Correlation between effects of 24 different cytochalasins on cellular structures and cellular events and those on actin in vitro

Abstract

To compare the effects of cytochalasins on the cellular level with those on the molecular level, 24 cytochalasins, 20 natural compounds and 4 derivatives, were used . The following effects were tested for each of 24 cytochalasins: (a) four high dose (2-20 AM) effects on the cellular level : rounding up of fibroblastic cells, contraction of actin cables, formation of hairy filaments containing actin, and inhibition of lymphocyte capping; (b) a low dose (0 .2-2 ,AM) effect : inhibition of membrane ruffling ; and (c) two in vitro effects: an inhibition of actin filament elongation (the high affinity effect [low dose effect] in vitro) and an effect on viscosity of actin filaments (the low affinity effect [high dose effect] in vitro) . These results indicated that there are almost the same hierarchic orders of relative effectiveness of different cytochalasins between low and high dose effects and between cellular and molecular effects. From the data obtained with the 24 cytochalasins, we have calculated correlation coefficients of 0.87 and 0.79 between an effect in vivo, inhibition of capping, and an effect in vitro, inhibition of actin filament elongation, as well as between inhibition of capping and another effect in vitro, effect on viscosity of actin filaments, respectively . Furthermore, a correlation coefficient between the high affinity effect and the low affinity effect determined in vitro was calculated to be 0.90 from the data obtained in this study. The strong positive correlation among low and high dose effects in vivo and those in vitro suggests that most of the effects caused by a cytochalasin, irrespective of doses or affected phenomena, might be attributed to the interaction between the drug and the common target protein, actin.In the course of the immunofluorescence microscope study on cytochalasin-treated cells using actin antibody, we have found that aspochalasin D, a 10-isopropylcytochalasin, strongly induced the formation of rodlets containing actin in the cytoplasm of the treated fibroblasts . In contrast, other cytochalasins, including cytochalasin B, cytochalasin C, cytochalasin D, and cytochalasin H, were found to induce the formation of nuclear rodlets. Among them, cytochalasin D was the most potent in the ability to induce the rodlets. Both cytoplasmic and nuclear rodlets found in the cytochalasin-treated cells were similar in ultrastructures to those induced by 5 to 10% (vol/vol) dimethyl sulfoxide in the same type of cells.The secondary metabolites of molds known as cytochalasins inhibit a variety of cellular movements, including cell division, motility, secretion, and phagocytosis, and cause change in cell shape (45). In addition, some, but not all, cytochalasins inhibit sugar transport by competing with sugars for binding to highaffinity sites in the plasma membrane (5, 34) . The inhibition of

HDL-mediated cholesterol uptake and targeting to lipid droplets in adipocytes

“…These compounds are known to disrupt the organization of the Golgi complex and were added for the indicated time before exposure to NBD-chol. The effects of cytochalasin D (20 M, 60 min), a compound known to disrupt the actin network (21), and N -ethyl-maleimide (NEM) (1 mM, 20 min), a V-type ATPase inhibitor (22), on NBD-chol influx were also assessed.…”

ArabidopsisFormin3 Directs the Formation of Actin Cables and Polarized Growth in Pollen Tubes

“…The organization and dynamics of specific actin microfilaments are regulated by various actin binding proteins that have the ability to bind either to monomeric or to filamentous actin or to both. As polar structures, actin filaments elongate mainly at their barbed end in the cell (Casella et al, 1981;Fox and Phillips, 1981;Tellam and Frieden, 1982;Yahara et al, 1982;Symons and Mitchison, 1991;Redmond et al, 1994). A key mechanism regulating actin assembly is the creation of new barbed ends by the de novo nucleation of new actin filaments (Blanchoin et al, 2000;Wear et al, 2000;Pollard et al, 2001).…”

Cellular Changes of Rat Embryonic Fibroblasts by an Actin-Polymerization Inhibitor, Bistheonellide A, from a Marine Sponge.

“…Amongthese, studies on cells treated with cytochalasins or fungus metabolites have shownthe necessity of actin filaments for many aspects of cellular functions (3). Cytochalasins bind to the barbed end of actin filaments and inhibit both association and dissociation of monomers at that end.…”