A hyaluronan receptor for endocytosis (HARE) link domain N-glycan is required for extracellular signal-regulated kinase (ERK) and nuclear factor-κB (NF-κB) signaling in response to the uptake of hyaluronan but not heparin, dermatan sulfate, or acetylated low density lipoprotein (LDL)

FTH1 protects against osteoarthritis by MAPK pathway inhibition of extracellular matrix degradation

OBJECTIVE

Ferritin heavy chain 1 (FTH1) is an important subunit of ferro-storing proteins and is indispensable for iron metabolism. Though it has been extensively studied in numerous organs and diseases, the relationship between FTH1 and osteoarthritis (OA) is unclear.

DESIGN

Primary murine chondrocytes and cartilage explants were treated with FTH1 siRNA for 72 h. Mice were injected with adenovirus expressing FTH1 after destabilized medial meniscus (DMM) surgery. These approaches were used to determine the effect of FTH1 expression on the pathophysiology of OA.

RESULTS

FTH1 expression was down regulated in OA patients and mice after DMM surgery. Knock down of FTH1 induced articular cartilage damage and extracellular matrix degradation in cartilage explants. Further, over expression of FTH1 reduced the susceptibility of chondrocytes to ferroptosis and reversed decrements in SOX9 and aggrecan after DMM surgery. Moreover, FTH1 relieved OA by inhibition of the chondrocyte MAPK pathway.

CONCLUSION

This study found FTH1 to play an essential role in extracellular matrix degradation, ferroptosis, and chondrocytes senescence during OA progression. Further, injection of adenovirus expressing FTH1 may be a potential strategy for OA prevention and therapy.

Chloroquine and cytosolic galectins affect endosomal escape of antisense oligonucleotides after Stabilin-mediated endocytosis

Non-DNA-binding Stabilin-2/HARE receptors expressed on liver sinusoidal endothelial cells specifically bind to and internalize several classes of phosphorothioate antisense oligonucleotides (PS-ASOs). After Stabilin-mediated uptake, PS-ASOs are trafficked within endosomes (>97%-99%), ultimately resulting in destruction in the lysosome. The ASO entrapment in endosomes lowers therapeutic efficacy, thereby increasing the overall dose for patients. Here, we use confocal microscopy to characterize the intracellular route transverse by PS-ASOs after Stabilin receptor-mediated uptake in stable recombinant Stabilin-1 and -2 cell lines. We found that PS-ASOs as well as the Stabilin-2 receptor transverse the classic path: clathrin-coated vesicle-early endosome-late endosome-lysosome. Chloroquine exposure facilitated endosomal escape of PS-ASOs leading to target knockdown by more than 50% as compared to untreated cells, resulting in increased PS-ASO efficacy. We also characterize cytosolic galectins as novel contributor for PS-ASO escape. Galectins knockdown enhances ASO efficacy by more than 60% by modulating EEA1, Rab5C, and Rab7A mRNA expression, leading to a delay in the endosomal vesicle maturation process. Collectively, our results provide additional insight for increasing PS-ASO efficacy by enhancing endosomal escape, which can further be utilized for other nucleic acid-based modalities.

Targeted Lymphoma Therapy Using a Gold Nanoframework-Based Drug Delivery System

Precision nanomedicine can be employed as an alternative to chemo- or radiotherapy to overcome challenges associated with the often narrow therapeutic window of traditional treatment approaches, while safely inducing effective, targeted antitumor responses. Herein, we report the formulation of a therapeutic nanocomposite comprising a hyaluronic acid (HA)-coated gold nanoframework (AuNF) delivery system and encapsulated IT848, a small molecule with potent antilymphoma and -myeloma properties that targets the transcriptional activity of nuclear factor kappa B (NF-κB). The porous AuNFs fabricated via a liposome-templated approach were loaded with IT848 and surface-functionalized with HA to formulate the nanotherapeutics that were able to efficiently deliver the payload with high specificity to myeloma and lymphoma cell lines in vitro. In vivo studies characterized biodistribution, pharmacokinetics, and safety of HA-AuNFs, and we demonstrated superior efficacy of HA-AuNF-formulated IT848 vs free IT848 in lymphoma mouse models. Both in vitro and in vivo results affirm that the AuNF system can be adopted for targeted cancer therapy, improving the drug safety profile, and enhancing its efficacy with minimal dosing. HA-AuNF-formulated IT848 therefore has strong potential for clinical translation.

