Cellular concentrations of plasmalogen species containing a polyunsaturated fatty acid significantly increase under hypoxia in human colorectal cancer, Caco2 cells.

Plasmalogen localized in the raft of mammalian cell membranes plays a role in the storage of polyunsaturated fatty acid (PUFA), and exists to a higher extent in malignant cells that survive, and even grow in hypoxic conditions. The biosynthesis of plasmalogen in mammalian cells has been reported to depend on aerobic conditions. Using liquid chromatography-tandem mass spectrometry, we found that the intracellular concentration of plasmalogen species containing a PUFA at the sn-2-position did not change for two days from the start of hypoxic culture in human colorectal cancer-derived Caco2 cells. At the third day of hypoxia, Caco2 cells showed the average increase rate of 2.6 times in ethanolamine plasmalogen and 2.9 times in choline plasmalogen depending on the molecular species compared with those in the second day of hypoxia. In normoxic culture, there was little quantitative change in any species of both ethanolamine and choline plasmalogens for three days. The up-regulations of mRNA of Ca2+-independent phospholipase A2ß and cytoplasmic phospholipase A2γ as well as the down-regulation of lysoplasmalogenase observed in hypoxia were suggested to be responsible for the increase of plasmalogen in Caco2 cells under hypoxia.

Distinct substrate specificities of human GlcNAc-6-sulfotransferases revealed by mass spectrometry-based sulfoglycomic analysis.

Sulfated glycans are known to be involved in several glycan-mediated cell adhesion and recognition pathways. Our mRNA transcript analyses on the genes involved in synthesizing GlcNAc-6-O-sulfated glycans in human colon cancer tissues indicated that GlcNAc6ST-2 (CHST4) is preferentially expressed in cancer cells compared with nonmalignant epithelial cells among the three known major GlcNAc-6-O-sulfotransferases. On the contrary, GlcNAc6ST-3 (CHST5) was only expressed in nonmalignant epithelial cells, whereas GlcNAc6ST-1 (CHST2) was expressed equally in both cancerous and nonmalignant epithelial cells. These results suggest that 6-O-sulfated glycans that are synthesized only by GlcNAc6ST-2 may be highly colon cancer-specific, as supported by immunohistochemical staining of cancer cells using the MECA-79 antibody known to be relatively specific to the enzymatic reaction products of GlcNAc6ST-2. By more precise MS-based sulfoglycomic analyses, we sought to further infer the substrate specificities of GlcNAc6STs via a definitive mapping of various sulfo-glycotopes and O-glycan structures expressed in response to overexpression of transfected GlcNAc6STs in the SW480 colon cancer cell line. By detailed MS/MS sequencing, GlcNAc6ST-3 was shown to preferentially add sulfate onto core 2-based O-glycan structures, but it does not act on extended core 1 structures, whereas GlcNAc6ST-1 prefers core 2-based O-glycans to extended core 1 structures. In contrast, GlcNAc6ST-2 could efficiently add sulfate onto both extended core 1- and core 2-based O-glycans, leading to the production of unique sulfated extended core 1 structures such as R-GlcNAc(6-SO3-)ß1-3Galß1-4GlcNAc(6-SO3-)ß1-3Galß1-3GalNAcα, which are good candidates to be targeted as cancer-specific glycans.

Inhibition of Endothelial SCUBE2 (Signal Peptide-CUB-EGF Domain-Containing Protein 2), a Novel VEGFR2 (Vascular Endothelial Growth Factor Receptor 2) Coreceptor, Suppresses Tumor Angiogenesis.

