Glycosyltransferase Extl1 promotes CCR7-mediated dendritic cell migration to restrain infection and autoimmunity

CCR7-triggered DC migration toward draining lymph nodes is critical for the initiation of protective immunity and maintenance of immune tolerance. How to promote CCR7-mediated DC migration to determine T cell responses under inflammatory and homeostatic conditions remains poorly understood. Here we demonstrate that the Extl1 (Exostosin like glycosyltransferase 1) promotes CCR7-triggered DC migration in a heparan sulfate proteoglycans (HSPG)-dependent manner. Mechanistically, Extl1 mediates HSPG production via its glycosyltransferase domain to inhibit C1q expression. Extl1/HSPG axis relieves C1q-mediated restriction of CCR7 surface expression and internalization, and thus enhances CCR7-dependent migratory signaling activation. Consequently, Extl1 is required for DC-mediated Th1 and Th17 responses in immune defense against bacterial infection and for Treg cell development in the prevention of autoimmunity. Our study adds mechanistic insights to the regulation of CCR7-triggered DC migration in immunity and tolerance and provides a potential target for the treatment of infectious and autoimmune diseases.

Physiology and Pathophysiology of Heparan Sulfate in Animal Models: Its Biosynthesis and Degradation

Heparan sulfate (HS) is a type of glycosaminoglycan that plays a key role in a variety of biological functions in neurology, skeletal development, immunology, and tumor metastasis. Biosynthesis of HS is initiated by a link of xylose to Ser residue of HS proteoglycans, followed by the formation of a linker tetrasaccharide. Then, an extension reaction of HS disaccharide occurs through polymerization of many repetitive units consisting of iduronic acid and N-acetylglucosamine. Subsequently, several modification reactions take place to complete the maturation of HS. The sulfation positions of N-, 2-O-, 6-O-, and 3-O- are all mediated by specific enzymes that may have multiple isozymes. C5-epimerization is facilitated by the epimerase enzyme that converts glucuronic acid to iduronic acid. Once these enzymatic reactions have been completed, the desulfation reaction further modifies HS. Apart from HS biosynthesis, the degradation of HS is largely mediated by the lysosome, an intracellular organelle with acidic pH. Mucopolysaccharidosis is a genetic disorder characterized by an accumulation of glycosaminoglycans in the body associated with neuronal, skeletal, and visceral disorders. Genetically modified animal models have significantly contributed to the understanding of the in vivo role of these enzymes. Their role and potential link to diseases are also discussed.

Glycosaminoglycans: Carriers and Targets for Tailored Anti-Cancer Therapy

The tumor microenvironment (TME) is composed of cancerous, non-cancerous, stromal, and immune cells that are surrounded by the components of the extracellular matrix (ECM). Glycosaminoglycans (GAGs), natural biomacromolecules, essential ECM, and cell membrane components are extensively altered in cancer tissues. During disease progression, the GAG fine structure changes in a manner associated with disease evolution. Thus, changes in the GAG sulfation pattern are immediately correlated to malignant transformation. Their molecular weight, distribution, composition, and fine modifications, including sulfation, exhibit distinct alterations during cancer development. GAGs and GAG-based molecules, due to their unique properties, are suggested as promising effectors for anticancer therapy. Considering their participation in tumorigenesis, their utilization in drug development has been the focus of both industry and academic research efforts. These efforts have been developing in two main directions; (i) utilizing GAGs as targets of therapeutic strategies and (ii) employing GAGs specificity and excellent physicochemical properties for targeted delivery of cancer therapeutics. This review will comprehensively discuss recent developments and the broad potential of GAG utilization for cancer therapy.

