Format

Send to

Choose Destination
Biophys J. 2014 Jun 3;106(11):2395-407. doi: 10.1016/j.bpj.2014.04.016.

Lipopolysaccharide-induced dynamic lipid membrane reorganization: tubules, perforations, and stacks.

Author information

1
Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico.
2
Center for Biomedical Engineering, University of New Mexico, Albuquerque, New Mexico.
3
Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico; Department of Biology, University of New Mexico, Albuquerque, New Mexico.
4
New Mexico Consortium, Los Alamos, New Mexico; Physical Chemistry and Applied Spectroscopy, Los Alamos National Laboratory, Los Alamos, New Mexico.
5
Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico. Electronic address: gbmon@lanl.gov.

Abstract

Lipopolysaccharide (LPS) is a unique lipoglycan, with two major physiological roles: 1), as a major structural component of the outer membrane of Gram-negative bacteria and 2), as a highly potent mammalian toxin when released from cells into solution (endotoxin). LPS is an amphiphile that spontaneously inserts into the outer leaflet of lipid bilayers to bury its hydrophobic lipidic domain, leaving the hydrophilic polysaccharide chain exposed to the exterior polar solvent. Divalent cations have long been known to neutralize and stabilize LPS in the outer membrane, whereas LPS in the presence of monovalent cations forms highly mobile negatively-charged aggregates. Yet, much of our understanding of LPS and its interactions with the cell membrane does not take into account its amphiphilic biochemistry and charge polarization. Herein, we report fluorescence microscopy and atomic force microscopy analysis of the interaction between LPS and fluid-phase supported lipid bilayer assemblies (sLBAs), as model membranes. Depending on cation availability, LPS induces three remarkably different effects on simple sLBAs. Net-negative LPS-Na(+) leads to the formation of 100-μm-long flexible lipid tubules from surface-associated lipid vesicles and the destabilization of the sLBA resulting in micron-size hole formation. Neutral LPS-Ca(2+) gives rise to 100-μm-wide single- or multilamellar planar sheets of lipid and LPS formed from surface-associated lipid vesicles. Our findings have important implications about the physical interactions between LPS and lipids and demonstrate that sLBAs can be useful platforms to study the interactions of amphiphilic virulence factors with cell membranes. Additionally, our study supports the general phenomenon that lipids with highly charged or bulky headgroups can promote highly curved membrane architectures due to electrostatic and/or steric repulsions.

PMID:
24896118
PMCID:
PMC4052278
DOI:
10.1016/j.bpj.2014.04.016
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Elsevier Science Icon for PubMed Central
Loading ...
Support Center