Hyaluronan Receptors as Mediators and Modulators of the Tumor Microenvironment

The tumor microenvironment (TME) is a dynamic and complex matter shaped by heterogenous cancer and cancer-associated cells present at the tumor site. Hyaluronan (HA) is a major TME component that plays pro-tumorigenic and carcinogenic functions. These functions are mediated by different hyaladherins expressed by cancer and tumor-associated cells triggering downstream signaling pathways that determine cell fate and contribute to TME progression toward a carcinogenic state. Here, the interaction of HA is reviewed with several cell-surface hyaladherins-CD44, RHAMM, TLR2 and 4, LYVE-1, HARE, and layilin. The signaling pathways activated by these interactions and the respective response of different cell populations within the TME, and the modulation of the TME, are discussed. Potential cancer therapies via targeting these interactions are also briefly discussed.

Advanced Glycation End-Products (AGEs): Formation, Chemistry, Classification, Receptors, and Diseases Related to AGEs

Advanced glycation end-products (AGEs) constitute a non-homogenous, chemically diverse group of compounds formed either exogeneously or endogeneously on the course of various pathways in the human body. In general, they are formed non-enzymatically by condensation between carbonyl groups of reducing sugars and free amine groups of nucleic acids, proteins, or lipids, followed by further rearrangements yielding stable, irreversible end-products. In the last decades, AGEs have aroused the interest of the scientific community due to the increasing evidence of their involvement in many pathophysiological processes and diseases, such as diabetes, cancer, cardiovascular, neurodegenerative diseases, and even infection with the SARS-CoV-2 virus. They are recognized by several cellular receptors and trigger many signaling pathways related to inflammation and oxidative stress. Despite many experimental research outcomes published recently, the complexity of their engagement in human physiology and pathophysiological states requires further elucidation. This review focuses on the receptors of AGEs, especially on the structural aspects of receptor-ligand interaction, and the diseases in which AGEs are involved. It also aims to present AGE classification in subgroups and to describe the basic processes leading to both exogeneous and endogeneous AGE formation.

Systemic Glycosaminoglycan Clearance by HARE/Stabilin-2 Activates Intracellular Signaling

Scavenger receptors perform essential functions, critical to maintaining mammalian physiologic homeostasis by continuously clearing vast numbers of biomolecules from blood, interstitial fluid and lymph. Stabilin-2 (Stab2) and the Hyaluronic Acid Receptor for Endocytosis (HARE), a proteolytic isoform of Stab2, are important scavenger receptors responsible for the specific binding and internalization (leading to degradation) of 22 discrete molecules, macromolecular complexes and cell types. One-third of these ligands are glycosaminoglycans (GAGs). Full-length Stab2, but not HARE, mediates efficient phagocytosis of apoptotic cells and bacteria via binding to target surface ligands. HARE, the C-terminal half of Stab2, mediates endocytosis of all the known soluble ligands. HA was the first ligand identified, in 1981, prior to receptor purification or cloning. Seven other GAG ligands were subsequently identified: heparin, dermatan sulfate, chondroitin and chondroitin sulfates A, C, D and E. Synthetic dextran sulfate is also a GAG mimic and ligand. HARE signaling during HA endocytosis was first discovered in 2008, and we now know that activation of HARE/Stab2 signaling is stimulated by receptor-mediated endocytosis or phagocytosis of many, but not all, of its ligands. This review focuses on the HARE-mediated GAG activation of intracellular signaling, particularly the Extracellular Signal-Regulated Kinase 1/2 pathway.

