CD62/P-selectin recognition of myeloid and tumor cell sulfatides

Cell surface RNAs control neutrophil recruitment

RNAs localizing to the outer cell surface have been recently identified in mammalian cells, including RNAs with glycan modifications known as glycoRNAs. However, the functional significance of cell surface RNAs and their production are poorly known. We report that cell surface RNAs are critical for neutrophil recruitment and that the mammalian homologs of the sid-1 RNA transporter are required for glycoRNA expression. Cell surface RNAs can be readily detected in murine neutrophils, the elimination of which substantially impairs neutrophil recruitment to inflammatory sites in vivo and reduces neutrophils' adhesion to and migration through endothelial cells. Neutrophil glycoRNAs are predominantly on cell surface, important for neutrophil-endothelial interactions, and can be recognized by P-selectin (Selp). Knockdown of the murine Sidt genes abolishes neutrophil glycoRNAs and functionally mimics the loss of cell surface RNAs. Our data demonstrate the biological importance of cell surface glycoRNAs and highlight a noncanonical dimension of RNA-mediated cellular functions.

PSGL-1 decorated with sialyl Lewisa/x promotes high affinity binding of myeloma cells to P-selectin but is dispensable for E-selectin engagement

Dissemination of multiple myeloma into the bone marrow proceeds through sequential steps mediated by a variety of adhesion molecules and chemokines that eventually results in the extravasation of malignant plasma cells into this protective niche. Selectins are a class of C-type lectins that recognize carbohydrate structures exposed on blood borne cells and participate in the first step of the extravasation cascade, serving as brakes to slow down circulating cells enabling them to establish firm adhesion onto the endothelium. Myeloma cells enriched for the expression of selectin ligands present an aggressive disease in vivo that is refractory to bortezomib treatment and can be reverted by small molecules targeting E-selectin. In this study, we have defined the molecular determinants of the selectin ligands expressed on myeloma cells. We show that PSGL-1 is the main protein carrier of sialyl Lewisa/x-related structures in myeloma. PSGL-1 decorated with sialyl Lewisa/x is essential for P-selectin binding but dispensable for E-selectin binding. Moreover, sialylation is required for E-selectin engagement whereas high affinity binding to P-selectin occurs even in the absence of sialic acid. This study provides further knowledge on the biology of selectin ligands in myeloma, opening the way to their clinical application as diagnostic tools and therapeutic targets.

The roles of P-selectin in cancer cachexia

P-selectin, a cell adhesion molecule of the selectin family, is expressed on the surface of activated endothelial cells (ECs) and platelets. Binding of P-selectin to P-selectin glycoprotein ligand-1 (PSGL-1) supports the leukocytes capture and rolling on stimulated ECs and increases the aggregation of leukocytes and activated platelets. Cancer cachexia is a systemic inflammation disorder characterized by metabolic disturbances, reduced body weight, loss of appetite, fat depletion, and progressive muscle atrophy. Cachexia status is associated with increased pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), which activates ECs to release P-selectin. Single-nucleotide polymorphisms (SNPs) loci of P-selectin encoding gene SELP are associated with higher level of plasma P-selectin and increase the susceptibility to cachexia in cancer patients. Elevated P-selectin expression has been observed in the hypothalamus, liver, and gastrocnemius muscle in animal models with cancer cachexia. Increased P-selectin may cause excessive inflammatory processes, muscle atrophy, and blood hypercoagulation, thus facilitating the development of cancer cachexia. In this review, physiological functions of P-selectin and its potential roles in cancer cachexia have been summarized. We also discuss the therapeutic potential of P-selectin inhibitors for the treatment of cancer cachexia.

Multivalent sialic acid materials for biomedical applications

Sialic acid is a kind of monosaccharide expressed on the non-reducing end of glycoproteins or glycolipids. It acts as a signal molecule combining with its natural receptors such as selectins and siglecs (sialic acid-binding immunoglobulin-like lectins) in intercellular interactions like immunological surveillance and leukocyte infiltration. The last few decades have witnessed the exploration of the roles that sialic acid plays in different physiological and pathological processes and the use of sialic acid-modified materials as therapeutics for related diseases like immune dysregulation and virus infection. In this review, we will briefly introduce the biomedical function of sialic acids in organisms and the utilization of multivalent sialic acid materials for targeted drug delivery as well as therapeutic applications including anti-inflammation and anti-virus.

Sulfatide in health and disease. The evaluation of sulfatide in cerebrospinal fluid as a possible biomarker for neurodegeneration

Sulfatide (3-O-sulfogalactosylceramide, SM4) is a glycosphingolipid, highly multifunctional and particularly enriched in the myelin sheath of neurons. The role of sulfatide has been implicated in various biological fields such as the nervous system, immune system, host-pathogen recognition and infection, beta cell function and haemostasis/thrombosis. Thus, alterations in sulfatide metabolism and production are associated with several human diseases such as neurological and immunological disorders and cancers. The unique lipid-rich composition of myelin reflects the importance of lipids in this specific membrane structure. Sulfatide has been shown to be involved in the regulation of oligodendrocyte differentiation and in the maintenance of the myelin sheath by influencing membrane dynamics involving sorting and lateral assembly of myelin proteins as well as ion channels. Sulfatide is furthermore essential for proper formation of the axo-glial junctions at the paranode together with axonal glycosphingolipids. Alterations in sulfatide metabolism are suggested to contribute to myelin deterioration as well as synaptic dysfunction, neurological decline and inflammation observed in different conditions associated with myelin pathology (mouse models and human disorders). Body fluid biomarkers are of importance for clinical diagnostics as well as for patient stratification in clinical trials and treatment monitoring. Cerebrospinal fluid (CSF) is commonly used as an indirect measure of brain metabolism and analysis of CSF sulfatide might provide information regarding whether the lipid disruption observed in neurodegenerative disorders is reflected in this body fluid. In this review, we evaluate the diagnostic utility of CSF sulfatide as a biomarker for neurodegenerative disorders associated with dysmyelination/demyelination by summarising the current literature on this topic. We can conclude that neither CSF sulfatide levels nor individual sulfatide species consistently reflect the lipid disruption observed in many of the demyelinating disorders. One exception is the lysosomal storage disorder metachromatic leukodystrophy, possibly due to the genetically determined accumulation of non-metabolised sulfatide. We also discuss possible explanations as to why myelin pathology in brain tissue is poorly reflected by the CSF sulfatide concentration. The previous suggestion that CSF sulfatide is a marker of myelin damage has thereby been challenged by more recent studies using more sophisticated laboratory techniques for sulfatide analysis as well as improved sample selection criteria due to increased knowledge on disease pathology.

