Discovery of a Small-Molecule Modulator of Glycosaminoglycan Sulfation

Chondroitin 4-O-sulfation regulates hippocampal perineuronal nets and social memory

Glycan alterations are associated with aging, neuropsychiatric, and neurodegenerative diseases, although the contributions of specific glycan structures to emotion and cognitive functions remain largely unknown. Here, we used a combination of chemistry and neurobiology to show that 4-O-sulfated chondroitin sulfate (CS) polysaccharides are critical regulators of perineuronal nets (PNNs) and synapse development in the mouse hippocampus, thereby affecting anxiety and cognitive abilities such as social memory. Brain-specific deletion of CS 4-O-sulfation in mice increased PNN densities in the area CA2 (cornu ammonis 2), leading to imbalanced excitatory-to-inhibitory synaptic ratios, reduced CREB activation, elevated anxiety, and social memory dysfunction. The impairments in PNN densities, CREB activity, and social memory were recapitulated by selective ablation of CS 4-O-sulfation in the CA2 region during adulthood. Notably, enzymatic pruning of the excess PNNs reduced anxiety levels and restored social memory, while chemical manipulation of CS 4-O-sulfation levels reversibly modulated PNN densities surrounding hippocampal neurons and the balance of excitatory and inhibitory synapses. These findings reveal key roles for CS 4-O-sulfation in adult brain plasticity, social memory, and anxiety regulation, and they suggest that targeting CS 4-O-sulfation may represent a strategy to address neuropsychiatric and neurodegenerative diseases associated with social cognitive dysfunction.

Increased 3-O-sulfated heparan sulfate in Alzheimer's disease brain is associated with genetic risk gene HS3ST1

HS3ST1 is a genetic risk gene associated with Alzheimer's disease (AD) and overexpressed in patients, but how it contributes to the disease progression is unknown. We report the analysis of brain heparan sulfate (HS) from AD and other tauopathies using a LC-MS/MS method. A specific 3-O-sulfated HS displayed sevenfold increase in the AD group (n = 14, P < 0.0005). Analysis of the HS modified by recombinant sulfotransferases and HS from genetic knockout mice revealed that the specific 3-O-sulfated HS is made by 3-O-sulfotransferase isoform 1 (3-OST-1), which is encoded by the HS3ST1 gene. A synthetic tetradecasaccharide (14-mer) carrying the specific 3-O-sulfated domain displayed stronger inhibition for tau internalization than a 14-mer without the domain, suggesting that the 3-O-sulfated HS is used in tau cellular uptake. Our findings suggest that the overexpression of HS3ST1 gene may enhance the spread of tau pathology, uncovering a previously unidentified therapeutic target for AD.

Inhibition of Astrocytic Carbohydrate Sulfotransferase 15 Promotes Nerve Repair After Spinal Cord Injury via Mitigation of CSPG Mediated Axonal Inhibition

Nerve tissue regeneration is a significant problem. After neural diseases and damage such as spinal cord injury (SCI), the accumulation of chondroitin sulfate proteoglycans (CSPG) comprising axonal inhibitory glycosaminoglycan chains in the microenvironment is a major barrier that obstructs nerve repair. Interfering with the production of glycosaminoglycans, especially the critical inhibitory chains, could be a potential therapeutic strategy for SCI, which is, however, poorly defined. This study identifies Chst15, the chondroitin sulfotransferase controlling the generation of axonal inhibitory chondroitin sulfate-E, as a therapeutic target of SCI. Using a recently reported small molecular Chst15 inhibitor, this study investigates the effects of Chst15 inhibition on astrocyte behaviors and the associated consequences of in vivo disruption of the inhibitory microenvironment. Deposition of CSPGs in the extracellular matrix and migration of astrocytes are both significantly impaired by Chst15 inhibition. Administration of the inhibitor in transected spinal cord tissues of rats effectively promotes motor functional restoration and nerve tissue regeneration by a mechanism related to the attenuation of inhibitory CSPGs, glial scar formation and inflammatory responses. This study highlights the role of Chst15 in the CSPG-mediated inhibition of neural recovery after SCI and proposes an effective neuroregenerative therapeutic strategy that uses Chst15 as a potential target.

