Sorting of lipids and proteins in membrane curvature gradients.

Full Abstract

The sorting of lipids and proteins in cellular trafficking pathways is a process of central importance in maintaining compartmentalization in eukaryotic cells. However, the mechanisms behind these sorting phenomena are currently far from being understood. Among several mechanistic suggestions, membrane curvature has been invoked as a means to segregate lipids and proteins in cellular sorting centers. To assess this hypothesis, we investigate the sorting of lipid analog dye trace components between highly curved tubular membranes and essentially flat membranes of giant unilamellar vesicles. Our experimental findings indicate that intracellular lipid sorting, contrary to frequent assumptions, is unlikely to occur by lipids fitting into membrane regions of appropriate curvature. This observation is explained in the framework of statistical mechanical lattice models that show that entropy, rather than curvature energy, dominates lipid distribution in the absence of strongly preferential lateral intermolecular interactions. Combined with previous findings of curvature induced phase segregation, we conclude that lipid cooperativity is required to enable efficient sorting. In contrast to lipid analog dyes, the peripheral membrane binding protein Cholera toxin subunit B is effectively curvature-sorted. The sorting of Cholera toxin subunit B is rationalized by statistical models. We discuss the implications of our findings for intracellular sorting mechanisms.

Author information

Author/s: Tian, A (A); Baumgart, T (T);

Affiliation: Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, USA.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.

Journal: Biophysical journal (Biophys J), published in United States. (Language: eng)

Reference: 2009-Apr; vol 96 (issue 7) : pp 2676-88

Dates: Created 2009/04/07; Completed 2009/06/29; Revised 2009/07/22;

PMID: 19348750, status: MEDLINE (last retrieved date: 8/20/2009)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MeSH Headings (categories) shown below.

Animals
Biomechanics
Carbocyanines - metabolism
Cattle
Cell Membrane - chemistry; metabolism
Cholera Toxin - metabolism
Fluorescence
Fluorescence Recovery After Photobleaching

Fluorescence Recovery After Photobleaching
Fluorescent Dyes - metabolism
Intracellular Membranes - metabolism
Lipid Metabolism
Microspheres
Phosphatidylcholines - metabolism
Proteins - metabolism
Unilamellar Liposomes - metabolism

Note: Bold headings indicate primary MeSH headings or qualifiers.

Associated Chemicals: Carbocyanines (0) ; Fluorescent Dyes (0) ; Phosphatidylcholines (0) ; Proteins (0) ; Unilamellar Liposomes (0) ; 1-palmitoyl-2-oleoylphosphatidylcholine (6753-55-5) ; Cholera Toxin (9012-63-9)

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