Signal transduction for chemotaxis in Dictyostelium amoebae.

The signal for chemotaxis in D. discoideum is cyclic AMP. This molecule binds to cell surface receptors and triggers the production of inositol (1,4,5)trisphosphate which releases Ca2+ from non-mitochondrial stores. The subsequent chain of signal transduction events brings about the polymerization of cytoskeletal actin (associated with pseudopodium formation) within five seconds and the formation of a peak of cyclic GMP within 10 s. Evidence from streamer F mutants indicates that the cyclic GMP regulates the association of myosin with the cytoskeleton that occurs at 25-50 s and that this phenomenon is concerned with elongation of the amoebae during chemotactic movement.