Effect of calyculin A on the surface structure of unfertilized sea urchin eggs.
Calyculin A, a potent inhibitor of type 1 and type 2A protein phosphatases, induces contractile ring formation when applied to unfertilized sea urchin eggs [Tosuji et al., 1992: Proc. Natl. Acad. Sci. USA 89:10613-10617]. We report here the elongation of microvilli in the unfertilized eggs exposed to calyculin A. The elongated microvilli and associated sperm-egg binding sites (egg receptor for sperm) then became concentrated into a constriction site corresponding to the cleavage furrow. The egg receptor for sperm was also in close connection to the microfilaments. Okadaic acid is another known inhibitor of protein phosphatase type-1 and type-2A. Its effect, however, is about a hundredfold feebler for type-1 phosphatase than type-2A. Even after treatment with okadaic acid, no change was observed, suggesting that these morphological changes were induced by calyculin A solely though its inhibitory effect on the type-1 protein phosphatase.
Tosuji
H
H
Department of Chemistry and BioScience, Faculty of Science, Kagoshima University, Kagoshima, Japan. tosuji@sci.kagoshima-u.ac.jp
Miyaji
K
K
Fusetani
N
N
Nakazawa
T
T
D020101:Acrosome Reaction; D000818:Animals; D003571:Cytochalasin B / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005306:Fertilization / Q000187:drug effects; D066298:In Vitro Techniques; D008387:Marine Toxins; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D019319:Okadaic Acid / Q000494:pharmacology; D010063:Ovum / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure*; D010080:Oxazoles / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D012617:Sea Urchins; D013084:Sperm-Ovum Interactions
D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; D019319:Okadaic Acid; D003571:Cytochalasin B; C059041:calyculin A; D010749:Phosphoprotein Phosphatases