Testican in Human Blood1

LncRNA THEMIS2-211, a tumor-originated circulating exosomal biomarker, promotes the growth and metastasis of hepatocellular carcinoma by functioning as a competing endogenous RNA

Hepatocellular carcinoma (HCC) is a major challenge for human health. Finding reliable diagnostic biomarkers and therapeutic targets for HCC is highly desired in the clinic. Currently, circulating exosomal lncRNA is a promising biomarker for the diagnosis of cancer and lncRNA is also a potential target in cancer therapy. Here, the diagnostic value of a panel based on exosomal lncRNA THEMIS2-211 and PRKACA-202, superior to that of AFP, was identified for diagnosing human HCC. Besides, the performance of exosomal lncRNA THEMIS2-211 alone exceeds that of AFP in diagnosing early-stage HCC patients (stage I). Furthermore, lncRNA THEMIS2-211 is highly expressed in HCC tissues and correlated with the poor prognosis of HCC patients. LncRNA THEMIS2-211 is upregulated and localized in the cytoplasm of HCC cells. LncRNA THEMIS2-211 exerts its biological function as an oncogene that promotes the proliferation, migration, invasion, EMT of HCC cells by physically interacting with miR-940 and therefore promoting SPOCK1 expressions. Rescue assays show the regulation of SPOCK1 by lncRNA THEMIS2-211 dependents on miR-940. The discovery of lncRNA THEMIS2-211 further illuminates the molecular pathogenesis of HCC and the THEMIS2-211/miR-940/SPOCK1 axis may act as a potential therapeutic target for HCC.

Studies on sporadic non-syndromic thoracic aortic aneurysms: II. Alterations of extra-cellular matrix components and focal adhesion proteins

Background Sporadic non-syndromic thoracic aortic aneurysms (SNSTAAs) are less well understood than familial non-syndromic or syndromic ones. Here, we focused on morphologic and molecular changes of the extracellular matrix of the tunica media of SNSTAAs. Design Single centre design. Methods Surgical media samples from seven SNSTAAs and seven controls underwent quantitative polymerase chain reaction, proteomics-bioinformatics, immunoblotting, histology and immunohistochemistry analysis. Results A down-regulation of Decorin mRNA with unchanged protein levels associated with a remarkable increase of collagen fibres. A reduced and distorted network of elastic fibres partnered with an attenuated expression of microfibril-associated glycoprotein1 despite the rise of MFAP2 gene-encoded mRNA levels. An increasingly proteolysed paxillin (55 kDa PXN), a focal adhesion protein, combined with an upregulated 62 kDa PXN holoprotein, without changes in amount and phosphorylation of focal adhesion kinase (pp125^FAK). The upregulation of SPOCK2-encoded Testican2 proteoglycan and of ectodysplasin (EDA) protein was coupled with a down-regulation of EDA2 receptor (EDA2R). Conclusions Several tunica media extracellular matrix-related changes favour SNSTAA development. A steady level of decorin and a microfibril-associated glycoprotein1 protein shortage cause the assembly of structurally defective collagen and elastic fibres. Up-regulation of PXN holoproteins perturbs PXN/pp125^FAK interaction and focal adhesion functioning. Testican2 up-regulation suppresses the membrane-type matrix metalloproteinase inhibiting activities of other SPOCK family members thus enhancing extracellular matrix proteolysis. Finally, the altered EDA•EDA2R signalling would impact on the remodelling of SNSTAA tunica media. Altogether, our results pave the way to a deeper molecular understanding of SNSTAAs necessary to identify their early diagnostic biochemical markers.

