Human brain sialoglycan ligand for CD33, a microglial inhibitory Siglec implicated in Alzheimer's disease.

Alzheimer's disease (AD) is characterized by accumulation of misfolded proteins. Genetic studies implicate microglia, brain-resident phagocytic immune cells, in AD pathogenesis. As positive effectors, microglia clear toxic proteins, whereas as negative effectors, they release proinflammatory mediators.

Detection and Analysis of Proteins Modified by O-Linked N-Acetylglucosamine.

O-GlcNAc is a common post-translational modification of nuclear, mitochondrial, and cytoplasmic proteins that regulates normal physiology and the cell stress response. Dysregulation of O-GlcNAc cycling is implicated in the etiology of type II diabetes, heart failure, hypertension, and Alzheimer's disease, as well as cardioprotection. These protocols cover simple and comprehensive techniques for detecting proteins modified by O-GlcNAc and studying the enzymes that add or remove O-GlcNAc.

Probing the binding specificities of human Siglecs by cell-based glycan arrays.

Siglecs are a family of sialic acid-binding receptors expressed by cells of the immune system and a few other cell types capable of modulating immune cell functions upon recognition of sialoglycan ligands. While human Siglecs primarily bind to sialic acid residues on diverse types of glycoproteins and glycolipids that constitute the sialome, their fine binding specificities for elaborated complex glycan structures and the contribution of the glycoconjugate and protein context for recognition of sialoglycans at the cell surface are not fully elucidated. Here, we generated a library of isogenic human HEK293 cells with combinatorial loss/gain of individual sialyltransferase genes and the introduction of sulfotransferases for display of the human sialome and to dissect Siglec interactions in the natural context of glycoconjugates at the cell surface.

Isolation, identification, and characterization of the human airway ligand for the eosinophil and mast cell immunoinhibitory receptor Siglec-8.

Background: The immunoinhibitory receptor Siglec-8 on the surface of human eosinophils and mast cells binds to sialic acid-containing ligands in the local milieu, resulting in eosinophil apoptosis, inhibition of mast cell degranulation, and suppression of inflammation. Siglec-8 ligands were found on postmortem human trachea and bronchi and on upper airways in 2 compartments, cartilage and submucosal glands, but they were surprisingly absent from the epithelium. We hypothesized that Siglec-8 ligands in submucosal glands and ducts are normally transported to the airway mucus layer, which is lost during tissue preparation.

Immunosuppressive Siglec-E ligands on mouse aorta are up-regulated by LPS via NF-κB pathway.

Aims: Siglec-E, the mouse ortholog of human Siglec-9, is an immunosuppressive cell surface receptor. Both Siglec-E and Siglec-9 are primarily found on neutrophils, macrophages, and monocytes. When Siglec-E binds to sialoglycan ligands in its extracellular environment, it halts the immune cells' inflammatory responses.

A Sulfonamide Sialoside Analogue for Targeting Siglec-8 and -F on Immune Cells.

The Siglec family of cell surface receptors have emerged as attractive targets for cell-directed therapies due to their restricted expression on immune cells, endocytic properties, and ability to modulate receptor signaling. Human Siglec-8, for instance, has been identified as a therapeutic target for the treatment of eosinophil and mast cell disorders. A promising strategy to target Siglecs involves the use of liposomal nanoparticles with a multivalent display of Siglec ligands.

Immunoregulatory Siglec ligands are abundant in human and mouse aorta and are up-regulated by high glucose.

Aim: Inflammation is a driving force in development of atherosclerosis, and hyperglycemia is a significant risk factor for angiopathy. Siglec-9, expressed on human neutrophils and macrophages, engages specific glycan ligands on tissues to diminish ongoing inflammation.

Materials And Method: Siglec-9 ligands on human aorta were characterized and the effects of high glucose exposure on the expression of ligands for Siglec-9 on human umbilical vein endothelial cells (HUV-EC-C) in vitro and ligands for the comparable siglec (Siglec-E) on mouse aorta in vivo were studied.

Sialylated keratan sulfate proteoglycans are Siglec-8 ligands in human airways.

