Potent induction of alpha(1,3)-fucosyltransferase VII in activated CD4+ T cells by TGF-beta 1 through a p38 mitogen-activated protein kinase-dependent pathway

P-Selectin Glycoprotein Ligand 1: A Potential HIV-1 Therapeutic Target

Antiretroviral therapy (ART), which is a life-long therapeutic option, remains the only currently effective clinical method to treat HIV-1 infection. However, ART may be toxic to vital organs including the liver, brain, heart, and kidneys, and may result in systemic complications. In this context, to consider HIV-1 restriction factors from the innate immune system to explore novel HIV therapeutics is likely to be a promising investigative strategy. In light of this, P-selectin glycoprotein ligand 1 (PSGL-1) has recently become the object of close scrutiny as a recognized cell adhesion molecule, and has become a major focus of academic study, as researchers believe that PSGL-1 may represent a novel area of interest in the research inquiry into the field of immune checkpoint inhibition. In this article, we review PSGL-1's structure and functions during infection and/or inflammation. We also outline a comprehensive review of its role and potential therapeutic utility during HIV-1 infection as published in contemporary academic literature.

Migratory DCs activate TGF-β to precondition naïve CD8+ T cells for tissue-resident memory fate

Epithelial resident memory T (eT_RM) cells serve as sentinels in barrier tissues to guard against previously encountered pathogens. How eT_RM cells are generated has important implications for efforts to elicit their formation through vaccination or prevent it in autoimmune disease. Here, we show that during immune homeostasis, the cytokine transforming growth factor β (TGF-β) epigenetically conditions resting naïve CD8⁺ T cells and prepares them for the formation of eT_RM cells in a mouse model of skin vaccination. Naïve T cell conditioning occurs in lymph nodes (LNs), but not in the spleen, through major histocompatibility complex class I-dependent interactions with peripheral tissue-derived migratory dendritic cells (DCs) and depends on DC expression of TGF-β-activating α_V integrins. Thus, the preimmune T cell repertoire is actively conditioned for a specialized memory differentiation fate through signals restricted to LNs.

Fucosyltransferase Induction during Influenza Virus Infection Is Required for the Generation of Functional Memory CD4+ T Cells

T cells mediating influenza viral control are instructed in lymphoid and nonlymphoid tissues to differentiate into memory T cells that confer protective immunity. The mechanisms by which influenza virus-specific memory CD4⁺ T cells arise have been attributed to changes in transcription factors, cytokines and cytokine receptors, and metabolic programming. The molecules involved in these biosynthetic pathways, including proteins and lipids, are modified to varying degrees of glycosylation, fucosylation, sialation, and sulfation, which can alter their function. It is currently unknown how the glycome enzymatic machinery regulates CD4⁺ T cell effector and memory differentiation. In a murine model of influenza virus infection, we found that fucosyltransferase enzymatic activity was induced in effector and memory CD4⁺ T cells. Using CD4⁺ T cells deficient in the Fut4/7 enzymes that are expressed only in hematopoietic cells, we found decreased frequencies of effector cells with reduced expression of T-bet and NKG2A/C/E in the lungs during primary infection. Furthermore, Fut4/7^-/- effector CD4⁺ T cells had reduced survival with no difference in proliferation or capacity for effector function. Although Fut4/7^-/- CD4⁺ T cells seeded the memory pool after primary infection, they failed to form tissue-resident cells, were dysfunctional, and were unable to re-expand after secondary infection. Our findings highlight an important regulatory axis mediated by cell-intrinsic fucosyltransferase activity in CD4⁺ T cell effectors that ensure the development of functional memory CD4⁺ T cells.

T-lymphocyte homing: an underappreciated yet critical hurdle for successful cancer immunotherapy

Advances in cancer immunotherapy have offered new hope for patients with metastatic disease. This unfolding success story has been exemplified by a growing arsenal of novel immunotherapeutics, including blocking antibodies targeting immune checkpoint pathways, cancer vaccines, and adoptive cell therapy (ACT). Nonetheless, clinical benefit remains highly variable and patient-specific, in part, because all immunotherapeutic regimens vitally hinge on the capacity of endogenous and/or adoptively transferred T-effector (T_eff) cells, including chimeric antigen receptor (CAR) T cells, to home efficiently into tumor target tissue. Thus, defects intrinsic to the multi-step T-cell homing cascade have become an obvious, though significantly underappreciated contributor to immunotherapy resistance. Conspicuous have been low intralesional frequencies of tumor-infiltrating T-lymphocytes (TILs) below clinically beneficial threshold levels, and peripheral rather than deep lesional TIL infiltration. Therefore, a T_eff cell 'homing deficit' may arguably represent a dominant factor responsible for ineffective immunotherapeutic outcomes, as tumors resistant to immune-targeted killing thrive in such permissive, immune-vacuous microenvironments. Fortunately, emerging data is shedding light into the diverse mechanisms of immune escape by which tumors restrict T_eff cell trafficking and lesional penetrance. In this review, we scrutinize evolving knowledge on the molecular determinants of T_eff cell navigation into tumors. By integrating recently described, though sporadic information of pivotal adhesive and chemokine homing signatures within the tumor microenvironment with better established paradigms of T-cell trafficking under homeostatic or infectious disease scenarios, we seek to refine currently incomplete models of T_eff cell entry into tumor tissue. We further summarize how cancers thwart homing to escape immune-mediated destruction and raise awareness of the potential impact of immune checkpoint blockers on T_eff cell homing. Finally, we speculate on innovative therapeutic opportunities for augmenting T_eff cell homing capabilities to improve immunotherapy-based tumor eradication in cancer patients, with special focus on malignant melanoma.

PSGL-1: A New Player in the Immune Checkpoint Landscape

P-selectin glycoprotein ligand-1 (PSGL-1) has long been studied as an adhesion molecule involved in immune cell trafficking and is recognized as a regulator of many facets of immune responses by myeloid cells. PSGL-1 also regulates T cell migration during homeostasis and inflammatory settings. However, recent findings indicate that PSGL-1 can also negatively regulate T cell function. Because T cell differentiation is finely tuned by multiple positive and negative regulatory signals that appropriately scale the magnitude of the immune response, PSGL-1 has emerged as an important checkpoint during this process. We summarize what is known regarding PSGL-1 structure and function and highlight how it may act as an immune checkpoint inhibitor in T cells.

TGF-β Controls the Formation of Kidney-Resident T Cells via Promoting Effector T Cell Extravasation

Tissue-resident memory T (T_RM) cells, a population of noncirculating memory T cells, are one of the essential components of immunological memory in both mouse and human. Although CD69⁺CD103⁺ T_RM cells represent a major T_RM cell population in barrier tissues including the mucosal surface and the skin, CD69⁺CD103^- T_RM cells dominate most nonbarrier tissues, such as the kidney. TGF-β is required for the differentiation of CD69⁺CD103⁺ T_RM cells in barrier tissues. However, the developmental control of CD69⁺CD103^- T_RM cells in nonbarrier tissues remains largely unknown and the involvement of TGF-β signaling is less clear. In this study we demonstrated that TGF-β promoted the formation of kidney-resident T cells via enhancing the tissue entry of effector T cells. Mechanistically, TGF-β enhanced E- and P-selectin and inflammatory chemokine-mediated extravasation of effector T cells. Thus TGF-β controls the first developmental checkpoint of T_RM cell differentiation in nonbarrier tissues.

