Cancer cell biology / edited by Takeo Nagayo, Wataru Mori.

Date:
[1980]
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Cancer cell biology / edited by Takeo Nagayo, Wataru Mori. Source: Wellcome Collection.

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    Functional Difference betzveen CDS and CIDS Atsumi and Takeichi (2) compared the morphological difference between aggre gates formed by the CDS and CIDS, respectively. LTE-cells (with CIDS alone) were associated into loose aggregates, in which individual cells remained rounded. TC-cells (with CDS alone) aggregated more tightly, adhering to neighboring cells from a wide contact area. At an ultrastructural level, the cells in LTE-cell aggregates were connected to one another by simple appositions of plasma membranes. No other junctional structures were observed. The simple appositions of plasma membranes were also the only junc tional structures in TC-cell aggregates at the early stage of their aggregation (15 min). However, after 30 to 60 min of TC-cell aggregation, two specialized junctions, gap and intermediate junctions, were noted. These results suggest that the CDS and CIDS bind cells by quite different means. The adhesion of cells to the CIDS seems to depend on a purely biochemical reaction between cell surface components, such as the reaction between antigen and antibody or lectin and its receptor, since none of these reactions requires physiological temperature. On the other hand, the fact that CDS action is temperature dependent suggests that the CDS must involve some cellular active processes including movement of the cell sur face. Moreover, the finding that gap and intermediate junctions are observed only in TC-cell aggregates suggests that the adhesion of cells to the CDS is a prerequisite for the formation of these specialized junctions. Identification of Molecules in CIDS The CIDS is inactivated by treating cells with 0.01% trypsin. Urushihara et al. (9) found that some proteinous substance is released from the cells by this treatment. This substance showed an activity neutralizing the inhibitory effect of anti-E-V79 Fab on LTE-cell aggregation. This active substance was purified by gel filtration, and its molecular weight was found to be approximately 80,000. An antibody against this purified substance was raised, and the effect of Fab fragments of this antibody on the aggregation of V79 cells was tested. The Fab was found to inhibit the aggregation of LTE-cells but not that of TC-cells. It was there fore postulated that this trypsin-released substance is a fragment of the CIDS molecule. The next step was an attempt to identify the original intact molecule from which the fragment was derived. The above mentioned antibody will be called hereafter the anti trypsin released fragment of the CIDS (anti-TRF). Surface proteins of LTE-cells were first labeled with 125 I by the lactoperoxidase- catalyzed iodination method, and then solubilized with detergents. Anti-TRF was added into this 125 I-labeled cell lysate and the immunoprecipitate formed was analyzed by SDS-electrophoresis. It was found that only one component among a number of radioiodinated cell surface components is immunoprecipitated by anti-TRF (10). This component, the molecular weight of which is about 125,000, was also labeled with 3 H-fucose and 3 H-glucosamine, suggesting that it is a glycoprotein. The mono- specificity of the anti-TRF was determined by two-dimensional electrophoresis of the immunoprecipitate collected from the lysate of cells metabolically labeled with