JBC, Vol. 254, Issue 2, 453-458, Jan, 1979
Biological effects of cesalin, an anti-tumor protein, on cultured mammalian cells
J. Elting and R. Montgomery
The effects of the protein cesalin were studied to determine the site of
its toxic action in KB cells for which the ID50 is 0.9 pg/ml. Several
effects have been noted: (i) respiration in KB cells was reduced by greater
than 50% within 1 h after cesalin addition, which could not be explained on
the basis of mitochondrial damage or from elevated intracellular ATP
levels, since these did not rise significantly until about 3 h after
cesalin addition; (ii) both DNA and RNA synthesis were inhibited, starting
about 3 h after addition of cesalin to KB cells, but the transport of
nucleosides and amino acids does not appear to be affected; (iii) no
decrease is observed in protein synthesis for at least 5 to 6 h; (iv)
cesalin can inhibit DNA synthesis and mitotic division independently of one
another. The interaction of cesalin with the cell surface is rapid and
after 5 min at 37 degrees C less than 10% of treated cells can be rescued
by addition of excess antiserum to cesalin. The cell surface receptors are
exposed throughout the cell cycle and the toxicity of cesalin is not
restricted to a particular phase of this cycle.
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