Heparan sulfate proteoglycans: structure, protein interactions and cell signaling.

Heparan sulfate proteoglycans are ubiquitously found at the cell surface and extracellular matrix in all the animal species. This review will focus on the structural characteristics of the heparan sulfate proteoglycans related to protein interactions leading to cell signaling. The heparan sulfate chains due to their vast structural diversity are able to bind and interact with a wide variety of proteins, such as growth factors, chemokines, morphogens, extracellular matrix components, enzymes, among others. There is a specificity directing the interactions of heparan sulfates and target proteins, regarding both the fine structure of the polysaccharide chain as well precise protein motifs. Heparan sulfates play a role in cellular signaling either as receptor or co-receptor for different ligands, and the activation of downstream pathways is related to phosphorylation of different cytosolic proteins either directly or involving cytoskeleton interactions leading to gene regulation. The role of the heparan sulfate proteoglycans in cellular signaling and endocytic uptake pathways is also discussed.

A comparative analysis of structure and spatial distribution of decorin in human leiomyoma and normal myometrium.

Leiomyoma is a benign smooth muscle tumor of the uterus that affects many women in active reproductive life. It is composed by bundles of smooth muscle cells surrounded by extracellular matrix. We have recently shown that the glycosylation of extracellular matrix proteoglycans is modified in leiomyoma: increased amounts of galactosaminoglycans with structural modifications are present. The data here presented show that decorin is present in both normal myometrium and leiomyoma but tumoral decorin is glycosylated with longer galactosaminoglycan side chains. Furthermore, these chains contain a higher ratio D-glucuronate/L-iduronate, as compared to normal tissue. To determine if these changes in proteoglycan glycosylation correlates with modifications in the extracellular matrix organization, we compared the general structural architecture of leiomyoma to normal myometrium. By histochemical and immunofluorescence methods, we found a reorganization of muscle fibers and extracellular matrix, with changes in the distribution of glycoproteins, proteoglycans, and collagen. Thin reticular fibers, possibly composed by types I and III collagen, were replaced by thick fibers, possibly richer in type I collagen. Type I collagen colocalized with decorin both in leiomyoma and normal myometrium, in contrast to type IV collagen that did not. The relative amount of decorin was increased and the distribution of decorin and collagen was totally modified in the tumor, as compared to the normal myometrium. These findings reveal that not only decorin structure is modified in leiomyoma but also the tissue architecture changed, especially concerning extracellular matrix.

Testing for urinary hyaluronate improves detection and grading of transitional cell carcinoma.

OBJECTIVE: The purpose of this study is to establish a method for the diagnosis and grading of transitional cell carcinoma (TCC), which is responsible for 90% of bladder tumors, using a recently developed ultrasensitive assay for the measurement of hyaluronan (HA). MATERIALS AND METHODS: Urine samples were collected prior to surgery (cystoscopy, transurethral resection for bladder cancer (TURBT), and cystectomy) in 350 patients. After the procedure, pathologic examination revealed that 160 patients had TCC. HA was measured directly in the urine by a noncompetitive enzyme-linked immunosorbent assay (ELISA)-like fluorometric assay. Using the receiver operator characteristic curve (ROC), t-test, Dunn test, Kruskal-Wallis test, and Mann-Whitney test, we evaluated the differences between groups (those with TCC vs. those without TCC). RESULTS: By analyzing the ROC curve, we chose a urinary HA cutoff value of 13.0 µg/l for indicating risk of TCC. Using the value this of 13.0 µg/l, we found that this test had an overall sensitivity of 82.3% and an overall specificity of 81.2%. The positive predictive value of this assay was 78.9%, the negative predictive negative value was 84.2%, and the predictive accuracy was 81.7%. Logistic regression analysis revealed that every 1 µg/l increase in HA increased a patient's likelihood of having TCC by 3.9%. The sensitivity of this test to detect superficial tumors was 76.6%, whereas its sensitivity for detecting invasive tumors was 94.6%. The urinary HA excretion of patients with TCC, classified according to the TNM staging system and the World Health Organization (WHO) grading system, were compared, and a significant difference was observed between the HA levels of patients with superficial tumors compared with invasive tumors (P = 0.005) as well as between patients with low- vs. high-grade carcinomas (P < 0.001). Patients with urinary HA levels >35 µg/l had a 4.63 times increased risk of having an aggressive, invasive, high grade tumor (P = 0.005). CONCLUSIONS: Our results support the postulate that urinary HA may be used as a tumor marker to aid in the diagnosis and grading of TCC. Additionally, more invasive tumors produce and release more HA in urine than superficial tumors, thus higher HA levels indicate more aggressive disease.

