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Phase partitioning of GM1 and its bodipy-labeled analog determine their different binding to cholera toxin

Abstract:
Driven by interactions between lipids and proteins, biological membranes display lateral heterogeneity that manifests itself in a mosaic of liquid-ordered (Lo) or raft, and liquid-disordered (Ld) or non-raft domains with a wide range of different properties and compositions. In giant plasma membrane vesicles and giant unilamellar vesicles, specific binding of Cholera Toxin (CTxB) to GM1 glycolipids is a commonly used strategy to label raft domains or Lo membrane environments. However, these studies often use acyl-chain labeled bodipy-GM1 (bdGM1), whose headgroup accessibility and membrane order or phase partitioning may differ from those of GM1, rendering the interpretation of CTxB binding data quite problematic. To unravel the molecular basis of CTxB binding to GM1 and bdGM1, we explored the partitioning and the headgroup presentation of these gangliosides in the Lo and Ld phases using atomistic molecular dynamics simulations complemented by CTxB binding experiments. The conformation of both GM1 and bdGM1 was shown to be largely similar in the Lo and Ld phases. However, bdGM1 showed reduction in receptor availability when reconstituted into synthetic bilayer mixtures, highlighting that membrane phase partitioning of the gangliosides plays a considerable role in CTxB binding. Our results suggest that the CTxB binding is predominately modulated by the partitioning of the receptor to an appropriate membrane phase. Further, given that the Lo and Ld partitioning of bdGM1 differs from those of GM1, usage of bdGM1 for studying GM1 behavior in cells can lead to invalid interpretation of experimental data.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.3389/fphys.2017.00252

Authors



More from this funder
Funding agency for:
Eggeling, C
Sezgin, E
Grant:
104924/14/Z/14
104924/14/Z/14
More from this funder
Funding agency for:
Rissanen, S
Grant:
Advanced Grant CROWDEDPRO-LIPIDS
More from this funder
Funding agency for:
Rissanen, S
Grant:
Advanced Grant CROWDEDPRO-LIPIDS
More from this funder
Funding agency for:
Rissanen, S
Grant:
Advanced Grant CROWDEDPRO-LIPIDS


Publisher:
Frontiers Media
Journal:
Frontiers in Physiology More from this journal
Volume:
8
Issue:
252
Pages:
1-7
Publication date:
2017-05-09
Acceptance date:
2017-04-10
DOI:
ISSN:
1664-042X


Language:
English
Keywords:
Pubs id:
pubs:698131
UUID:
uuid:d7fa752c-c3c1-46cf-b217-9b1144a6b780
Local pid:
pubs:698131
Source identifiers:
698131
Deposit date:
2017-06-02

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