Possible roles of phospholipase A(2) in the biological activities of Acanthamoeba castellanii (T4 Genotype).

Using phospholipases A(2)-specific spectrophotometric assays, it was shown thatA. castellaniilysates and their conditioned medium exhibit phospholipase activities. The extracellular levels of PLA(2)detected were significantly reduced compared with the cell-associated enzyme (P<0.05). Sphinganine, a PLA(2)inhibitor showed robust amoebistatic properties but had no effect on the viability ofA. castellanii. The potency of sphinganine was demonstrated effectively towards purified PLA(2)derived from porcine pancreas. Using sphinganine, it was observed that PLA(2)is involved in neither binding nor cytotoxicity of the human brain microvascular endothelial cells due toA. castellanii. Unlike as was the case forDictyosteliumamoebae, PLA(2)appeared to be involved inA. castellaniiphagocytosis of the fluorescently-labelled polystyrene beads. Horseradish peroxidase was used as a tracer molecule to develop assays to study pinocytosis inA. castellanii. The findings revealed that sphinganine impedes phagocytosis but augments pinocytosis inA. castellaniisuggesting distinct nature of processes. A complete understanding of the role of phospholipases in the biology and pathogenesis ofA. castellaniiinfections will determine their potential as therapeutic targets.