Role of the Hyaluronan Receptor, Stabilin-2/HARE, in Health and Disease

Stabilin-2/HARE is the primary clearance receptor for circulating hyaluronan (HA), a polysaccharide found in the extracellular matrix (ECM) of metazoans. HA has many biological functions including joint lubrication, ocular turgor pressure, skin elasticity and hydration, cell motility, and intercellular signaling, among many others. The regulatory system for HA content in the tissues, lymphatics, and circulatory systems is due, in part, to Stabilin-2/HARE. The activity of this receptor was discovered about 40 years ago (early 1980s), cloned in the mid-1990s, and has been characterized since then. Here, we discuss the overall domain organization of this receptor and how it correlates to ligand binding, cellular signaling, and its role in known physiological disorders such as cancer.

Development and application of hyaluronic acid in tumor targeting drug delivery

Hyaluronic acid (HA) is a natural polysaccharide that has gained much attention due to its biocompatibility, enzyme degradation capacity and active tumor targeting capacity. Its receptor, CD44, is overexpressed in many kinds of cancers and is associated with tumor progress, infiltration and metastasis. Therefore, many researchers have developed various HA-based drug delivery systems for CD44-mediated tumor targeting. In this review, we systemically overview the basic theory of HA, its receptor and hyaluronidase, then we categorize the studies in HA-based drug delivery systems according to the functions of HA, including tumor-targeting materials, enzyme-sensitive biodegradable modality, pH-sensitive component, reduction-sensitive component, and the gel backbone. Finally, the perspective is discussed.

Heparin Differentially Impacts Gene Expression of Stromal Cells from Various Tissues

Pooled human platelet lysate (pHPL) is increasingly used as replacement of animal serum for manufacturing of stromal cell therapeutics. Porcine heparin is commonly applied to avoid clotting of pHPL-supplemented medium but the influence of heparin on cell behavior is still unclear. Aim of this study was to investigate cellular uptake of heparin by fluoresceinamine-labeling and its impact on expression of genes, proteins and function of human stromal cells derived from bone marrow (BM), umbilical cord (UC) and white adipose tissue (WAT). Cells were isolated and propagated using various pHPL-supplemented media with or without heparin. Flow cytometry and immunocytochemistry showed differential cellular internalization and lysosomal accumulation of heparin. Transcriptome profiling revealed regulation of distinct gene sets by heparin including signaling cascades involved in proliferation, cell adhesion, apoptosis, inflammation and angiogenesis, depending on stromal cell origin. The influence of heparin on the WNT, PDGF, NOTCH and TGFbeta signaling pathways was further analyzed by a bead-based western blot revealing most alterations in BM-derived stromal cells. Despite these observations heparin had no substantial effect on long-term proliferation and in vitro tri-lineage differentiation of stromal cells, indicating compatibility for clinically applied cell products.

Extracellular DAMPs in Plants and Mammals: Immunity, Tissue Damage and Repair

Innate immune receptors, well known mediators of response to non-self-molecules and inflammation, also act as mediators of immunity triggered by 'damage-associated molecular patterns' (DAMPs). Pathogen-associated molecular patterns (PAMPs) cause inflammation in mammals and a rapid immune response in plants, while DAMPs trigger more complex responses, including immunity, tissue maintenance and repair. DAMPs, their receptors and downstream transduction mechanisms are often conserved within a kingdom or, due to convergent evolution, are similar across the kingdoms of life. Herein, we describe the dynamics and functionality of specific extracellular DAMP classes and their receptors in immunity, inflammation and repair of tissue damage in plants and mammals.

The endothelial cell receptor stabilin-2 regulates VWF-FVIII complex half-life and immunogenicity

Quantitative abnormalities of the von Willebrand factor-factor VIII (VWF-FVIII) complex associate with inherited bleeding or thrombotic disorders. Receptor-mediated interactions between plasma VWF-FVIII and phagocytic or immune cells can influence their hemostatic and immunogenic activities. Genetic association studies have demonstrated that variants in the STAB2 gene, which encodes the scavenger receptor stabilin-2, associate with plasma levels of VWF-FVIII. However, the mechanistic basis and pathophysiological consequences of this association are unknown. We have demonstrated that stabilin-2-expressing cells bind and internalize human VWF and FVIII in a VWF-dependent manner, and stabilin-2-deficient mice displayed prolonged human VWF-FVIII half-life compared with controls. The stabilin-2 variant p.E2377K significantly decreased stabilin-2 expression and impaired VWF endocytosis in a heterologous expression system, and common STAB2 variants associated with plasma VWF levels in type 1 von Willebrand disease patients. STAB2-deficient mice displayed a decreased immunogenic response to human VWF-FVIII complex, while coinfusion of human VWF-FVIII with the stabilin-2 ligand hyaluronic acid attenuated the immune response to exogenous FVIII. Collectively, these data suggest that stabilin-2 functions as both a clearance and an immunoregulatory receptor for VWF-FVIII, making stabilin-2 a novel molecular target for modification of the half-life of VWF-FVIII and the immune response to VWF-FVIII concentrates.

