Glycoprotein degradation. Glycosidases in fibroblasts transformed by oncogenic viruses

Ref cell hydrolases: Glycosidase activities in human erythrocyte plasma membranes

Human erythrocyte plasma membranes were found to contain the following glycosidases: α- and β-glucosidase, α- and β-galactosidase, α- and β-fucosidase, β-N-acetylglucosaminidase, β-N-acetylgalactosaminidase, β-xylosidase and α-mannosidase. All the enzymes except β-fucosidase had activity interpreted to be on the external surface of the plasma membrane. The enzymes had optimum pH values of 5.2 to 5.0 and temperatures of 37 to 40°C. The enzymes were not greatly activated by divalent cations but Hg(++) and Pb(++) were inhibitory. The enzyme extract of the human erythrocyte plasma membranes liberated carbohydrate from intact red cells, which lead to the speculation that the glycosidases might function to modify the erythrocyte plasma membrane.

Microenvironmental Regulation of the Initiated Cell

In the classical skin model of tumor initiation, keratinocytes treated once with carcinogen retain their normal appearance and growth behavior indefinitely unless promoted to growth into papillomas. Because many of the papillomas regress and may recur with further promotion, their cells can also be considered as initiated. The growth of initiated keratinocytes can be inhibited either in vitro or in vivo by close association with an excess of normal keratinocytes, but it is enhanced by dermal fibroblasts. Chick embryo fibroblasts (CEF) in culture produce transformed foci after infection with Rous sarcoma virus (RSV) on a background of normal CEF in a medium containing 10% or less calf serum (CS), but they retain normal appearance and growth regulation in 10% fetal bovine serum (FBS) or 20% CS. Transformation of a carcinogen-treated line of mouse embryo fibroblasts is prevented, and can be reversed, in high concentrations of FBS in the presence of an excess of normal cells. FBS has high, broad-spectrum antiprotease activity. Increased protease production occurs in a variety of transformed cells and is correlated with progression in tumors. Protease treatment stimulates DNA synthesis and mitosis in confluent, contact-inhibited normal cell cultures. Synthetic inhibitors of proteases suppress transformation in carcinogen-treated cultures and inhibit tumor formation in animals. Several different classes of protease may be overexpressed in the same transformed cells. It is proposed that excessive protease production accounts for major features of neoplastic transformation of initiated cells, but that transformation can be held in check by protease inhibitors present in serum and released from surrounding cells. It would be informative to determine whether high concentrations of FBS would inhibit the neoplastic development of initiated keratinocytes.

The salubrious effect of tamoxifen [correction of Tamaxifen] on serum marker enzymes, glycoproteins, and lysosomal enzymes level in breast cancer woman

Tumour markers correlate strongly with prognosis based on tumour burden and surgical resectability. If chemotherapy is extremely effective in certain stage of the disease, the sensitive marker may be of great use in monitoring disease response and drug treatment. Hence, this study was launched to evaluate the changes in tumour marker enzymes like lactate dehydrogenase (LDH), glutamate oxaloacetate transaminase (SGOT), glutamate pyruvate transaminase (SGPT), alkaline phosphatase, and acid phosphatase in before and after 3 and 6 months tamoxifen treated breast cancer patients. In addition, the changes in serum glycoproteins viz., hexose, hexosamine, and sialic acid and lysosomal enzymes such as N-acetyl-beta-D-glucosaminidase, beta-D-galactosidase, and beta-D-glucuronidase were analysed in these patients. These values were compared with their age matched healthy control subjects. At 6 months evaluation, the tamoxifen treated postmenopausal breast cancer women showed a statistically significant decreased (p < 0.001, 0.05 respectively) levels of LDH, SGOT, SGPT, alkaline and acid phosphatases than their baseline values. Similarly, the levels of hexose, hexosamine, and sialic acid and N-acetyl-beta-D-glucosaminidase, beta-D-galactosidase, and beta-D-glucuronidase were decreased significantly (p < 0.001) in tamoxifen received postmenopausal women. The result of this study suggested that tamoxifen potentially retard the metastasis of breast cancer as well as the bone demineralisation in postmenopausal breast cancer women. Thus, tamoxifen may also have its antitumour activity through its beneficial effects on tumour marker enzymes and serum proteins in breast cancer women.

Effect of radiation on serum glycoproteins and glycosidases in patients with cervical carcinoma

OBJECTIVE

The serum glycan moieties of glycoproteins and the activities of glycosidases were analyzed in order to elucidate the metabolism of glycoprotein in uterine cervical cancer.

METHODS

Serum was collected from patients at different stages of cervical cancer before and after treatment. The results were analyzed using Student's t-test.

