Effect of phospholipase A2 from bee venom on in vitro endosome fusion

MAYORGA, L.S; BERÓN,, W; COLOMBO, M.I.

BIOCELL

INST HISTOL EMBRIOL-CONICET

Lugar: Mendoza; Año: 1993 vol. 17 p. 151 - 163

0327-9545

Transport along the endocytic and exocytic pathways requires specific and regulated membrane fusion steps. The actual mechanism that mediaies fusion is still poorly understood. One factor that is probably involved in fusion is a phospholiphaseA, (PLA2) (Mayorga et al., Proc. Natl. Acad. Sci. USA, 1993, 90: 10255-10259). We have tested the effect of an extraceilular PLA2 isolated from bee venom (Bee PLA2) in an in vitro endosome fusion assay. The enzyme inhibited fusion at very low concentrations. The effect was specific for Bee PLA2. Three other extracellular and one intracellular PLA2´s did not affect fusion. In the presence of amphiphilic peptides (e.g., mastoparan, melittin) that are also potent inhibitors of fusion, Bee PLA2 promoted fusion. Bee PLA2-induced fusion presents characteristics similar to hose described for calcium-dependent fusion between endosomes. Bee PLA2 is likely interacting with the fusion machine and inhibiting the formation of a wmpetent fusion complex. Amphiphilic peptides can stimulate PLA2 activity and may cause a local release of arachidonic acid that would lead to membrane fusion.