The clinical impact of glycobiology: targeting selectins, Siglecs and mammalian glycans

Carbohydrates - namely glycans - decorate every cell in the human body and most secreted proteins. Advances in genomics, glycoproteomics and tools from chemical biology have made glycobiology more tractable and understandable. Dysregulated glycosylation plays a major role in disease processes from immune evasion to cognition, sparking research that aims to target glycans for therapeutic benefit. The field is now poised for a boom in drug development. As a harbinger of this activity, glycobiology has already produced several drugs that have improved human health or are currently being translated to the clinic. Focusing on three areas - selectins, Siglecs and glycan-targeted antibodies - this Review aims to tell the stories behind therapies inspired by glycans and to outline how the lessons learned from these approaches are paving the way for future glycobiology-focused therapeutics.

The sugar code: letters and vocabulary, writers, editors and readers and biosignificance of functional glycan-lectin pairing

Ubiquitous occurrence in Nature, abundant presence at strategically important places such as the cell surface and dynamic shifts in their profile by diverse molecular switches qualifies the glycans to serve as versatile biochemical signals. However, their exceptional structural complexity often prevents one noting how simple the rules of objective-driven assembly of glycan-encoded messages are. This review is intended to provide a tutorial for a broad readership. The principles of why carbohydrates meet all demands to be the coding section of an information transfer system, and this at unsurpassed high density, are explained. Despite appearing to be a random assortment of sugars and their substitutions, seemingly subtle structural variations in glycan chains by a sophisticated enzymatic machinery have emerged to account for their specific biological meaning. Acting as 'readers' of glycan-encoded information, carbohydrate-specific receptors (lectins) are a means to turn the glycans' potential to serve as signals into a multitude of (patho)physiologically relevant responses. Once the far-reaching significance of this type of functional pairing has become clear, the various modes of spatial presentation of glycans and of carbohydrate recognition domains in lectins can be explored and rationalized. These discoveries are continuously revealing the intricacies of mutually adaptable routes to achieve essential selectivity and specificity. Equipped with these insights, readers will gain a fundamental understanding why carbohydrates form the third alphabet of life, joining the ranks of nucleotides and amino acids, and will also become aware of the importance of cellular communication via glycan-lectin recognition.

Peptide Antagonists for P-selectin Discriminate between Sulfatide-Dependent Platelet Aggregation and PSGL-1-Mediated Cell Adhesion

BACKGROUND

Membrane-exposed sulfatides are proposed to contribute to P-selectin-dependent platelet aggregation. Here, we demonstrated that P-selectin-mediated platelet aggregation on a collagen-coated surface under flow indeed depended on sulfatides and that this interaction differed considerably from the interaction of P-selectin with P-selectin Glycoprotein Ligand-1 (PSGL-1), which underlies leukocyte-endothelium adhesion.

METHODS AND RESULTS

Upon platelet activation, sulfatides were translocated to the platelet surface to form focal hot-spots. Interestingly, P-selectin was observed to exclusively interact with liposomes with a sulfatide density higher than 21% (w/w), indicating that the binding profile of P-selectin for sulfatide-rich liposomes was dependent on sulfatide density. Sulfatide-liposome binding to P-selectin and sulfatide/P-selectin-dependent platelet aggregation was blunted by peptide antagonists, carrying the EWVDV motif within N-terminal extensions, such as CDVEWVDVSC (half maximal inhibitory concentration IC₅₀ = 0.2 μM), but not by the EWVDV core motif itself (IC₅₀ > 1000 μM), albeit both being equally potent inhibitors of PSGL-1/P-selectin interaction (IC₅₀= 7-12 μM).

CONCLUSIONS

Our data suggest that the sulfatide/P-selectin interaction implicates multiple binding pockets, which only partly overlap with that of PSGL-1. These observations open ways to selectively interfere with sulfatide/P-selectin-dependent platelet aggregation without affecting PSGL-1-dependent cell adhesion.

A Hypoxia-Inducible HIF1-GAL3ST1-Sulfatide Axis Enhances ccRCC Immune Evasion via Increased Tumor Cell-Platelet Binding

Clear cell renal cell carcinoma (ccRCC) is the most common form of kidney cancer and the major cause of mortality for individuals with von Hippel-Lindau (VHL) disease. ccRCC is characterized most frequently by inactivation of VHL tumor suppressor protein that mediates degradation of the alpha subunit of the hypoxia-inducible factor (HIF) transcription factor family. HIF has been implicated in disease progression and the aim of this study was to identify novel HIF target genes that may contribute to ccRCC. We show that GAL3ST1, an enzyme that catalyzes the sulfonation of the plasma membrane sulfolipid sulfatide, is among the top 50 upregulated genes in ccRCC tissue relative to matched normal tissue. Increased expression of GAL3ST1 in primary ccRCC correlates with decreased survival. We show that GAL3ST1 is a HIF target gene whose expression is induced upon VHL loss leading to the accumulation of its enzymatic product sulfatide. Notably, platelets bind more efficiently to renal cancer cells with high GAL3ST1-sulfatide expression than to GAL3ST1-sulfatide-negative counterparts, which protects ccRCC cells against natural killer cell-mediated cytotoxicity. These results suggest that GAL3ST1 is a HIF-responsive gene that may contribute to ccRCC development via promoting cancer cell evasion of immune surveillance. IMPLICATIONS: Cancer development is in part dependent on evasion of immune response. We identify a HIF target gene product GAL3ST1 that may play a role in this critical process.

Sialyl Lewisx-P-selectin cascade mediates tumor-mesothelial adhesion in ascitic fluid shear flow

Organ-specific colonization suggests that specific cell–cell recognition is essential. Yet, very little is known about this particular interaction. Moreover, tumor cell lodgement requires binding under shear stress, but not static, conditions. Here, we successfully isolate the metastatic populations of cancer stem/tumor-initiating cells (M-CSCs). We show that the M-CSCs tether more and roll slower than the non-metastatic (NM)-CSCs, thus resulting in the preferential binding to the peritoneal mesothelium under ascitic fluid shear stress. Mechanistically, this interaction is mediated by P-selectin expressed by the peritoneal mesothelium. Insulin-like growth factor receptor-1 carrying an uncommon non-sulfated sialyl-Lewis^x (sLe^x) epitope serves as a distinct P-selectin binding determinant. Several glycosyltransferases, particularly α1,3-fucosyltransferase with rate-limiting activity for sLe^x synthesis, are highly expressed in M-CSCs. Tumor xenografts and clinical samples corroborate the relevance of these findings. These data advance our understanding on the molecular regulation of peritoneal metastasis and support the therapeutic potential of targeting the sLe^x-P-selectin cascade.