RESULTS

The glycan moieties such as sialic acid and fucose were significantly elevated even in the early stages of carcinoma, whereas a significant elevation in hexose and hexosamine levels was observed only in the advanced stages. Among the investigated lysosomal glycohydrolases, beta-D-galactosidase, N-acetyl-beta-D-glucosaminidase and alpha-L-fucosidase activities were elevated significantly at all stages except for stage I. The altered levels of glycoproteins and glycosidases were reduced to near-normal levels after radiotherapy.

CONCLUSION

The levels of glycan moieties and the activities of glycosidases can be used as diagnostic markers to assess the stage of cancer and can be used as prognostic markers during therapy.

Transformed SV3T3 cells have a reduced lysosomal compartment and lower levels of enzyme activity than 3T3 cells

The secreted and intracellular activities of a number of lysosomal hydrolases were higher in 3T3 cells than in SV40-transformed cells. The number of lysosomes and their total volume were also much larger in 3T3 cells and the surface area of their lysosomal membranes was almost twice that of SV3T3 cells. These differences alone were not sufficiently large, however, to account for the disparity seen in activity of some enzymes. Gel electrophoresis showed that a number of protein components present in lysosomal membranes purified from 3T3 cells were absent from SV3T3 membrane preparations. The absence of these components may be correlated with the reduced enzyme activity of SV3T3 cells particularly with respect to beta-glucosidase and acid phosphatase, both of which are normally found associated with lysosomal membranes.

Glycosidases in cancer and invasion

Glycosidases have been demonstrated to be elevated in the interstitial fluid of tumors, sera of animals and patients with tumors, and in some tumor tissue as compared to normal adjacent tissue. Elevations of serum beta-N-acetylglucosaminidase and beta-glucuronidase most commonly have been found to occur and these enzymes have been shown to be secreted into the extracellular medium by many different tumor cell types in vitro. The mechanism of cellular release of these hydrolytic enzymes probably involves tumor lysosomal exocytosis. Increased tumor glycosidase levels may promote increased tumor cell shedding from primary tumors, local invasion and perhaps be responsible directly, or indirectly for structural changes in tumor cell surface glycoconjugates. These cell surface changes could facilitate tumor cell thrombus formation, secondary site implantation and attachment in the microcirculation to endothelial cells and/or subendothelial basement membrane components. Other studies have demonstrated a correlation between metastatic cell potential and increased endoglycosidase and polysaccharide lyase activity. Generally, metastatic tumor cell variants have been found to be more invasive and capable of degrading proteoglycan basement membrane components, in part due to these increased levels of degradative enzymes. Hence, it is of considerable interest to develop inhibitors against these enzymes. Initial studies with glucuronidase inhibitors in the therapy of bladder tumors have been promising and with the advent of better agents and the use of appropriate in vitro metastatic models it may be possible to design and develop agents which interfere in various metastatic events and limit tumor progression.

Glycosidases in normal and regenerating chicken liver, hepatoma Mc-29, Rous sarcoma, in turkey poult liver and hemocytoblastomes, provoked by the leukosis virus strain Mc-31

Four glycosidases (beta-galactosidase, alpha-mannosidase, alpha-fucosidase and beta-N-acetylglucosaminidase) were studied in chicken normal and regenerating liver, in turkey poult liver and in virus induced avian tumors--chicken hepatoma (strain Mc-29), Rous sarcoma (strain Schmidt-Ruppin) and turkey poult hemocytoblastoma nodules (strain Mc-31). The multiple forms of beta-N-acetylglucosaminidase were assayed as well. A particular enzyme pattern was found in the tumor lines under investigation. A characteristic property of hepatoma cells was the elevation of beta-galactosidase activity and of the former enzyme and that of beta-N-acetylglucosaminidase for the hemocytoblastoma. In Rous sarcoma the glycosidase activities (except that of alpha-fucosidase) were much lower, compared to the other two solid tumors. All enzyme activities were compared with those in the normal liver of the corresponding avian species, and with the liver of tumor bearing fowls and with regenerating chicken liver. Unlike the rat liver in the avian normal and tumor tissues the percentual ratio between the multiple forms A and B of beta-N-acetylglucosaminidase was found to be 30:70%.

Involvement of protease in L-glutamine control of nucleic acid and polyphosphate metabolism in cells transformed by 9,10-dimethyl-1,2-benzanthracene, SV40 and H-ras oncogene

Mammalian cells transformed with either 9,10-dimethyl-1,2-benzanthracene, SV40 or H-ras oncogene dramatically changed their ability to synthesize DNA and RNA and metabolize polyphosphate when L-glutamine was withdrawn from the growth medium or when heat shocked (growth at 42 degrees C). Untransformed, DNA and RNA synthesis decreased by 50-80% when glutamine was withdrawn, but polyphosphate accumulated whether or not glutamine was supplied. Heat shock did not alter this response. Transformed isogenic cells responded differently; at 37 degrees C, they decreased their synthesis of DNA and RNA if starved for glutamine, whereas at 42 degrees C, synthesis was optimal without glutamine. Transformed cells accumulated polyphosphate at 37 degrees C when starved for glutamine, but at 42 degrees C, no polyphosphate accumulated. This apparent non-dependence on glutamine by transformed cells when heat shocked was found to be due to the production of glutamine from serum proteins through induction of a protease(s).