OBJECTIVE: SCUBE2 (signal peptide-CUB-EGF domain-containing protein 2), expressed on the endothelial cell surface, functions as a novel coreceptor for VEGFR2 (vascular endothelial growth factor receptor 2) and enhances VEGF-induced signaling in adult angiogenesis. However, whether SCUBE2 plays a role in pathological angiogenesis and whether anti-SCUBE2 antibody is an effective strategy for blocking tumor angiogenesis remain unknown. The aim of this study was to investigate the pathological role and targeting therapy of SCUBE2 in tumor vasculature. APPROACH AND RESULTS: Immunohistochemistry revealed that SCUBE2 is highly expressed in endothelial cells of numerous carcinomas. Genetic endothelial cell knockout of SCUBE2 and pharmacological inhibition with the anti-SCUBE2 monoclonal antibody SP.B1 significantly reduced xenograft tumor growth, decreased tumor vascular density, increased apoptosis, and decreased the proliferation of tumor cells. Mechanistic studies revealed that SP.B1 binds to SCUBE2 and induces its internalization for lysosomal degradation, thereby reducing its cell surface level and inhibiting the binding of and downstream signaling of VEGF, including VEGFR2 phosphorylation and AKT/MAPK (mitogen-activated protein kinase) activation. Importantly, dual combination therapy with anti-SCUBE2 monoclonal antibody and anti-VEGF antibody or chemotherapy was more effective than single-agent therapy. CONCLUSIONS: Endothelial cell surface SCUBE2 is a VEGFR2 coreceptor essential for pathological tumor angiogenesis, and anti-SCUBE2 monoclonal antibody acting as an internalization inducer may provide a potent combination therapy for tumor angiogenesis.

Roles of p53 Family Structure and Function in Non-Canonical Response Element Binding and Activation.

The p53 canonical consensus sequence is a 10-bp repeat of PuPuPuC(A/T)(A/T)GPyPyPy, separated by a spacer with up to 13 bases. C(A/T)(A/T)G is the core sequence and purine (Pu) and pyrimidine (Py) bases comprise the flanking sequence. However, in the p53 noncanonical sequences, there are many variations, such as length of consensus sequence, variance of core sequence or flanking sequence, and variance in number of bases making up the spacer or AT gap composition. In comparison to p53, the p53 family members p63 and p73 have been found to have more tolerance to bind and activate several of these noncanonical sequences. The p53 protein forms monomers, dimers, and tetramers, and its nonspecific binding domain is well-defined; however, those for p63 or p73 are still not fully understood. Study of p63 and p73 structure to determine the monomers, dimers or tetramers to bind and regulate noncanonical sequence is a new challenge which is crucial to obtaining a complete picture of structure and function in order to understand how p63 and p73 regulate genes differently from p53. In this review, we will summarize the rules of p53 family non-canonical sequences, especially focusing on the structure of p53 family members in the regulation of specific target genes. In addition, we will compare different software programs for prediction of p53 family responsive elements containing parameters with canonical or non-canonical sequences.

Concerted mass spectrometry-based glycomic approach for precision mapping of sulfo sialylated N-glycans on human peripheral blood mononuclear cells and lymphocytes.

Despite well-recognized biological importance, mass spectrometry (MS)-based glycomic identification of sulfo-, sialylated terminal glyco-epitopes on the N-glycans of various immune cell types remains technically challenging and rarely reported. Previous studies with monoclonal antibody have implicated a regulated expression of 6-sulfo-α2-6-sialyl LacNAc on B cells in peripheral lymph nodes and the circulating peripheral blood lymphocytes but its occurrence on leukemia cells or lymphomas have not been critically addressed. In this study, we have extended our previously developed MS-based sulfoglycomic platform by incorporating additional complementary analytical approaches in order to achieve a high sensitivity mapping and relative quantification of the detected sulfated glycotopes down to the level of defining their sialyl linkages. We showed that discovery mode sulfoglycomics and precise location of sulfate were best achieved by multimode MS analyses of fractionated, permethylated sulfated N-glycans. On the other hand, the relative degree of sulfation on individual N-glycans could be more efficiently inferred from the respective extracted ion chromatograms of native, non-sulfated and sulfated target N-glycans in single LC-MS/MS runs. The GlcNAc-6-O-sulfated α2-6-sialyl LacNAc, which constitutes the higher affinity ligand for the human inhibitory co-receptor of B cells, CD22, was found to be commonly carried on a range of complex type N-glycans from human CD19+ and CD4+ lymphocytes. We further showed that its occurrence on the most abundant α2-6-disialylated biantennary structure from the peripheral blood mononuclear cells of patients diagnosed as B-cell chronic lymphocytic leukemia varied within ±2-fold abundance from the mean value determined for isolated CD19+ lymphocytes and cultured B-CLL cells.