Tumor cell in the peritoneum are often exposed to shear forces generated by ascitic flow during metastasis. Here, the authors show that metastatic cancer stem cells tether more and roll slower than the non-metastatic counterparts, and that sialyl-Lewis^x -P-selectin axis mediates peritoneal metastasis.

Sulfatide decreases the resistance to stress-induced apoptosis and increases P-selectin-mediated adhesion: a two-edged sword in breast cancer progression

Background

We have previously shown that galactosylceramide (GalCer) affects the tumourigenic and metastatic properties of breast cancer cells by acting as an anti-apoptotic molecule. Since GalCer is a precursor molecule in the synthesis of sulfatides, the present study was aimed to define the role of sulfatides in apoptosis and breast cancer progression.

Methods

Expression of GAL3ST1 in breast cancer cell lines and breast cancer tissue specimens was analysed using real-time PCR, western blotting and immunohistochemistry analysis. The amount of sulfatide, GalCer and ceramide was analysed by thin-layer chromatography binding assay and by the modified hydrophilic interaction liquid chromatography coupled with electrospray mass spectrometry methodology. The tumourigenicity of cancer cells was analysed by an in-vivo tumour growth assay. Apoptotic cells were detected based on caspase-3 activation and the TUNEL assay. The interaction of breast cancer cells with P-selectin or E-selectin was analysed using the flow adhesion assay. The ability of sulfatide-expressing cells to activate and aggregate platelets was studied using the flow-cytometry-based aggregation assay.

Results

Using two models of breast cancer, T47D cells with blocked synthesis of sulfatide and MDA-MB-231 cells with neosynthesis of this glycosphingolipid, we showed that high sulfatide levels resulted in increased sensitivity of cancer cells to apoptosis induced by hypoxia and doxorubicin in vitro, and decreased their tumourigenicity after transplantation into athymic nu/nu mice. Accordingly, a clinical study on GAL3ST1 expression in invasive ductal carcinoma revealed that its elevated level is associated with better prognosis. Using MDA-MB-231 cells with neosynthesis of sulfatide we also showed that sulfatide is responsible for adhesion of breast cancer cells to P-selectin-expressing cells, including platelets. Sulfatide also acted as an activating molecule, increasing the expression of P-selectin.

Conclusions

This study demonstrates that increased synthesis of sulfatide sensitises cancer cells to microenvironmental stress factors such as hypoxia and anticancer drugs such as doxorubicin. However, sulfatide is probably not directly involved in apoptotic cascades, because its increased synthesis by GAL3ST1 decreased the amounts of its precursor, GalCer, a known anti-apoptotic molecule. On the other hand, our data support the view that sulfatides are malignancy-related adhesive molecules involved in activating and binding P-selectin-expressing platelets to breast cancer cells.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-1058-z) contains supplementary material, which is available to authorized users.

Recent advances toward the development of inhibitors to attenuate tumor metastasis via the interruption of lectin-ligand interactions

Aberrant glycosylation is a well-recognized phenomenon that occurs on the surface of tumor cells, and the overexpression of a number of ligands (such as TF, sialyl Tn, and sialyl Lewis X) has been correlated to a worse prognosis for the patient. These unique carbohydrate structures play an integral role in cell-cell communication and have also been associated with more metastatic cancer phenotypes, which can result from binding to lectins present on cell surfaces. The most well studied metastasis-associated lectins are the galectins and selectins, which have been correlated to adhesion, neoangiogenesis, and immune-cell evasion processes. In order to slow the rate of metastatic lesion formation, a number of approaches have been successfully developed which involve interfering with the tumor lectin-substrate binding event. Through the generation of inhibitors, or by attenuating lectin and/or carbohydrate expression, promising results have been observed both in vitro and in vivo. This article briefly summarizes the involvement of lectins in the metastatic process and also describes different approaches used to prevent these undesirable carbohydrate-lectin binding events, which should ultimately lead to improvement in current cancer therapies.

Re-configuration of sphingolipid metabolism by oncogenic transformation

The sphingolipids are one of the major lipid families in eukaryotes, incorporating a diverse array of structural variants that exert a powerful influence over cell fate and physiology. Increased expression of sphingosine kinase 1 (SPHK1), which catalyses the synthesis of the pro-survival, pro-angiogenic metabolite sphingosine 1-phosphate (S1P), is well established as a hallmark of multiple cancers. Metabolic alterations that reduce levels of the pro-apoptotic lipid ceramide, particularly its glucosylation by glucosylceramide synthase (GCS), have frequently been associated with cancer drug resistance. However, the simple notion that the balance between ceramide and S1P, often referred to as the sphingolipid rheostat, dictates cell survival contrasts with recent studies showing that highly potent and selective SPHK1 inhibitors do not affect cancer cell proliferation or survival, and studies demonstrating higher ceramide levels in some metastatic cancers. Recent reports have implicated other sphingolipid metabolic enzymes such as acid sphingomyelinase (ASM) more strongly in cancer pathogenesis, and highlight lysosomal sphingolipid metabolism as a possible weak point for therapeutic targeting in cancer. This review describes the evidence implicating different sphingolipid metabolic enzymes and their products in cancer pathogenesis, and suggests how newer systems-level approaches may improve our overall understanding of how oncogenic transformation reconfigures sphingolipid metabolism.

Structural and immunological characterization of sulphatides: relevance of sulphate moieties in Trypanosoma cruzi glycoconjugates

Sulphoglycosphingolipids, present on the surface of diverse cells, participate in the regulation of various cellular events. However, little is known about the structure and the role of sulphoglycosphingolipids in trypanosomatids. Herein, sulphated dihexosylceramide structures - composed mainly of sphingosine as the long chain base acylated with stearic acid - have been determined for the first time in Trypanosoma cruzi epimastigotes by UV-MALDI-TOF-MS analysis. Interestingly, inhibition ELISA assays using cruzipain as antigen and polyclonal rabbit antibodies specific for cruzipain, the major cysteine proteinase of T. cruzi, or for its C-terminal domain, have demonstrated (i) that sulphate epitopes are shared between cruzipain and sulphatides of T. cruzi, (ii) that cross-reactivity maps to the C-terminal domain and (iii) the existence of other antigenic determinants in the glycolipidic structures. These features provide evidence that sulphate groups are antigenic in sulphate-containing parasite glycoconjugates. Furthermore, IgG2 antibody levels inversely correlate with disease severity in chronic Chagas disease patients, suggesting that IgG2 antibodies specific for sulphated epitopes might be associated with protective immunity and might be considered as potential surrogates of the course of chronic Chagas disease.