Imprinting of Skin/Inflammation Homing in CD4+ T Cells Is Controlled by DNA Methylation within the Fucosyltransferase 7 Gene

E- and P-selectin ligands (E- and P-ligs) guide effector memory T cells into skin and inflamed regions, mediate the inflammatory recruitment of leukocytes, and contribute to the localization of hematopoietic precursor cells. A better understanding of their molecular regulation is therefore of significant interest with regard to therapeutic approaches targeting these pathways. In this study, we examined the transcriptional regulation of fucosyltransferase 7 (FUT7), an enzyme crucial for generation of the glycosylated E- and P-ligs. We found that high expression of the coding gene fut7 in murine CD4⁺ T cells correlates with DNA demethylation within a minimal promoter in skin/inflammation-seeking effector memory T cells. Retinoic acid, a known inducer of the gut-homing phenotype, abrogated the activation-induced demethylation of this region, which contains a cAMP responsive element. Methylation of the promoter or mutation of the cAMP responsive element abolished promoter activity and the binding of CREB, confirming the importance of this region and of its demethylation for fut7 transcription in T cells. Furthermore, studies on human CD4⁺ effector memory T cells confirmed demethylation within FUT7 corresponding to high FUT7 expression. Monocytes showed an even more extensive demethylation of the FUT7 gene whereas hepatocytes, which lack selectin ligand expression, exhibited extensive methylation. In conclusion, we show that DNA demethylation within the fut7 gene controls selectin ligand expression in mice and humans, including the inducible topographic commitment of T cells for skin and inflamed sites.

Functions of Smad Transcription Factors in TGF-β1-Induced Selectin Ligand Expression on Murine CD4 Th Cells

Selectins are carbohydrate-binding adhesion molecules that control leukocyte traffic. Induction of selectin ligands on T cells is controlled primarily by cytokines, including TGF-β1, and requires p38α MAPK, but transcriptional mechanisms that underlie cytokine-driven selectin ligand expression are poorly understood. In this study, we show, using mice with conditional deletions of the TGF-β1-responsive transcription factors Smad2, Smad3, or Smad4, that induction of selectin ligands on CD4 cells in response to TGF-β1 requires Smad4 plus either Smad2 or Smad3. Analysis of CD4 cells from mice with only one functional Smad4 allele revealed a sharp gene dosage effect, suggesting the existence of a threshold of TGF-β1 signal strength required for selectin ligand induction. Both Smad4 plus either Smad2 or Smad3 were selectively required for induction of Fut7 and Gcnt1, glycosyltransferases critical for selectin ligand biosynthesis, but they were not required for St3gal4 or St3gal6 induction. Smad4 plus either Smad2 or Smad3 were also required for induction of Runx transcription factors by TGF-β1. Enforced expression of Runx2, but not Runx1 or Runx3, in Smad2/Smad3 doubly deficient CD4 cells restored selectin ligand expression to wild-type levels. In contrast, enforced expression of Runx1, Runx2, or Runx3 failed to restore differentiation of TGF-β1-dependent Th cell lineages, including Th17, Th9, and induced regulatory T cells. These results show that Smads are directly required for Th cell differentiation independent of Runx induction but only indirectly required via Runx2 for TGF-β1-induced selectin ligand induction on murine CD4 T cells.

A key role for Fut1-regulated angiogenesis and ICAM-1 expression in K/BxN arthritis

OBJECTIVES

Angiogenesis contributes to the pathogenesis of rheumatoid arthritis. Fucosyltransferases (Futs) are involved in angiogenesis and tumour growth. Here, we examined the role of Fut1 in angiogenesis and K/BxN serum transfer arthritis.

METHODS

We examined Fut1 expression in human dermal microvascular endothelial cells (HMVECs) by quantitative PCR. We performed a number of angiogenesis assays to determine the role of Fut1 using HMVECs, Fut1 null (Fut1(-/-)), and wild type (wt) endothelial cells (ECs) and mice. K/BxN serum transfer arthritis was performed to determine the contribution of Fut1-mediated angiogenesis in Fut1(-/-) and wt mice. A static adhesion assay was implemented with RAW264.7 (mouse macrophage cell line) and mouse ECs. Quantitative PCR, immunofluorescence and flow cytometry were performed with Fut1(-/-) and wt ECs for adhesion molecule expression.

RESULTS

Tumour necrosis factor-α induced Fut1 mRNA and protein expression in HMVECs. HMVECs transfected with Fut1 antisense oligodeoxynucleotide and Fut1(-/-) ECs formed significantly fewer tubes on Matrigel. Fut1(-/-) mice had reduced angiogenesis in Matrigel plug and sponge granuloma angiogenesis assays compared with wt mice. Fut1(-/-) mice were resistant to K/BxN serum transfer arthritis and had decreased angiogenesis and leucocyte ingress into inflamed joints. Adhesion of RAW264.7 cells to wt mouse ECs was significantly reduced when Fut1 was lacking. Fut1(-/-) ECs had decreased intercellular adhesion molecule-1 (ICAM-1) expression at mRNA and protein levels compared with wt ECs. ICAM-1 was also decreased in Fut1(-/-) arthritic ankle cryosections compared with wt ankles.

CONCLUSIONS

Fut1 plays an important role in regulating angiogenesis and ICAM-1 expression in inflammatory arthritis.

Diverse inflammatory cytokines induce selectin ligand expression on murine CD4 T cells via p38α MAPK

Selectins are glycan-binding adhesion molecules that mediate the initial steps of leukocyte recognition of endothelium. Cytokines control numerous aspects of CD4 Th cell differentiation, but how cytokines control the induction of ligands for E- and P-selectin on Th cell subsets remains poorly understood. Among 20 cytokines that affect Th cell differentiation, we identified six that induce expression of selectin ligands on murine CD4 T cells above the low levels associated with TCR engagement: IL-12, IL-18, IL-27, IL-9, IL-25, and TGF-β1. Collectively, these six cytokines could potentially account for selectin ligand expression on all of the currently defined nonsessile Th cell lineages, including Th1, Th2, Th9, and Th17 cells, as well as regulatory T cells. Induction of selectin ligand expression by each of these six cytokines was almost completely inhibited by pharmacologic inhibition of p38 MAPK, but not other MAPKs, or by conditional genetic deletion of p38α MAPK. Analysis of the expression of key glycosyltransferase genes revealed that p38α signaling was selectively required for induction of Fut7 and Gcnt1 but not for the induction of St3gal4 or St3gal6. Constitutively active MKK6, an immediate upstream activator of p38 MAPK, induced selectin ligand expression equivalent to that of cytokines, and this induction was completely dependent on the expression of p38α. Our results identify the repertoire of cytokines responsible for selectin ligand induction on CD4 T cells and provide a mechanistic link between Th cell development and T cell migration.

Endogenous airway mucins carry glycans that bind Siglec-F and induce eosinophil apoptosis

BACKGROUND

Sialic acid-binding, immunoglobulin-like lectin (Siglec) F is a glycan-binding protein selectively expressed on mouse eosinophils. Its engagement induces apoptosis, suggesting a pathway for ameliorating eosinophilia in the setting of asthma and other eosinophil-associated diseases. Siglec-F recognizes sialylated sulfated glycans in glycan-binding assays, but the identities of endogenous sialoside ligands and their glycoprotein carriers in vivo are unknown.

OBJECTIVES

To use mouse lung-derived materials to isolate, biochemically identify, and biologically characterize naturally occurring endogenous glycan ligands for Siglec-F.