Endothelial SCUBE2 Interacts With VEGFR2 and Regulates VEGF-Induced Angiogenesis.

OBJECTIVE: Vascular endothelial growth factor (VEGF), a major mediator of angiogenesis, exerts its proangiogenic action by binding to VEGFR2 (VEGF receptor 2), the activity of which is further modulated by VEGFR2 coreceptors such as neuropilins. However, whether VEGFR2 is regulated by additional coreceptors is not clear. To investigate whether SCUBE2 (signal peptide-CUB-EGF domain-containing protein 2), a peripheral membrane protein expressed in vascular endothelial cells (ECs) known to bind other signaling receptors, functions as a VEGFR2 coreceptor and to verify the role of SCUBE2 in the VEGF-induced angiogenesis. APPROACH AND RESULTS: SCUBE2 lentiviral overexpression in human ECs increased and short hairpin RNA knockdown inhibited VEGF-induced EC growth and capillary-like network formation on Matrigel. Like VEGF, endothelial SCUBE2 was upregulated by hypoxia-inducible factor-1α at both mRNA and protein levels. EC-specific Scube2 knockout mice were not defective in vascular development but showed impaired VEGF-induced neovascularization in implanted Matrigel plugs and recovery of blood flow after hind-limb ischemia. Coimmunoprecipitation and ligand-binding assays showed that SCUBE2 forms a complex with VEGF and VEGFR2, thus acting as a coreceptor to facilitate VEGF binding and augment VEGFR2 signal activity. SCUBE2 knockdown or genetic knockout suppressed and its overexpression promoted the VEGF-induced activation of downstream proangiogenic and proliferating signals, including VEGFR2 phosphorylation and mitogen-activated protein kinase or AKT activation. CONCLUSIONS: Endothelial SCUBE2 may be a novel coreceptor for VEGFR2 and potentiate VEGF-induced signaling in adult angiogenesis.

Sialyl Lewis x (CD15s) identifies highly differentiated and most suppressive FOXP3high regulatory T cells in humans.

CD4(+) regulatory T (Treg) cells expressing CD25 and the transcription factor forkhead box P3 (FOXP3) are indispensable for immunological self-tolerance and homeostasis. FOXP3(+)CD25(+)CD4(+) T cells in humans, however, are heterogeneous in function and differentiation status, including suppressive or nonsuppressive cells as well as resting or activated Treg cells. We have searched for cell surface markers specific for suppression-competent Treg cells by using a panel of currently available monoclonal antibodies reactive with human T cells. We found that CD15s (sialyl Lewis x) was highly specific for activated, terminally differentiated, and most suppressive FOXP3(high) effector Treg (eTreg) cells and able to differentiate them in various clinical settings from nonsuppressive FOXP3(+) T cells secreting inflammatory cytokines. For example, CD15s(+)FOXP3(+) eTreg cells were increased in sarcoidosis, whereas it was nonsuppressive CD15s(-)FOXP3(+) T cells that were expanded in lupus flares. FOXP3(+) cells induced from conventional CD4(+) T cells by T-cell receptor stimulation hardly expressed CD15s. CD15s(+)CD4(+) T-cell depletion was sufficient to evoke and enhance in vitro immune responses against tumor or viral antigens. Collectively, we have identified CD15s as a biomarker instrumental in both phenotypic and functional analysis of FOXP3(+)CD4(+) T-cell subpopulations in health and disease. It allows specific targeting of eTreg cells, rather than whole FOXP3(+)CD4(+) T cells, in controlling immune responses.

Anaplasma marginale Outer Membrane Protein A Is an Adhesin That Recognizes Sialylated and Fucosylated Glycans and Functionally Depends on an Essential Binding Domain.