Human siglecs are a family of 14 sialic acid-binding proteins, most of which are expressed on subsets of immune cells where they regulate immune responses. Siglec-8 is expressed selectively on human allergic inflammatory cells-primarily eosinophils and mast cells-where engagement causes eosinophil apoptosis and inhibits mast cell mediator release. Evidence supports a model in which human eosinophils and mast cells bind to Siglec-8 sialoglycan ligands on inflammatory target tissues to resolve allergic inflammation and limit tissue damage.

Preparation of legionaminic acid analogs of sialo-glycoconjugates by means of mammalian sialyltransferases.

Legionaminic acids are analogs of sialic acid that occur in several bacteria. The most commonly occurring form is Leg5Ac7Ac, which differs from Neu5Ac only at the C7 (acetamido) and C9 (deoxy) positions. While these differences greatly reduce the susceptibility of Leg compounds to sialidases, several sialyltransferases have been identified that can use CMP-Leg5Ac7Ac as a donor (Watson et al.

Expression of ligands for Siglec-8 and Siglec-9 in human airways and airway cells.

Background: Balanced activation and inhibition of the immune system ensures pathogen clearance while avoiding hyperinflammation. Siglecs, sialic acid-binding proteins found on subsets of immune cells, often inhibit inflammation: Siglec-8 on eosinophils and Siglec-9 on neutrophils engage sialoglycan ligands on airways to diminish ongoing inflammation. The identities of human siglec ligands and their expression during inflammation are largely unknown.

Synthesis and evaluation of bivalent ligands for binding to the human melanocortin-4 receptor.

Membrane proteins, especially G-protein coupled receptors (GPCRs), are interesting and important theragnostic targets since many of them serve in intracellular signaling critical for all aspects of health and disease. The potential utility of designed bivalent ligands as targeting agents for cancer diagnosis and/or therapy can be evaluated by determining their binding to the corresponding receptors. As proof of concept, GPCR cell surface proteins are shown to be targeted specifically using multivalent ligands.

Salicylanilide derivatives block Mycobacterium tuberculosis through inhibition of isocitrate lyase and methionine aminopeptidase.

The global burden of tuberculosis, its health and socio-economic impacts, the presence of drug-resistant forms and a potential threat of latent tuberculosis should serve as a strong impetus for the development of novel antituberculosis agents. We reported the in vitro activity of salicylanilide benzoates and pyrazine-2-carboxylates against Mycobacterium tuberculosis (minimum inhibitory concentrations as low as 0.5 μmol/L).

Cytomegalovirus capsid protease: biological substrates are cleaved more efficiently by full-length enzyme (pUL80a) than by the catalytic domain (assemblin).

We compared the full-length capsid maturational protease (pPR, pUL80a) of human cytomegalovirus with its proteolytic domain (assemblin) for the ability to cleave two biological substrates, and we found that pPR is more efficient with both. Affinity-purified, refolded enzymes and substrates were combined under defined reaction conditions, and cleavage was monitored and quantified following staining of the resulting electrophoretically separated fragments. The enzymes were stabilized against self-cleavage by a single point mutation in each cleavage site (ICRMT-pPR and IC-assemblin).

Design and synthesis of trivalent ligands targeting opioid, cholecystokinin, and melanocortin receptors for the treatment of pain.

It has been known that co-administration of morphine with either cholecystokinin (CCK) receptor or melanocortin (MC) receptor antagonists enhance morphine's analgesic efficacy by reducing serious side effects such as tolerance and addiction. Considering these synergistic effects, we have designed trivalent ligands in which all three different pharmacophores for opioid, CCK, and MC receptors are combined in such a way as to conserve their own topographical pharmacophore structures. These ligands, excluding the cyclic compound, were synthesized by solid phase synthesis using Rink-amide resin under microwave assistance in very high yields.

Correlation of LUMO localization with the alpha-amylase inhibition constant in a Tendamistat-based series of linear and cyclic peptides.

The glycosidase alpha-amylase is responsible for the hydrolysis of alpha(1-->4) glycosidic linkages found in dietary starch as one means for controlling blood sugar level. The effect of alpha-amylase is detrimental, however, in the disease state diabetes mellitus, where blood glucose levels are elevated due to a biochemical defect. Inhibition of the enzyme's activity would reduce glucose absorption by the small intestine.