The histochemistry of glycosidases in human benign and malignant breast tissue

Histochemical methods for the localization of four glycosidases (beta-glucuronidase, beta-N-acetyl glucosaminidase, beta-D-galactosidase and alpha-mannosidase) have been applied to 40 cases of human normal and hyperplastic breast tissue and 100 human breast carcinomas. All tissues have been fixed in formol-calcium at 4 degrees C and washed in gum sucrose. beta-Glucuronidase and beta-N-acetyl glucosaminidase have consistently been detected in essentially all cells of normal and hyperplastic tissue. A similar distribution has been found for better differentiated carcinomas but the number of cells with detectable enzyme decreases in the more poorly differentiated tumour. beta-D-Galactosidase and alpha-mannosidase have only been demonstrated in very occasional cells in normal breast tissue. The incidence increases in hyperplastic tissue, and in approximately half the carcinomas many cells have detectable enzyme. The localization of beta-D-galactosidase has not been related to tumour differentiation but the better differentiated carcinomas tend to have few cells with demonstrable alpha-mannosidase. Although it has been suggested that glycosidases can have an effect on membrane function no differences have been found between those carcinomas having a few or many cells with detectable enzyme and the presence or absence of axillary lymph node metastasis. Total enzyme activity cannot be detected in fixed tissue, nor can an accurate quantitative assessment be made, but under the conditions of this study it is possible to conclude that there are differences between normal and malignant breast tissue in the localization of glycosidases.

The resolution of two populations of lysosomal organelles containing endocytosed Wistaria floribunda agglutinin from murine fibroblasts

Subcellular fractionation of Balb/c 3T3 fibroblasts exposed to Wistaria floribunda agglutinin was performed to localize fractions containing internalized lectin. Employing two sequential self-generating silica sol density gradients, the postnuclear supernatant of cell homogenates was resolved into five distinct cellular components. Lysosome enzyme activities were displayed by two populations of vesicles, each separated from plasma membrane, golgi, and mitochondria markers. The more dense of these fractions exhibited morphological and biochemical properties ascribed to secondary lysosomes. The more buoyant population was similar to that reported by Rome et al [11] who noted that it may be a product of vesiculated golgi endoplasmic reticulum lysosome (GERL). Treatment with W floribunda agglutinin of cells, surface radioiodinated demonstrated that plasma membrane proteins were localized within both the buoyant and dense lysosome populations in as little as 10 min after exposure to lectin. Prolonged incubation of the cells with W floribunda agglutinin resulted in maintenance of this distribution. However, when nonradiactive cells were exposed to 125I-labeled W floribunda agglutinin for 10 min, radioactivity was detected only in the buoyant population of lysosomes as well as the plasma membrane/golgi fraction. Treatment of cells with W floribunda agglutinin for 30 min resulted in appearance of lectin associated radioactivity in the dense lysosome fraction in addition to those populations containing radioactivity seen after a 10-min incubation. These data indicate that the endocytosis of W floribunda agglutinin differed substantially from the internalization of a portion of the plasma membrane proteins. Furthermore, we found radioactivity associated with both plasma membrane proteins W floribunda agglutinin in regions of the density gradient fractionation that virtually lacked golgi and lysosome markers. These fractions may have represented populations of nonlysosome vesicles formed during the process of endocytosis.

Effects of angiotensin II and angiotensin II antagonist saralasin on cell growth and renin in 3T3 and SV3T3 cells

Components of the renin-angiotensin system were studied in established cell culture lines of 3T3 and SV3T3 mouse fibroblasts. The renin content in 3T3 cells was significantly higher than in virus-transformed SV3T3 cells. With time after infection, renin decreased in Simian virus 40 transformed cells, while it increased steadily in mock-infected 3T3 cells. In contrast to renin, angiotensinase activity was higher in SV3T3 cells. Angiotensin II stimulated cell proliferation in 3T3 mouse fibroblasts and decreased their renin content in a dose-related manner. In contrast, saralasin, an angiotensin receptor antagonist, inhibited cell growth in 3T3 and SV3T3 cells and caused an increase of cellular renin concentration. The angiotensin fragments angiotensin (2-8) heptapeptide and angiotensin (4-8) pentapeptide had no effect on cell growth. A significant negative correlation was found between cell proliferation and renin levels in 3T3 and SV3T3 cells irrespective of the treatment. Our results indicate (1) that angiotensin II may be involved in cell growth regulation, (2) that a negative feedback exist between angiotensin II added and intracellular renin content, and (3) that virus infection causes a decrease in intracellular renin synthesis, while non-specific angiotensinase activity is increased under this condition.

