pH-Dependent fusion of liposomes using titratable polycations

Uster, Paul S.; Deamer, David W.

doi:10.1021/bi00322a001

Cited by 92 publications

(39 citation statements)

References 50 publications

(56 reference statements)

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“…For example, melittin interacts with and fuses vesicles over a wide pH range (Morgan et al, 1983) and polyhistidine fuses liposomes only at low pH (Uster & Deamer, 1985). In addition, tryptophan fluorescence spectroscopy and CD have been used to study the interactions of polypeptides such as diphtheria toxin (Blewitt et al, 1985) and tetanus toxin (Cabiaux et al, 1985) with bilayers and many polypeptides such as diphtheria toxin (Cabiaux et al, 1984) and colicin (Pattus et aL, 1985) fuse liposomes at low pH.…”

Section: Discussionmentioning

confidence: 99%

Membrane Fusion by Peptide Analogues of Influenza Virus Haemagglutinin

Wharton¹,

Martin²,

Ruigrok³

et al. 1988

Journal of General Virology

226

191

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SUMMARYWe have studied the interactions of synthetic peptides corresponding to the sequence of the amino terminus of the HA2 subunit of influenza virus haemagglutinin with artificial lipid membranes. The peptides could fuse cholesterol-free liposomes at neutral as well as acid pH; however, liposomes containing cholesterol could only be fused below pH 6. The fusion process caused leakage of aqueous liposomal contents. Peptides with amino acid substitutions had fusion properties similar to whole haemagglutinin molecules with the corresponding sequence changes. Non-fusogenic peptides still interacted with the membrane but did not cause leakage of liposomal contents. A correlation between the ~-helical content of peptide and its fusogenicity was noted, but this was not absolute. The results reported here support suggestions for a role of the amino terminus of HA2 in virus-endosome fusion. INTRODUCTIONInfluenza virus haemagglutinin (HA) mediates the fusion of viral and endosomal membranes which is required to initiate infection of cells (reviewed by White et al., 1983;Wharton, 1987). At the low pH of the endosome (between 5 and 6) a conformational change occurs in HA, which is a prerequisite for fusion activity. A number of studies have shown that this change involves a decrease in subunit contacts within the HA trimer (Skehel et al., 1982;Daniels et al., 1983bDaniels et al., , 1985Ruigrok et al., 1986) and the exposure of the highly conserved hydrophobic amino terminus of HA2 (Skehel et al., 1982; Daniels et al., 1983Daniels et al., a, 1985Doms et al., 1985). It has been proposed that this hydrophobic region interacts with lipid membranes during the fusion process and support for this proposition comes from the observation that aggregation of bromelainreleased HA (BHA), which is specifically induced at the pH of fusion, involves the HA2 aminoterminal region (Daniels et aL, 1983a; R. W. H. Ruigrok et al., unpublished results). Also, variant HAs with amino acid substitutions in the amino-terminal region of HA2 constructed by site-directed mutagenesis have fusion and membrane association characteristics different to those of wild-type HA (Gething et al., 1986). In a recently published report, Lear & De Grado (1987) have shown that the peptide corresponding to the amino terminus of HA2 B/Lee/40 is capable of fusing liposomes at neutral pH. In addition, Murata et al. (1987) have demonstrated pH-dependent fusion of liposomes by a peptide corresponding to the amino terminus of HA2 of A/PR/8/34 virus. In the study reported here we synthesized a peptide with the sequence of the 23 amino-terminal residues of HA2 of X31 (H3N2) which was capable of interacting with and fusing membranes. Using specifically modified analogues of this region, we also showed that interaction with membranes was not sufficient for fusion, that the fusion characteristics of peptides were affected by the lipid composition of the liposomes, and that peptides with sequences equivalent to the amino-terminal regions of variants had fusion properties simila...

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Section: Discussionmentioning

confidence: 99%

Membrane Fusion by Peptide Analogues of Influenza Virus Haemagglutinin

Wharton¹,

Martin²,

Ruigrok³

et al. 1988

Journal of General Virology

226

191

View full text Add to dashboard Cite

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“…Maximum fusion of the negatively charged liposomes by PLL occurred at a charge ratio of around 1. However, PLH induced the corresponding liposome fusion at a charge ratio of 0.2 or less (Uster & Deamer 1985).…”

Section: Histidinementioning

confidence: 92%

Polycation gene delivery systems: escape from endosomes to cytosol

Cho

Kim

Park

2003

Journal of Pharmacy and Pharmacology

341

169

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Clinical success of gene therapy based on oligonucleotides (ODNs), ribozymes, RNA and DNA will be greatly dependent on the availability of effective delivery systems. Polycations have gained increasing attention as a non-viral gene delivery vector in the past decades. Significant progress has been made in understanding complex formation between polycations and nucleic acids, entry of the complex into the cells and subsequent entry into the nucleus. Sophisticated molecular architectures of cationic polymers have made the vectors more stable and less susceptible to binding by enzymes or proteins. Incorporation of specific ligands to polycations has resulted in more cell-specific uptake by receptor-mediated mechanisms. However, there are still other barriers limiting the transfection efficiency of polycation gene delivery systems. There is a consensus that polycation-DNA complexes (polyplexes) enter cells via the endocytotic pathway. It is not clearly understood, however, how the polyplexes escape (if they do) from endosomes, how DNA is released from the polyplexes or how the released DNA is expressed. The primary focus of this article is to review various polycation gene delivery systems, which are designed to translocate DNA from endosomes into cytosol. Many polycation gene delivery systems have tried to mimic the mechanisms that viruses use for the endosomal escape. Polycation gene delivery systems are usually coupled with synthetic amphipathic peptides mimicking viral fusogenic peptides, histidine-based gene delivery systems for pH-responsive endosomal escape, polycations with intrinsic endosomolytic activity by the proton sponge mechanism and polyanions to mimic the anionic amphiphilic peptides.

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“…However, in spite of strong, nearly quantitative electrostatic adsorption of polycations onto the surface of anionic liposomes, the polycations were shown to be completely removed by complexation with added anionic homopolymers [18,23,26,34,35,36]. This means that both synthetic and natural polyanions are able to disrupt multilayer formation and effect its integrity in biological environments.…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%