Fascinating Fasciclins: A Surprisingly Widespread Family of Proteins that Mediate Interactions between the Cell Exterior and the Cell Surface

The Fasciclin 1 (FAS1) domain is an ancient structural motif in extracellular proteins present in all kingdoms of life and particularly abundant in plants. The FAS1 domain accommodates multiple interaction surfaces, enabling it to bind different ligands. The frequently observed tandem FAS1 arrangement might both positively and negatively regulate ligand binding. Additional protein domains and post-translational modifications are partially conserved between different evolutionary clades. Human FAS1 family members are associated with multiple aspects of health and disease. At the cellular level, mammalian FAS1 proteins are implicated in extracellular matrix structure, cell to extracellular matrix and cell to cell adhesion, paracrine signaling, intracellular trafficking and endocytosis. Mammalian FAS1 proteins bind to the integrin family of receptors and to protein and carbohydrate components of the extracellular matrix. FAS1 protein encoding plant genes exert effects on cellulosic and non-cellulosic cell wall structure and cellular signaling but to establish the modes of action for any plant FAS1 protein still requires biochemical experimentation. In fungi, eubacteria and archaea, the differential presence of FAS1 proteins in closely related organisms and isolated biochemical data suggest functions in pathogenicity and symbiosis. The inter-kingdom comparison of FAS1 proteins suggests that molecular mechanisms mediating interactions between cells and their environment may have evolved at the earliest known stages of evolution.

What is special about 200 kDa hyaluronan that activates hyaluronan receptor signaling?

The polydispersity of hyaluronan (HA) presents challenges for analyzing its solution properties, such as the relationship between mass and particle size. The broad mass range of natural HA (≤50-fold) makes molecular characterization difficult and ambiguous compared to molecules with known molecular weights (e.g., proteins). Biophysical studies show that large >MDa HA behaves like a random coil, whereas very small (e.g., 10 kDa) HA behaves like a rod. However, the mass range for this conformational transition is not easily determined in natural polydisperse HA. Some HA receptors (e.g., CD44 and HARE) initiate signaling responses upon binding HA in the 100-300 kDa range, but not larger MDa HA. Size-dependent responses are studied using nonnatural HA: purified narrow-size range HA [Pandey MS, Baggenstoss BA, Washburn J, Harris EN, Weigel PH. 2013. The hyaluronan receptor for endocytosis (HARE) activates NF-κB-mediated gene expression in response to 40-400 kDa, but not smaller or sarger, hyaluronans. J Biol Chem. 288:14068-14079] and very narrow size range Select-HA made chemo-enzymatically [Jing W, DeAngelis PL. 2004. Synchronized chemoenzymatic synthesis of monodisperse hyaluronan polymers. J Biol Chem. 279:42345-42349]. Here, we used size exclusion chromatography and multiangle light scattering to determine the weight-average molar mass and diameter of ~60 very narrow size preparations from 29 to 1650 kDa. The ratio of HA mass to HA diameter showed a transition in the 150-250 kDa size range (~65 nm). The HA rod-to-coil transition occurs within the size range that specifically activates cell signaling by some receptors. Thus, size-specific signaling could be due to unique external receptor•HA conformation changes that enable transmembrane-mediated activation of cytoplasmic domains. Alternatively and more likely, transition-size HA may enable multiple receptors to bind the same HA, creating new internal signal-competent cytoplasmic domain complexes.