Tools for mammalian glycoscience research

Cellular carbohydrates or glycans are critical mediators of biological function. Their remarkably diverse structures and varied activities present exciting opportunities for understanding many areas of biology. In this primer, we discuss key methods and recent breakthrough technologies for identifying, monitoring, and manipulating glycans in mammalian systems.

From Steroid and Drug Metabolism to Glycobiology, Using Sulfotransferase Structures to Understand and Tailor Function

Sulfotransferases are ubiquitous enzymes that transfer a sulfo group from the universal cofactor donor 3'-phosphoadenosine 5'-phosphosulfate to a broad range of acceptor substrates. In humans, the cytosolic sulfotransferases are involved in the sulfation of endogenous compounds such as steroids, neurotransmitters, hormones, and bile acids as well as xenobiotics including drugs, toxins, and environmental chemicals. The Golgi associated membrane-bound sulfotransferases are involved in post-translational modification of macromolecules from glycosaminoglycans to proteins. The sulfation of small molecules can have profound biologic effects on the functionality of the acceptor, including activation, deactivation, or enhanced metabolism and elimination. Sulfation of macromolecules has been shown to regulate a number of physiologic and pathophysiological pathways by enhancing binding affinity to regulatory proteins or binding partners. Over the last 25 years, crystal structures of these enzymes have provided a wealth of information on the mechanisms of this process and the specificity of these enzymes. This review will focus on the general commonalities of the sulfotransferases, from enzyme structure to catalytic mechanism as well as providing examples into how structural information is being used to either design drugs that inhibit sulfotransferases or to modify the enzymes to improve drug synthesis. SIGNIFICANCE STATEMENT: This manuscript honors Dr. Masahiko Negishi's contribution to the understanding of sulfotransferase mechanism, specificity, and roles in biology by analyzing the crystal structures that have been solved over the last 25 years.

Purification, structural characterization, and anticoagulant activity evaluation of chondroitin sulfate from codfish (Gadus macrocephalus) bones

Chondroitin sulfate (CCS) was purified from discarded codfish (Gadus macrocephalus) bones, and its chemical structure and anticoagulant activity were assessed. CCS was obtained via enzymatic lysis and ion-exchange column chromatography, with a yield of approximately 0.15%. High-performance gel performance chromatography revealed CCS to be a largely homogeneous polysaccharide with a relatively low molecular weight of 12.3 kDa. FT-IR spectroscopy, NMR spectroscopy, and SAX-HPLC indicated that CCS was composed of monosulfated disaccharides (ΔDi4S 73.85% and ΔDi6S 19.06%) and nonsulfated disaccharides (ΔDi0S 7.09%). In vitro anticoagulation analyses revealed that CCS was able to significantly prolong activated partial thromboplastin time (APTT) and thrombin time (TT) (p < 0.05). At a CCS concentration of 5 μg/mL and 25 μg/mL, APTT and TT were approximately 1.08 and 1.12 times higher, respectively, compared to the negative control group. The results indicated that CCS might offer value as a dietary fiber supplement with the potential to prevent the incidence of coagulation-related thrombosis.

Chondroitin Sulfate Proteoglycan 4,6 sulfation regulates sympathetic nerve regeneration after myocardial infarction