METHODS

Lungs from normal and mucin-deficient mice, as well as mouse tracheal epithelial cells, were investigated in vitro and in vivo for the expression of Siglec-F ligands. Western blotting and cytochemistry used Siglec-F-Fc as a probe for directed purification, followed by liquid chromatography-tandem mass spectrometry of recognized glycoproteins. Purified components were tested in mouse eosinophil-binding assays and flow cytometry-based cell death assays.

RESULTS

We detected mouse lung glycoproteins that bound to Siglec-F; binding was sialic acid dependent. Proteomic analysis of Siglec-F binding material identified Muc5b and Muc4. Cross-affinity enrichment and histochemical analysis of lungs from mucin-deficient mice assigned and validated the identity of Muc5b as one glycoprotein ligand for Siglec-F. Purified mucin preparations carried sialylated and sulfated glycans, bound to eosinophils and induced their death in vitro. Mice conditionally deficient in Muc5b displayed exaggerated eosinophilic inflammation in response to intratracheal installation of IL-13.

CONCLUSIONS

These data identify a previously unrecognized endogenous anti-inflammatory property of airway mucins by which their glycans can control lung eosinophilia through engagement of Siglec-F.

Identification of two regulatory elements controlling Fucosyltransferase 7 transcription in murine CD4+ T cells

Fucosyltransferase VII encoded by the gene Fut7 is essential in CD4(+) T cells for the generation of E- and P-selectin ligands (E- and P-lig) which facilitate recruitment of lymphocytes into inflamed tissues and into the skin. This study aimed to identify regulatory elements controlling the inducible Fut7 expression in CD4(+) T cells that occurs upon activation and differentiation of naive T cells into effector cells. Comparative analysis of the histone modification pattern in non-hematopoetic cells and CD4(+) T cell subsets revealed a differential histone modification pattern within the Fut7 locus including a conserved non-coding sequence (CNS) identified by cross-species conservation comparison suggesting that regulatory elements are confined to this region. Cloning of the CNS located about 500 bp upstream of the Fut7 locus, into a luciferase reporter vector elicited reporter activity after transfection of the αβ-WT T cell line, but not after transfection of primary murine CD4(+) Th1 cells. As quantification of different Fut7 transcripts revealed a predominance of transcripts lacking the first exons in primary Th1 cells we searched for an alternative promoter. Cloning of an intragenic region spanning a 1kb region upstream of exon 4 into an enhancer-containing vector indeed elicited promoter activity. Interestingly, also the CNS enhanced activity of this intragenic minimal promoter in reporter assays in primary Th1 cells suggesting that both elements interact in primary CD4(+) T cells to induce Fut7 transcription.

Defining the functional boundaries of the murine α1,3-fucosyltransferase Fut7 reveals a remarkably compact locus

Fut7 encodes an α1,3-fucosyltransferase critical for biosynthesis of glycan ligands for all three selectins. Consistent with this function, Fut7 expression is limited to hematopoietic cells and high endothelial cells which express selectin ligands. Mechanisms that govern Fut7 expression are poorly defined. To begin to understand the molecular genetic basis for transcriptional regulation of Fut7, a transgenic, gain-of-function, genetic complementation approach in mice was used to define the "functional boundaries" of the murine Fut7 locus, defined here as any uninterupted stretch of genomic DNA that contains all cis-acting genetic elements essential for accurate physiologic expression. A 12.7-kb contiguous genomic interval, which lies completely between the highly conserved flanking Npdc1 and Abca2 loci on chromosome 2 and which contains the complete transcriptional unit plus ∼7.4 kb upstream of the transcriptional start site and ∼2 kb downstream of the transcriptional termination and polyadenylation sites, was used as a transgene (Tg) on a Fut7 null background. Tg+ mice exhibited restoration of Fut7 gene expression and physiologic levels of selectin ligand expression and function on neutrophils, activated T cells, and high endothelial cells and corrected the functional defects in these cells found in Fut7 null mice without leading to detectable expression of Fut7 in normally non-expressing tissues. These results demonstrate that all genetic information essential for appropriate and selective expression of Fut7 in diverse cell types and in response to distinct developmental signals is contained within this comparatively small genetic region.

A novel role for inducible Fut2 in angiogenesis

RATIONALE

Angiogenesis plays an important role in wound healing and tumor growth. Fucosyltransferases synthesize fucosylated glycans and may play a major role in vascular biology.

OBJECTIVE

To examine the role of an alpha(1,2) fucosyltransferase (Fut2) in angiogenesis.

METHODS AND RESULTS

We found that Fut2 mRNA and protein expression is inducible in human dermal microvascular endothelial cells (HMVECs). After finding that Fut2 is inducible in HMVECs, we examined if Fut2 contributes to angiogenesis. We found that Fut2 null endothelial cell (EC) migration and tube formation were significantly less compared to wild type (wt) ECs. Angiogenesis was impaired in Fut2 null compared to wt mice in the mouse Matrigel plug and the sponge granuloma angiogenesis assays. To assess the characteristics of Fut2 null ECs in vivo, we performed Matrigel plug angiogenesis assays in wt mice using Fut2 null and wt mouse ECs. We found a significant decrease in Fut2 null EC incorporation in neoangiogenesis compared to wt ECs. ERK1/2 activation, fibroblast growth factor receptor2, and vascular endothelial growth factor expression were less in Fut2 null ECs, suggesting a possible mechanism of impaired angiogenesis when Fut2 is lacking.

CONCLUSIONS

These data suggest a novel role for Fut2 as a regulator of angiogenesis.

Smad7 inhibits TGF-β1-induced MCP-1 upregulation through a MAPK/p38 pathway in rat peritoneal mesothelial cells

PURPOSE

The TGF-β1/Smad signaling pathway is subject to inhibition by Smad7. High expression of Smad7 in the peritoneum of rats can delay and attenuate not only peritoneal fibrosis, but also monocyte infiltration into the peritoneum. The aim of this study was to investigate the anti-inflammatory mechanism of Smad7 in peritoneal fibrosis.

METHODS

Rat peritoneal mesothelial cells were stimulated with TGF-β1, and the expression of MCP-1 protein and mRNA was measured. Furthermore, the expression of MCP-1 was determined following inhibition of TGF-β/Smad or p38 signaling using Smad7 transfection or SB203580 (10 μmol/L), respectively. The effect of exogenous Smad7 and SB203580 on activation of the TGF-β/Smad and p38 signaling pathways was also studied.

RESULTS

TGF-β1 significantly upregulated the expression of MCP-1 at both the protein and mRNA level in a time-dependent manner. Exogenous Smad7 and SB203580 markedly inhibited TGF-β1-induced MCP-1 expression. Moreover, high expression of exogenous Smad7 not only inhibited phosphorylation of Smad2 and Smad3, but also diminished the level of phosphorylated p38. However, SB203580 had no effect on the phosphorylation of Smad2 and Smad3.

CONCLUSIONS

TGF-β1 exhibits pro-inflammatory effects through the upregulation of MCP-1 in peritoneal fibrosis. Smad7 inhibits TGF-β1 induced MCP-1 upregulation through a MAPK/p38-dependent pathway.