A holistic approach to dissecting SPARC family protein complexity reveals FSTL-1 as an inhibitor of pancreatic cancer cell growth

SPARC is a matricellular protein that is involved in both pancreatic cancer and diabetes. It belongs to a wider family of proteins that share structural and functional similarities. Relatively little is known about this extended family, but evidence of regulatory interactions suggests the importance of a holistic approach to their study. We show that Hevin, SPOCKs, and SMOCs are strongly expressed within islets, ducts, and blood vessels, suggesting important roles for these proteins in the normal pancreas, while FSTL-1 expression is localised to the stromal compartment reminiscent of SPARC. In direct contrast to SPARC, however, FSTL-1 expression is reduced in pancreatic cancer. Consistent with this, FSTL-1 inhibited pancreatic cancer cell proliferation. The complexity of SPARC family proteins is further revealed by the detection of multiple cell-type specific isoforms that arise due to a combination of post-translational modification and alternative splicing. Identification of splice variants lacking a signal peptide suggests the existence of novel intracellular isoforms. This study underlines the importance of addressing the complexity of the SPARC family and provides a new framework to explain their controversial and contradictory effects. We also demonstrate for the first time that FSTL-1 suppresses pancreatic cancer cell growth.

Carrier of Wingless (Cow), a secreted heparan sulfate proteoglycan, promotes extracellular transport of Wingless

Morphogens are signaling molecules that regulate growth and patterning during development by forming a gradient and activating different target genes at different concentrations. The extracellular distribution of morphogens is tightly regulated, with the Drosophila morphogen Wingless (Wg) relying on Dally-like (Dlp) and transcytosis for its distribution. However, in the absence of Dlp or endocytic activity, Wg can still move across cells along the apical (Ap) surface. We identified a novel secreted heparan sulfate proteoglycan (HSPG) that binds to Wg and promotes its extracellular distribution by increasing Wg mobility, which was thus named Carrier of Wg (Cow). Cow promotes the Ap transport of Wg, independent of Dlp and endocytosis, and this function addresses a previous gap in the understanding of Wg movement. This is the first example of a diffusible HSPG acting as a carrier to promote the extracellular movement of a morphogen.

Genome-wide association analyses identify SPOCK as a key novel gene underlying age at menarche

For females, menarche is a most significant physiological event. Age at menarche (AAM) is a trait with high genetic determination and is associated with major complex diseases in women. However, specific genes for AAM variation are largely unknown. To identify genetic factors underlying AAM variation, a genome-wide association study (GWAS) examining about 380,000 SNPs was conducted in 477 Caucasian women. A follow-up replication study was performed to validate our major GWAS findings using two independent Caucasian cohorts with 854 siblings and 762 unrelated subjects, respectively, and one Chinese cohort of 1,387 unrelated subjects—all females. Our GWAS identified a novel gene, SPOCK (Sparc/Osteonectin, CWCV, and Kazal-like domains proteoglycan), which had seven SNPs associated with AAM with genome-wide false discovery rate (FDR) q<0.05. Six most significant SNPs of the gene were selected for validation in three independent replication cohorts. All of the six SNPs were replicated in at least one cohort. In particular, SNPs rs13357391 and rs1859345 were replicated both within and across different ethnic groups in all three cohorts, with p values of 5.09×10⁻³ and 4.37×10⁻³, respectively, in the Chinese cohort and combined p values (obtained by Fisher's method) of 5.19×10⁻⁵ and 1.02×10⁻⁴, respectively, in all three replication cohorts. Interestingly, SPOCK can inhibit activation of MMP-2 (matrix metalloproteinase-2), a key factor promoting endometrial menstrual breakdown and onset of menstrual bleeding. Our findings, together with the functional relevance, strongly supported that the SPOCK gene underlies variation of AAM.

Menarche is a physical milestone in a woman's life. Age at menarche (AAM) is related to many common female health problems. AAM is mainly determined by genetic factors. However, the specific genes and the associated mechanisms underlying AAM are largely unknown. Here, taking advantage of the most recent technological advances in the field of human genetics, we identified multiple genetic variants in a gene, SPOCK, which are associated with AAM variation in a group of Caucasian women. This association was subsequently confirmed not only in two independent groups of Caucasian women but also across ethnic boundaries in one group of Chinese women. In addition, SPOCK has a function in regulating a key factor involved in menstrual cycles, MMP-2, which provides further support to our findings. Our study provides a solid basis for further investigation of the gene, which may help to reveal the underlying mechanisms for the timing of menarche and for AAM's relationship with women's health in general.

