Inositol 1,4,5-trisphosphate induces calcium release from a non-mitochondrial pool in amoebae of Dictyostelium

Abstract

Evidence is presented for two distinct Ca 2+ pools in amoebae of Dictyostelium discoideum. One pool, presumably mitochondrial, was sensitive to the mitochondrial inhibitors oligomycin and dinitrophenol and showed an affinity for Ca 2+ in the μM concentration range. The other Ca 2+ pool, which was insensitive to these inhibitors, was of lower capacity but had higher affinity (in the nM range). Inositol 1,4,5-trisphosphate (5 μM) added to saponin-permeabilized amoebae induced a rapid release of Ca 2+ from the latter pool but had no effect on the presumed mitochondrial pool. Controls using addition of inositol 1,4-bisphosphate (the hydrolytic product of IP 3) induced no such Ca 2+ release. The results provide strong support for the involvement of IP 3 in signal transmission during chemotaxis of D. discoideum.