Cyclic AMP and Ca2+ as regulators of zygote formation in the cellular slime mold Dictyostelium mucoroides

Regulatory Mechanism in Sexual and Asexual Cycles of Dictyostelium

“…As 2'-deoxy-cAMP (a cAMP analog) with a high affinity for the surface cAMP receptor inhibited zygote formation, it was suggested that cAMP operates by binding to a surface receptor to mediate downstream signaling events (Suzuki et al, 1992). The inhibitory effect of cAMP on zygote formation was nullified, when K252a, a potent inhibitor of protein kinases (PKA, PKC, and PKG) was coapplied with cAMP.…”

“…These results strongly suggest that ethylene may directly induce zygote formation. As was expected, cAMP, the second regulator, exhibits an inhibitory effect on the process of zygote formation (Suzuki et al, 1992). When the number of binucleate cells stained with DAPI was counted, the number was decreased by the addition of cAMP, while it was increased by the addition of phosphodiesterase (PDE), which hydrolyzed cAMP to 5' AMP.…”

“…That is, the percentage of zygotes was elevated by the presence of extracellular Ca 2+ in D. discoideum and Dm 7 and by the increase of intracellular Ca 2+ in D. discoideum (Chagla et al, 1980;Lydan & O'Day, 1988a;Suzuki et al, 1992;Szabo et al,1982). …”

Ethylene as a potent inducer of sexual development

“…Ca 2+ has also been proposed to be a critical factor for zygote formation including cell fusion in Dictyostelium. The percentage of zygotes is elevated by the presence of increased extracellular Ca 2+ in D. discoideum and Dm-7 (Chagla et al 1980;Szabo et al 1982;Suzuki et al 1992). In this connection, phorbol esters such as 12O-tetradecanoylphorbol-13-acetate (TPA), potent activators of protein kinase C (PKC), enhance the formation of zygotes in D. discoideum (Gunther et al 1995).…”

“…A likely model of the signal transduction pathways involved in zygote formation. From several pharmacological studies, cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) have been shown to function as an inhibitory factor for zygote formation (Suzuki et al 1992;Kawai et al 1993). On the other hand, Lydan & O'Day (1988, 1993a It has been reported that the Ca 2+ -and PKC-mediated signaling pathway is involved in cell fusion during myogenesis (Shainberg et al 1969;Paterson & Strohman 1972;David et al 1990).…”