Heparan sulfate proteoglycans: a GAGgle of skeletal-hematopoietic regulators

This review summarizes our current understanding of the presence and function of heparan sulfate proteoglycans (HSPGs) in skeletal development and hematopoiesis. Although proteoglycans (PGs) comprise a large and diverse group of cell surface and matrix molecules, we chose to focus on HSPGs owing to their many proposed functions in skeletogenesis and hematopoiesis. Specifically, we discuss how HSPGs play predominant roles in establishing and regulating niches during skeleto-hematopoietic development by participating in distinct developmental processes such as patterning, compartmentalization, growth, differentiation, and maintenance of tissues. Special emphasis is placed on our novel hypothesis that mechanistically links endochondral skeletogenesis to the establishment of the hematopoietic stem cell (HSC) niche in the marrow. HSPGs may contribute to these developmental processes through their unique abilities to establish and mediate morphogen, growth factor, and cytokine gradients; facilitate signaling; provide structural stability to tissues; and act as molecular filters and barriers.

The role of heparan sulphate in inflammation

The polysaccharide heparan sulphate is ubiquitously expressed as a proteoglycan in extracellular matrices and on cell surfaces. Heparan sulphate has marked sequence diversity that allows it to specifically interact with many proteins. This Review focuses on the multiple roles of heparan sulphate in inflammatory responses and, in particular, on its participation in almost every stage of leukocyte transmigration through the blood-vessel wall. Heparan sulphate is involved in the initial adhesion of leukocytes to the inflamed endothelium, the subsequent chemokine-mediated transmigration through the vessel wall and the establishment of both acute and chronic inflammatory reactions.

Expression profiling of clonal lymphocyte cell cultures from Rett syndrome patients

Background

More than 85% of Rett syndrome (RTT) patients have heterozygous mutations in the X-linked MECP2 gene which encodes methyl-CpG-binding protein 2, a transcriptional repressor that binds methylated CpG sites. Because MECP2 is subject to X chromosome inactivation (XCI), girls with RTT express either the wild type or mutant MECP2 in each of their cells. To test the hypothesis that MECP2 mutations result in genome-wide transcriptional deregulation and identify its target genes in a system that circumvents the functional mosaicism resulting from XCI, we performed gene expression profiling of pure populations of untransformed T-lymphocytes that express either a mutant or a wild-type allele.

Methods

Single T lymphocytes from a patient with a c.473C>T (p.T158M) mutation and one with a c.1308-1309delTC mutation were subcloned and subjected to short term culture. Gene expression profiles of wild-type and mutant clones were compared by oligonucleotide expression microarray analysis.

Results

Expression profiling yielded 44 upregulated genes and 77 downregulated genes. We compared this gene list with expression profiles of independent microarray experiments in cells and tissues of RTT patients and mouse models with Mecp2 mutations. These comparisons identified a candidate MeCP2 target gene, SPOCK1, downregulated in two independent microarray experiments, but its expression was not altered by quantitative RT-PCR analysis on brain tissues from a RTT mouse model.

Conclusion

Initial expression profiling from T-cell clones of RTT patients identified a list of potential MeCP2 target genes. Further detailed analysis and comparison to independent microarray experiments did not confirm significantly altered expression of most candidate genes. These results are consistent with other reported data.

Testican-1 is dispensable for mouse development

Testicans are proteoglycans belonging to the BM-40/SPARC/osteonectin family of extracellular calcium-binding proteins. Testican-1 is strongly expressed in the brain and has been reported to modulate neuronal attachment and matrix metalloproteinase activation. Characterization of the mouse testican-1 gene (Ticn1), consisting of 12 exons out of which exon 3 is alternatively spliced, allowed the construction of a gene targeting construct. Mice deficient in testican-1 showed no obvious morphological or behavioral abnormalities, were fertile, and had normal life spans. Despite the fact that neither of the testican-1 homologues expressed in the brain, testican-2, testican-3 and SC1/hevin, showed an increased expression in Ticn1 null mice, these results, together with those from other gene targetings, indicate extensive functional redundancy among brain proteoglycans.