PSGL-1 function in immunity and steady state homeostasis

The substantial importance of P-selectin glycoprotein ligand 1 (PSGL-1) in leukocyte trafficking has continued to emerge beyond its initial identification as a selectin ligand. PSGL-1 seemed to be a relatively simple molecule with an extracellular mucin domain extended as a flexible rod, teleologically consistent with its primary role in tethering leukocytes to endothelial selectins. The rolling interaction between leukocyte and endothelium mediated by this selectin-PSGL-1 interaction requires branched O-glycan extensions on specific PSGL-1 amino acid residues. In some cells, such as neutrophils, the glycosyltransferases involved in formation of the O-glycans are constitutively expressed, while in other cells, such as T cells, they are expressed only after appropriate activation. Thus, PSGL-1 supports leukocyte recruitment in both innate and adaptive arms of the immune response. A complex array of amino acids within the selectins engage multiple sugar residues of the branched O-glycans on PSGL-1 and provide the molecular interactions responsible for the velcro-like catch bonds that support leukocyte rolling. Such binding of PSGL-1 can also induce signaling events that influence cell phenotype and function. Scrutiny of PSGL-1 has revealed a better understanding of how it performs as a selectin ligand and yielded unexpected insights that extend its scope from supporting leukocyte rolling in inflammatory settings to homeostasis including stem cell homing to the thymus and mature T-cell homing to secondary lymphoid organs. PSGL-1 has been found to bind homeostatic chemokines CCL19 and CCL21 and to support the chemotactic response to these chemokines. Surprisingly, the O-glycan modifications of PSGL-1 that support rolling mediated by selectins in inflammatory conditions interfere with PSGL-1 binding to homeostatic chemokines and thereby limit responsiveness to the chemotactic cues used in steady state T-cell traffic. The multi-level influence of PSGL-1 on cell traffic in both inflammatory and steady state settings is therefore substantially determined by the orchestrated addition of O-glycans. However, central as specific O-glycosylation is to PSGL-1 function, in vivo regulation of PSGL-1 glycosylation in T cells remains poorly understood. It is our purpose herein to review what is known, and not known, of PSGL-1 glycosylation and to update understanding of PSGL-1 functional scope.

Regulatory T cells sequentially migrate from inflamed tissues to draining lymph nodes to suppress the alloimmune response

To determine the site and mechanism of suppression by regulatory T (Treg) cells, we investigated their migration and function in an islet allograft model. Treg cells first migrated from blood to the inflamed allograft where they were essential for the suppression of alloimmunity. This process was dependent on the chemokine receptors CCR2, CCR4, and CCR5 and P- and E-selectin ligands. In the allograft, Treg cells were activated and subsequently migrated to the draining lymph nodes (dLNs) in a CCR2, CCR5, and CCR7 fashion; this movement was essential for optimal suppression. Treg cells inhibited dendritic cell migration in a TGF-beta and IL-10 dependent fashion and suppressed antigen-specific T effector cell migration, accumulation, and proliferation in dLNs and allografts. These results showed that sequential migration from blood to the target tissue and to dLNs is required for Treg cells to differentiate and execute fully their suppressive function.

Expression and regulation of fucosyltransferase 4 in human endometrium

It has been suggested that selectin ligands expressed by the endometrial epithelium are essential for the initial adhesion of the blastocyst to the luminal epithelium of human endometrium. One of the enzymes responsible for the production of selectin ligands is fucosyltransferase 4 (FUT4), a member of α1,3 fucosyltransferases. The aims of the present study were to characterizeFUT4mRNA and protein in human endometrium during the menstrual cycle and to investigate the hormonal regulation ofFUT4whose mRNA expression was quantified by real-time PCR in fresh endometrial tissue from cycling women and protein expression was analyzed by immunohistochemistry and Western blotting. Hormonal regulation ofFUT4transcription was investigated using an endometrial explant system.FUT4mRNA was significantly upregulated in fresh tissues during early and mid-secretory phases when compared with other phases of the menstrual cycle. FUT4 protein was localized to glandular and luminal epithelium and the expression levels followed the same pattern as forFUT4mRNA. Our data also show that, in proliferative explants, progesterone significantly increasedFUT4transcription and translation after 24 h in culture. The inductive effect of progesterone onFUT4transcription was lost after 48 h of treatment. Estrogen did not have any significant effects. These data suggest that the upregulation of selectin ligands in the human endometrium at the time of implantation may be mediated, at least in part, by the regulation ofFUT4expression.

Targeting selectins and selectin ligands in inflammation and cancer

Inflammation and cancer metastasis are associated with extravasation of leukocytes or tumor cells from blood into tissue. Such movement is believed to follow a coordinated and sequential molecular cascade initiated, in part, by the three members of the selectin family of carbohydrate-binding proteins: E-selectin (CD62E), L-selectin (CD62L) and P-selectin (CD62P). E-selectin is particularly noteworthy in disease by virtue of its expression on activated endothelium and on bone-skin microvascular linings and for its role in cell rolling, cell signaling and chemotaxis. E-selectin, along with L- or P-selectin, mediates cell tethering and rolling interactions through the recognition of sialo-fucosylated Lewis carbohydrates expressed on structurally diverse protein-lipid ligands on circulating leukocytes or tumor cells. Major advances in understanding the role of E-selectin in inflammation and cancer have been advanced by experiments assaying E-selectin-mediated rolling of leukocytes and tumor cells under hydrodynamic shear flow, by clinical models of E-selectin-dependent inflammation, by mice deficient in E-selectin and by mice deficient in glycosyltransferases that regulate the binding activity of E-selectin ligands. Here, the authors elaborate on how E-selectin and its ligands may facilitate leukocyte or tumor cell recruitment in inflammatory and metastatic settings. Antagonists that target cellular interactions with E-selectin and other members of the selectin family, including neutralizing monoclonal antibodies, competitive ligand inhibitors or metabolic carbohydrate mimetics, exemplify a growing arsenal of potentially effective therapeutics in controlling inflammation and the metastatic behavior of cancer.

Long-Term Commitment to Inflammation-Seeking Homing in CD4+ Effector Cells

Access of T effector cells to sites of inflammation is a prerequisite for an efficient action in immune defense and is mediated by different, partly tissue-specific sets of adhesion molecules. To what extent lymphocytes memorize the site of initial priming and develop organ-specific homing properties is still a matter of debate. Notably, data on the stability of homing receptor expression on T cells in vivo are largely lacking. We approached this question by the adoptive transfer of CD4(+) T cells sorted for the expression of P-selectin ligands, which contribute to migration into inflamed sites in skin and other tissues. We observed long-term expression of P-selectin ligands on roughly one-third of effector cells. On those cells that had lost P-selectin ligands, re-expression upon Ag challenge was observed but only within pLNs, similar to the organ-selective induction upon the primary activation of naive T cells. The frequency of cells stably expressing P-selectin ligands was higher when cells were repeatedly stimulated under permissive conditions in the presence of IL-12, indicating a gradual fixation of this phenotype. In line with that finding, isolated P-selectin ligand positive memory T cells showed the highest frequency of long-term expressing cells. A tissue-specific environment was not required for the long-term maintenance of P-selectin ligand expression on the subfraction of effector cells. These data indicate that the expression of selectin ligands can become clonally imprinted under certain conditions, but also that a major fraction of the cells remains flexible and subject to environmental modulation upon restimulation.

