The fusion between rat brain microsomes and liposomes is investigated by measuring the release of octadecylrhodamine B (R18) fluorescence selj-quenching. In the experimental conditions used in this work, the method allows a rapid and quantitative evaluation of the mixing ofmicrosome and liposome lipid phases. The decrease of pH below 7 produces an extensive fusion between microsomes and acidic phospholipid liposomes. Microsomal protein is necessary for fusion, which is inactivated by exposure of microsomes to pronase. Therefore, H+ -induced fusion differs from Ca2+-induced fusion since the latter does not require microsomal protein. The pretreatment of microsomes with trinitrobenzenesulfonic acid (TNBS) in non penetrating conditions does not affect the extent of fusion. On the other hand, N ethoxycarbonyl-2-ethoxy- 1,2-dihydroquinoline (EEDQ), a reagent able to react with carboxyl groups, causes an extensive inactivation of fusion. Therefore, the H+ -induced fusion described here depends on some microsomal protein and may have physiological significance because it occurs at pH values present in the living celi. H+-dependent fusion can be also considered as a means to enrich membranes in some selected lipid.
Microsomal protein mediates a pH-dependent fusion of liposomes to rat brain microsomes
CORAZZI, Lanfranco;ARIENTI, Giuseppe
1990
Abstract
The fusion between rat brain microsomes and liposomes is investigated by measuring the release of octadecylrhodamine B (R18) fluorescence selj-quenching. In the experimental conditions used in this work, the method allows a rapid and quantitative evaluation of the mixing ofmicrosome and liposome lipid phases. The decrease of pH below 7 produces an extensive fusion between microsomes and acidic phospholipid liposomes. Microsomal protein is necessary for fusion, which is inactivated by exposure of microsomes to pronase. Therefore, H+ -induced fusion differs from Ca2+-induced fusion since the latter does not require microsomal protein. The pretreatment of microsomes with trinitrobenzenesulfonic acid (TNBS) in non penetrating conditions does not affect the extent of fusion. On the other hand, N ethoxycarbonyl-2-ethoxy- 1,2-dihydroquinoline (EEDQ), a reagent able to react with carboxyl groups, causes an extensive inactivation of fusion. Therefore, the H+ -induced fusion described here depends on some microsomal protein and may have physiological significance because it occurs at pH values present in the living celi. H+-dependent fusion can be also considered as a means to enrich membranes in some selected lipid.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.