Sulfatide attenuates experimental Staphylococcus aureus sepsis through a CD1d-dependent pathway

Natural killer T (NKT) lymphocytes are implicated in the early response to microbial infection. Further, sulfatide, a myelin self-glycosphingolipid, activates a type II NKT cell subset and can modulate disease in murine models. We examined the role of NKT cells and the effect of sulfatide treatment in a murine model of Staphylococcus aureus sepsis. The lack of CD1d-restricted NKT cells did not alter survival after a lethal inoculum of S. aureus. In contrast, sulfatide treatment significantly improved the survival rate of mice with S. aureus sepsis, accompanied by decreased levels of tumor necrosis factor alpha and interleukin-6 in the blood. The protective effect of sulfatide treatment depended on CD1d but not on type I NKT cells, suggesting that activation of type II NKT cells by sulfatide has beneficial effects on the outcome of S. aureus sepsis in this model.

Structure, sulfatide binding properties, and inhibition of platelet aggregation by a disabled-2 protein-derived peptide

Disabled-2 (Dab2) targets membranes and triggers a wide range of biological events, including endocytosis and platelet aggregation. Dab2, through its phosphotyrosine-binding (PTB) domain, inhibits platelet aggregation by competing with fibrinogen for α(IIb)β(3) integrin receptor binding. We have recently shown that the N-terminal region, including the PTB domain (N-PTB), drives Dab2 to the platelet membrane surface by binding to sulfatides through two sulfatide-binding motifs, modulating the extent of platelet aggregation. The three-dimensional structure of a Dab2-derived peptide encompassing the sulfatide-binding motifs has been determined in dodecylphosphocholine micelles using NMR spectroscopy. Dab2 sulfatide-binding motif contains two helices when embedded in micelles, reversibly binds to sulfatides with moderate affinity, lies parallel to the micelle surface, and when added to a platelet mixture, reduces the number and size of sulfatide-induced aggregates. Overall, our findings identify and structurally characterize a minimal region in Dab2 that modulates platelet homotypic interactions, all of which provide the foundation for rational design of a new generation of anti-aggregatory low-molecular mass molecules for therapeutic purposes.

The Increased Expression of HLA-DR and ICAM-1 Molecules by Human Bronchial Epithelial Cells, Induced by Activated Mononuclear Cells, is Downregulated by Nedocromil Sodium

To test the hypothesis that mononuclear cell products could increase the expression of HLA-DR and ICAM-1 molecules in bronchial epithelial cells (BECs), subconfluent cultures of human BECs, obtained from surgically resected bronchi, were incubated with PHA-activated blood mononuclear cell conditioned media (BCM-CM) or recombinant IFN-gamma. The presence of HLA-DR and ICAM-1 molecules on BECs was then evaluated by specific antibody staining and flow-cytometry analysis. The addition to BEC cultures of different concentrations of PHA-stimulated BMC-CM, or of IFN-gamma induced a dosedependent increase of HIA-DR and ICAM-1 expression, while no effect was observed with unstimulated BMC-CM. The ability of nedocromil sodium and, as control, of dexamethasone, to prevent the upregulation of HLA-DR and ICAM-1 expression on BECs was then tested. Increasing concentrations (10(-7) to 10(-4) M) of nedocromil significandy inhibited HLA-DR and ICAM-1 expression by BECs in a dose-dependent fashion. A similarly dose-dependent inhibitory effect was also observed with dexamethasone, which, however, was less active than nedocromil on HL-ADR expression and more active on ICAM-1 expression. Finally, nedocromil and dexamethasone showed a significant synergistic effect on the expression of both cell surface molecules at the lowest concentrations tested.

Edematogenic activity of a sulfated galactan from the red marine algae Gelidium crinale

CONTEXT

The red algae Gelidium crinale (Turner) Gaillon (Gelidiaceae), encountered along the Southeast and Northeast Brazilian sea coast, contains a sulfated galactan presenting a similar saccharide backbone compared to λ carrageenan. Inflammatory effects of other galactans were reported, but not for that obtained from G. crinale (SG-Gc).

OBJECTIVE

To investigate the in vivo edematogenic effect of SG-Gc in comparison to λ carrageenan.

METHODS

SG-Gc was isolated by ion exchange chromatography. Paw edema was induced by subcutaneous (s.c.) intraplantar injection of SG-Gc or λ carrageenan and evaluated by hydroplethysmometry. Data were expressed as the increase in paw volume subtracted from the basal volume or area under curve-AUC. To investigate the participation of early and late-phase inflammatory mediators, rats were treated with pyrilamine, compound 48/80, indomethacin, NG-nitro-L-arginine methyl ester (L-NAME), or pentoxifylline before SG-Gc.

RESULTS

SG-Gc edematogenic effect was initiated at 0.5 h, peaked at 2 h (1.26 ± 0.05 mL) and lasted until 6 h (0.21 ± 0.03 mL), whereas the carrageenan-induced edema started at 1 h. The first phase (1-3 h) of SG-Gc-induced edema was 176 ± 15 (AUC) versus carrageenan (114.5 ± 14), whereas the second phase (3-5 h) was 95 ± 12 (AUC) versus carrageenan (117.5 ± 11). Treatment with compound 48/80, pyrilamine, indomethacin, L-NAME, and pentoxifylline inhibited the effect of SG-Gc by 32, 40, 69, 72, and 49%, respectively.

DISCUSSION AND CONCLUSION

SG-Gc and λ carrageenan induce different profile of inflammatory response in the paw edema model, that involves histamine, cytokines, prostaglandins, and nitric oxide (NO), but with different degree of participation.

CCL20, γδ T cells, and IL-22 in corneal epithelial healing

After corneal epithelial abrasion, leukocytes and platelets rapidly enter the corneal stroma, and CCR6(+) IL-17(+) γδ T cells migrate into the epithelium. γδ T-cell-deficient (TCRδ(-/-)) mice have significantly reduced inflammation and epithelial wound healing. Epithelial CCL20 mRNA increased 19-fold at 3 h, and protein increased ∼ 16-fold at 6 h after injury. Systemic or topical treatment of wild-type C57BL/6 mice with anti-CCL20 reduced γδ T-cell accumulation in the cornea by >50% with a concomitant decrease in epithelial healing and stromal inflammation. In addition to CCR6 and IL-17, corneal γδ T cells stained positively for RORγt, IL-23R, and IL-22. Anti-IL-22 reduced peak cell division of the healing epithelium by 52%. Treatment of TCRδ(-/-) mice with rIL-22 significantly promoted wound closure, with peak epithelial cell division increased >3-fold. In addition, rIL-22 restored neutrophil and platelet influx in the TCRδ(-/-) mice to wild-type levels and increased CXCL1 production by wounded corneal explants >2-fold. These results indicate that an important aspect of the healing response to corneal epithelial abrasion includes CCL20-dependent influx of CCR6(+) IL-17(+) IL-22(+) γδ T cells and that IL-22 contributes to the inflammatory response and promotes epithelial healing.