HYAL-2-WWOX-SMAD4 Signaling in Cell Death and Anticancer Response

Hyaluronidase HYAL-2 is a membrane-anchored protein and also localizes, in part, in the lysosome. Recent study from animal models revealed that both HYAL-1 and HYAL-2 are essential for the metabolism of hyaluronan (HA). Hyal-2 deficiency is associated with chronic thrombotic microangiopathy with hemolytic anemia in mice due to over accumulation of high molecular size HA. HYAL-2 is essential for platelet generation. Membrane HYAL-2 degrades HA bound by co-receptor CD44. Also, in a non-canonical signal pathway, HYAL-2 serves as a receptor for transforming growth factor beta (TGF-β) to signal with downstream tumor suppressors WWOX and SMAD4 to control gene transcription. When SMAD4 responsive element is overly driven by the HYAL-2–WWOX–SMAD4 signaling complex, cell death occurs. When rats are subjected to traumatic brain injury, over accumulation of a HYAL-2–WWOX complex occurs in the nucleus to cause neuronal death. HA induces the signaling of HYAL-2–WWOX–SMAD4 and relocation of the signaling complex to the nucleus. If the signaling complex is overexpressed, bubbling cell death occurs in WWOX-expressing cells. In addition, a small synthetic peptide Zfra (zinc finger-like protein that regulates apoptosis) binds membrane HYAL-2 of non-T/non-B spleen HYAL-2⁺ CD3⁻ CD19⁻ Z lymphocytes and activates the cells to generate memory anticancer response against many types of cancer cells in vivo. Whether the HYAL-2–WWOX–SMAD4 signaling complex is involved is discussed. In this review and opinion article, we have updated the current knowledge of HA, HYAL-2 and WWOX, HYAL-2–WWOX–SMAD4 signaling, bubbling cell death, and Z cell activation for memory anticancer response.

Lysoplex: An efficient toolkit to detect DNA sequence variations in the autophagy-lysosomal pathway

The autophagy-lysosomal pathway (ALP) regulates cell homeostasis and plays a crucial role in human diseases, such as lysosomal storage disorders (LSDs) and common neurodegenerative diseases. Therefore, the identification of DNA sequence variations in genes involved in this pathway and their association with human diseases would have a significant impact on health. To this aim, we developed Lysoplex, a targeted next-generation sequencing (NGS) approach, which allowed us to obtain a uniform and accurate coding sequence coverage of a comprehensive set of 891 genes involved in lysosomal, endocytic, and autophagic pathways. Lysoplex was successfully validated on 14 different types of LSDs and then used to analyze 48 mutation-unknown patients with a clinical phenotype of neuronal ceroid lipofuscinosis (NCL), a genetically heterogeneous subtype of LSD. Lysoplex allowed us to identify pathogenic mutations in 67% of patients, most of whom had been unsuccessfully analyzed by several sequencing approaches. In addition, in 3 patients, we found potential disease-causing variants in novel NCL candidate genes. We then compared the variant detection power of Lysoplex with data derived from public whole exome sequencing (WES) efforts. On average, a 50% higher number of validated amino acid changes and truncating variations per gene were identified. Overall, we identified 61 truncating sequence variations and 488 missense variations with a high probability to cause loss of function in a total of 316 genes. Interestingly, some loss-of-function variations of genes involved in the ALP pathway were found in homozygosity in the normal population, suggesting that their role is not essential. Thus, Lysoplex provided a comprehensive catalog of sequence variants in ALP genes and allows the assessment of their relevance in cell biology as well as their contribution to human disease.

Activation of ERK and NF-κB during HARE-Mediated Heparin Uptake Require Only One of the Four Endocytic Motifs

