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Biophys J. 2015 Mar 10;108(5):1104-13. doi: 10.1016/j.bpj.2014.12.050.

Cytoskeletal pinning controls phase separation in multicomponent lipid membranes.

Author information

1
Institut Curie, Centre de Recherche, Paris, France; CNRS, UMR 168, Physico-chimie Curie, Paris, France; CNRS, UMR 3666, Endocytic Trafficking and Therapeutic Delivery Group, Paris, France.
2
Max Planck Institute of Biochemistry, Department of Cellular and Molecular Biophysics, Am Klopferspitz 18, Martinsried, Germany. Electronic address: petrov@biochem.mpg.de.
3
Max Planck Institute of Biochemistry, Department of Cellular and Molecular Biophysics, Am Klopferspitz 18, Martinsried, Germany. Electronic address: schwille@biochem.mpg.de.

Abstract

We study the effect of a minimal cytoskeletal network formed on the surface of giant unilamellar vesicles by the prokaryotic tubulin homolog, FtsZ, on phase separation in freestanding lipid membranes. FtsZ has been modified to interact with the membrane through a membrane targeting sequence from the prokaryotic protein MinD. FtsZ with the attached membrane targeting sequence efficiently forms a highly interconnected network on membranes with a concentration-dependent mesh size, much similar to the eukaryotic cytoskeletal network underlying the plasma membrane. Using giant unilamellar vesicles formed from a quaternary lipid mixture, we demonstrate that the artificial membrane-associated cytoskeleton, on the one hand, suppresses large-scale phase separation below the phase transition temperature, and, on the other hand, preserves phase separation above the transition temperature. Our experimental observations support the ideas put forward in our previous simulation study: In particular, the picket fence effect on phase separation may explain why micrometer-scale membrane domains are observed in isolated, cytoskeleton-free giant plasma membrane vesicles, but not in intact cell membranes. The experimentally observed suppression of large-scale phase separation much below the transition temperatures also serves as an argument in favor of the cryoprotective role of the cytoskeleton.

PMID:
25762322
PMCID:
PMC4375424
DOI:
10.1016/j.bpj.2014.12.050
[Indexed for MEDLINE]
Free PMC Article

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