Interfacial enzyme activation, non-lamellar phase formation and membrane fusion. Is there a conducting thread?
Previous studies from this laboratory have shown that the enzymic generation of diacylglycerol in bilayers by phospholipase C may lead to membrane fusion through the formation of transient non-lamellar lipidic intermediates. The present paper intends to explore the correlations existing among the three main processes involved, namely (a) the induction (or inhibition) of lamellar-to-non-lamellar phase transitions in lipid mixtures through the addition of small (< 5 mol%) proportions of other lipids, (b) the promotion, by the latter lipids, of fusion in otherwise stable phospholipid vesicles (large unilamellar liposomes) under conditions leading to inverted hexagonal/inverted cubic phase formation in bulk lipid systems, and (c) the modulation, by the same small proportions of lipids, of phospholipase C hydrolysis of phosphatidylcholine in liposome bilayers. It is concluded that phospholipase C may give rise to non-lamellar lipidic structures that in turn permit liposomal fusion to occur, but neither enzyme activity is directly modulated by non-lamellar phase formation, nor will whatever kind of enzyme-induced non-lamellar structure give rise to fusion. Moreover, only under certain kinetic conditions will the enzyme give rise to the organization of non-lamellar structures that are conducive to the fusion event.
Goñi
F M
FM
Departamento de Bioquímica, Universidad del País Vasco, Bilbao, Spain.
Basáñez
G
G
Begoña Ruiz-Argüello
M
M
Alonso
A
A
D000818:Animals; D002462:Cell Membrane / Q000737:chemistry*; D006868:Hydrolysis; D008055:Lipids; D008561:Membrane Fusion; D010738:Type C Phospholipases
D008055:Lipids; D010738:Type C Phospholipases