Effects of Cytochalasins on Lymphocytes: Some Distinctive Features of Cytochalasin-E

Cytochalasin-E (CE) has specific properties that distinguishes it from other cytochalasin congeners. We have taken advantage of these in investigating the mechanisms operative in the effects of cytochalasins on lymphocyte proliferative responses to phytomitogens. Like the other cytochalasins, CE inhibits these responses only when present during the early phases of exposure of lymphocytes to mitogens, but not when added later on. The effects of CE are irreversible since prior incubation of lymphocyte in CE renders them incapable of response. Unlike the effects of cytochalasin A, the only other irreversibly active congener, lymphocytes preincubated in CE completely recover the ability to respond if they are cultured in cytochalasin-free medium for 48 hours. Unlike cytochalasins A and B, cytochalasin-E does not inhibit glucose transport into lymphocytes and all. We have shown that human lymphocytes bind cytochalasins at 3 distinct classes of sites named L, M, and H (J. Biol. Chem. 256:1290-1300, 1981). CE binds irreversibly to the L and H-sites on the short to medium term but does not bind to the glucose displaceable M-site at all. CE may have potential usefulness as affinity label towards isolation of specific binding sites since the chemical structure offers feasible approaches towards isotopic labelling.