Membrane fusion is an essential and characteristic function of all plant and animal cells. It involves a complex set of membrane interactions, few of which are understood in detail. The overall goals of this proposal are to understand membrane fusion in a simple lipid system so that the knowledge acquired can be applied to understanding biological membrane fusion, answering some fundamental problems of membrane electrostatics, and developing liposomes that efficiently deliver materials to cells. The proposal is prompted by the discovery that some o-alkyl-phosphtidylcholinium compounds, a new class of phospholipids with a net positive charge that very recently became available through another project, form giant vesicles that fuse with vesicles of anionic lipids. Because these vesicles can be manipulated electrophoretically under the fluorescence microscope, a unique opportunity arises to examine bilayer fusion in considerably greater detail than possible heretofore. Since this phenomenon was discovered, it has been found that a) bilayer vesicles can fuse without leakage, b) bilayers can undergo hemifusion (fusion of the two monolayers that come into contact when vesicles adhere to one another) in several morphologically different ways, c) the vesicle composition (kind and proportion of uncharged lipid included with charged lipid) has a controlling influence on the proportion of possible outcomes, i.e. whether fusion, one of the modes of hemifusion, or stable adhesion predominates, and d) the physical properties of cationic phospholipids change in fundamental ways when they are mixed with anionic lipids, in particular, the area occupied by a molecule in a monolayer is reduced and these mixtures can transiently form a three- dimensional pattern of interconnected bilayers (cubic phase). It is hypothesized that, in fusion of oppositely-charged vesicles, destabilization of the contact region between adherent membranes is due to charge neutralization, leading to reorganization of the contacting surfaces and fusion. Cationic lipids have been prepared that form phases which should promote fusion as well as in fluorescent versions that will facilitate monitoring details of membrane fusion.
The specific aims are: 1. To identify cationic phospholipids that are prone to formation of membrane-destabilizing phases under conditions of vesicle adhesion. 2. To characterize the process of fusion between negative vesicles and positive vesicles containing lipids identified as fusion-prone. 3. To measure membrane electrostatic properties relevant to these processes. 4. To apply information from aims 1-3 to fusion of liposomes with cells and to functional tests of viral membrane components.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM057305-01A1
Application #
2761815
Study Section
Biophysical Chemistry Study Section (BBCB)
Project Start
1999-05-01
Project End
2001-04-30
Budget Start
1999-05-01
Budget End
2000-04-30
Support Year
1
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Northwestern University at Chicago
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
City
Evanston
State
IL
Country
United States
Zip Code
60201
Tenchov, Boris G; MacDonald, Robert C; Lentz, Barry R (2013) Fusion peptides promote formation of bilayer cubic phases in lipid dispersions. An x-ray diffraction study. Biophys J 104:1029-37
Buchanan, Kyle D; Huang, Shao-Ling; Kim, Hyunggun et al. (2010) Encapsulation of NF-kappaB decoy oligonucleotides within echogenic liposomes and ultrasound-triggered release. J Control Release 141:193-8
Lei, Guohua; MacDonald, Robert C (2008) Effects on interactions of oppositely charged phospholipid vesicles of covalent attachment of polyethylene glycol oligomers to their surfaces: adhesion, hemifusion, full fusion and ""endocytosis"". J Membr Biol 221:97-106
Siegel, D P; Tenchov, B G (2008) Influence of the lamellar phase unbinding energy on the relative stability of lamellar and inverted cubic phases. Biophys J 94:3987-95
Koynova, Rumiana; Wang, Li; MacDonald, Robert C (2007) Synergy in lipofection by cationic lipid mixtures: superior activity at the gel-liquid crystalline phase transition. J Phys Chem B 111:7786-95
Koynova, Rumiana; Macdonald, Robert C (2007) Natural lipid extracts and biomembrane-mimicking lipid compositions are disposed to form nonlamellar phases, and they release DNA from lipoplexes most efficiently. Biochim Biophys Acta 1768:2373-82
Koynova, Rumiana; Tarahovsky, Yury S; Wang, Li et al. (2007) Lipoplex formulation of superior efficacy exhibits high surface activity and fusogenicity, and readily releases DNA. Biochim Biophys Acta 1768:375-86
Wang, Li; MacDonald, Robert C (2007) Synergistic effect between components of mixtures of cationic amphipaths in transfection of primary endothelial cells. Mol Pharm 4:615-23
Wang, Li; Koynova, Rumiana; Parikh, Harsh et al. (2006) Transfection activity of binary mixtures of cationic o-substituted phosphatidylcholine derivatives: the hydrophobic core strongly modulates physical properties and DNA delivery efficacy. Biophys J 91:3692-706
Koynova, Rumiana; Wang, Li; MacDonald, Robert C (2006) An intracellular lamellar-nonlamellar phase transition rationalizes the superior performance of some cationic lipid transfection agents. Proc Natl Acad Sci U S A 103:14373-8

Showing the most recent 10 out of 21 publications