Induction of organ-selective CD4+ regulatory T cell homing

Compelling evidence suggests that Foxp3(+)CD25(+)CD4(+) Treg play a fundamental role in immunoregulation. We have previously demonstrated that Treg have to enter peripheral tissues to suppress ongoing inflammation. However, relatively little is known about how Treg acquire the expression of homing receptors required for tissue- or inflammation-specific migration. Migratory properties of conventional naïve T cells are shaped by the tissue microenvironment and organ-specific dendritic cells during priming. Here, we show that this basic concept also holds true for CD25(+)CD4(+) Treg: Priming of Treg within peripheral LN led to the expression of selectin ligands, which facilitate migration into inflamed skin, whereas activation within mesenteric LN led to induction of the integrin alpha(4)beta(7), which is required for migration into mucosal tissues. Furthermore, we could establish in vitro culture systems containing either dendritic cells from mesenteric and peripheral LN, or retinoic acid and IL-12 as polarizing compounds to induce mucosa- and skin-seeking Treg, respectively. Together, our results demonstrate that Treg, similarly to conventional T cells, can be configured with organ-selective homing properties allowing efficient targeting into distinct tissues.

The essential role of chemokines in the selective regulation of lymphocyte homing

Knowledge of lymphocyte migration has become a major issue in our understanding of acquired immunity. The selective migration of naïve, effector, memory and regulatory T-cells is a multiple step process regulated by a specific arrangement of cytokines, chemokines and adhesion receptors that guide these cells to specific locations. Recent research has outlined two major pathways of lymphocyte trafficking under homeostatic and inflammatory conditions, one concerning tropism to cutaneous tissue and a second one related to mucosal-associated sites. In this article we will outline our present understanding of the role of cytokines and chemokines as regulators of lymphocyte migration through tissues.

Microenvironment-dependent requirement of STAT4 for the induction of P-selectin ligands and effector cytokines on CD4+ T cells in healthy and parasite-infected mice

T effector cells require selectin ligands to migrate into inflamed regions. In vitro, IL-12 promotes induction of these ligands as well as differentiation of CD4+ T cells into IFN-gamma-producing Th1 but not Th2 cells. STAT4 is strongly involved in these processes. However, the presence of selectin ligands on various T effector cell subsets in vivo points to more complex regulatory pathways. To clarify the role of the IL-12/STAT4 signaling pathway, we analyzed the impact of STAT4 deficiency on the expression of P-selectin ligands (P-lig) on CD4+ T cells in vitro and in vivo, including conditions of infection. In vitro, we found significant expression of P-lig upon activation not only in the presence, but also in the absence, of IL-12, which was independent of STAT4. TGF-beta, an alternative inducer of selectin ligands in human T cells, was not effective in murine CD4+ T cells, suggesting a role of additional signaling pathways. In vivo, a significant impact of STAT4 for the generation of P-lig+CD4+ T cells was observed for cells from peripheral lymph nodes, but not for those from spleen or lung. However, upon infection with the Th2-inducing parasite Nippostrongylus brasiliensis, P-lig expression became dependent on STAT4 signaling. Interestingly, also the frequency of IL-4-producing cells was greatly diminished in absence of STAT4. These data reveal a hitherto unknown contribution of STAT4 to the generation of Th2 cells in parasite infection and suggest that signals inducing inflammation-seeking properties in vivo vary depending on environmental conditions, such as type of organ and infection.

Activation of murine CD4+ and CD8+ T lymphocytes leads to dramatic remodeling of N-linked glycans

Differentiation and activation of lymphocytes are documented to result in changes in glycosylation associated with biologically important consequences. In this report, we have systematically examined global changes in N-linked glycosylation following activation of murine CD4 T cells, CD8 T cells, and B cells by MALDI-TOF mass spectrometry profiling, and investigated the molecular basis for those changes by assessing alterations in the expression of glycan transferase genes. Surprisingly, the major change observed in activated CD4 and CD8 T cells was a dramatic reduction of sialylated biantennary N-glycans carrying the terminal NeuGcalpha2-6Gal sequence, and a corresponding increase in glycans carrying the Galalpha1-3Gal sequence. This change was accounted for by a decrease in the expression of the sialyltransferase ST6Gal I, and an increase in the expression of the galactosyltransferase, alpha1-3GalT. Conversely, in B cells no change in terminal sialylation of N-linked glycans was evident, and the expression of the same two glycosyltransferases was increased and decreased, respectively. The results have implications for differential recognition of activated and unactivated T cells by dendritic cells and B cells expressing glycan-binding proteins that recognize terminal sequences of N-linked glycans.

Alloantigen-presenting plasmacytoid dendritic cells mediate tolerance to vascularized grafts

The induction of alloantigen-specific unresponsiveness remains an elusive goal in organ transplantation. Here we identify plasmacytoid dendritic cells (pDCs) as phagocytic antigen-presenting cells essential for tolerance to vascularized cardiac allografts. Tolerizing pDCs acquired alloantigen in the allograft and then moved through the blood to home to peripheral lymph nodes. In the lymph node, alloantigen-presenting pDCs induced the generation of CCR4+ CD4+ CD25+ Foxp3+ regulatory T cells (Treg cells). Depletion of pDCs or prevention of pDC lymph node homing inhibited peripheral Treg cell development and tolerance induction, whereas adoptive transfer of tolerized pDCs induced Treg cell development and prolonged graft survival. Thus, alloantigen-presenting pDCs home to the lymph nodes in tolerogenic conditions, where they mediate alloantigen-specific Treg cell development and allograft tolerance.

Innate immune responses to herpes simplex virus type 2 influence skin homing molecule expression by memory CD4+ lymphocytes

Herpes simplex virus (HSV) infections of humans are characterized by intermittent, lytic replication in epithelia. Circulating HSV-specific CD4 T cells express lower levels of preformed cutaneous lymphocyte-associated antigen (CLA), a skin-homing receptor, than do circulating HSV-specific CD8 T cells but, paradoxically, move into infected skin earlier than CD8 cells. Memory CD4 T cells develop strong and selective expression of CLA and E-selectin ligand while responding to HSV antigen in vitro. We now show that interleukin-12, type I interferon, and transforming growth factor beta are each involved in CLA expression by memory HSV type 2 (HSV-2)-specific CD4 T cells in peripheral blood mononuclear cells (PBMC). A reduction of the number of monocytes and dendritic cells from PBMC reduces CLA expression by HSV-2-responsive CD4 lymphoblasts, while their reintroduction restores this phenotype, identifying these cells as possible sources of CLA-promoting cytokines. Plasmacytoid dendritic cells are particularly potent inducers of CLA on HSV-reactive CD4 T cells. These observations are consistent with cooperation between innate and acquired immunity to promote a pattern of homing receptor expression that is physiologically appropriate for trafficking to infected tissues.

Synthesis of {alpha}(1,3) fucosyltransferases IV- and VII-dependent eosinophil selectin ligand and recruitment to the skin

Selectins mediate the initial adhesion of leukocytes to endothelial cells in many contexts of inflammation-dependent leukocyte recruitment. The glycans that contribute to P- and E-selectin counterreceptor activity arise through glycosylation reactions in which the terminal steps are catalyzed by alpha(1,3) fucosyltransferases (FTs). We examined how selectin ligand activities are controlled in eosinophils by characterizing FT expression profiles and regulatory mechanisms in eosinophils isolated from human blood. We found that FT-IV and FT-VII mRNAs were up-regulated by transforming growth factor-beta1, but the FT-IV transcript consistently predominated in eosinophils. To further define the physiological role of FT-IV and FT-VII in expression of eosinophil selectin ligand, we characterized models of dermal eosinophilia in FT-IV- and/or FT-VII-deficient mice in vivo. FT-IV deficiency yielded a significant decrease in eosinophil recruitment to the skin. Likewise, deficiency of FT-VII also yielded a decrease in eosinophil recruitment. Eosinophil recruitment that remained in the absence of FT-VII was further inhibited by blocking P- or E-selectin and was essentially absent in mice deficient in both enzymes. These observations indicate that FT-IV and FT-VII are both important contributors to selectin-dependent eosinophil recruitment to the skin and may represent therapeutic targets for treating diseases in which eosinophil recruitment contributes to pathophysiology.

