence↗
PubMed2002

Phosphorylation of the N-terminal and C-terminal CD3-epsilon-ITAM tyrosines is differentially regulated in T cells.

Tyrosine phosphorylation of immunoreceptor tyrosine-based activation motifs (ITAMs) within CD3 chains is crucial for the recruitment of protein tyrosine kinases and effector molecules into the T cell receptor. Thus, phenylalanine substitution at the N-terminal tyrosine residue of the CD3-epsilon-ITAM abolished signal transduction functions of this ITAM, including phosphorylation at the C-terminal ITAM tyrosine, and its association with ZAP-70. In contrast, mutation at the C-terminal tyrosine of CD3-epsilon-ITAM did not prevent phosphorylation at the N-terminal tyrosine, nor its association with Lck, or p85 PI 3-K regulatory subunit. In contrast to the ZAP-70/diphosphorylated CD8-epsilon-ITAM interaction, the Lck/monophosphorylated CD8-epsilon-ITAM interaction was sensitive to octylglucoside, an agent that disrupts Lck interaction with membrane rafts. Therefore, association of Lck with membrane rafts seems to be essential for stabilization of Lck/CD3-epsilon protein-protein interactions. Overall, the data suggest that the sequential and coordinated phosphorylation of CD3-epsilon-ITAM tyrosines provides to CD3-epsilon the potential to interact with multiple downstream effectors and signaling pathways.

Amino Acid Motifs↗
PubMed2002

A "three-pronged" binding mechanism for the SAP/SH2D1A SH2 domain: structural basis and relevance to the XLP syndrome.

The SH2 domain protein SAP/SH2D1A, encoded by the X-linked lymphoproliferative (XLP) syndrome gene, associates with the hematopoietic cell surface receptor SLAM in a phosphorylation-independent manner. By screening a repertoire of synthetic peptides, the specificity of SAP/SH2D1A has been mapped and a consensus sequence motif for binding identified, T/S-x-x-x-x-V/I, where x represents any amino acid. Remarkably, this motif contains neither a Tyr nor a pTyr residue, a hallmark of conventional SH2 domain-ligand interactions. The structures of the protein, determined by NMR, in complex with two distinct peptides provide direct evidence in support of a "three-pronged" binding mechanism for the SAP/SH2D1A SH2 domain in contrast to the "two-pronged" binding for conventional SH2 domains. Differences in the structures of the two complexes suggest considerable flexibility in the SH2 domain, as further confirmed and characterized by hydrogen exchange studies. The structures also explain binding defects observed in disease-causing SAP/SH2D1A mutants and suggest that phosphorylation-independent interactions mediated by SAP/SH2D1A likely play an important role in the pathogenesis of XLP.

Antigens, CD↗
PubMed2002

Molecular dissection of the signaling and costimulatory functions of CD150 (SLAM): CD150/SAP binding and CD150-mediated costimulation.

CD150 signaling lymphocytic activation molecule (SLAM), a T/B/dendritic cell surface glycoprotein, is a costimulatory receptor involved in T-cell activation and is also a receptor for measles virus. CD150-induced signal transduction is controlled by SAP/SH2D1A, the gene that is aberrant in X-linked lymphoproliferative disease and familial hemophagocytic lymphohistiocytosis. This report shows that CD150 colocalizes with the T-cell receptor (TCR) following CD3 triggering in human peripheral blood T cells and is rapidly and reversibly tyrosine phosphorylated on TCR cross-linking. The Src-like kinases Lck and Fyn phosphorylate tyrosine residues in the cytoplasmic tail of CD150. The results demonstrate that the SAP protein has 2 modes of binding to CD150. Binding to the motif Thr-Ile-Tyr281Ala-Gln-Val occurs in a phosphotyrosine-independent fashion and to the motif Thr-Val-Tyr327Ala-Ser-Val in a phosphotyrosine-dependent manner. Within both SAP binding motifs the threonine residue at position -2 to tyrosine is essential to stabilize the interaction irrespective of tyrosine phosphorylation, a feature unique to the SAP SH2 domain. A leucine residue, Leu278, further stabilizes nonphospho binding of SAP to Tyr281 of CD150. SAP blocking of the tyrosine phosphatase SHP-2 occurs primarily on Tyr281 of CD150 because SHP-2 requires both Tyr281 and Tyr327 for binding to CD150, and SAP binds to nonphosphorylated Tyr281. CD150 exhibits lateral mobility, segregating into intercellular contacts. The lateral mobility and homophilic clustering of CD150 between neighboring cells is not dependent on SAP/CD150 interaction.