Altered gene expression in CHO cells following polyamine starvation

AIM

To investigate the impact of polyamine deprivation on the transcriptome of CHO cells RESULTS: Polyamines play a central but poorly-understood role in cell proliferation. Most studies to date have utilised chemical inhibitors to probe polyamine function. Here we exploit the fact that CHO cells grown in serum-free medium have an absolute requirement for putrescine supplementation due to their deficiency in activity of the enzyme arginase. A gene expression microarray (Affymetrix) analysis of CHO-K1 cells starved of polyamines for 3 days showed that cessation of growth, associated with increased G1/S transition and inhibition of M/G1 transition was accompanied by increased mRNA levels of mitotic complex checkpoint genes (Mad2l1, Tkk, Bub1b) and in the transition of G1- to S-phase (such as Skp2 and Tfdp1). mRNAs associated with DNA homologous recombination and repair (including Fanconi's anaemia-related genes) and with RNA splicing were consistently increased. Alterations in mRNA levels for genes related to protein processing in the ER, to ER stress, and to p53-related and apoptosis pathways were also observed. mRNAs showing highest levels of fold-change included several which code for membrane-localised proteins and receptors (Thbs1, Tfrc1, Ackr3, Extl1).

CONCLUSIONS

Growth-arrest induced by polyamine deprivation was associated with significant alterations in levels of mRNAs associated with cell cycle progression, DNA repair, RNA splicing, ER trafficking and membrane signalling as well as p53 and apoptosis-related pathways.

Signaling at the Crossroads: Matrix-Derived Proteoglycan and Reactive Oxygen Species Signaling

SIGNIFICANCE

Proteoglycans (PGs), besides their structural contribution, have emerged as dynamic components that mediate a multitude of cellular events. The various roles of PGs are attributed to their structure, spatial localization, and ability to act as ligands and receptors. Reactive oxygen species (ROS) are small mediators that are generated in physiological and pathological conditions. Besides their reactivity and ability to induce oxidative stress, a growing body of data suggests that ROS signaling is more relevant than direct radical damage in development of human pathologies. Recent Advances: Cell surface transmembrane PGs (syndecans, cluster of differentiation 44) represent receptors in diverse and complex transduction networks, which involve redox signaling with implications in cancer, fibrosis, renal dysfunction, or Alzheimer's disease. Through NADPH oxidase (NOX)-dependent ROS, the extracellular PG, hyaluronan is involved in osteoclastogenesis and cancer. The ROS sources, NOX1 and NOX4, increase biglycan-induced inflammation, while NOX2 is a negative regulator.

CRITICAL ISSUES

The complexity of the mechanisms that bring ROS into the light of PG biology might be the foundation of a new research area with significant promise for understanding health and disease. Important aspects need to be investigated in PG/ROS signaling: the discovery of specific targets of ROS, the precise ROS-induced chemical modifications of these targets, and the study of their pathological relevance.

FUTURE DIRECTIONS

As we become more and more aware of the interactions between PG and ROS signaling underlying intracellular communication and cell fate decisions, it is quite conceivable that this field will allow to identify new therapeutic targets.-Antioxid. Redox Signal. 27, 855-873.

Implementation of infrared and Raman modalities for glycosaminoglycan characterization in complex systems

Glycosaminoglycans (GAGs) are natural, linear and negatively charged heteropolysaccharides which are incident in every mammalian tissue. They consist of repeating disaccharide units, which are composed of either sulfated or non-sulfated monosaccharides. Depending on tissue types, GAGs exhibit structural heterogeneity such as the position and degree of sulfation or within their disaccharide units composition being heparin, heparan sulfate, chondroitine sulfate, dermatan sulfate, keratan sulfate, and hyaluronic acid. They are covalently linked to a core protein (proteoglycans) or as free chains (hyaluronan). GAGs affect cell properties and functions either by direct interaction with cell receptors or by sequestration of growth factors. These evidences of divert biological roles of GAGs make their characterization at cell and tissue levels of importance. Thus, non-invasive techniques are interesting to investigate, to qualitatively and quantitatively characterize GAGs in vitro in order to use them as diagnostic biomarkers and/or as therapeutic targets in several human diseases including cancer. Infrared and Raman microspectroscopies and imaging are sensitive enough to differentiate and classify GAG types and subtypes in spite of their close molecular structures. Spectroscopic markers characteristic of reference GAG molecules were identified. Beyond these investigations of the standard GAG spectral signature, infrared and Raman spectral signatures of GAG were searched in complex biological systems like cells. The aim of the present review is to describe the implementation of these complementary vibrational spectroscopy techniques, and to discuss their potentials, advantages and disadvantages for GAG analysis. In addition, this review presents new data as we show for the first time GAG infrared and Raman spectral signatures from conditioned media and live cells, respectively.