Interleukin-4 induced down-regulation of skin homing receptor expression by human viral-specific CD8 T cells may contribute to atopic risk of cutaneous infection

Factors controlling the expression of cutaneous lymphocyte-associated antigen (CLA) by T cells are poorly understood, but data from murine and human CD4(+) T cell systems have suggested that cytokines play an important role. However, there are no data examining the influence of cytokines on the expression of CLA by human antigen-specific CD8(+) T cells. Peripheral blood mononuclear cells (PBMC) were isolated from 10 HLA-A*0201-positive healthy individuals. Using HLA-peptide tetrameric complexes refolded with immunodominant peptides from Epstein-Barr virus (EBV), cytomegalovirus (CMV) and influenza A virus, we investigated the temporal associations of CLA expression by viral-specific CD8(+) T cells following stimulation with antigen. Ex vivo influenza matrix-specific CD8(+) T cells expressed significantly (P < 0.05) greater levels of CLA than EBV BMLF1 and CMV pp65-specific CD8(+) T cells (mean 9.7% influenza matrix versus 1.4% BMLF1 versus 1.1% pp65) and these differences were sustained on culture. However, regardless of viral specificity, interleukin (IL)-12 and IL-4 induced significant (P < 0.05) dose-dependent up-regulation and down-regulation of CLA expression, respectively, with IL-4 showing a dominant negative effect. In many cases, IL-4 resulted in complete abrogation of detectable CLA expression by the viral-specific CD8(+) T cells. Overall these data demonstrate that CLA expression by human viral-specific CD8(+) T cells is highly dynamic and that IL-4 causes significant down-regulation. Disorders associated with a type 2 cytokine shift may reduce the efficiency of skin homing by viral-specific CD8(+) T cells. Furthermore, the ability to modify the local and systemic microenvironment may offer novel therapeutic strategies that influence tissue-specific T cell homing.

Inducing P-selectin ligand formation in CD8 T cells: IL-2 and IL-12 are active in vitro but not required in vivo

In vitro studies have demonstrated that IL-2 and IL-12 can support formation of P-selectin ligands (P-SelL) in activated T cells, ligands that are variably required for efficient lymphocyte recruitment to sites of inflammation. To ascertain whether these cytokines were required for P-SelL formation in vivo, TCR transgenic CD8 T cells specific for male Ag (HY) were transferred into male mice under conditions in which either IL-2 and/or IL-15 or IL-12Rp40 were absent. P-SelL formation at day 2 was unperturbed in HY-TCR IL-2(null) CD8 T cells responding in doubly deficient IL-2(null)IL-12(null) or IL-2(null)IL-15(null) male recipients. HY-specific CD8 T cell proliferative responses detected in both spleen and peritoneum occurred vigorously, but only splenic CD8 T cells up-regulated P-SelL, demonstrating that in vivo induction of P-SelL is an active, nonprogrammed event following T cell activation and that despite the efficacy of IL-2 and IL-12 in supporting P-SelL formation in vitro, these cytokines appear to be dispensable for this purpose in vivo.

Dendritic cells govern induction and reprogramming of polarized tissue-selective homing receptor patterns of T cells: important roles for soluble factors and tissue microenvironments

Tissue-selective homing is established during naive T cell activation by the tissue microenvironment and tissue-specific dendritic cells (DC). The factors driving induction and maintenance of T cell homing patterns are still largely unknown. Here we show that soluble factors produced during the interaction of T cells with CD11c(+) DC isolated from skin- or small intestine-associated tissues differentially modulate expression of the corresponding tissue-selective homing receptors (E-selectin ligands and alpha4beta7 integrin/CCR9, respectively) on murine CD8(+) T cells. Injection of tissue-specific DC via different routes induces T cells with homing receptors characteristic of the corresponding local tissue microenvironment, independent of the origin of the DC. These data indicate an important role for signals delivered in trans. Moreover, DC can reprogram the homing receptor expression on T cells previously polarized in vitro for homing to skin or small intestine. Importantly, skin-homing memory T cells stimulated directly ex vivo can also be reprogrammed by intestinal DC to a gut-homing phenotype. Our results show that tissue-selective homing receptor expression on effector and memory T cells is governed by inductive as well as suppressive signals from both DC and tissue microenvironments.

Enforced fucosylation of neonatal CD34+ cells generates selectin ligands that enhance the initial interactions with microvessels but not homing to bone marrow

Hematopoietic progenitor/stem cell homing to the bone marrow requires the concerted action of several adhesion molecules. Endothelial P- and E-selectins play an important role in this process, but their ligands on a large subset of neonate-derived human CD34+ cells are absent, leading to a reduced ability to interact with the bone marrow (BM) microvasculature. We report here that this deficiency results from reduced α1,3-fucosyltransferase (FucT) expression and activity in these CD34+ cells. Incubation of CD34+ cells with recombinant human FucTVI rapidly corrected the deficiency in nonbinding CD34+ cells and further increased the density of ligands for both P- and E-selectins on all cord blood–derived CD34+ cells. Intravital microscopy studies revealed that these FucTVI-treated CD34+ cells displayed a marked enhancement in their initial interactions with the BM microvasculature, but unexpectedly, homing into the BM was not improved by FucTVI treatment. These data indicate that, although exogenous FucT enzyme activity can rapidly modulate selectin binding avidity of cord blood CD34+ cells, further studies are needed to understand how to translate a positive effect on progenitor cell adhesion in bone marrow microvessels into one that significantly influences migration and lodgement into the parenchyma.

Expression of selectin ligands on murine effector and IL-10-producing CD4+ T cells from non-infected and infected tissues

Endothelial selectins are crucial for the recruitment of leukocytes into sites of inflammation. On T cells, ligands for selectins become induced upon differentiation into the effector/memory stage. Initial in vitro studies suggested a correlation between the Th1 phenotype and ligand expression, but whether this also holds true in vivo remained uncertain. We here analyzed selectin ligands on CD4+ T cells producing IFN-gamma, IL-4 or IL-10, prototypic cytokines of the Th1, Th2 and Tr1 subset, respectively. We analyzed mice infected with influenza virus, the bacterium Listeria, and the parasites Toxoplasma (all Th1 models) or Nippostrongylus (Th2 model). A link between the Th1 phenotype and ligand expression was not found in vivo. Surprisingly, the potentially regulatory IL-10-producing T cells displayed the highest frequency of ligand-positive cells in general. Within the inflamed tissues, the frequencies of P-selectin-binding cells increased in the dominant subset, either Th1 or Th2. Up-regulation was also found for E-selectin ligands during influenza, but not Nippostrongylus infection. In conclusion, conditions driving T cell polarization into either Th1 or Th2 in vivo do not affect the expression of selectin ligands, but acquisition of P-selectin binding and hence migration into inflamed tissues is boosted by an inflammatory milieu.