Mouse Testican-2

Mouse testican-2 was cloned, sequenced, and shown to be a proteoglycan with a multidomain structure closely similar to that of the human ortholog, previously described as a calcium binding extracellular matrix molecule of the BM-40/SPARC/osteonectin family (Vannahme, C., Schübel, S., Herud, M., Gösling, S., Hülsmann, H., Paulsson, M., Hartmann, U., and Maurer, P. (1999). J. Neurochem. 73, 12-20). Recombinant mouse testican-2 was used to prepare specific antibodies that allowed the detection of testican-2 in various brain structures but also in lung, testis, and in several endocrine glands. Although the testican-2 expressed in EBNA-293 cells carried both heparan sulfate and chondroitin/dermatan sulfate glycosaminoglycan chains, the tissue form always contained only heparan sulfate. Both tissue-derived and recombinant testican-2 carried N-linked glycans. Tissue-derived forms of testican-2 were detected as proteoglycans of varying size, whereas a portion of the molecules produced by EBNA-293 cells were core proteins, lacking glycosaminoglycans. Both the proteoglycan and core protein forms of testican-2 inhibited neurite extension from cultured primary cerebellar neurons and may play regulatory roles in the development of the central nervous system.

Dual concentration-dependent activity of thyroglobulin type-1 domain of testican: specific inhibitor and substrate of cathepsin L

The thyroglobulin type-1 (Tg-1) domain is a protein module that occurs in a variety of secreted and membrane proteins and is recognised as a potent inhibitor of cysteine peptidases. We present here some properties of the Tg-1 domain of human testican, a modularly organised proteoglycan secreted mainly by brain cells, the exactin vivofunction of which is not yet clear. The domain was prepared as a recombinant protein in aPichia pastorisexpression system and its activity was demonstrated by specific and selective inhibition of cathepsin L (Ki=0.14 nM). Interaction at high enzyme and inhibitor concentrations resulted in degradation of the domain by cathepsin L, which was not observed under conditions used for the determination of kinetic parameters. No inhibitory activity could be detected for cathepsin K, but it exhibited a very similar degradation pattern. Homology modelling provided a good explanation for the different behaviour observed with the two enzymes. Firstly, the steric fit between the interfaces of testican domain and cathepsin L is stabilised by numerous favourable forces, while no such interactions are evident in the complex with cathepsin K, and repulsive interactions even prevent access of the domain to the active site of papain. Secondly, the prolonged first loop of the domain occupies a position near the catalytic cysteine residue in a more substrate-like manner, enabling cleavage of the Gly22-Ala23bond.

Testican-1, an inhibitor of pro-MMP-2 activation, is expressed in cartilage

OBJECTIVE

Recently, testican-1 has been described to be an inhibitor of MT1-MMP and MT3-MMP mediated pro-MMP-2 activation. As MT1-MMP mediated pro-MMP-2 activation is of significance for cartilage destruction in osteoarthritis, we studied the expression and localization of testican-1 in human articular cartilage.

METHODS

Cartilage samples from the medial and lateral tibia plateau were obtained from osteoarthritic patients who underwent joint replacements, and were graded histomorphologically by Mankin score. Testican-1 expression was assessed in RNA isolated directly from cartilage as well as in freshly isolated chondrocytes by reverse transcriptase-polymerase chain reaction (RT-PCR) and quantified by real-time RT-PCR. Testican-1 protein was localized by immunohistochemistry in human osteoarthritic cartilage samples, in human fetal knee joint, and in knees from mice.

RESULTS

Testican-1 mRNA could be detected in cartilage and in freshly isolated chondrocytes both from moderately and from severely damaged osteoarthritic cartilage. In the same donor, expression in chondrocytes from more severely affected regions was decreased compared with chondrocytes from less affected regions. By immunolocalization, testican-1 protein could be detected in chondrocytes predominantly of the superficial and transitional zones. Matrix staining in these zones was greatly reduced in samples from more severely affected osteoarthritic cartilage. A similar distribution was found in the articular cartilage of knees from 7-week-old mice. In addition to articular cartilage, testican-1 was also present in growth plate cartilage.