Inherited CHST11/MIR3922 deletion is associated with a novel recessive syndrome presenting with skeletal malformation and malignant lymphoproliferative disease

Glycosaminoglycans (GAGs) such as chondroitin are ubiquitous disaccharide carbohydrate chains that contribute to the formation and function of proteoglycans at the cell membrane and in the extracellular matrix. Although GAG-modifying enzymes are required for diverse cellular functions, the role of these proteins in human development and disease is less well understood. Here, we describe two sisters out of seven siblings affected by congenital limb malformation and malignant lymphoproliferative disease. Using Whole-Genome Sequencing (WGS), we identified in the proband deletion of a 55 kb region within chromosome 12q23 that encompasses part of CHST11 (encoding chondroitin-4-sulfotransferase 1) and an embedded microRNA (MIR3922). The deletion was homozygous in the proband but not in each of three unaffected siblings. Genotyping data from the 1000 Genomes Project suggest that deletions inclusive of both CHST11 and MIR3922 are rare events. Given that CHST11 deficiency causes severe chondrodysplasia in mice that is similar to human limb malformation, these results underscore the importance of chondroitin modification in normal skeletal development. Our findings also potentially reveal an unexpected role for CHST11 and/or MIR3922 as tumor suppressors whose disruption may contribute to malignant lymphoproliferative disease.

Chondroitin sulfate N-acetylgalactosaminyltransferase-2 contributes to the replication of infectious bursal disease virus via interaction with the capsid protein VP2

Infectious bursal disease virus (IBDV) is a birnavirus that causes a highly contagious immunosuppressive disease in young chickens. The capsid protein VP2 of IBDV plays multiple roles in its life cycle. To more comprehensively understand the functions of VP2 involved in the communication between virus and host, we used yeast two-hybrid screening to identify the cellular factors that interact with this protein. We found that chondroitin sulfate N-acetylgalactosaminyltransferase-2 (CSGalNAcT2), a typical type II transmembrane protein located in Golgi apparatus, could interact with VP2, and we confirmed this interaction by co-immunoprecipitation and confocal laser scanning microscopy assays. Additionally, up-regulation of CSGalNAcT2 during IBDV infection was observed. Overexpression and siRNA-mediated knockdown of CSGalNAcT2 assays suggested that CSGalNAcT2 promoted IBDV replication. Moreover, this enhancing effect of CSGalNAcT2 could be inhibited by Brefeldin A, which is a Golgi-disturbing agent. This indicated that the integrity of Golgi apparatus structure was involved in the function of CSGalNAcT2. Taken together, we concluded that CSGalNAcT2, located in the Golgi apparatus, contributed to the replication of IBDV via interaction with VP2.

Chondroitin sulphate N-acetylgalactosaminyl-transferase-1 inhibits recovery from neural injury

Extracellular factors that inhibit axon growth and intrinsic factors that promote it affect neural regeneration. Therapies targeting any single gene have not yet simultaneously optimized both types of factors. Chondroitin sulphate (CS), a glycosaminoglycan, is the most abundant extracellular inhibitor of axon growth. Here we show that mice carrying a gene knockout for CS N-acetylgalactosaminyltransferase-1 (T1), a key enzyme in CS biosynthesis, recover more completely from spinal cord injury than wild-type mice and even chondroitinase ABC-treated mice. Notably, synthesis of heparan sulphate (HS), a glycosaminoglycan promoting axonal growth, is also upregulated in TI knockout mice because HS-synthesis enzymes are induced in the mutant neurons. Moreover, chondroitinase ABC treatment never induces HS upregulation. Taken together, our results indicate that regulation of a single gene, T1, mediates excellent recovery from spinal cord injury by optimizing counteracting effectors of axon regeneration—an extracellular inhibitor of CS and intrinsic promoters, namely, HS-synthesis enzymes.

