The importance of transglutaminase in tumour growth and metastasis

Hand, D., 1988. The importance of transglutaminase in tumour growth and metastasis. PhD, Nottingham Trent University.

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Measurement of transglutaminase activity in chemically-induced hepatocellular carcinomas showed that it was significantly reduced. Subcellular fractionation studies revealed that this reduction occurred primarily in the cytosol fraction of the cell. Leaching studies with the particulate fraction of the cell indicated that the activity tightly associated with this fraction was not reduced in tumours. This was confirmed by separation of a cytosolic and a particulate form of transglutaminase activity using anion-exchange chromatography, which indicated that there was a specific reduction in the cytosolic enzyme in the tumours whilst the particulate enzyme was unaffected.

Comparison of the cytosolic transglutaminase existing freely in the cytosol with that loosely attached to the membrane fraction indicated that the association of this enzyme with the membrane fraction was not accompanied by any changes in molecular weight, Km for putrescine incorporation into N,N'-dimethylcasein and sensitivity to activation by Ca2+. Similarly, the cytosolic enzyme from hepatocellular carcinomas was found to be identical to that from normal liver when the same characteristics were compared. This indicated that the reduction in cytosolic transglutaminase was most likely to be due to reduced expression of this enzyme by the tumour cells.

Normal liver and hepatocellular carcinomas were found to be equally capable of incorporating [ 14 C]- methylamine into tissue slice proteins in a Ca2+ -dependent manner. This was attributed to the action of the particulate enzyme since the radiolabel was mostly located in a plasma membrane rich fraction. SDS-polyacrylamide gel electrophoresis revealed that most of the radiolabel was located in a high molecular weight proteinaceous material (Mr > 106) and that the amount of incorporation into this material was equivalent in normal liver and tumours. Incorporation into smaller proteins was reduced in the tumour tissue and was attributable to the action of the cytosolic transglutaminase. This incorporation occurred mainly into proteins of Mr 43,600 and Mr 38,900. In the tumours a protein of Mr 35,900 was also found to be labelled.

Measurement of transglutaminase activity and polyamine levels in pre- and post- metastatic sarcoma tissue revealed that there was a 4-5 fold reduction in transglutaminase activity at the onset of metastases which was paralleled by a large increase in free putrescine levels (20 fold) during this same time period. A change in the levels of covalently-bound polyamine in pre- and post-metastatic P tissue was found to correlate with the changes seen in transglutaminase activity. These results indicate that transglutaminase may play an important role in mediating events associated with the metastatic process and that alterations in the levels of free and bound polyamines may also be of importance during this process.

Item Type: Thesis
Creators: Hand, D.
Date: 1988
ISBN: 9781369325119
Divisions: Schools > School of Science and Technology
Record created by: Laura Ward
Date Added: 25 Jun 2021 13:29
Last Modified: 01 Nov 2023 15:26

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