Amino Acid Sequence↗
PubMed2002

Identification and characterization of SF2000 and SF2001, two new members of the immune receptor SLAM/CD2 family.

The SLAM family of human genes currently consists of seven related members of the immunoglobulin superfamily, membrane-associated proteins, including CD150 (SLAM), CD244 (2B4), CD84, CD229 ( Ly-9), BLAME, CD48, and 19A. These genes are expressed to varying degrees in subsets of immune cells (T, B, natural killer, and myeloid cells) and may function as ligands or receptors. This set of genes, related to CD2 and CD58 on Chromosome (Chr) 1p98, are found clustered close together in the human genome on Chr 1q22. Four of these family members (CD150, CD244, CD84, CD229) contain conserved tyrosine motifs in their cytoplasmic tails that enable them to bind intracellular signaling molecules SAP and EAT-2. SAP is mutated in human X-linked lymphoproliferative disease (XLP), and studies in XLP patients have shown that improper signaling via molecules that bind SAP contributes to the disease. We have identified two new members of the SLAM family (SF), which we term SF2000 and SF2001, which are expressed in immune cells and map in the SLAM gene cluster. SF2001 does not contain SAP-binding motifs in its short cytoplasmic tail. SF2000, which is co-expressed with SAP in T cells, binds both SAP and EAT-2. The data suggest that signaling through SF2000, together with CD150, CD244, CD84, and CD229, is controlled by SAP and therefore contributes to the pathogenesis of XLP.

Amino Acid Sequence↗
PubMed2002

Role of tumor necrosis factor receptor 2 (TNFR2) in colonic epithelial hyperplasia and chronic intestinal inflammation in mice.

BACKGROUND & AIMS: Tumor necrosis factor (TNF) induces multiple effects including cell proliferation and death by ligation with TNF receptor type II (TNFR2). We studied the role of TNFR2 in chronic inflammation-induced colonic epithelial alteration. METHODS: TNFR2 expression in colonic epithelial cells (CECs) was assessed by ribonuclease protection assay (RPA) and immunohistochemistry (IHC) in patients with inflammatory bowel disease (IBD) and murine colitis models. TNFR2 expression was also analyzed using COLO205 cells. The role of TNFR2 in colonic epithelial homeostasis was examined by generating interleukin 6-deficient TCR alpha KO (alpha IL-6DKO) or TNFR2-deficient TCR alpha (alpha TNFR2DKO) mice. RESULTS: TNFR2 expression was up-regulated in CEC in both human ulcerative colitis and Crohn's disease. In vitro studies showed that TNFR2 expression was up-regulated by a cooperative effect of key proinflammatory cytokines. By RPA, the increased expression of TNFR2 was detectable in TCR alpha KO mice with colitis compared with TCR alpha KO mice without colitis or wild-type mice. In alpha IL-6DKO mice, TNFR2 expression, proliferation, and nuclear factor kappa B activation of CECs were markedly reduced compared with TCR alpha KO mice. alpha TNFR2 mice also showed significantly less colonic epithelial proliferation compared with TCR alpha KO mice. CONCLUSIONS: Expression of TNFR2 is consistently increased on CECs in both murine colitis models as well as patients with IBD. TNFR2 may play an important role in colonic inflammation-associated alteration in the intestinal epithelium.

Animals↗
PubMed2002

A spectrum of mutations in SH2D1A that causes X-linked lymphoproliferative disease and other Epstein-Barr virus-associated illnesses.

X-linked lymphoproliferative disease (Duncan's Disease) was first encountered by David T. Purtilo in 1969. The first communication describing the disease was published in 1975. In 1989 the disease locus was mapped to Xq25. Ten years later the gene (SH2D1A, SAP, DSHP), which is absent or mutated in XLP patients was identified. Since that the protein crystal structure of this small, SH2-domain containing protein has been solved, target molecules of the protein have been identified, physiological and pathological protein/protein interactions have been characterized, and the mouse model of the gene mutation has been developed. That said, a complete understanding of the function of the normal SH2D1A protein in immunoregulation and of the altered immune responses in XLP patients is not yet at hand. Therein lies the legacy of Purtilo's discovery for, as with other primary immunodeficiencies, these "experiments of nature" offer a window on the beauty of the immune system. In due course, the manner by which this gene orchestrates an elegant response (akin to a Mozart divertimento) to EBV infection shall be defined.

Animals↗