title: Recruitment of a phospholipase C/sphingomyelinase into non-lamellar lipid droplets during hydrolysis of lipid bilayers.
abstract: When giant unilamellar vesicles (GUVs) composed of sphingomyelin, phosphatidylcholine, phosphatidylethanolamine, and cholesterol are treated with PlcHR(2), a phospholipase C/sphingomyelinase from Pseudomonas aeruginosa, the initial stages of lipid hydrolysis do not cause large changes in vesicle morphology (Ibarguren et al., 2011). However, when hydrolysis progresses confocal fluorescence microscopy reveals the formation of lipid aggregates, whose morphology is not compatible with that of bilayers. Smaller vesicles or droplets can also be seen inside the GUV. Our studies indicate that these aggregates or droplets are enriched in the non-lamellar lipid ceramide, an end-product of PlcHR(2) reaction. Moreover, the aggregates/droplets appear enriched in the hydrolytic enzyme PlcHR(2). At a final stage GUVs containing the enzyme-enriched droplets disintegrate and vanish from the microscope field. The observed non-lamellar enzyme-rich structures may be related to intermediates in the process of aggregation and fusion although the experimental design prevents vesicle free diffusion in the aqueous medium, thus actual aggregation or fusion cannot be observed.
authors.affiliation: Unidad de Biofísica (Centro Mixto CSIS-UPV/EHU), Departamento de Bioquímica, Universidad del País Vasco, Barrio Sarriena s/n, 48940 Bilbao, Spain.
authors.forename: Maitane
authors.initials: M
authors.lastname: Ibarguren
authors.forename: Jesús
authors.initials: J
authors.lastname: Sot
authors.forename: L Ruth
authors.initials: LR
authors.lastname: Montes
authors.forename: Adriana I
authors.initials: AI
authors.lastname: Vasil
authors.forename: Michael L
authors.initials: ML
authors.lastname: Vasil
authors.forename: Félix M
authors.initials: FM
authors.lastname: Goñi
authors.forename: Alicia
authors.initials: A
authors.lastname: Alonso
mesh_terms: D002518:Ceramides / Q000737:chemistry / Q000378:metabolism; D004075:Diglycerides / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000201:enzymology* / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism*; D053835:Unilamellar Liposomes / Q000737:chemistry / Q000378:metabolism*
chemical_list: D002518:Ceramides; D004075:Diglycerides; D008051:Lipid Bilayers; D053835:Unilamellar Liposomes; D010738:Type C Phospholipases