Urinary hyaluronan as a marker for the presence of residual transitional cell carcinoma of the urinary bladder.

OBJECTIVE: The purpose of this report is to evaluate the value of urinary hyaluronan (HA) as a maker of residual transitional cell carcinoma (TCC). PATIENTS AND METHODS: Urine samples were collected from 83 patients hospitalized for transurethral resection (TUR). Patient ages ranged from 36 to 86 years. Samples were taken both before and after surgery. HA analysis was performed using an "ELISA-like" fluorometric assay. RESULTS: Patients were divided into two groups: a control group whose previous diagnosis was negative for tumors (n=22) and another with positive diagnosis for tumors (n=61) which was further sub-divided into with and without residual tumor. After the second procedure 47 individuals did not display residual tumor, whereas 14 (23%) did. The average HA in the control group was 8.3 microg/L pre- and 7.1 post-operatively, hence, no change occurred (p=0.471). In the group with TCC patients, the HA dropped from 885.5 microg/L to 215.3 microg/L with residual tumors and from 234.3 microg/L to 11.2 microg/L for those without residual tumor. Using a cut-off value of 20 microg/L, the sensitivity to detect residual tumor is 92.9% and specificity is 83%. CONCLUSION: HA in addition to being one of the best markers for the initial evaluation of bladder carcinoma can be used to determine the presence of a residual tumor. This is associated with poor prognosis.

Melanocyte transformation associated with substrate adhesion impediment.

Exclude experimental models of malignant transformation employ chemical and physical carcinogens or genetic manipulations to study tumor progression. In this work, different melanoma cell lines were established after submitting a nontumorigenic melanocyte lineage (melan-a) to sequential cycles of forced anchorage impediment. The great majority of these cells underwent anoikis when maintained in suspension. After one deadhesion cycle, phenotypic alterations were noticeable in the few surviving cells, which became more numerous and showed progressive alterations after each adhesion impediment step. No significant differences in cell surface expression of integrins were detected, but a clear electrophoretic migration shift, compatible with an altered glycosylation pattern, was observed for beta1 chain in transformed cell lines. In parallel, a progressive enrichment of tri- and tetra-antennary N-glycans was apparent, suggesting increased N-acetylglucosaminyltransferase V activity. Alterations both in proteoglycan glycosylation pattern and core protein expression were detected during the transformation process. In conclusion, this model corroborates the role of adhesion state as a promoting agent in transformation process and demonstrates that cell adhesion disturbances may act as carcinogenic stimuli, at least for a nontumorigenic immortalized melanocyte lineage. These findings have intriguing implications for in vivo carcinogenesis, suggesting that anchorage independence may precede, and contribute to, neoplastic conversion.

Heparan sulfate proteoglycans: structure, protein interactions and cell signaling

Heparan sulfate proteoglycans are ubiquitously found at the cell surface and extracellular matrix in all the animal species. This review will focus on the structural characteristics of the heparan sulfate proteoglycans related to protein interactions leading to cell signaling. The heparan sulfate chains due to their vast structural diversity are able to bind and interact with a wide variety of proteins, such as growth factors, chemokines, morphogens, extracellular matrix components, enzymes, among others. There is a specificity directing the interactions of heparan sulfates and target proteins, regarding both the fine structure of the polysaccharide chain as well precise protein motifs. Heparan sulfates play a role in cellular signaling either as receptor or co-receptor for different ligands, and the activation of downstream pathways is related to phosphorylation of different cytosolic proteins either directly or involving cytoskeleton interactions leading to gene regulation. The role of the heparan sulfate proteoglycans in cellular signaling and endocytic uptake pathways is also discussed.