Chondroitin sulfates play a major role in breast cancer metastasis: a role for CSPG4 and CHST11 gene expression in forming surface P-selectin ligands in aggressive breast cancer cells

Introduction

We have previously demonstrated that chondroitin sulfate glycosaminoglycans (CS-GAGs) on breast cancer cells function as P-selectin ligands. This study was performed to identify the carrier proteoglycan (PG) and the sulfotransferase gene involved in synthesis of the surface P-selectin-reactive CS-GAGs in human breast cancer cells with high metastatic capacity, as well as to determine a direct role for CS-GAGs in metastatic spread.

Methods

Quantitative real-time PCR (qRT-PCR) and flow cytometry assays were used to detect the expression of genes involved in the sulfation and presentation of chondroitin in several human breast cancer cell lines. Transient transfection of the human breast cancer cell line MDA-MB-231 with the siRNAs for carbohydrate (chondroitin 4) sulfotransferase-11 (CHST11) and chondroitin sulfate proteoglycan 4 (CSPG4 ) was used to investigate the involvement of these genes in expression of surface P-selectin ligands. The expression of CSPG4 and CHST11 in 15 primary invasive breast cancer clinical specimens was assessed by qRT-PCR. The role of CS-GAGs in metastasis was tested using the 4T1 murine mammary cell line (10 mice per group).

Results

The CHST11 gene was highly expressed in aggressive breast cancer cells but significantly less so in less aggressive breast cancer cell lines. A positive correlation was observed between the expression levels of CHST11 and P-selectin binding to cells (P < 0.0001). Blocking the expression of CHST11 with siRNA inhibited CS-A expression and P-selectin binding to MDA-MB-231 cells. The carrier proteoglycan CSPG4 was highly expressed on the aggressive breast cancer cell lines and contributed to the P-selectin binding and CS-A expression. In addition, CSPG4 and CHST11 were over-expressed in tumor-containing clinical tissue specimens compared with normal tissues. Enzymatic removal of tumor-cell surface CS-GAGs significantly inhibited lung colonization of the 4T1 murine mammary cell line (P = 0.0002).

Conclusions

Cell surface P-selectin binding depends on CHST11 gene expression. CSPG4 serves as a P-selectin ligand through its CS chain and participates in P-selectin binding to the highly metastatic breast cancer cells. Removal of CS-GAGs greatly reduces metastatic lung colonization by 4T1 cells. The data strongly indicate that CS-GAGs and their biosynthetic pathways are promising targets for the development of anti-metastatic therapies.

A Novel Antinociceptive Sulphated Polysaccharide of the Brown Marine Alga Spatoglossum Schroederi

Sulfated polysaccharides (SP) of brown algae (Phaeophyta) are composed mainly of α- L-fucose, being classified as fucans, with recognized role in inflammation but not in nociception, which was already described for SP obtained from red algae. Here the SP of the brown marine alga S. schroederi (named Ss-SP) was isolated and assayed for the antinociceptive effect. Ss-SP was isolated by DEAE-cellulose, analyzed by agarose gel electrophoresis and evaluated in nociception models (Formalin, Hot plate, Von Frey) using Swiss mice (20-25g). Anion exchange chromatography provided four major fractions being F1 (Ss-SP) that of highest metachromatic activity and sugar content. Ss-SP inhibited both phases of the formalin test. In the first phase the paw licking (55.2±8.07s) was reduced by 45% (30.5±6.51s) and 40% (32.85±8.66s) at 0.1 and 1 μg/kg, respectively. In the second phase, Ss-SP was also inhibitory about 39%, but only at 1 mg/kg (83.0±15.70s) compared to formalin (136.8±10.27s). This inhibitory effect suggests a mixed mechanism similar to morphine, which was not confirmed in the hot plate test, a model of pain associated with central neurotransmission. However, Ss-SP reduced the animal reaction in response to stimulation withVon Frey filament at the 2nd and 3rd h (20.8±6.86% versus carrageenan: 47.9±5.83%; 33.3±7.71% versus carrageenan: 62.5±9.83%). Accordingly, the paw edema induced by carrageenan (0.08±0.01g) was potently reduced in 45.35% by Ss-SP pre-treatment (0.02±0.003g), corroborating the anti-inflammatory activity demonstrated for brown seaweed polysaccharides. In conclusion our data revealed for the first time the antinociceptive effect of Ss-SP which could be used as a new source of analgesic substances.

In vivo anti-inflammatory effect of a sulfated polysaccharide isolated from the marine brown algae Lobophora variegata

CONTEXT

Lobophora variegata J.V. Lamouroux (Dictyotaceae) is a brown marine alga widely encountered in the Brazilian sea coast that presents high content of fucans. Anti-inflammatory effects of fucans are reported mostly in models in vitro, but little is known about its effects in vivo.

OBJECTIVE

To investigate vascular and cellular effects of a sulfated polysaccharide from the brown marine algae L. variegata (SP-Lv) in acute inflammatory models.

MATERIALS AND METHODS

SP-Lv was isolated by DEAE-cellulose and analyzed by agarose gel electrophoresis and evaluated for its inhibitory effect on paw edema, vascular permeability, leukocyte migration and peritoneal nitrite content induced by zymosan in Wistar rats. Anticoagulant activities and possible systemic toxicity were also evaluated.

RESULTS

SP-Lv inhibited the paw edema (120 min: 1.42 ± 0.11 vs. 0.95 ± 0.05 mL), plasma exudation (21.53 ± 0.62 vs. 11.96 ± 0.68 μg/g), nitrite content (4.42 ± 0.33 vs. 2.86 ± 0.003 μM) and leukocyte migration (5.15 ± 1.21 vs. 1.99 ± 0.16 cells/10(3) mL) induced by zymosan. SP-Lv and L-NAME reduced the paw edema (60-120 min) elicited by L-arginine. However, at 180 min SP-Lv effect was more accentuated and sustained until 240 min, while that of L-NAME was abolished. Similarly to indomethacin, SP-Lv inhibited the entire edema time-course induced by phospholipase A(2), except for the time of 60 min.

DISCUSSION AND CONCLUSION

The anti-edematogenic effect of SP-Lv seems to occur via inhibition of nitric oxide synthase and cyclooxygenase activities. These results suggest a potential applicability of polysaccharides from alga origin in acute inflammatory conditions.

