Inositol 1,4,5-trisphosphate induces cyclic GMP formation in Dictyostelium discoideum.

Chemotactic signalling in the cellular slime mould Dictyostelium discoideum employs signalling molecules such as folate and cyclic AMP. These bind to specific cell surface receptors and rapidly trigger internal responses that induce chemotactic movement of the amoebae. Previous studies have shown that actin is polymerised within 3-5 sec of cyclic AMP or folate binding and that a peak of cyclic GMP is formed within 9-12 sec. Release of Ca2+ from intracellular stores has been implicated as a secondary messenger. Here we present evidence that D-myo-inositol 1,4,5-trisphosphate, when added to permeabilized amoebae of Dictyostelium, can mimic the action of chemoattractants on normal intact amoebae in inducing cyclic GMP formation. Our data suggest that IP3, which is known to act as an intermediary messenger between cell surface hormone receptors and release of Ca2+ from internal stores in mammalian cells, functions in a similar capacity during chemotaxis of this primitive eukaryote.