concanavalin-a and 1-methyladenine

Resumption of meiosis in starfish oocytes is induced by 1-methyladenine (1-MeAde) produced by ovarian follicle cells under the influence of a gonad-stimulating substance (GSS). With respect to 1-MeAde production, the effect of GSS on follicle cells results in the receptor-mediated formation of cyclic AMP (cAMP). It has also been reported that methylation is involved in 1-MeAde production by GSS. This study was undertaken to determine whether cAMP is the agent responsible for mediating methylation in 1-MeAde biosynthesis by isolated follicle cells of the starfish Asterina pectinifera. Methionine and selenomethionine enhanced 1-MeAde production by GSS in follicle cells. These stimulatory effects were dependent on the GSS concentration. Production of 1-MeAde by GSS was inhibited by ethionine and selenoethionine, competitive inhibitors of methionine. Like GSS, 1-MeAde production induced by concanavalin A, trypsin, and 3-isobutyl-1-methylxanthine (IBMX), which stimulated cAMP accumulation in follicle cells, was influenced by methionine and its related compounds. In contrast, although 1-methyladenosine (1-MeAde-R) induced 1-MeAde production by follicle cells without increasing cAMP levels, methionine and its related compounds had no effect. Use of [methyl-14C]methionine showed that a radiolabel was incorporated into 1-MeAde during incubation with GSS and IBMX, but not with 1-MeAde-R. These results strongly suggest that cAMP plays an important role in the process of methylation during 1-MeAde biosynthesis induced by GSS.

Topics: 1-Methyl-3-isobutylxanthine; Adenine; Adenosine; Animals; Concanavalin A; Cyclic AMP; Female; Methionine; Methionine Adenosyltransferase; Methylation; Ovarian Follicle; Starfish; Trypsin

Resumption of meiosis in starfish oocytes is induced by 1-methyladenine (1-MeAde) produced by ovarian follicle cells under the influence of a gonad-stimulating substance (GSS). It has also been reported that concanavalin A (Con A) and two serine proteolytic enzymes (trypsin and Pronase) can stimulate 1-MeAde production. This study was undertaken to determine if 1-MeAde production induced by these compounds is mediated through elevation of cAMP in starfish (Asterina pectinifera) follicle cells. GSS at a concentration of 0.1 mg/ml significantly stimulated 1-MeAde accumulation in extracellular medium after 1-2 hr of follicle cell incubations. GSS also caused a four- to fivefold increase in intracellular levels of cAMP. The continuous presence of GSS was required for the maintenance of elevated levels of cAMP and 1-MeAde. Basal levels of intracellular cGMP were only about 20% of those of cAMP and were not influenced by treatment with GSS. At 1 mM, 3-isobutyl-1-methylxanthine (IBMX), a potent phosphodiesterase inhibitor, stimulated both 1-MeAde and cAMP production in a concentration-dependent manner. Con A and two serine proteases also raised both cAMP and 1-MeAde production. Con A-induced (1.0 mg/ml) increases in cAMP and 1-MeAde were greater than the response to GSS (0.1 mg/ml) and were completely suppressed by treatment with alpha-methyl-D-mannoside (10 mM), a competitive inhibitor of Con A. These results strongly suggest that cAMP is a second messenger in the production of 1-MeAde by starfish ovarian follicle cells.

Topics: Adenine; Animals; Concanavalin A; Cyclic AMP; Cyclic GMP; Female; Ovary; Peptide Hydrolases; Peptides; Phosphodiesterase Inhibitors; Starfish

Maturation of starfish oocytes is induced by 1-methyladenine produced in follicle cells under the influence of a gonad-stimulating hormonal peptide released from the nervous system. Concanavalin A stimulates isolated follicle cells to produce 1-methyladenine, which suggests that it has the same capacity as the peptide hormone to indirectly induce oocyte maturation.

Topics: Adenine; Animals; Castration; Concanavalin A; Depression, Chemical; Female; Invertebrate Hormones; Mannose; Methylglycosides; Ovum