Fifteen different ligands, including heparin (Hep), are cleared from lymph and blood by the Hyaluronan (HA) Receptor for Endocytosis (HARE; derived from Stabilin-2 by proteolysis), which contains four endocytic motifs (M1-M4). Endocytosis of HARE•Hep complexes is targeted to coated pits by M1, M2, and M3 (Pandey et al, Int. J. Cell Biol. 2015, article ID 524707), which activates ERK1/2 and NF-κB (Pandey et al J. Biol. Chem. 288, 14068-79, 2013). Here, we used a NF-κB promoter-driven luciferase gene assay and cell lines expressing different HARE cytoplasmic domain mutants to identify motifs needed for Hep-mediated signaling. Deletion of M1, M2 or M4 singly had no effect on Hep-mediated ERK1/2 activation, whereas signaling (but not uptake) was eliminated in HARE(ΔM3) cells lacking NPLY2519. ERK1/2 signaling in cells expressing WT HARE(Y2519A) or HARE(Y2519A) lacking M1, M2 and M4 (containing M3-only) was decreased by 75% or eliminated, respectively. Deletion of M3 (but not M1, M2 or M4) also inhibited the formation of HARE•Hep•ERK1/2 complexes by 67%. NF-κB activation by HARE-mediated uptake of Hep, HA, dermatan sulfate or acetylated LDL was unaffected in single-motif deletion mutants lacking M1, M2 or M4. In contrast, cells expressing HARE(ΔM3) showed loss of HARE-mediated NF-κB activation during uptake of each of these four ligands. NF-κB activation by the four signaling ligands was also eliminated in HARE(Y2519A) or HARE(M3-only;Y2519A) cells. We conclude that the HARE NPLY2519 motif is necessary for both ERK1/2 and NF-κB signaling and that Tyr2519 is critical for these functions.

Suppression of EC-SOD by oxLDL During Vascular Smooth Muscle Cell Proliferation

Reactive oxygen species (ROS) produced by endothelial cells and macrophages play important roles in atherogenesis because they promote the formation of oxidized low-density lipoproteins (oxLDL). Extracellular-superoxide dismutase (EC-SOD) is mainly produced by vascular smooth muscle cells (VSMCs), is secreted into the extracellular space, and protects cells from the damaging effects of the superoxide anion. Thus, the expression of EC-SOD in VSMCs is crucial for protecting cells against atherogenesis; however, oxLDL-induced changes in the expression of EC-SOD in VSMCs have not yet been examined. We herein showed that oxLDL decreased EC-SOD mRNA and protein levels by binding to lectin-like oxidized LDL receptor-1 (LOX-1). Moreover, we demonstrated the significant role of mitogen-activated protein kinase (MEK)/extracellular-regulated protein kinase (ERK) signaling in oxLDL-elicited reductions in the expression of EC-SOD and proliferation of VSMCs. The results obtained with the FCS treatment indicate that oxLDL-elicited reductions in the expression of EC-SOD are related to the proliferation of VSMCs. We herein showed for the first time that luteolin, a natural product, restored oxLDL-induced decreases in the expression of EC-SOD and proliferation of VSMCs. Collectively, the results of the present study suggest that oxLDL accelerates the development of atherosclerosis by suppressing the expression of EC-SOD and also that luteolin has potential as a treatment for atherosclerosis. J. Cell. Biochem. 117: 2496-2505, 2016. © 2016 Wiley Periodicals, Inc.

Getting to the Outer Leaflet: Physiology of Phosphatidylserine Exposure at the Plasma Membrane

Phosphatidylserine (PS) is a major component of membrane bilayers whose change in distribution between inner and outer leaflets is an important physiological signal. Normally, members of the type IV P-type ATPases spend metabolic energy to create an asymmetric distribution of phospholipids between the two leaflets, with PS confined to the cytoplasmic membrane leaflet. On occasion, membrane enzymes, known as scramblases, are activated to facilitate transbilayer migration of lipids, including PS. Recently, two proteins required for such randomization have been identified: TMEM16F, a scramblase regulated by elevated intracellular Ca(2+), and XKR8, a caspase-sensitive protein required for PS exposure in apoptotic cells. Once exposed at the cell surface, PS regulates biochemical reactions involved in blood coagulation, and bone mineralization, and also regulates a variety of cell-cell interactions. Exposed on the surface of apoptotic cells, PS controls their recognition and engulfment by other cells. This process is exploited by parasites to invade their host, and in specialized form is used to maintain photoreceptors in the eye and modify synaptic connections in the brain. This review discusses what is known about the mechanism of PS exposure at the surface of the plasma membrane of cells, how actors in the extracellular milieu sense surface exposed PS, and how this recognition is translated to downstream consequences of PS exposure.