Sympathetic denervation of the heart following ischemia/reperfusion induced myocardial infarction (MI) is sustained by chondroitin sulfate proteoglycans (CSPGs) in the cardiac scar. Denervation predicts risk of sudden cardiac death in humans. Blocking CSPG signaling restores sympathetic axon outgrowth into the cardiac scar, decreasing arrhythmia susceptibility. Axon growth inhibition by CSPGs is thought to depend on the sulfation status of the glycosaminoglycans (CS-GAGs) attached to the core protein. Tandem sulfation of CS-GAGs at the 4^th (4S) and 6^th (6S) positions of n-acetyl-galactosamine inhibits outgrowth in several types of neurons within the central nervous system, but it is not known if sulfation is similarly critical during peripheral nerve regeneration. We asked if CSPG sulfation prevented sympathetic axon outgrowth. Neurite outgrowth of dissociated rat sympathetic neurons across purified CSPGs is restored in vitro by reducing 4S with the 4-sulfatase enzyme Arylsulfatase-B (ARSB). Additionally, we co-cultured mouse cardiac scar tissue with mouse sympathetic ganglia ex vivo and found that reducing 4S with ARSB restored axon outgrowth to control levels. We examined levels of the enzymes responsible for adding and removing sulfation to CS-GAGs by western blot to determine if they were altered in the left ventricle after MI. We found that CHST15 (4S dependent 6-sulfotransferase) was upregulated, and ARSB was downregulated after MI. Increased CHST15 combined with decreased ARSB suggests a mechanism for production and maintenance of sulfated CSPGs in the cardiac scar. We altered tandem sulfated 4S,6S CS-GAGs in vivo by transient siRNA knockdown of Chst15 and found that reducing 4S,6S restored Tyrosine Hydroxylase (TH) positive sympathetic nerve fibers in the cardiac scar and reduced arrhythmias using a mouse model of MI. Overall, our results suggest that modulating CSPG-sulfation after MI may be a therapeutic target to promote sympathetic nerve regeneration in the cardiac scar and reduce post-MI cardiac arrhythmias.

Functions of chondroitin/dermatan sulfate containing GalNAc4,6-disulfate

Chondroitin sulfate (CS) and dermatan sulfate (DS) containing GalNAc4,6-disulfate (GalNAc4S6S) were initially discovered in marine animals. Following the discovery, these glycosaminoglycans have been found in various animals including human. In the biosynthesis of CS/DS containing GalNAc4S6S, three groups of sulfotransferases are involved; chondroitin 4-sulfotransferases (C4STs), dermatan 4-sulfotransferase-1 (D4ST-1) and GalNAc 4-sulfate 6-O-sulfotransferase (GalNAc4S-6ST). GalNAc4S-6ST and its products have been shown to play important roles in the abnormal pathological conditions such as central nervous system injury, cancer development, abnormal tissue fibrosis, development of osteoporosis, and infection with viruses or nematodes. CS/DS containing GalNAc4S6S has been shown to increase with the functional differentiation of mast cells, macrophages and neutrophils. Genetic approaches using knockout or knockdown of GalNAc4S-6ST, blocking of the epitopes containing GalNAc4S6S by specific antibodies and chemical technology that enabled the synthesis of oligosaccharides with defined sulfation patterns have been applied successfully to these investigations. These studies contributed significantly to the basic understanding of the functional roles of CS/DS containing GalNAc4S6S in various abnormal conditions, and appear to provide promising clues to the development of possible measures to treat them.

Synthesis, characterization, and in vitro antibacterial activity of some new pyridinone and pyrazole derivatives with some in silico ADME and molecular modeling study

A new series of pyridine-2-one and pyrazole derivatives were designed and synthesized based on cyanoacrylamide derivatives containing 2,4-dichlro aniline and 6-methyl 2-amino pyridine as an aryl group. Condensation of cyanoacrylamide derivatives 3a–d with different active methylene (malononitrile, ethyl cyanoacetate cyanoacetamide, and ethyl acetoacetate) in the presence of piperidine as basic catalyst afforded the corresponding pyridinone derivatives 4a–c, 5, 9, and 13. Furthermore, the reaction of cyanoacrylamide derivatives 3a–d with bi-nucleophile as hydrazine hydrate and thiosemicarbazide afforded the corresponding pyrazole derivatives 14a,b and 16. The newly designed derivatives were confirmed and established based on the elemental analysis and spectra data (IR, 1H NMR, 13C NMR, and mass). The in vitro antibacterial activity was evaluated against four bacterial strains with weak to good antibacterial activity. Moreover, the results indicated that the most active derivatives 3a, 4a, 4b, 9, and 16 might lead to antibacterial agents, especially against B. subtilis and P. vulgaris. The DFT calculations were performed to estimate its geometric structure and electronic properties. In addition, the most active pyridinone and pyrazole derivatives were further evaluated for in silico physicochemical, drug-likeness, and toxicity prediction. These derivatives obeyed all Lipinski’s and Veber’s rules without any violation and displayed non-immunotoxin, non-mutagenic, and non-cytotoxic. Molecular docking simulation was performed inside the active site of Topoisomerase IV (PDB:3FV5). It displayed binding energy ranging from -14.97 kcal/mol to -18.86 kcal/mol with hydrogen bonding and arene–cation interaction. Therefore, these derivatives were suggested to be good antibacterial agents via topoisomerase IV inhibitor.