Chemotrap-1: an engineered soluble receptor that blocks chemokine-induced migration of metastatic cancer cells in vivo

Cancer and dendritic cells recognize and migrate toward chemokines secreted from lymphatics and use this mechanism to invade the lymphatic system, and cancer cells metastasize through it. The lymphatic-secreted chemokine ligand CCL21 has been identified as a key regulatory molecule in the switch to a metastatic phenotype in melanoma and breast cancer cells. However, it is not known whether CCL21 inhibition is a potential therapeutic strategy for inhibition of metastasis. Here, we describe an engineered CCL21-soluble inhibitor, Chemotrap-1, which inhibits migration of metastatic melanoma cells in vivo. Two-hybrid, pull-down, and coimmunoprecipitation assays allowed us to identify a naturally occurring human zinc finger protein with CCL21 chemokine-binding properties. Further analyses revealed a short peptide (∼70 amino acids), with a predicted coiled-coil structure, which is sufficient for association with CCL21. This CCL21 chemokine-binding peptide was then fused to the Fc region of human IgG1 to generate Chemotrap-1, a human chemokine-binding Fc fusion protein. Surface plasmon resonance and chemotaxis assays showed that Chemotrap-1 binds CCL21 and inhibits CCL21-induced migration of melanoma cells in vitro with subnanomolar affinity. In addition, Chemotrap-1 blocked migration of melanoma cells toward lymphatic endothelial cells in vitro and in vivo. Finally, Chemotrap-1 strongly reduced lymphatic invasion, tracking, and metastasis of CCR7-expressing melanoma cells in vivo. Together, these results show that CCL21 chemokine inhibition by Chemotrap-1 is a potential therapeutic strategy for metastasis and provide further support for the hypothesis that lymphatic-mediated metastasis is a chemokine-dependent process.

Heparin as an inhibitor of cancer progression

Heparin is frequently used in the treatment of cancer-associated thromboembolism. Accumulating clinical evidence indicates that cancer patients treated with unfractionated and low-molecular weight heparin (LMWH) survive longer than patients treated by other anticoagulants, especially patients in the early stage of the disease. Experimental analysis from a number of animal models constantly provides evidence for the ability of heparin to attenuate metastasis. The non-anticoagulant activity of heparin on metastasis includes the ability to inhibit cell-cell-interaction through blocking of P- and L-selectin, to inhibit extracellular matrix protease heparanase, and to inhibit angiogenesis. This chapter summarizes current experimental evidence on the biology of heparin during cancer progression, with the focus on potential mechanism of heparin antimetastatic activity.

Sulfatides partition disabled-2 in response to platelet activation

BACKGROUND

Platelets contact each other at the site of vascular injury to stop bleeding. One negative regulator of platelet aggregation is Disabled-2 (Dab2), which is released to the extracellular surface upon platelet activation. Dab2 inhibits platelet aggregation through its phosphotyrosine-binding (PTB) domain by competing with fibrinogen for alphaIIbbeta3 integrin receptor binding by an unknown mechanism.

METHODOLOGY/PRINCIPAL FINDINGS

Using protein-lipid overlay and liposome-binding assays, we identified that the N-terminal region of Dab2, including its PTB domain (N-PTB), specifically interacts with sulfatides. Moreover, we determined that such interaction is mediated by two conserved basic motifs with a dissociation constant (K(d)) of 0.6 microM as estimated by surface plasmon resonance (SPR) analysis. In addition, liposome-binding assays combined with mass spectroscopy studies revealed that thrombin, a strong platelet agonist, cleaved N-PTB at a site located between the basic motifs, a region that becomes protected from thrombin cleavage when bound to sulfatides. Sulfatides on the platelet surface interact with coagulation proteins, playing a major role in haemostasis. Our results show that sulfatides recruit N-PTB to the platelet surface, sequestering it from integrin receptor binding during platelet activation. This is a transient recruitment that follows N-PTB internalization by an actin-dependent process.

CONCLUSIONS/SIGNIFICANCE

Our experimental data support a model where two pools of Dab2 co-exist at the platelet surface, in both sulfatide- and integrin receptor-bound states, and their balance controls the extent of the clotting response.

Identification of amino acid residues responsible for von Willebrand factor binding to sulfatide by charged-to-alanine-scanning mutagenesis

von Willebrand factor (VWF) performs its hemostatic functions through binding to various proteins. The A1 domain of VWF contains binding sites of not only physiologically important ligands, but also exogenous modulators that induce VWF-platelet aggregation. Sulfatides, 3-sulfated galactosyl ceramides, that are expressed on oligodendrocytes, renal tubular cells, certain tumor cells and platelets, have been suggested to interact with VWF under some pathological conditions. The binding of VWF to sulfatide requires the A1 domain, but its binding sites have not been precisely identified. Here, we report that alanine mutations at Arg1392, Arg1395, Arg1399 and Lys1423 led to decreased VWF–sulfatide binding. These sites have been reported to be the binding sites for platelet membrane glycoprotein (GP) Ib and/or snake venom botrocetin, and, interestingly, are identical to the monoclonal antibody (mAb) NMC4 epitope previously reported to inhibit the VWF-GPIb interaction. We observed that NMC4 also inhibited VWF interaction with sulfatides in a dose-dependent manner. Thus, we conclude that VWF binding sites of sulfatide overlap those of platelet GPIb and botrocetin.

A lipid binding domain in sphingosine kinase 2

The lipid second messenger sphingosine 1-phosphate (S1P) is a critical mediator of cellular proliferation and survival signals, and is essential for vasculogenesis and neurogenesis. S1P formation is catalysed by sphingosine kinases 1 and 2 (Sphk1 and Sphk2). We have found that the endogenous glycolipid sulfatide (3-O-sulfogalactosylceramide) binds to and inhibits the activity of Sphk2 and the closely related ceramide kinase (Cerk), but not Sphk1. Using sulfatide as a probe, we mapped the lipid binding domain to the N-terminus of Sphk2 (residues 1-175), a region of sequence that is absent in Sphk1, but aligns with a pleckstrin homology domain in Cerk. Accordingly, Sphk2 bound to phosphatidylinositol monophosphates but not to abundant cellular phospholipids. Deleting the N-terminal domain reduced Sphk2 membrane localisation in cells. We have therefore identified a lipid binding domain in Sphk2 that is important for the enzyme's sub-cellular localisation.

