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Fluorescence based studies of endophilin B proteins and their interactions with lipid membranes
Author(s) -
Boukari Hacene,
Shiu Brian,
Banerjee Soojay,
Silver Jonathan,
Youle Richard J.,
Bezrukov Sergey M.,
Rostovtseva Tatiana K.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a258
Subject(s) - vesicle , chemistry , membrane , biophysics , liposome , fluorescence correlation spectroscopy , lipid bilayer , fluorescence microscope , cytoplasm , microbiology and biotechnology , fluorescence , membrane protein , biochemistry , biology , physics , quantum mechanics , organic chemistry , molecule
Endophilin B proteins belong to a subfamily of endophilins, cytoplasmic proteins, and are involved in membrane dynamics. During apoptosis endophilin B1 interacts with the proapoptotic protein Bax and targets mitochondria. Recently, a novel protein endophilin B2 was found that associates with B1 in yeast two‐hybrid screening. Here we used confocal fluorescence microscopy to study the direct effect of endophilin B1 and B2 on lipid membrane shape deformation of giant unilamellar vesicles (GUVs) as a model for their possible effects on the mitochondrial outer membrane. We found that B2 induces massive shape transition of GUVs, manifested by generation of small vesicles, tubules, buds, and liposome fission and fusion. Under the same experimental conditions B1 does not exert a similar effect. However, after pre‐incubation with Bax, B1 causes extensive tubulation of GUVs. We applied fluorescence correlation spectroscopy to determine the behavior and interactions of fluorescently‐labeled B1 and B2 with Bax. We found that Bax induces aggregation/oligomerization of B1 whereas there were no measurable effects with B2. Furthermore, B2 also promotes oligomerization of B1. These results demonstrate differences between the two endophilins B in their interactions with lipid membranes and provide an assay that might be used to investigate how the interaction between endophilin B1, B2, and Bax alters membrane properties.