Purification of alpha-L-fucosidase from various sources by affinity chromatography

An affinity column for alpha-L-fucosidases was constructed by linking p-amino-phenyl 1-thio-alpha-L-fucopyranoside to Sepharose 4B through linkers of succinyl 3,3'-diamino-dipropylamine. Excellent purification of alpha-L-fucosidase from rat epididymis, Clostridium perfringens and Limulus polyphemus (horse shoecrab) could be effected inone step with good yield. An affinity column purification step can be introduced at any point in published purification procedures. The purified enzyme is essentially free of other glycosidases and proteolytic enzymes. The column material is stable and can be reused for at least two years.

The demonstration of acid phosphatase in cultured 3T3 mouse cells

Acid phosphatase has been demonstrated ultrastructurally in 3T3 and SV40-3T3 mouse cells using sodium beta-glycerophosphate and p-nitrophenyl phosphate as substrate. The former substrate only demonstrates the enzyme in lysosomes and elements of the Golgi apparatus while the latter demonstrates it in the cisternae of the endoplasmic reticulum and in the cell surface as well as at lysosomal sites. The significance of surface acid phosphatase activity is discussed in terms of sublethal autolysis.

Demonstration of enzymes related to myelinogenesis in established human brain cell cultures

CNP, CGalT and PAPS-CST, enzymes involved in myelinogenesis were demonstrated in cultures derived from human brain. Little or no CNP activity could be found in cultures derived from non-neurogenic tissue. Transformation of brain cultures by PML-SV40 virus resulted in a 3 to 10-fold increase in the specific activity of CNP.

A histochemical study of acid phosphatase in normal and virus-transformed cultured fibroblasts

The distribution of acid phosphatase has been investigated in normal and virus-transformed cultured hamster and mouse fibroblasts. The enzyme was found to be present in lysosomes, autophagic vacuoles and elements of the Golgi apparatus. It was also found to be associated with a surface coat in some virus-transformed mouse cells and in the cytoplasm of both normal and transformed hamster cells.

Glycosidases in normal and dimethylhydrazine-treated rats and mice with special reference to the colonic tumours

Activities of 12 glycosidases and of β-D-glucuronidase were measured in liver, kidney and in the gastrointestinal tract of rats and mice. The activities of different enzymes varied not only within one tissue but also among different tissues. In rats injected with 1,2-dimethylhydrazine, a many fold increase in N-acetyl-β-D-glucosaminidase, N-acetyl-β-D-galactosaminidase, β-D-galactosidase and α-L-fucosidase was found in colonic tumours and colonic mucosa. These enzymes were elevated significantly in the kidney of tumour bearing animals as well. Liver and other parts of the gastrointestinal tract showed an increase only in N-acetyl-hexosaminidase with the appearance of colonic tumours. In treated mice, 2 N-acetylhexosaminidases were elevated in colon, duodenum, liver and kidney. However, in liver and kidney, β-D-galactosidase was also significantly increased.

Non-selective inhibition of transformed cell growth by a protease inhibitor

The protease inhibitors N-tosyl-L-phenylalanylchloromethyl ketone (TPCK) and N-tosyl-L-lysylchloromethyl ketone (TLCK) have previously been shown to selectively inhibit growth of simian virus 40-transformed cells, suggesting that proteolytic enzymes play a role in loss of cellular growth control following viral transformation. In contrast, this study shows that TPCK-mediated growth inhibition is non-selective, since the growth of both simian virus 40-transformed and untransformed 3T3 cells is similarly reduced by TPCK treatment. Under certain conditions, TPCK treatment of simian virus 40-transformed cells yields a reversible "growth plateau" condition which mimics, but is not equivalent to, contact inhibition of growth. The growth inhibitory effects of TPCK are due to inhibition of protein synthesis, since TPCK treatment resulted in a diminution of protein synthesis and since the "growth plateau" effect was also observed in cultures treated with cycloheximide.

Enzyme activity in invasive tumors of human breast and colon

Elevated levels of glycoprotein:sialyltransferase activity (EC 2.4.99.1; CMP-N-acetylneuraminate: D-galactosyl-glycoprotein N-acetylneuraminyltransferase) were found in human malignant neoplastic tissues compared to normal, benign, and "preneoplastic" tissues. This increase was not due to the cell density of the tissue. Elevated levels of certain proteases and glycosidases were also found. The increase in transferase activity may be associated with altered membrane synthesis in the neoplastic state; changes in the activity of degradative enzymes may be associated with tumor invasiveness and maintenance of the neoplastic state. Measurements on human tumors are possibly more directly relevant to cancer than those described for transformed fibroblastic cells in vitro.