H-Ras and phosphoinositide 3-kinase cooperate to induce alpha(1,3)-fucosyltransferase VII expression in Jurkat T cells

The alpha(1,3)-fucosyltransferase FucT-VII is essential for the biosynthesis of selectin ligands, but the signaling pathways mediating FucT-VII induction in T cells and other lymphocytes are poorly understood. We have shown previously that sustained activation of Ras in Jurkat T cells induces FucT-VII transcription, which requires the Raf-MEK-ERK pathway. In this study we report that FucT-VII induction is specific to the H-Ras isoform. Jurkat T cells retrovirally transduced with constitutively active H-Ras but not N- or K-Ras up-regulated expression of FucT-VII. Pharmacological inhibition studies also revealed that phosphoinositide 3-kinase (PI3K) activity is required for H-Ras-mediated FucT-VII induction. However, the ability of H-Ras to selectively induce FucT-VII is not a function of the inability of the N- or K-Ras isoforms to activate Raf or PI3K pathways. The use of effector-loop domain mutants of H-Ras, which are impaired for their ability to interact selectively with individual effectors alone or in combination with active Raf, indicated that induction of FucT-VII requires the concomitant activation of at least three signaling pathways. These studies show that H-Ras mediates FucT-VII induction in Jurkat T cells via the activation of the Raf, PI3K, and a distinct, H-Ras-specific effector signaling pathway.

Inhibition of fucosyltransferase VII by gallic acid and its derivatives

Gallic acid (GA) and several gallate derivatives were identified as inhibitors of fucosyltransferase VII (FucT VII). The inhibition by GA and (-)-epigallocatechin gallate (EGCG) is time-dependent and irreversible. GA and EGCG showed inhibition with IC(50) of 60 and 700 nM, respectively, after pre-incubation with FucT VII in the presence of MnCl(2). Absence of MnCl(2) results in significantly weaker inhibition. Complexation of Mn(2+) with GA, EGCG, and gallate esters was observed. Such complexation, however, is not rate-limiting for the inhibition of FucT VII. Therefore, time-dependent inhibition of fucosyltransferases by GA and EGCG is likely due to the slow inactivation by the inhibitors or Mn-inhibitor complex. Although Mg(2+) or Ca(2+) can replace Mn(2+) for FucT VII activation, none forms a complex with GA or EGCG and hence results in weaker inhibition of FucT VII. GA and EGCG also inhibit FucT IV and alpha2,3-(N)-sialyltransferase in the low micromolar range. The structure-function divergence could be observed, as EGCG, but not GA or gallate esters, inhibits Zn(2+) containing metalloproteases such as TNFalpha convertase, matrix metalloproteases 2 and 7.

Dendritic cell immunization route determines CD8+ T cell trafficking to inflamed skin: role for tissue microenvironment and dendritic cells in establishment of T cell-homing subsets

The effector/memory T cell pool branches in homing subsets selectively trafficking to organs such as gut or skin. Little is known about the critical factors in the generation of skin-homing CD8+ T cells, although they are crucial effectors in skin-restricted immune responses such as contact hypersensitivity and melanoma defense. In this study, we show that intracutaneous, but not i.v. injection of bone marrow-derived dendritic cells induced skin-homing CD8+ T cells with up-regulated E-selectin ligand expression and effector function in contact hypersensitivity. The skin-homing potential and E-selectin ligand expression remained stable in memory phase without further Ag contact. In contrast, i.p. injection induced T cells expressing the gut-homing integrin alpha(4)beta(7). Although differential expression of these adhesion molecules was strictly associated with the immunization route, the postulated skin-homing marker CCR4 was transiently up-regulated in all conditions. Interestingly, dendritic cells from different tissues effectively induced the corresponding homing markers on T cells in vitro. Our results suggest a crucial role for the tissue microenvironment and dendritic cells in the instruction of T cells for tissue-selective homing and demonstrate that Langerhans cells are specialized to target T cells to inflamed skin.

Induction of FucT-VII by the Ras/MAP kinase cascade in Jurkat T cells

Induction of the alpha1,3-fucosyltransferase FucT-VII in T lymphocytes is crucial for selectin ligand formation, but the signaling and transcriptional pathways that govern FucT-VII expression are unknown. Here, using a novel, highly phorbol myristate acetate (PMA)-responsive variant of the Jurkat T-cell line, we identify Ras and downstream mitogen-activated protein (MAP) kinase pathways as essential mediators of FucT-VII gene expression. PMA induced FucT-VII in only a subset of treated cells, similar to expression of FucT-VII in normal activated CD4 T cells. Introduction of constitutively active Ras or Raf by recombinant retroviruses induced FucT-VII expression only in that subset of cells expressing the highest levels of Ras, suggesting that induction of FucT-VII required a critical threshhold of Ras signaling. Both PMA treatment and introduction of active Ras led to rolling on E-selectin. Pharmacologic inhibition studies confirmed the involvement of the classic Ras-Raf-MEK-extracellular signal-regulated kinase (Ras-Raf-MEK-ERK) pathway in FucT-VII induction by PMA, Ras, and Raf. These studies also revealed a second, Ras-induced, Raf-1-independent pathway that participated in induction of FucT-VII. Strong activation of Ras represents a major pathway for induction of FucT-VII gene expression in T cells.

Phosphorylation of Nrf2 at Ser40 by protein kinase C in response to antioxidants leads to the release of Nrf2 from INrf2, but is not required for Nrf2 stabilization/accumulation in the nucleus and transcriptional activation of antioxidant response element-mediated NAD(P)H:quinone oxidoreductase-1 gene expression

The antioxidant response element (ARE) and transcription factor Nrf2 regulate basal expression and antioxidant induction of NAD(P)H:quinone oxidoreductase-1 (NQO1) and other detoxifying genes. Under normal conditions, Nrf2 is targeted for proteasomal degradation by INrf2. Oxidative stress causes release of Nrf2 from INrf2. Nrf2 translocates to the nucleus, binds to the ARE, and activates gene expression. In this study, we demonstrate that protein kinase C (PKC) plays a significant role in the regulation of ARE-mediated NQO1 gene expression and induction in response to t-butylhydroquinone. Treatment of HepG2 cells with the PKC inhibitors staurosporine and calphostin C repressed ARE-mediated induction of a luciferase reporter as well as that of the endogenous NQO1 gene. Similar experiments with inhibitors of MEK/ERK, p38, phosphatidylinositol 3-kinase, and tyrosine kinases failed to repress ARE-mediated gene expression. The PKC inhibitor staurosporine blocked the nuclear translocation of Nrf2, suggesting that Nrf2 might be the target for PKC regulation. A Prosite search revealed the presence of seven putative PKC sites in mouse Nrf2. The PKC site at Ser40 is conserved among species and lies in the Neh2 domain, which interacts with INrf2. We demonstrate that phosphorylation of Ser40 is necessary for Nrf2 release from INrf2, but is not required for Nrf2 stabilization/accumulation in the nucleus and transcriptional activation of ARE-mediated NQO1 gene expression. A peptide that competes with endogenous Nrf2 for INrf2 binding was able to induce ARE activity more effectively than t-butylhydroquinone, and Nrf2 that accumulated in the nucleus as a result was not phosphorylated.

p38 MAP kinase modulates Smad-dependent changes in human prostate cell adhesion

Transforming growth factor beta (TGFbeta) regulates cell adhesion, proliferation, and differentiation in a variety of cells. Smad proteins are receptor-activated transcription factors that translocate to the nucleus in response to TGFbeta. We demonstrate here that TGFbeta increases cell adhesion in metastatic PC3-M prostate cancer cells. TGFbeta treatment of PC3-M cells leads to nuclear translocation of R-Smad proteins. We show that Smad proteins are necessary, but not sufficient, for TGFbeta-mediated cell adhesion. After showing that TGFbeta upregulated p38 MAP kinase activity in PC3-M cells, we show that inhibition of p38 MAP kinase partially blocked TGFbeta-mediated increase in cell adhesion, as well as nuclear translocation of Smad3. Finally, we show that Smad3 is phosphorylated by p38 MAP kinase in vitro. These findings implicate crosstalk between the MAP kinase and Smad signaling pathways in TGFbeta's regulation of cell adhesion in human prostate cells. This represents a mechanism by which the pleiotropic effects of TGFbeta may be channeled to modulate cell adhesion.

