These observations indicated that the recombinant phospholipase-D LiRecDT1 can interact with B16-F10 membrane constituents, exhibits hydrolytic

activity toward phospholipids, and can directly metabolize phospholipids that are structurally organized on cell membranes or are extracted from B16-F10 cytoplasmic membranes to generate bioactive molecules. In spite of binding to and causing metabolism of membrane phospholipids, even under the highest purified tested phospholipase-D concentration and longest exposure time (300 μg for 72 h; a concentration sufficient to kill mice and rabbits and even cause serious problems in humans; da Silva et al., 2004; Kusma et al., 2008), the B16-F10 cells exhibited no change in viability (using Trypan selleck blue

assay). Additionally, they did not suffer any type of morphological modification, such as cytoplasmic vacuolation, rounding up of cells and detaching from the substrate, cell aggregation, or cell lysis (observed through inverted microscope). These findings suggested an absence of deleterious effects of phospholipase-D on these cells as well as a lack of cellular damage, such as a breakdown of membrane integrity, under the assayed experimental conditions. Additionally, experiments using Fluo-4, which is a cell-permeant, Calcium-sensitive selleck chemical fluorophore, indicated an increase in fluorescence after LiRecDT1 treatment Methane monooxygenase (detected in two individual experimental assays: a spectrofluorimetric assay and fluorescence microscopy), demonstrating that the activity of LiRecDT1 on membrane phospholipid metabolism in B16-F10 cells could stimulate a calcium influx into the cytoplasm of the cells. This finding is in agreement with data in the literature indicating that treatment of fibroblasts with another exogenous phospholipase-D (obtained from S. chromofuscus) resulted in a cytoplasmic calcium influx ( van Dijk

et al., 1998). Moreover, the occurrence of an influx of Calcium ions inside cells following phospholipase-D treatment is supported by results showing that Calcium is required for brown spider phospholipase-D-induced hemolysis and by those of Yang et al. (2000), who reported that lysophosphatidic acid (a product generated following LiRecDT1 treatment of B16-F10 cells) induces calcium entry in human erythrocytes. Finally, the influx of ions Calcium inside cells following recombinant brown spider phospholipase-D treatment was not a consequence of leakage at the cell membrane because, as noted above, the viability of cells was unchanged, even following exposure to a high concentration of purified LiRecDT1 (as demonstrated by a Trypan blue assay detecting the breakdown of membrane integrity).