Sulfatide is required for efficient replication of influenza A virus

Sulfatide is abundantly expressed in various mammalian organs, including the intestines and trachea, in which influenza A viruses (IAVs) replicate. However, the function of sulfatide in IAV infection remains unknown. Sulfatide is synthesized by two transferases, ceramide galactosyltransferase (CGT) and cerebroside sulfotransferase (CST), and is degraded by arylsulfatase A (ASA). In this study, we demonstrated that sulfatide enhanced IAV replication through efficient translocation of the newly synthesized IAV nucleoprotein (NP) from the nucleus to the cytoplasm, by using genetically produced cells in which sulfatide expression was down-regulated by RNA interference against CST mRNA or overexpression of the ASA gene and in which sulfatide expression was up-regulated by overexpression of both the CST and CGT genes. Treatment of IAV-infected cells with an antisulfatide monoclonal antibody (MAb) or an anti-hemagglutinin (HA) MAb, which blocks the binding of IAV and sulfatide, resulted in a significant reduction in IAV replication and accumulation of the viral NP in the nucleus. Furthermore, antisulfatide MAb protected mice against lethal challenge with pathogenic influenza A/WSN/33 (H1N1) virus. These results indicate that association of sulfatide with HA delivered to the cell surface induces translocation of the newly synthesized IAV ribonucleoprotein complexes from the nucleus to the cytoplasm. Our findings provide new insights into IAV replication and suggest new therapeutic strategies.

Therapeutic potential of selectin antagonists in psoriasis

Psoriasis is a systemic chronic inflammatory disorder. One of the major characteristics is an excess of infiltration of inflammatory cells, mainly lymphocytes, into the skin. Because the adhesion family of selectins is suggested to play a relevant role in this process, selectins have emerged as an interesting target for drug discovery and development in psoriasis. Different strategies targeting selectins have been described. This review discusses these approaches and summarises the current development of selectin antagonists for the treatment of psoriasis. An expert opinion will give the authors' personal opinion about selectin antagonism in psoriasis and which approach might be preferable.

Sulfatide binding properties of murine and human antiganglioside antibodies

Antiganglioside antibodies form an important component of the innate and adaptive B cell repertoire, where they provide antimicrobial activity through binding encapsulated bacterial glycans. In an aberrant role, they target peripheral nerve gangliosides to induce autoimmune nerve injury. An important characteristic of antiganglioside antibodies is their ability to selectively recognize highly defined glycan structures. Since sialylated and sulfated glycans often share lectin recognition patterns, we here explored the possibility that certain antiganglioside antibodies might also bind 3-O-sulfo-beta-D-galactosylceramide (sulfatide), an abundant constituent of plasma and peripheral nerve myelin, that could thereby influence any immunoregulatory or autoimmune properties. Out of 25 antiganglioside antibodies screened in solid phase assays, 20 also bound sulfatide (10(-5) to 10(-6) M range) in addition to their favored ganglioside glycan epitope ( approximately 10(-7) M range). Solution inhibition studies demonstrated competition between ganglioside and sulfatide, indicating close proximity or sharing of the antigen binding variable region domain. Sulfatide and 3-O-sulfo-beta-D-galactose were unique in having this property amongst a wide range of sulfated glycans screened, including 4- and 6-O-sulfo-beta-D-galactose analogues. Antiganglioside antibody binding to 3-O-sulfo-beta-D-galactose was highly dependent upon the spatial presentation of the ligand, being completely inhibited by conjugation to protein or polyacrylamide (PAA) matrices. Binding was also absent when sulfatide was incorporated into plasma membranes, including myelin, under conditions in which antibody binding to ganglioside was retained. These data demonstrate that sulfatide binding is a common property of antiganglioside antibodies that may provide functional insights into, and consequences for this component of the innate immune repertoire.

De novo expression of MECA-79 glycoprotein-determinant on developing B lymphocytes in gut-associated lymphoid tissues

Rabbit is one of several species that depend on development of B lymphocytes in gut-associated lymphoid tissues for primary immunoglobulin-repertoire diversification. The rabbit appendix is an important site of early B-lymphocyte development. We previously reported that peripheral lymph node addressin detected by monoclonal antibody (mAb) MECA-79 played a role in recruitment of immature blood-borne B cells into neonatal rabbit appendix. Here, we report expression of an approximately 127 000 MW O-linked sulphated proteoglycan on developing B cells in appendix and Peyer's patches recognized by the mAb MECA-79. Binding of the mAb to B lymphocytes was sensitive to enzyme treatment with O-sialoglycoprotease and expression was partially inhibited by sodium chlorate, a metabolic inhibitor of sulphation. The proportions of MECA-79(+) B lymphocytes gradually increased from < 0.5% at 3 days to > 70% at 6 weeks in appendix and Peyer's patches. The proportions of MECA-79(+) B lymphocytes in spleen and peripheral blood were very low (0.5-2%). However, the MECA-79 determinant was detected on B cells in splenic germinal centres after immunization. In situ labelling of appendix cells showed that the MECA-79 determinant was expressed on fluorescein-labelled B lymphocytes that migrated from appendix into mesenteric lymph nodes. B-cell MECA-79 may be involved in interactions with T cells and/or dendritic cells. Alternatively, because we found that lymphatic endothelium in the thymus-dependent area of appendix, a site for lymphocyte exit, expressed P-selectin (CD62P), interaction of the MECA-79 determinant on B cells with CD62P may have a role in the exit of B lymphocytes from rabbit appendix.

Establishment of a quantitative, qualitative, and high-throughput analysis of sulfatides from small amounts of sera by matrix-assisted laser desorption ionization-time of flight mass spectrometry

Based on our previous measurements of sulfatides, we further developed a quantitative, qualitative, and high-throughput analytical method for serum sulfatides as forms of lysosulfatides by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Using 0.1N NaOH in 90% MeOH for saponification instead of absolute MeOH, as previously used, we succeeded in eliminating the formation of lysosulfatide artifacts, facilitating much more sensitive detection. The use of MonoTip C18 allowed quantitation of serum sulfatides from 100 50-mul serum specimens within 1 working day. Purification of lysosulfatides with MonoTip C18 also gave rise to clear MALDI-TOF MS spectra, allowing overall analysis of sphingoid molecular species of sulfatides in serum. The composition was as follows: d18:1 (61.3+/-2.8%), d18:2 (13.3+/-1.7%), t18:0 (11.8+/-1.5%), d18:0 (7.6+/-0.8%), d20:0 (3.0+/-1.2%), t20:0 (2.3+/-0.8%), and d20:1 (1.6+/-0.5%). This is also the first detailed report on sphingoid molecular species of sulfatides in human serum. We believe that this method is suitable for daily clinical analysis of sulfatides in various clinical samples such as blood, urine, cerebrospinal fluid, and specimens from biopsies.