Interleukin-12 alone can not enhance the expression of the cutaneous lymphocyte associated antigen (CLA) by superantigen-stimulated T lymphocytes

It has been reported that bacterial superantigens induce interleukin (IL)-12 dependent expression of the cutaneous lymphocyte associated antigen (CLA) and that this may be relevant to the association between certain skin diseases and infections including psoriasis and streptococcal tonsillitis. We have confirmed that the streptococcal pyrogenic superantigen C (SpeC) increases CLA expression by both CD4+ and CD8+ T cells when PBMCs are incubated in medium enriched with fetal calf serum (FCS). However, such an increase could not be induced in medium enriched with human serum (HS) even when recombinant IL-12 was added to the PBMCs cultures. Strikingly, CD4+ T cells incubated with SpeC in HS showed a marked reduction in CLA expression, which was not due to apoptosis. In contrast, SpeC did induce T cell proliferation and expression of CD25, CD54 and CD103 in the presence of HS indicating that the absence of SpeC induced CLA expression in HS was not due to SpeC inhibitors. Although addition of low amounts of lipopolysaccharide endotoxin (LPS) caused a highly significant increase in CLA expression in the absence of SpeC in cultures enriched with HS, a combination of LPS and SpeC did not increase CLA expression beyond that induced by LPS alone. The superantigen-induced CLA expression in FCS was partially inhibited by anti-IL-12 but not by anti-IL-18 or antibodies to transforming growth factor (TGF)-beta. It is concluded that IL-12 alone can not increase CLA expression but requires the help of other factor(s) present in FCS but not in HS. Although LPS can induce CLA expression it does not seem to be the factor that interacts with IL-12 to induce superantigen-mediated CLA expression in cultures enriched with FCS.

Transactivation of the fucosyltransferase VII gene by human T-cell leukemia virus type 1 Tax through a variant cAMP-responsive element

Human T-cell leukemic virus type 1 (HTLV-1)-infected T cells express the fucosyltransferase (Fuc-T) VII gene involved in the biosynthesis of the leukocyte sialyl Lewis X, which may be related to tissue infiltration in patients with malignant adult T-cell leukemia. HTLV-1 induces Fuc-T VII transcription through the viral transactivator Tax, although the underlying molecular mechanism remains unknown. In the present study, we analyzed the role of the cis-activating element in Tax activation using reporter constructs bearing the 5'-regulatory region of Fuc-T VII in Jurkat T cells. A sequence (GGCTGTGGGGGCGTCATATTGCCCTGG) covering a half-palindromic cyclic adenosine monophosphate (cAMP)-responsive element (CRE) was found to be required for Tax activation of the Fuc-T VII promoter. We further demonstrated that transcription factors of the CRE-binding protein (CREB)/activating transcription factor (ATF) family bind to this CRE-like sequence and that Tax binds in association with CREB and the coactivator CREB-binding protein (CBP) in Jurkat T cells. This element, containing the G+C-rich flanking sequences, is homologous to the Tax-responsive viral CREs in the HTLV-1 long terminal repeat (LTR)-promoter. Furthermore, CREM alpha, an isoform of CREB deficient in the glutamine-rich domains, was found to activate the Fuc-T VII promoter in a phosphorylation-independent manner, similar to the viral CRE in HTLV-1 LTR but in contrast to the phosphorylation-dependent activation of the cellular CREs by Tax. These findings indicate that the Fuc-T VII promoter is transactivated by Tax in concert with CBP through a CRE-like sequence in a manner similar to that of viral CRE in HTLV-1 LTR.

Induction of neuron-specific glycosylation by Tollo/Toll-8, a Drosophila Toll-like receptor expressed in non-neural cells

Specific glycan expression is an essential characteristic of developing tissues. Our molecular characterization of a mutation that abolishes neural-specific glycosylation in the Drosophila embryo demonstrates that cellular interactions influence glycan expression. The HRP epitope is an N-linked oligosaccharide expressed on a subset of neuronal glycoproteins. Embryos homozygous for the TM3 balancer chromosome lack neural HRP-epitope expression. Genetic and molecular mapping of the relevant locus reveals that Tollo/Toll-8, a member of the Toll-like receptor family, is altered on the TM3 chromosome. In wild-type embryos, Tollo/Toll-8 is expressed by ectodermal cells that surround differentiating neurons and precedes HRP-epitope appearance. Re-introduction of Tollo/Toll-8 into null embryos rescues neural-specific glycan expression. Thus, loss of an ectodermal cell surface protein alters glycosylation in juxtaposed differentiating neurons. The portfolio of expressed oligosaccharides in a cell reflects its identity and also influences its interactions with other cells and with pathogens. Therefore, the ability to induce specific glycan expression complements the previously identified developmental and innate immune functions of Toll-like receptors.

Sweet 'n' sour: the impact of differential glycosylation on T cell responses

The fate and functional activity of T lymphocytes depend largely on the precise timing of gene expression and protein production. However, it is clear that post-translational modification of proteins affects their functional properties. Although modifications such as phosphorylation have been intensely studied by immunologists, less attention has been paid to the impact that changes in glycosylation have on protein function. However, there is considerable evidence that glycosylation plays a key role in immune regulation. We will focus here on examples in which differential glycosylation affects the development, survival or reactivity of T cells.

Glycosylation in the control of selectin counter-receptor structure and function

Leukocyte trafficking is characterized by sequential cell adhesion and activation events that deliver specific leukocyte subsets to distinct extravascular locations under different pathophysiological circumstances. E-, P- and/or L-selectin-dependent leukocyte-endothelial cell adhesive interactions contribute essentially to this process. Selectin counter-receptor activity on leukocyte and high endothelial venules is borne by specific glycoproteins whose ability to support adhesion requires specific post-translational modifications. These modifications are typified by serine/threonine-linked oligosaccharides capped with the sialyl Lewis x moiety, an alpha2-3sialylated, alpha1-3ucosylated tetrasaccharide synthesized by specific glycosyltransferases. Recent advances in glycan structure analysis and in characterizing mice with targeted deletions of glycosyltransferase and sulfotransferase genes discloses an essential role for 6-O GlcNAc sulfate modification of the sialyl Lewis x tetrasaccharide in L-selectin counter-receptor activity. Related studies identify novel extended Core 1 type O-glycans bearing the 6-sulfosialyl Lewis x moiety, define the molecular nature of the MECA-79 epitope, and disclose a requirement for the alpha1-3fucosyltransferases FucT-IV and FucT-VII in the elaboration of L-selectin counter-receptor activities. Parallel studies also demonstrate that these 2 fucosyltransferases, a core 2 GlcNAc transferase, and core 2-type sialyl Lewis x determinants make essential contributions to leukocyte P-selectin counter-receptor activity, and figure prominently in the control of leukocyte E-selectin counter-receptor activity.