Anaplasma marginale causes bovine anaplasmosis, a debilitating and potentially fatal tick-borne infection of cattle. Because A. marginale is an obligate intracellular organism, its adhesins that mediate entry into host cells are essential for survival. Here, we demonstrate that A. marginale outer membrane protein A (AmOmpA; AM854) contributes to the invasion of mammalian and tick host cells. AmOmpA exhibits predicted structural homology to OmpA of A. phagocytophilum (ApOmpA), an adhesin that uses key lysine and glycine residues to interact with α2,3-sialylated and α1,3-fucosylated glycan receptors, including 6-sulfo-sialyl Lewis x (6-sulfo-sLex). Antisera against AmOmpA or its predicted binding domain inhibits A. marginale infection of host cells. Residues G55 and K58 are contributory, and K59 is essential for recombinant AmOmpA to bind to host cells. Enzymatic removal of α2,3-sialic acid and α1,3-fucose residues from host cell surfaces makes them less supportive of AmOmpA binding. AmOmpA is both an adhesin and an invasin, as coating inert beads with it confers adhesiveness and invasiveness. Recombinant forms of AmOmpA and ApOmpA competitively antagonize A. marginale infection of host cells, but a monoclonal antibody against 6-sulfo-sLex fails to inhibit AmOmpA adhesion and A. marginale infection. Thus, the two OmpA proteins bind related but structurally distinct receptors. This study provides a detailed understanding of AmOmpA function, identifies its essential residues that can be targeted by blocking antibody to reduce infection, and determines that it binds to one or more α2,3-sialylated and α1,3-fucosylated glycan receptors that are unique from those targeted by ApOmpA.

FUT8 promotes breast cancer cell invasiveness by remodeling TGF-ß receptor core fucosylation.

BACKGROUND: Core fucosylation (addition of fucose in α-1,6-linkage to core N-acetylglucosamine of N-glycans) catalyzed by fucosyltransferase 8 (FUT8) is critical for signaling receptors involved in many physiological and pathological processes such as cell growth, adhesion, and tumor metastasis. Transforming growth factor-ß (TGF-ß)-induced epithelial-mesenchymal transition (EMT) regulates the invasion and metastasis of breast tumors. However, whether receptor core fucosylation affects TGF-ß signaling during breast cancer progression remains largely unknown. METHOD: In this study, gene expression profiling and western blot were used to validate the EMT-associated expression of FUT8. Lentivirus-mediated gain-of-function study, short hairpin RNA (shRNA) or CRISPR/Cas9-mediated loss-of-function studies and pharmacological inhibition of FUT8 were used to elucidate the molecular function of FUT8 during TGF-ß-induced EMT in breast carcinoma cells. In addition, lectin blot, luciferase assay, and in vitro ligand binding assay were employed to demonstrate the involvement of FUT8 in the TGF-ß1 signaling pathway. The role of FUT8 in breast cancer migration, invasion, and metastasis was confirmed using an in vitro transwell assay and mammary fat pad xenograft in vivo tumor model. RESULTS: Gene expression profiling analysis revealed that FUT8 is upregulated in TGF-ß-induced EMT; the process was associated with the migratory and invasive abilities of several breast carcinoma cell lines. Gain-of-function and loss-of-function studies demonstrated that FUT8 overexpression stimulated the EMT process, whereas FUT8 knockdown suppressed the invasiveness of highly aggressive breast carcinoma cells. Furthermore, TGF-ß receptor complexes might be core fucosylated by FUT8 to facilitate TGF-ß binding and enhance downstream signaling. Importantly, FUT8 inhibition suppressed the invasive ability of highly metastatic breast cancer cells and impaired their lung metastasis. CONCLUSIONS: Our results reveal a positive feedback mechanism of FUT8-mediated receptor core fucosylation that promotes TGF-ß signaling and EMT, thus stimulating breast cancer cell invasion and metastasis.

Unmasking of CD22 Co-receptor on Germinal Center B-cells Occurs by Alternative Mechanisms in Mouse and Man.