Graphical abstract

Small molecule inhibitors of mammalian glycosylation

Glycans are one of the fundamental biopolymers encountered in living systems. Compared to polynucleotide and polypeptide biosynthesis, polysaccharide biosynthesis is a uniquely combinatorial process to which interdependent enzymes with seemingly broad specificities contribute. The resulting intracellular cell surface, and secreted glycans play key roles in health and disease, from embryogenesis to cancer progression. The study and modulation of glycans in cell and organismal biology is aided by small molecule inhibitors of the enzymes involved in glycan biosynthesis. In this review, we survey the arsenal of currently available inhibitors, focusing on agents which have been independently validated in diverse systems. We highlight the utility of these inhibitors and drawbacks to their use, emphasizing the need for innovation for basic research as well as for therapeutic applications.

Transcriptome analysis of tumor-derived mesenchymal progenitor cells shows that CHST15 is a fibrosis regulator of retroperitoneal liposarcoma

Background

Retroperitoneal liposarcoma (RPLS) is a rare, biologically heterogeneous tumor with distinct clinical characteristics, such as frequent local recurrence, repeated relapse, and rare distant metastasis. No effective targeted therapy is available for RPLS. Here, we aim to determine the pathological functions and therapeutic potential of carbohydrate sulfotransferase 15 (CHST15) in RPLS.

Methods

Tumor-derived mesenchymal progenitor cells (MPCs) and normal adipose derived mesenchymal stem cells (MSCs) were obtained from patients with RPLS. MPCs and MSCs were isolated and characterized based on surface markers, proliferation, and differentiation using flow cytometry and molecular staining. Transcriptome analysis was performed to decipher expression profile of differentiation-related genes in 3 paired MSCs and MPCs. Further confirmation of genes were performed using quantitative real-time polymerase chain reaction (qRT-PCR). Plasmids overexpressing CHST15 were transfected into adipose MSCs to examine fibrosis-related gene expression at mRNA level by real-time PCR.

Results

The tumor stromal-derived MPCs expressed CD105, CD73, and CD90, and exhibited osteogenic and adipogenic differentiation potential in vitro. The proliferation of tumor-derived MPCs was significantly lower than that of normal adipose-derived MSCs (P<0.001). Transcriptome analysis revealed upregulation of IL-7R, ALPL, PKNOX2, and CHST15 in tumor-derived MPCs. CHST15 was highly expressed in tumor-derived MPCs (P<0.001). CHST15 mediated fibrosis-related FGF2 gene expression in MSCs (P<0.05) and MPCs (P<0.001).

Conclusions

CHST15 is upregulated in tumor-derived MPCs and regulates fibrosis in RPLS. This provides clues for development of novel therapeutic strategies by targeting CHST15-induced MPC activation in RPLS.

Pathogenesis of COVID-19 described through the lens of an undersulfated and degraded epithelial and endothelial glycocalyx

The glycocalyx surrounds every eukaryotic cell and is a complex mesh of proteins and carbohydrates. It consists of proteoglycans with glycosaminoglycan side chains, which are highly sulfated under normal physiological conditions. The degree of sulfation and the position of the sulfate groups mainly determine biological function. The intact highly sulfated glycocalyx of the epithelium may repel severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) through electrostatic forces. However, if the glycocalyx is undersulfated and 3-O-sulfotransferase 3B (3OST-3B) is overexpressed, as is the case during chronic inflammatory conditions, SARS-CoV-2 entry may be facilitated by the glycocalyx. The degree of sulfation and position of the sulfate groups will also affect functions such as immune modulation, the inflammatory response, vascular permeability and tone, coagulation, mediation of sheer stress, and protection against oxidative stress. The rate-limiting factor to sulfation is the availability of inorganic sulfate. Various genetic and epigenetic factors will affect sulfur metabolism and inorganic sulfate availability, such as various dietary factors, and exposure to drugs, environmental toxins, and biotoxins, which will deplete inorganic sulfate. The role that undersulfation plays in the various comorbid conditions that predispose to coronavirus disease 2019 (COVID-19), is also considered. The undersulfated glycocalyx may not only increase susceptibility to SARS-CoV-2 infection, but would also result in a hyperinflammatory response, vascular permeability, and shedding of the glycocalyx components, giving rise to a procoagulant and antifibrinolytic state and eventual multiple organ failure. These symptoms relate to a diagnosis of systemic septic shock seen in almost all COVID-19 deaths. The focus of prevention and treatment protocols proposed is the preservation of epithelial and endothelial glycocalyx integrity.

