Assembly-disassembly of actin bundles in starfish oocytes: an analysis of actin-associated proteins in the isolated cortex.
One rapid response of starfish oocytes to the maturation-inducing hormone, 1-methyladenine (1-MA), is the formation of transient actin-filled spikes on the cell surface. The presence and distribution of G- and F-actin and several actin-associated proteins were examined in cortices isolated from oocytes before, during, and after spike formation by using antibodies and the F-actin-specific stain, NBD-phallacidin. Before 1-MA addition, staining with antiactin and NBD-phallacidin indicates that most of the actin in the cortex is either G-actin or oligomeric actin, but rather little is F-actin. Application of the hormone results in the conversion and redistribution of this cortical actin into large bundles of F-actin which form the cores of spikes. When the spikes recede, F-actin disappears, and the amount of all forms of actin bound in the cortex appears to decrease. Antibodies to sea urchin egg myosin, fascin and a 220-kDa protein were used to examine these actin-associated proteins during the times that the organization of actin changes. Myosin and the 220-kDa protein are bound to the cortex and uniformly distributed before 1-MA application while fascin appears to be unbound. When spikes appear after 1-MA addition, fascin and the 220-kDa protein are localized coincidently with the spikes, whereas myosin remains uniformly distributed throughout the cortex and is excluded from the spikes. After spike resorption, fascin and the 220-kDa protein appear to lose their cortical binding while myosin retains its localization unchanged. These results indicate that actin, fascin and the 220-kDa protein undergo major organizational changes in the cortex in response to 1-MA.
D000199:Actins / Q000378:metabolism*; D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000546:Amanitins; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D004527:Egg Proteins / Q000378:metabolism; D005260:Female; D005455:Fluorescent Antibody Technique; D005456:Fluorescent Dyes; D046911:Macromolecular Substances; D008840:Microfilament Proteins; D009218:Myosins / Q000378:metabolism; D009865:Oocytes / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D013215:Starfish / Q000502:physiology*
D000199:Actins; D000546:Amanitins; D002352:Carrier Proteins; D004527:Egg Proteins; D005456:Fluorescent Dyes; D046911:Macromolecular Substances; D008840:Microfilament Proteins; C020324:fascin; C008407:1-methyladenine; C028877:7-nitrobenz-2-oxa-1,3-diazole-phallacidin; D009218:Myosins; D000225:Adenine