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Phase Behavior of Charged Vesicles Under Symmetric and Asymmetric Solution Conditions Monitored with Fluorescence Microscopy
Published on: October 24, 2017
Temperature-dependent phase behavior and protein partitioning in giant plasma membrane vesicles
S A Johnson1, B M Stinson, M S Go
1Department of Chemistry, University of Pennsylvania, Philadelphia, PA, 19104, USA.
Biochimica Et Biophysica Acta
|March 17, 2010
Summary
Cell membranes exhibit liquid-ordered and liquid-disordered phase separation, influencing cellular signaling. Protein binding modulates these phase transitions, revealing insights into membrane lateral heterogeneity.
Area of Science:
- Cell biology
- Biophysics
- Membrane biophysics
Background:
- Plasma membrane lateral heterogeneity, characterized by liquid-ordered (Lo) and liquid-disordered (Ld) phases, is crucial for cellular signaling.
- This phase coexistence allows for the compartmentalization of molecules, potentially fine-tuning signal transduction.
- Giant plasma membrane vesicles (GPMVs) derived from cells provide a model system to study these membrane dynamics.
Purpose of the Study:
- To compare the temperature dependence of fluid phase segregation in HeLa and rat basophilic leukemia (RBL) cells.
- To investigate the role of peripheral protein binding in modulating membrane phase transition temperatures.
- To examine the partitioning behavior of specific proteins within these phase-separated domains.
Main Methods:
- Preparation of giant plasma membrane vesicles (GPMVs) from HeLa and RBL cells.
- Observation of reversible phase segregation in GPMVs at sub-physiological temperatures.
- Analysis of temperature dependence of phase separation and phase transition temperatures.
- Investigation of the effects of cholera toxin subunit B (CTB) and Annexin V binding on phase transitions.
- Studying the partitioning of signal proteins and membrane raft-associated proteins, including caveolin-1.
Main Results:
- Both HeLa and RBL cells exhibit monotonic temperature dependence in phase-separated vesicle formation.
- A broad distribution of phase transition temperatures was observed in both cell types.
- Peripheral protein binding, notably CTB and Annexin V, was found to modulate phase transition temperatures.
- While some proteins showed expected liquid-ordered (Lo) phase partitioning, others, like caveolin-1, deviated from typical membrane raft association.
Conclusions:
- Peripheral protein binding acts as a regulator of plasma membrane lateral heterogeneity in vivo.
- The partitioning of proteins into Lo phases is not always consistent with current membrane raft models.
- These findings contribute to understanding the dynamic regulation of cellular signaling through membrane composition and organization.
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