Proteoglicanos de heparam sulfato são encontrados tanto superfície celular quanto na matriz extracelular em todas as espécies animais. Esta revisão tem enfoque nas características estruturais dos proteoglicanos de heparam sulfato e nas interações destes proteoglicanos com proteínas que levam à sinalização celular. As cadeias de heparam sulfato, devido a sua variedade estrutural, são capazes de se ligar e interagir com ampla gama de proteínas, como fatores de crescimento, quimiocinas, morfógenos, componentes da matriz extracelular, enzimas, entreoutros. Existe uma especificidade estrutural que direciona as interações dos heparam sulfatos e proteínas alvo. Esta especificidade está relacionada com a estrutura da cadeia do polissacarídeo e os motivos conservados da cadeia polipeptídica das proteínas envolvidas nesta interação. Os heparam sulfatos possuem papel na sinalização celular como receptores ou coreceptores para diferentes ligantes. Esta ligação dispara vias de sinalização celular levam à fosforilação de diversas proteínas citosólicas ou com ou sem interações diretas com o citoesqueleto, culminando na regulação gênica. O papel dos proteoglicanos de heparam sulfato na sinalização celular e vias de captação endocítica também são discutidas nesta revisão.

Modulation of hyaluronan in the migratory pathway of mouse primordial germ cells.

In the present report we followed the distribution of hyaluronan during the phases of separation, migration, and colonization of the primordial germ cell migratory process. Hyaluronan was detected by the use of two cytochemical methods: (1) ruthenium hexammine trichloride (RHT) associated with enzymatic treatment with hyaluronate lyase and (2) a binding specific probe for hyaluronan. After RHT treatment the proteoglycans and/or glycosaminoglycans were observed as a meshwork formed by electron-dense granules connected by thin filaments. After enzymatic digestion, no filaments could be detected in the migratory pathway. Quantitative analysis showed a close correlation between cell migration and the concentration of RHT-positive filaments. It was also shown that high amounts of hyaluronan were expressed in the separation phase and migration phases whereas during the colonization phase the amount of hyaluronan was clearly diminished. This study showed that the presence of primordial germ cells in each compartment of the migratory pathway was always accompanied by a high expression of hyaluronan. These results indicate that hyaluronan is an important molecule in the migratory process, providing the primordial germ cells with a hydrated environment that facilitates their movement toward the genital ridges.

Practical determination of hyaluronan by a new noncompetitive fluorescence-based assay on serum of normal and cirrhotic patients.

A practical fluorescence-based assay method for determination of hyaluronan (HA) was developed. Plates were coated with hyaluronan-binding proteins (HABP) obtained from bovine cartilage and successively incubated with samples containing standard solutions of hyaluronan or serum from normal and cyrrhotic patients, biotin-conjugated HABP, and europium-labeled streptavidin. After release of europium from streptavidin with enhancement solution the final fluorescence is measured in a fluorometer. The method is specific for HA even in the presence of substantial amounts of other glycosaminoglycans (chondroitin, dermatan sulfate, and heparan sulfate, and heparin) or proteins. It is possible to quantify HA between 0.2 and 500.0 microg/L. Analyses of HA concentration in 545 normal subjects and 40 cirrhotic patients gave average values of 14.5 and 542.0 microg/L, respectively. It was also shown that older subjects (> or =51 years old) have more HA (28.0 microg/L) than younger subjects (12.0 to 14.0 microg/L). This new sandwich technique has shown high precision and sensitivity similar to those of a recently described fluorescence-based assay method, being able to measure HA in amounts as small as 0.2 microg/L. In addition, this noncompetitive assay avoids preincubation, consumes less time (<5 h) than the previous competitive fluorescence-based assay (>72 h), and avoids the use of radioactive materials.