title: Membrane cholesterol modulates the cytolytic mechanism of myotoxin II, a Lys49 phospholipase A2 homologue from the venom of Bothrops asper.
abstract: Lys49 phospholipase A2 (PLA2) homologues present in crotalid snake venoms lack enzymatic activity, yet they induce skeletal muscle necrosis by a membrane permeabilizing mechanism whose details are only partially understood. The present study evaluated the effect of altering the membrane cholesterol content on the cytolytic activity of myotoxin II, a Lys49 PLA2 isolated from the venom of Bothrops asper, using the myogenic cell line C2C12 as a model target. Cell membrane cholesterol depletion by methyl-β-cyclodextrin (MβCD) treatment enhanced the cytolytic action of myotoxin II, as well as of its bioactive C-terminal synthetic peptide p(115-129) . Conversely, cell membrane cholesterol enrichment by preformed cholesterol-MβCD complexes reduced the cytolytic effect of myotoxin II. The toxic actions of myotoxin I, a catalytically active PLA2 from the same venom, as well as of the cytolytic peptide melittin from bee venom, also increased in cholesterol-depleted cells. Although physical and functional changes resulting from variations in membrane cholesterol are complex, these findings suggest that membrane fluidity could be a relevant parameter to explain the observed modulation of the cytolytic mechanism of myotoxin II, possibly influencing bilayer penetration. In concordance, the cytolytic effect of myotoxin II decreased in direct proportion to lower temperature, a physical factor that affects membrane fluidity. In conclusion, physicochemical properties that depend on membrane cholesterol content significantly influence the cytolytic mechanism of myotoxin II, reinforcing the concept that the primary site of action of Lys49 PLA2 myotoxins is the plasma membrane.
authors.affiliation: Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica.
authors.forename: José
authors.initials: J
authors.lastname: Rangel
authors.forename: Orestes
authors.initials: O
authors.lastname: Quesada
authors.forename: José María
authors.initials: JM
authors.lastname: Gutiérrez
authors.forename: Yamileth
authors.initials: Y
authors.lastname: Angulo
authors.forename: Bruno
authors.initials: B
authors.lastname: Lomonte
mesh_terms: D000818:Animals; D017837:Bothrops; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D003435:Crotalid Venoms / Q000737:chemistry*; D054501:Group II Phospholipases A2 / Q000494:pharmacology* / Q000633:toxicity; D045022:Lactate Dehydrogenases / Q000187:drug effects / Q000378:metabolism; D008239:Lysine; D008555:Melitten / Q000494:pharmacology; D051379:Mice; D032446:Myoblasts / Q000187:drug effects / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D030162:Reptilian Proteins / Q000494:pharmacology* / Q000633:toxicity; D013696:Temperature; D047392:beta-Cyclodextrins / Q000494:pharmacology
chemical_list: D003435:Crotalid Venoms; D010446:Peptide Fragments; D030162:Reptilian Proteins; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D008555:Melitten; D002784:Cholesterol; D045022:Lactate Dehydrogenases; D054501:Group II Phospholipases A2; C076780:myotoxin I; C061056:myotoxin II, Bothrops asper; D008239:Lysine