P-selectin mediates metastatic progression through binding to sulfatides on tumor cells

Hematogenous carcinoma metastasis is associated with tumor cell emboli formation, which is now known to be facilitated by selectins. P-selectin-mediated interactions of platelets with cancer cells are based mostly on mucin- and glycosaminoglycan-type selectin ligands. We previously showed that mouse colon carcinoma cells (MC-38) carry P-selectin ligands of nonmucin origin, which were not identified. Here we show that P-selectin ligands recognized on MC-38 cells are sulfated glycolipids, thereby facilitating experimental metastasis in a syngeneic mouse model. Metabolic inhibition of sulfation by incubation of cells with sodium chlorate almost completely abrogated P-selectin binding. Metabolic labeling of MC-38 cells with (35)S sulfate revealed only a single band as detected by high-performance thin layer chromatography analysis of a total lipid extract. Matrix-assisted laser desorption/ionization tandem time-of-flight/time-of-flight analysis (MALDI-TOF-TOF) analysis of the purified sulfate-containing lipid fraction identified the selectin ligand to be a sulfated galactosylceramide SM4 (HSO(3)-3Galbeta-1Cer). Modulation of glycolipid biosynthesis in MC-38 cells altered P-selectin binding, thereby confirming sulfoglycolipids to be major P-selectin ligands. In addition, P-selectin was also found to recognize lactosylceramide sulfate SM3 (HSO(3)-3Galbeta-4Glcbeta-1Cer) and gangliotriaosylceramide sulfate SM2 [GalNAcbeta-4(HSO(3)-3)Galbeta-4Glcbeta-1Cer] in human hepatoma cells. Finally, the enzymatic removal of sulfation from the cell surface of MC-38 cells resulted in decreased P-selectin binding and led to attenuation of metastasis. Thus, SM4 sulfatide serves as a native ligand for P-selectin contributing to cell-cell interactions and to facilitation of metastasis.

A disaccharide-based inhibitor of glycosylation attenuates metastatic tumor cell dissemination

PURPOSE

The binding of hematogenously borne malignant cells that express the carbohydrate sialyl Lewis X (sLe(X)) to selectin adhesion receptors on leukocytes, platelets, and endothelial cells facilitates metastasis. The glycosylation inhibitor, per-O-acetylated GlcNAcbeta1,3Galbeta-O-naphthalenemethanol (AcGnG-NM), inhibits the biosynthesis of sLe(X) in tumor cells. To evaluate the efficacy of AcGnG-NM as an antimetastatic agent, we examined its effect on experimental metastasis and on spontaneous hematogenous dissemination of murine Lewis lung carcinoma and B16BL6 melanoma cells.

EXPERIMENTAL DESIGN

Tumor cells were treated in vitro with AcGnG-NM, and the degree of selectin ligand inhibition and experimental metastasis was analyzed in wild-type and P-selectin-deficient mice. Conditions were developed for systemic administration of AcGnG-NM, and the presence of tumor cells in the lungs was assessed using bromodeoxyuridine labeling in vivo. The effect of AcGnG-NM on inflammation was examined using an acute peritonitis model.

RESULTS

In vitro treatment of Lewis lung carcinoma cells with AcGnG-NM reduced expression of sLe(X)- and P-selectin-dependent cell adhesion to plates coated with P-selectin. Treatment also reduced formation of lung foci when cells were injected into syngeneic mice. Systemic administration of the disaccharide significantly inhibited spontaneous dissemination of the cells to the lungs from a primary s.c. tumor, whereas an acetylated disaccharide not related to sLe(X) in structure had no effect. AcGnG-NM did not alter the level of circulating leukocytes or platelets, the expression of P-selectin ligands on neutrophils, or sLe(X)-dependent inflammation.

CONCLUSION

Taken together, these data show that AcGnG-NM provides a targeted glycoside-based therapy for the treatment of hematogenous dissemination of tumor cells.

Rapid demonstration of diversity of sulfatide molecular species from biological materials by MALDI-TOF MS

By combining the partition method for enrichment of sulfatides without any chromatographic procedures and the preparation method of lysosulfatides, we succeeded in analyzing these sulfated glycosphingolipids from biological materials by matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS) to reduce the complexity of mass fragmentation patterns within a day. We found that sulfated GalCer (HSO3-3Gal beta 1Cer) (SM4s [galactosylsulfatide]) was composed of different species. While composition of SM4s specifically depended on source materials, it always contained hydroxy fatty acids of various degrees. In addition to the common sphingoid 4-sphingenine (d18:1), uncommon/unusual sphingoids phytosphingosine (4-hydroxysphinganine) (t18:0), eicosasphinganine (d20:0), 4-eicosasphingenine (d20:1), and sphingadienine (d18:2) were easily detected. Finally, in addition to SM4s, sulfatide sulfated LacCer (HSO3-3Gal beta 4Glc beta 1Cer) (SM3 [sulfated lactosylceramide]) and sulfated Gg3Cer (GalNAc beta 4(HSO3-3)Gal beta 4Glc beta 1Cer) (SM2 [sulfated gangliotriaosylceramide]) were clearly detected in renal tubule cells. The major SM4s was composed of ceramides possessing d18:1 with C22 hydroxy fatty acids (C22:0 h), C23:0 h, and C24:0 h, whereas the major SM3/SM2 were composed of ceramides possessing t18:0 with C22 normal fatty acids (C22:0), C23:0, C24:0. Namely, in these two series of sulfatides, either fatty acids or sphingoids were hydroxylated, and chain lengths of these components were exactly the same, consequently resulting in a similar polarity of ceramide moieties in these sulfatide species. These results demonstrated diversities of sulfatide molecular species, not only with respect to sugar moieties but also to ceramide moieties, which are probably important for specific effective functions in particular microenvironments such as lipid membrane microdomains.

Binding of active matrilysin to cell surface cholesterol sulfate is essential for its membrane-associated proteolytic action and induction of homotypic cell adhesion

Regulation of cell surface molecules by matrix metalloproteinases (MMPs), as well as MMPs-catalyzed degradation of extracellular matrix, is important for tumor invasion and metastasis. Our previous study (Kioi, M., Yamamoto, K., Higashi, S., Koshikawa, N., Fujita, K., and Miyazaki, K. (2003) Oncogene 22, 8662-8670) demonstrated that active matrilysin specifically binds to the surface of colon cancer cells and induces notable cell aggregation due to processing of the cell membrane protein(s). Furthermore, these aggregated cells showed a dramatically enhanced metastatic potential. To elucidate the mechanism of matrilysin-induced cell aggregation, we attempted to identify the matrilysin-binding substance on the cell surface. Here, we demonstrate that cholesterol sulfate on the cell surface is a major matrilysin-binding substance. We found that active matrilysin bound to the cell membrane and cholesterol sulfate incorporated into liposomes with similar affinities. Treatment of colon cancer cells with beta-cyclodextrin significantly reduced not only matrilysin binding to the cell surface but also matrilysin-dependent proteolysis and cell aggregation. Interestingly, replenishment of cholesterol sulfate, but not cholesterol, neutralized the effects of beta-cyclodextrin. Taken together, it is likely that binding of matrilysin to cholesterol sulfate facilitates the matrilysin-catalyzed modulation of cell surface proteins, thus inducing the cancer cell aggregation.