CONCLUSIONS

Testican-1 is a component of cartilage, both of the joint and of the growth plate. Given its activity as an inhibitor of MT1-MMP mediated pro-MMP-2 activation, it is reasonable to speculate that it participates in the regulation of matrix turnover in cartilage.

Testican-1: A Differentially Expressed Proteoglycan with Protease Inhibiting Activities

Testican-1 is a highly conserved, multidomain proteoglycan that is most prominently expressed in the thalamus of the brain, and is upregulated in activated astroglial cells of the cerebrum. Several functions of this gene product have now been demonstrated in vitro including membrane-type matrix metalloproteinase inhibition, cathepsin L inhibition, and low-affinity calcium binding. The purified gene product has been shown to inhibit cell attachment and neurite extensions in culture. Functions of testican in vivo have yet to be demonstrated in knockout mice or other models. Testican has been shown to carry substantial amounts of chondroitin sulfate as well as other oligosaccharides, but the biological significance of these embellishments is not yet known.

Human proteoglycan testican-1 inhibits the lysosomal cysteine protease cathepsin L

Testican-1, a secreted proteoglycan enriched in brain, has a single thyropin domain that is highly homologous to domains previously shown to inhibit cysteine proteases. We demonstrate that purified recombinant human testican-1 is a strong competitive inhibitor of the lysosomal cysteine protease, cathepsin L, with a Ki of 0.7 nM, but it does not inhibit the structurally related lysosomal cysteine protease cathepsin B. Testican-1 inhibition of cathepsin L is independent of its chondroitin sulfate chains and is effective at both pH 5.5 and 7.2. At neutral pH, testican-1 also stabilizes cathepsin L, slowing pH-induced denaturation and allowing the protease to remain active longer, although the rate of proteolysis is reduced. These data indicate that testican-1 is capable of modulating cathepsin L activity both in intracellular vesicles and in the extracellular milieu.

Testican-1 inhibits attachment of Neuro-2a cells

Testican-1 is a highly conserved, multidomain, chondroitin sulfate proteoglycan that is most abundantly transcribed in the brain by neurons. This testican messenger RNA is not detected in normal quiescent astrocytes, but is up regulated when these cells are activated in response to injury such as cerebral stroke. Other chondroitin sulfate proteoglycans found in glial scars, including neurocan, have been shown to inhibit neural cell attachment and neurite extensions and may thus impede axonal regeneration. Here we report the expression and purification of a proteoglycan form of recombinant testican and its effects on neuron-derived cells in culture. We demonstrate that testican inhibits attachment of Neuro-2a cells and their ability to form neurite extensions. Both testican proteoglycan and the core glycoprotein that has been depleted of chondroitin sulfate inhibit cell attachment. Pre-treatment of the culture substratum with testican inhibits Neuro-2a attachment, but pre-treatment of the cells with testican does not inhibit their attachment. Testican, therefore, blocks attachment sites on cultureware and may also block attachment sites in the extracellular matrix of the brain.

Characterization of SMOC-1, a novel modular calcium-binding protein in basement membranes

We have isolated the novel gene SMOC-1 that encodes a secreted modular protein containing an EF-hand calcium-binding domain homologous to that in BM-40. It further consists of two thyroglobulin-like domains, a follistatin-like domain and a novel domain. Recombinant expression in human cells showed that SMOC-1 is a glycoprotein with a calcium-dependent conformation. Results from Northern blots, reverse transcriptase-PCR, and immunoblots revealed a widespread expression in many tissues. Immunofluorescence studies with an antiserum directed against recombinant human SMOC-1 demonstrated a basement membrane localization of the protein and additionally its presence in other extracellular matrices. Immunogold electron microscopy confirmed the localization of SMOC-1 within basement membranes in kidney and skeletal muscle as well as its expression in the zona pellucida surrounding the oocyte.