CD22 is an inhibitory B-cell co-receptor whose function is modulated by sialic acid (Sia)-bearing glycan ligands. Glycan remodeling in the germinal center (GC) alters CD22 ligands, with as yet no ascribed biological consequence. Here, we show in both mice and humans that loss of high affinity ligands on GC B-cells unmasks the binding site of CD22 relative to naive and memory B-cells, promoting recognition of trans ligands. The conserved modulation of CD22 ligands on GC B-cells is striking because high affinity glycan ligands of CD22 are species-specific. In both species, the high affinity ligand is based on the sequence Siaα2-6Galß1-4GlcNAc, which terminates N-glycans. The human ligand has N-acetylneuraminic acid (Neu5Ac) as the sialic acid, and the high affinity ligand on naive B-cells contains 6-O-sulfate on the GlcNAc. On human GC B-cells, this sulfate modification is lost, giving rise to lower affinity CD22 ligands. Ligands of CD22 on naive murine B-cells do not contain the 6-O-sulfate modification. Instead, the high affinity ligand for mouse CD22 has N-glycolylneuraminic acid (Neu5Gc) as the sialic acid, which is replaced on GC B-cells with Neu5Ac. Human naive and memory B-cells express sulfated glycans as high affinity CD22 ligands, which are lost on GC B-cells. In mice, Neu5Gc-containing glycans serve as high affinity CD22 ligands that are replaced by Neu5Ac-containing glycans on GC B-cells. Our results demonstrate that loss of high affinity CD22 ligands on GC B-cells occurs in both mice and humans through alternative mechanisms, unmasking CD22 relative to naive and memory B-cells.

Major glycan structure underlying expression of the Lewis X epitope in the developing brain is O-mannose-linked glycans on phosphacan/RPTPß.

Glycosylation is a major protein modification. Although proteins are glycosylated/further modulated by several glycosyltransferases during trafficking from the endoplasmic reticulum to the Golgi apparatus, a certain glycan epitope has only been detected on a limited number of proteins. Of these glycan epitopes, Lewis X is highly expressed in the early stage of a developing brain and plays important roles in cell-cell interaction. The Lewis X epitope is comprised of a trisaccharide (Galß1-4 (Fucα1-3) GlcNAc), and a key enzyme for the expression of this epitope is α1,3-fucosyltransferase 9. However, the scaffolding glycan structure responsible for the formation of the Lewis X epitope as well as its major carrier protein has not been fully characterized in the nervous system. Here we showed that the Lewis X epitope was mainly expressed on phosphacan/receptor protein tyrosine phosphatase ß (RPTPß) in the developing mouse brain. Expression of the Lewis X epitope was markedly reduced in ß1,4-galactosyltransferase 2 (ß4GalT2) gene-deficient mice, which indicated that ß4GalT2 is a major galactosyltransferase required for the Lewis X epitope. We also showed that the Lewis X epitope almost disappeared due to the knockout of protein O-mannose ß1,2-N-acetylglucosaminyltransferase 1, an N-acetylglucosaminyltransferase essential for the synthesis of O-mannosylated glycans, which indicated that the O-mannosylated glycan is responsible for presenting the Lewis X epitope. Since O-mannosylated glycans on phosphacan/RPTPß could also present human natural killer-1, another glycan epitope specifically expressed in the nervous system, our results revealed the importance of O-mannosylated glycan chains in the presentation of functional glycan epitopes in the brain.

Hypoxia remodels the composition of the constituent ceramide species of HexCer and Hex2Cer with phytosphingosine and hydroxy fatty acids in human colon cancer LS174T cells.