A novel chondroitin AC lyase from Pedobacter xixiisoli: Cloning, expression, characterization and the application in the preparation of oligosaccharides

Chondroitin AC lyase can efficiently hydrolyze chondroitin sulfate (CS) to low molecule weight chondroitin sulfate, which has been widely used in clinical therapy, including anti-tumor, anti-oxidation, hypolipidemic, and anti-inflammatory. In this work, a novel chondroitin AC lyase from Pedobacter xixiisoli (PxchonAC) was cloned and overexpressed in Escherichia coli BL21 (DE3). The characterization of PxchonAC showed that it has specific activities on chondroitin sulfate A, Chondroitin sulfate C and hyaluronic acid with 428.77, 270.57, and 136.06 U mg^-1, respectively. The K_m and V_max of PxchonAC were 0.61 mg mL^-1 and 670.18 U mg^-1 using chondroitin sulfate A as the substrate. The enzyme had a half-life of roughly 660 min at 37 °C in the presence of Ca²⁺ and remained a residual activity of 54 % after incubated at 4 °C for 25 days. Molecular docking revealed that Asn123, His223, Tyr232, Arg286, Arg290, Asn372, and Glu374 were mainly involved in the substrate binding. The enzymatic hydrolysis product was analyzed by gel permeation chromatography, demonstrating PxchonAC could hydrolyze CS efficiently.

Synthesis of structurally defined chondroitin sulfate: Paving the way to the structure-activity relationship studies

Chondroitin sulfate (CS) is one of the major and widespread glycosaminoglycans, a family of structurally complex, linear, anionic hetero-co-polysaccharides. CS plays a vital role in various normal physiological and pathological processes, thus, showing varieties of biological activities, such as anti-oxidation, anti-atherosclerosis, anti-thrombosis, and insignificant immunogenicity. However, the heterogeneity of the naturally occurring CS potentially leads to function unspecific and limits further structure-activity relationship studies. Therefore, the synthesis of CS with well-defined and uniform chain lengths is of major interest for the development of reliable drugs. In this review, we examine the remarkable progress that has been made in the chemical, enzymatic and chemoenzymatic synthesis of CS and its derivatives, providing a broad spectrum of options to access CS of well controlled chain lengths.

The potential of memory enhancement through modulation of perineuronal nets

With an increasingly aging global population, the incidence of neurological diseases such as dementia is set to increase to unmanageable levels, yet there are currently only symptomatic therapies available for treatment. The mechanisms underlying the development of some forms of dementia, such as Alzheimer's disease (AD), are not yet completely elucidated with several competing hypotheses existing. During the closure of the critical period in the brain, significant compositional changes occur to the neural extracellular matrix (ECM). Specifically, condensed mesh-like structures called perineuronal nets (PNNs) form around subsets of neurons and have a profound effect on axonal growth and limit neuronal plasticity. These PNNs act as a morphological checkpoint and can influence memory and cognition. Manipulating these important ECM structures may provide the key to reactivating plasticity and restoring memory, both of which are severely impaired in AD and other associated neurological diseases. This review explores the current understanding of how PNNs are manipulated and examines potential new methods for PNN modulation. LINKED ARTICLES: This article is part of a themed section on Therapeutics for Dementia and Alzheimer's Disease: New Directions for Precision Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.18/issuetoc.

