Inositol(1,3,4,5) tetrakisphosphate plays an important role in calcium mobilization from Entamoeba histolytica.

Calcium release from internal stores of Entamoeba histolytica, a parasitic protozoan, was observed by measuring fluorescence of Fura-2. Emptying of inositol(1,4,5)trisphosphate (Ins(1,4,5)P3)-sensitive calcium pools in permeabilized E. histolytica did not significantly affect subsequent calcium release by inositol(1,3,4,5)tetrakis-phosphate (Ins(1,3,4,5)P4). Similarly, prior depletion of Ins(1,3,4,5)P4-sensitive stores did not have any influence on subsequent calcium release by Ins(1,4,5)P3. The EC50 for calcium release was 0.15 microM with Ins(1,4,5)P3 and 0.68 microM with Ins(1,3,4,5)P4. In conclusion, the Ins(1,3,4,5)P4-sensitive calcium store in E. histolytica is separate and independent from the Ins(1,4,5)P3-sensitive pool.