Oxygen-requiring enzymes, such as Δ4-desaturase (dihydroceramide desaturase), sphingolipid Δ4-desaturase/C-4-hydroxylase, and fatty acid 2-hydroxylase are involved in ceramide synthesis. We prepared free ceramides, sphingomyelins and glycosphingolipids (GSLs) from cancer cells cultivated under conditions of normoxia and hypoxia, and analyzed these compounds using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Human colon cancer LS174T cells were employed because these cells highly express hydroxyl fatty acids and phytosphingosine (t18:0) which are expected to be greatly influenced by changes in oxygen levels. As expected, the populations of dihydro-species of free ceramide and sphingomyelin with C16:0 non-hydroxy fatty acid were elevated, and the populations of HexCers and Hex2Cers, composed of C16:0 or C16:0 hydroxy fatty acid (C16:0h), and sphingosine (d18:1) or t18:0, were decreased under hypoxia. However, appreciable populations of HexCer and Hex2Cer species of C24:0 or C24:0h and t18:0 remained. These results suggest that the individual species of GSLs with fatty acids possessing different alkyl chain lengths, either non-hydroxy fatty acids or hydroxyl fatty acids, may be metabolized individually.

Transcription factors c-Myc and CDX2 mediate E-selectin ligand expression in colon cancer cells undergoing EGF/bFGF-induced epithelial-mesenchymal transition.

Sialyl Lewis x (sLe(x)) and sialyl Lewis a (sLe(a)) glycans are expressed on highly metastatic colon cancer cells. They promote extravasation of cancer cells and tumor angiogenesis via interacting with E-selectin on endothelial cells. Recently, epithelial-mesenchymal transition (EMT) has been noted as a critical phenotypic alteration in metastatic cancer cells. To address the association between sLe(x/a) expression and EMT, we assessed whether sLe(x/a) are highly expressed on colon cancer cells undergoing EMT. Treatment of HT29 and DLD-1 cells with EGF and/or basic FGF (bFGF) induced EMT and significantly increased sLe(x/a) expression resulting in enhanced E-selectin binding activity. The transcript levels of the glycosyltransferase genes ST3GAL1/3/4 and FUT3 were significantly elevated and that of FUT2 was significantly suppressed by the treatment. We provide evidence that ST3GAL1/3/4 and FUT3 are transcriptionally up-regulated by c-Myc with probable involvement of Ser62 phosphorylation, and that FUT2 is transcriptionally down-regulated through the attenuation of CDX2. The contribution of c-Myc and CDX2 to the sLe(x/a) induction was proved to be significant by knockdown or forced expression experiments. Interestingly, the cells undergoing EMT exhibited significantly increased VEGF secretion, which can promote tumor angiogenesis in cooperation with sLe(x/a). Finally, immunohistological study indicated high E-selectin ligand expression on cancer cells undergoing EMT in vivo, supporting their coexistence observed in vitro. These results suggest a significant link between sLe(x/a) expression and EMT in colon cancer cells and a pivotal role of c-Myc and CDX2 in regulating sLe(x/a) expression during EMT.

Individual profiles of free ceramide species and the constituent ceramide species of sphingomyelin and neutral glycosphingolipid and their alteration according to the sequential changes of environmental oxygen content in human colorectal cancer Caco-2 cells.

We previously performed a systematic analysis of free ceramide (Cers) species, the constituent ceramide species of sphingomyelins and neutral glycosphingolipids (NGSLs) using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with high-energy collision-induced dissociation. As a result, distinct species differences were found among Cers, sphingomyelins and NGSLs in the kidneys. Using this method, we investigated various sphingolipid species from human colon cancer Caco-2 cells as well as the influence of environmental oxygen on these species in detail. Unexpectedly, even in normoxia, all Cers species were composed of dihydrosphingosine (d18:0) and non-hydroxy fatty acid (NFA), and 34% of sphingomyelins were composed of dihydrosphingomyelins with NFA. In contrast, major constituent ceramide species of NGSLs were composed of the usual long-chain base of sphingosine (d18:1) and hydroxy fatty acid (HFA). When the cells were cultured under hypoxic condition for 3 days, all the Cers and nearly 80% of the sphingomyelins were dihydrosphingolipids composed of d18:0-NFAs, but a significant proportion of d18:1-HFAs still remained in the NGSLs. When the cells were transferred from conditions of hypoxia to normoxia again (reoxygenation), Cer species composed of d18:1-NFAs, which were not found in Cers under the original normoxic conditions, appeared. Such Cers were probably synthesized as precursors for the constituent ceramides of sphingomyelins and NGSLs.

