CONTROL OF CONCANAVALIN A RECEPTOR MOBILITY BY CYTOPLASMIC ACTIN IN HUMAN TUMOUR CELLS

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Abstract
Tissue culture monolayers of seven human intracranial tumours comprising 2 astrocytomas, 3 meningiomas, 1 secondary squamous cell carcinoma and 1 secondary adenocarcinoma were examined by a double immunofluorescent staining technique to demonstrate Concanavalin A (Con A) surface receptors and cytoplasmic actta in the same cell. Tumour cells, treated with fluoresceinisothiocyanate-labelled Con A (FITC-Con A) showed staining in cell margins or in a random distribution over the cell surface. Incubating the cells with FITC-Con A at 37° for increasing periods of time resulted first in staining of clusters and later of perinuclear globules. Cells, preteated with 4% paraformaldehyde at 4° for 10 min or with cytochalastn B at 37° for 30 min showed Staining restricted to cell margins. In the cytochalasin B-treated cells, tile peripheral staining was in the form of coarse clusters. Double fluorochrome studies showed that the anti-action antibody (AAA) staining occurred in sites closely related to those stained by FITC-Con A both in untreated as well as in cytochalsin B-treated cells. The findings suggest that Con A receptors, as an example of a stable cell membrane determinant in human tumour cells, are associated with actin and that their mobility on the cell surface is dependent on an intact cytoplasmic actin system.