HPSE-1 expression and functionality in differentiating neural cells

Molecular characterization and expression of RPS23 and HPSE and their association with hematologic parameters in sheep

Ribosomal protein S23 (RPS23) and Heparanase (HPSE) were located on chromosome 5 and chromosome 6, respectively, which play vital roles in protein synthesis and immunity. The objective of this study was to clone RPS23 and HPSE and to detect the expression levels of RPS23 and HPSE and the polymorphisms of RPS23 and HPSE associated with the hematologic parameters by using qRT-PCR, DNA sequencing and KASPar assay. The quantitative real-time PCR (RT-qPCR) showed that the two genes were expressed widely in the ten tissues of sheep. The expression levels of RPS23 and HPSE were the highest in lung and liver, respectively. The expression levels of RPS23 and HPSE in lung and liver increased from 0 to 3 months, decreased from 3 to 6 months, respectively. Furthermore, two mutations g.720 A > G and g.1077 G > A were detected in the RPS23 and HPSE, respectively, which were confirmed to be significantly associated with hematologic parameters. These results supported RPS23 g.720 A > G and HPSE g.1077 G > A as genetic markers of sheep.

Roles of glycosaminoglycans as regulators of ligand/receptor complexes

Glycosaminoglycans (GAGs) play a widespread role in embryonic development, as deletion of enzymes that contribute to GAG synthesis lead to deficiencies in cell migration and tissue modelling. Despite the biochemical and structural characterization of individual protein/GAG interactions, there is no concept available that links the molecular mechanisms of GAG/protein engagements to tissue development. Here, we focus on the role of GAG polymers in mediating interactions between cell surface receptors and their ligands. We categorize several switches that lead to ligand activation, inhibition, selection and addition, based on recent structural studies of select receptor/ligand complexes. Based on these principles, we propose that individual GAG polymers may affect several receptor pathways in parallel, orchestrating a cellular response to an environmental cue. We believe that it is worthwhile to study the role of GAGs as molecular switches, as this may lead to novel drug candidates to target processes such as angiogenesis, neuroregeneration and tumour metastasis.

Upregulated Expression of Heparanase and Heparanase 2 in the Brains of Alzheimer's Disease

BACKGROUND

Heparan sulfate proteoglycans (HSPGs) promote amyloid-β peptide and tau fibrillization in Alzheimer's disease (AD) and provide resistance against proteolytic breakdown. Heparanase (HPSE) is the only enzyme that cleaves heparan sulfate (HS). Heparanase 2 (HPSE2) lacks HS-degrading activity, although it is able to interact with HS with high affinity.

OBJECTIVE

To analyze HPSE and HPSE2 expressions at different stages of AD.

METHODS

RT-PCR was used to analyze transcription levels of both heparanases at different stages of AD, and immunohistochemistry was performed to localize each one in different parts of the brain.

RESULTS

Both proteins appeared overexpressed at different stages of AD. Immunohistochemistry indicated that the presence of the heparanases was related to AD pathology, with intracellular deposits found in degenerated neurons. At the extracellular level, HPSE was observed only in neuritic plaques with a fragmented core, while HPSE2 appeared in those with compact cores as well.

CONCLUSION

Given the involvement of HSPGs in AD pathology, there would seem to be a relationship between the regulation of heparanase expression, the features of the disease, and a possible therapeutic alternative.

Increased expression of heparanase in osteogenic differentiation of rat marrow stromal cells

Heparanase (HPSE) is a type of endoglycosidase that decomposes the heparan sulfate (HS) lateral chains of heparan sulfate proteoglycans (HSPGs), releases related growth factors and participates in angiogenesis and bone formation. HPSE is expressed in osteoblasts and is involved in fracture healing. However, the role of HPSE in osteogenic differentiation requires in-depth investigation. To investigate the expression of HPSE in the osteogenic differentiation of rat marrow stromal cells (MSCs), the protein and mRNA expression levels of HPSE on days 0, 1, 3, 7, 10, 14 and 21 of osteogenic differentiation of MSCs in 2- and 10-month-old rats were detected using western blotting and reverse transcription-polymerase chain reaction (RT-PCR), respectively. From the third day of osteogenic differentiation onwards, all HPSE protein and mRNA expression levels in 2-month-old rats were significantly increased compared with basal levels (days 0 and 1; P<0.05). The protein and mRNA expression levels reached a peak on days 10 and 14, respectively, followed by a gradual decline. The same pattern was observed in 10-month-old rats; however, when compared with with basal levels, the differences were not statistically significant (P>0.05). The protein and mRNA levels of HPSE in the 2-month-old rats were significantly higher compared with the respective levels in the 10-month-old rats (P<0.05). HPSE is involved in the osteogenic differentiation of rat MSCs. The protein and mRNA expression levels of HPSE in aged rats are weaker compared with those in young rats, which may be related to the declined osteogenic differentiation ability.

Heparanase enhances nerve-growth-factor-induced PC12 cell neuritogenesis via the p38 MAPK pathway

Heparanase is involved in the cleavage of the HS (heparan sulfate) chain of HSPGs (HS proteoglycans) and hence participates in remodelling of the ECM (extracellular matrix) and BM (basement membrane). In the present study we have shown that NGF (nerve growth factor) promoted nuclear enrichment of EGR1 (early growth response 1), a transcription factor for heparanase, and markedly induced heparanase expression in rat adrenal pheochromocytoma (PC12) cells. K252a, an antagonist of the NGF receptor TrkA (tyrosine kinase receptor A), decreased heparanase protein expression induced by NGF in PC12 cells. Suramin, a heparanase inhibitor, decreased heparanase in PC12 cells and blocked NGF-induced PC12 neuritogenesis. Stable overexpression of heparanase activated p38 MAPK (mitogen-activated protein kinase) by phosphorylation and enhanced the neurite outgrowth induced by NGF, whereas knock down of heparanase impaired this process. However, overexpression of latent pro-heparanase with a Y156A mutation still led to enhanced NGF-induced neurite outgrowth and increased p38 MAPK phosphorylation. Inhibition of p38 MAPK by SB203580 suppressed the promotion of NGF-induced neuritogenesis by the wild-type and mutant heparanase. The impaired differentiation by knock down of heparanase could be restored by transfection of wild-type or mutant heparanase in PC12 cells. The results of the present study suggest that heparanase, at least in the non-enzymatic form, may promote NGF-induced neuritogenesis via the p38 MAPK pathway.