Colonic epithelial cells express specific ligands for mucosal macrophage immunosuppressive receptors siglec-7 and -9.

Immune cells are known to express specific recognition molecules for cell surface glycans. However, mechanisms involved in glycan-mediated cell-cell interactions in mucosal immunity have largely been left unaccounted for. We found that several glycans preferentially expressed in nonmalignant colonic epithelial cells serve as ligands for sialic acid-binding Ig-like lectins (siglecs), the immunosuppressive carbohydrate-recognition receptors carried by immune cells. The siglec ligand glycans in normal colonic epithelial cells included disialyl Lewis(a), which was found to have binding activity to both siglec-7 and -9, and sialyl 6-sulfo Lewis(x), which exhibited significant binding to siglec-7. Expression of these siglec-7/-9 ligands was impaired upon carcinogenesis, and they were replaced by cancer-associated glycans sialyl Lewis(a) and sialyl Lewis(x), which have no siglec ligand activity. When we characterized immune cells expressing siglecs in colonic lamina propriae by flow cytometry and confocal microscopy, the majority of colonic stromal immune cells expressing siglec-7/-9 turned out to be resident macrophages characterized by low expression of CD14/CD89 and high expression of CD68/CD163. A minor subpopulation of CD8(+) T lymphocytes also expressed siglec-7/-9. Siglec-7/-9 ligation suppressed LPS-induced cyclooxygenase-2 expression and PGE(2) production by macrophages. These results suggest that normal glycans of epithelial cells exert a suppressive effect on cyclooxygenase-2 expression by resident macrophages, thus maintaining immunological homeostasis in colonic mucosal membranes. Our results also imply that loss of immunosuppressive glycans by impaired glycosylation during colonic carcinogenesis enhances inflammatory mediator production.

Induction of 6-sulfated glycans with cell adhesion activity via T-bet and GATA-3 in human helper T cells.

BACKGROUND: Cell surface 6-sulfated glycans play important roles in various immunological events through cell-to-cell interactions. The 6-sulfation process is mediated by 6-sulfotransferase family isoenzymes. We previously demonstrated that GlcNAc6ST-1, one of the isoenzyme genes, is induced by GATA-3 and NF-κB in human helper T (Th) cells. However, transcriptional regulation of HEC-GlcNAc6ST, another isoenzyme important in Th cells, remains unclear. METHODS: 5'-RACE analysis, chromatin immunoprecipitation, and reporter assays were performed to reveal transcriptional regulation of HEC-GlcNAc6ST. RNA-knockdown and forced expression experiments were performed to demonstrate the contribution of HEC-GlcNAc6ST to the 6-sulfated glycan expression. RESULTS: We identified potential binding sites of Sp1, T-bet, and GATA-3 in the HEC-GlcNAc6ST promoter. Reporter assays indicated that transfection of Sp1 enhanced the activity, whereas mithramycin A, an Sp1-specific inhibitor, repressed it. Transfection of T-bet increased the activity, which was inhibited by introducing a mutation into the potential T-bet binding site. GATA-3 alone could not elevate the activity, although co-transfection of protein kinase A, which is known to enhance IL-5 transcription in Th2 cells through phosphorylation of GATA-3, caused elevation. RNA-knockdown and forced expression of HEC-GlcNAc6ST in Jurkat cells down- and up-regulated α2,6-sialylated 6-sulfo N-acetyllactosamine, a preferential ligand for B-cell-specific CD22 antigen, respectively. From these results, we concluded that T-bet and GATA-3 as well as Sp1 control the expression of glycan with cell-adhesion activity by regulating HEC-GlcNAc6ST transcription in Th cells. GENERAL SIGNIFICANCE: These results may provide a clue to biological regulation of Th-cell interaction with selectins and other carbohydrate-recognition molecules by T-bet and GATA-3.