Heparin Binding Proteins as Therapeutic Target: An Historical Account and Current Trends

The polyanionic nature and the ability to interact with proteins with different affinities are properties of sulfated glycosaminoglycans (GAGs) that determine their biological function. In designing drugs affecting the interaction of proteins with GAGs the challenge has been to generate agents with high binding specificity. The example to emulated has been a heparin-derived pentasaccharide that binds to antithrombin-III with high affinity. However, the portability of this model to other biological situations is questioned on several accounts. Because of their structural flexibility, oligosaccharides with different sulfation and uronic acid conformation can display the same binding proficiency to different proteins and produce comparable biological effects. This circumstance represents a formidable obstacle to the design of drugs based on the heparin scaffold. The conceptual framework discussed in this article is that through a direct intervention on the heparin-binding functionality of proteins is possible to achieve a high degree of action specificity. This objective is currently pursued through two strategies. The first makes use of small molecules for which in the text we provide examples from past and present literature concerning angiogenic factors and enzymes. The second approach entails the mutagenesis of the GAG-binding site of proteins as a means to generate a new class of biologics of therapeutic interest.

Emerging and Re-Emerging Warheads for Targeted Covalent Inhibitors: Applications in Medicinal Chemistry and Chemical Biology

Targeted covalent inhibitors (TCIs) are designed to bind poorly conserved amino acids by means of reactive groups, the so-called warheads. Currently, targeting noncatalytic cysteine residues with acrylamides and other α,β-unsaturated carbonyl compounds is the predominant strategy in TCI development. The recent ascent of covalent drugs has stimulated considerable efforts to characterize alternative warheads for the covalent-reversible and irreversible engagement of noncatalytic cysteine residues as well as other amino acids. This Perspective article provides an overview of warheads-beyond α,β-unsaturated amides-recently used in the design of targeted covalent ligands. Promising reactive groups that have not yet demonstrated their utility in TCI development are also highlighted. Special emphasis is placed on the discussion of reactivity and of case studies illustrating applications in medicinal chemistry and chemical biology.

Structure-based design of nucleoside-derived analogues as sulfotransferase inhibitors

Regulated sulfation of biomolecules by sulfotransferases (STs) plays a role in many biological processes with implications for a number of disease areas. A structure-based approach and molecular docking were used to design a library of ST inhibitors.

Heparan Sulfate as a Therapeutic Target in Tauopathies: Insights From Zebrafish

Microtubule-associated protein tau (MAPT) hyperphosphorylation and aggregation, are two hallmarks of a family of neurodegenerative disorders collectively referred to as tauopathies. In many tauopathies, including Alzheimer's disease (AD), progressive supranuclear palsy (PSP) and Pick's disease, tau aggregates are found associated with highly sulfated polysaccharides known as heparan sulfates (HSs). In AD, amyloid beta (Aβ) peptide aggregates associated with HS are also characteristic of disease. Heparin, an HS analog, promotes misfolding, hyperphosphorylation and aggregation of tau protein in vitro. HS also provides cell surface receptors for attachment and uptake of tau seeds, enabling their propagation. These findings point to HS-tau interactions as potential therapeutic targets in tauopathies. The zebrafish genome contains genes paralogous to MAPT, genes orthologous to HS biosynthetic and chain modifier enzymes, and other genes implicated in AD. The nervous system in the zebrafish bears anatomical and chemical similarities to that in humans. These homologies, together with numerous technical advantages, make zebrafish a valuable model for investigating basic mechanisms in tauopathies and identifying therapeutic targets. Here, we comprehensively review current knowledge on the role of HSs in tau pathology and HS-targeting therapeutic approaches. We also discuss novel insights from zebrafish suggesting a role for HS 3-O-sulfated motifs in tau pathology and establishing HS antagonists as potential preventive agents or therapies for tauopathies.

Perineuronal nets in brain physiology and disease

Perineuronal nets (PNNs) in the brain are condensed glycosaminoglycan-rich extracellular matrix structures with heterogeneous composition yet specific organization. They typically assemble around a subset of fast-spiking interneurons that are implicated in learning and memory. Owing to their unique structural organization, PNNs have neuroprotective capacities but also participate in signal transduction and in controlling neuronal activity and plasticity. In this review, we define PNN structure in detail and describe its various biochemical and physiological functions. We further discuss the role of PNNs in brain disorders such as schizophrenia, bipolar disorder, Alzheimer disease and addictions. Lastly, we describe therapeutic approaches that target PNNs to alter brain physiology and counter brain dysfunction.