The glycosaminoglycan chondroitin sulphate inhibits axon growth. Here the authors show that mice deficient in chondroitin sulphate biosynthesis have increased levels of heparan sulphate, which is more efficient than chondroitinase in supporting recovery from spinal cord injury.

Differential gene expression of the intermediate and outer interzone layers of developing articular cartilage in murine embryos

Nascent embryonic joints, interzones, contain a distinct cohort of progenitor cells responsible for the formation of the majority of articular tissues. However, to date the interzone has largely been studied using in situ analysis for candidate genes in the context of the embryo rather than using an unbiased genome-wide expression analysis on isolated interzone cells, leaving significant controversy regarding the exact role of the intermediate and outer interzone layers in joint formation. Therefore, in this study, using laser capture microdissection (three biological replicates), we selectively harvested the intermediate and outer interzones of mouse embryos at gestational age 15.5 days, just prior to cavitation, when the differences between the layers should be most profound. Microarray analysis (Agilent Whole Mouse Genome Oligo Microarrays) was performed and the differential gene expression between the intermediate interzone cells and outer interzone cells was examined by performing a two-sided paired Student's t-test and pathway analysis. One hundred ninety-seven genes were differentially expressed (≥ 2-fold) between the intermediate interzone and the outer interzone with a P-value ≤ 0.01. Of these, 91 genes showed higher expression levels in the intermediate interzone and 106 were expressed higher in the outer interzone. Pathway analysis of differentially expressed genes suggests an important role for inflammatory processes in the interzone layers, especially in the intermediate interzone, and hence in joint and articular cartilage development. The high representation of genes relevant to chondrocyte hypertrophy and endochondral ossification in the outer interzone suggests that it undergoes endochondral ossification.

The exostosin family: proteins with many functions

Heparan sulfates are complex sulfated molecules found in abundance at cell surfaces and in the extracellular matrix. They bind to and influence the activity of a variety of molecules like growth factors, proteases and morphogens and are thus involved in various cell-cell and cell-matrix interactions. The mammalian EXT proteins have glycosyltransferase activities relevant for HS chain polymerization, however their exact role in this process is still confusing. In this review, we summarize current knowledge about the biochemical activities and some proposed functions of the members of the EXT protein family and their roles in human disease.

Heparan sulfate proteoglycans in the control of B cell development and the pathogenesis of multiple myeloma

Heparan sulfate proteoglycans (HSPGs) have essential functions during embryonic development and throughout postnatal life. To exert these functions, they undergo a series of processing reactions by heparan-sulfate-modifying enzymes (HSMEs), which endows them with highly modified heparan sulfate (HS) domains that provide specific docking sites for a large number of bioactive molecules. The development and antigen-dependent differentiation of normal B lymphocytes, as well as the growth and progression of B-lineage malignancies, are orchestrated by an array of growth factors, cytokines and chemokines many of which display HS binding. As discussed in this review, tightly regulated HSPG expression is a requirement for normal B cell maturation, differentiation and function. In addition, the HSPG syndecan-1 functions as a versatile co-receptor for signals from the bone marrow microenvironment, essential for the survival of long-lived plasma cells and multiple myeloma (MM) plasma cells. Targeting of HSMEs or HS chains on MM cells increases their sensitivity to drugs currently used in MM treatment, including bortezomib, lenalidomide or dexamethasone. Taken together, these findings render the HS biosynthetic machinery a promising target for MM treatment.