KSGal6ST generates galactose-6-O-sulfate in high endothelial venules but does not contribute to L-selectin-dependent lymphocyte homing.

The addition of sulfate to glycan structures can regulate their ability to serve as ligands for glycan-binding proteins. Although sulfate groups present on the monosaccharides glucosamine, uronate, N-acetylglucosamine and N-acetylgalactosamine are recognized by defined receptors that mediate important functions, the functional significance of galactose-6-O-sulfate (Gal6S) is not known. However, in vitro studies using synthetic glycans and sulfotransferase overexpression implicate Gal6S as a binding determinant for the lymphocyte homing receptor, L-selectin. Only two sulfotransferases have been shown to generate Gal6S, namely keratan sulfate galactose 6-O-sulfotransferase (KSGal6ST) and chondroitin 6-O-sulfotransferase-1 (C6ST-1). In the present study, we use mice deficient in KSGal6ST and C6ST-1 to test whether Gal6S contributes to ligand recognition by L-selectin in vivo. First, we establish that KSGal6ST is selectively expressed in high endothelial venules (HEVs) in lymph nodes and Peyer's patches. We also determine by mass spectrometry that KSGal6ST generates Gal6S on several classes of O-glycans in peripheral lymph nodes. Furthermore, KSGal6ST, but not C6ST-1, is required for the generation of the Gal6S-containing glycan, 6,6'-disulfo-3'sLN (Siaα2→3[6S]Galß1→4[6S]GlcNAc) or a closely related structure in lymph node HEVs. Nevertheless, L-selectin-dependent short-term homing of lymphocytes is normal in KSGal6ST-deficient mice, indicating that the Gal6S-containing structures we detected do not contribute to L-selectin ligand recognition in this setting. These results refine our understanding of the biological ligands for L-selectin and introduce a mouse model for investigating the functions of Gal6S in other contexts.

Hypoxia increases cellular levels of phosphatidic acid and lysophospholipids in undifferentiated Caco-2 cells.

Cancer cells are known to survive in a hypoxic microenvironment by altering their lipid metabolism as well as their energy metabolism. In this study, Caco-2 cells derived from human colon cancer, were found to have elevated intracellular levels of phosphatidic acid and its lysoform, lysophosphatidic acid (LPA), under hypoxic conditions. Our results suggested that the elevation of LPA in Caco-2 cells was mainly due to the combined increases in cellular levels of lysophosphatidylcholine and lysophosphatidylethanolamine by phospholipase A2 and subsequent hydrolysis to LPA by lysophospholipase D. We detected the Ca2+ -stimulated choline-producing activities toward exogenous lysophosphatidylcholines in whole Caco-2 cell homogenates, indicating their involvement in the LPA production in intact Caco-2 cells.

A Simple and Affordable Method to Create Nonsense Mutation Clones of p53 for Studying the Premature Termination Codon Readthrough Activity of PTC124.

(1) Background: A premature termination codon (PTC) can be induced by a type of point mutation known as a nonsense mutation, which occurs within the coding region. Approximately 3.8% of human cancer patients have nonsense mutations of p53. However, the non-aminoglycoside drug PTC124 has shown potential to promote PTC readthrough and rescue full-length proteins. The COSMIC database contains 201 types of p53 nonsense mutations in cancers. We built a simple and affordable method to create different nonsense mutation clones of p53 for the study of the PTC readthrough activity of PTC124. (2) Methods: A modified inverse PCR-based site-directed mutagenesis method was used to clone the four nonsense mutations of p53, including W91X, S94X, R306X, and R342X. Each clone was transfected into p53 null H1299 cells and then treated with 50 µM of PTC124. (3) Results: PTC124 induced p53 re-expression in H1299-R306X and H1299-R342X clones but not in H1299-W91X and H1299-S94X clones. (4) Conclusions: Our data showed that PTC124 more effectively rescued the C-terminal of p53 nonsense mutations than the N-terminal of p53 nonsense mutations. We introduced a fast and low-cost site-directed mutagenesis method to clone the different nonsense mutations of p53 for drug screening.