Expression of heparanase in vascular cells and astrocytes of the mouse brain after focal cerebral ischemia

Heparanase is a heparan sulfate degrading endoglycosidase. Previous work has demonstrated that heparanase plays important roles in various biological processes including angiogenesis, wound healing and metastasis. However, the role of heparanase in the post-ischemic brain is not well defined. Transient focal cerebral ischemia in adult mice was induced by ligations of the right middle cerebral artery (MCA) and both common carotid arteries (CCAs). All mice were subjected to bromodeoxyuridine (BrdU) injection and sacrificed at different time points after stroke for immunohistochemical and Western blot analyses. Heparanase expression increased after ischemia in both cell-specific and time-dependent manners. Three to 7 days after stroke, levels of the 50-kD heparanase, basic fibroblast growth factor (FGF-2), and angiopoietin-2 (Ang-2) increased in the peri-infarct region. At early time points, heparanase expression was largely confined to proliferating vascular endothelial cells. At 14 days after ischemia, this expression had shifted to astrocytes in the same region. These data show that cerebral ischemia markedly increases heparanase levels in endothelial cells and then in astrocytes. The unique features of the heparanase upregulation imply that heparanase may play specific roles in the pathological and regenerative processes during the acute and sub-acute/chronic phases in the post-stroke brain.

Heparanase in primary human osteoblasts

Heparanase (HPSE) is known to be involved in fracture repair in mice, but its presence and function in human bone formation remains unclear. Our aim was to determine the expression of HPSE in human bone forming osteoblasts and to better understand its role in osteogenesis. HPSE protein expression and enzymatic activity were demonstrated in osteoblasts isolated from trabecular bone specimens of patients with osteoporosis (OP) and from healthy subjects, although the levels differed markedly. Thus, low levels of HPSE expression were observed in osteoporotic osteoblasts, including in the nucleus compared to those from healthy subjects. Notably, HPSE gene expression was associated with alkaline phosphatase (ALP) activity, the bone turnover marker. Gene profile studies demonstrated that osteogenic genes were downregulated in osteoporotic osteoblasts. We further exposed osteoblasts to exogenous HPSE and found that the level of histone H3 phosphorylation was increased. We provide evidence, for the first time, demonstrating that HPSE expresses and functions in human osteoblasts. Our data suggest that previously undescribed function of HPSE-mediated osteoblastogenesis through regulation of osteogenic gene expression and histone H3 modification. HPSE upregulation may be a novel therapeutic approach in the prevention and treatment of OP.

Mammalian heparanase: what is the message?

Heparan sulphate proteoglycans are ubiquitous macromolecules of cell surfaces and extracellular matrices. Numerous extracellular matrix proteins, growth factors, morphogens, cytokines, chemokines and coagulation factors are bound and regulated by heparan sulphate. Degradation of heparan sulphate thus potentially profoundly affects cell and tissue function. Although there is evidence that several heparan sulphate-degrading endoglucuronidases (heparanases) might exist, so far only one transcript encoding a functional heparanase has been identified: heparanase-1. In the first part of this review, we discuss the current knowledge about heparan sulphate proteoglycans and the functional importance of their versatile interactions. In the second part, we summarize recent findings that have contributed to the characterization of heparanase-1, focusing on the molecular properties, working mechanism, substrate specificity, expression pattern, cellular activation and localization of this enzyme. Additionally, we review data implicating heparanase-1 in several normal and pathological processes, focusing on tumour metastasis and angiogenesis, and on evidence for a potentially direct signalling function of the molecule. In that context, we also briefly discuss heparanase-2, an intriguing close homologue of heparanase-1, for which, so far, no heparan sulphate-degrading activity could be demonstrated.

Brain heparanase expression is up-regulated during postnatal development and hypoxia-induced neovascularization in adult rats

Heparanase is an endo-beta-d-glucuronidase which specifically cleaves extracellular and cell surface heparan sulphates at intra-chain sites. Its enzymatic activity is strongly implicated in cell dissemination associated with tumor metastasis and inflammation. Indeed, heparanase gene is expressed in various tumors and its over-expression is correlated with increased tumor vascularity and metastatic potential of tumor cells. However, heparanase expression in non-invasive and non-immune tissue, including brain, has received less attention. Using RT-qPCR, western blot and histological analysis, we demonstrate in the adult rat that heparanase transcript is differentially expressed according to brain area, and that heparanase protein is mainly detected in neurons. Furthermore, we provide evidence that heparanase transcript and protein reach their greatest levels at early postnatal stages, in particular within the neocortex characterized by intensive structural plasticity. Using the in vitro model of PC12-induced neuronal differentiation, we suggest that developmental regulation of heparanase may coincide with axonal and dendritic pathfinding. At adulthood, we demonstrate that the increased heparanase transcript level correlates in the hippocampus with enhanced angiogenesis following repeated hypoxia exposures. Taken together, our results emphasize the potential importance of heparanase in brain homeostasis, both during development and adaptative responses to severe environmental challenges.