Direct Visualization of the Action of Triton X-100 on Giant Vesicles of Erythrocyte Membrane Lipids

Author(s)

Casadei, Bruna R. ^[1] ; Domingues, Cleyton C. ^[1] ; de Paula, Eneida ^[1] ; Riske, Karin A. ^[2]

Affiliation

^[1] Univ Estadual Campinas, Inst Biol, Dept Bioquim, Campinas, SP - Brazil

^[2] Univ Fed Sao Paulo, Dept Biofis, Sao Paulo - Brazil

• Document type: Journal article
• Source: BIOPHYSICAL JOURNAL; v. 106, n. 11, p. 2417-2425, JUN 3 2014.
• Web of Science Citations: 16

Abstract

The raft hypothesis proposes that microdomains enriched in sphingolipids, cholesterol, and specific proteins are transiently formed to accomplish important cellular tasks. Equivocally, detergent-resistant membranes were initially assumed to be identical to membrane rafts, because of similarities between their compositions. In fact, the impact of detergents in membrane organization is still controversial. Here, we use phase contrast and fluorescence microscopy to observe giant unilamellar vesicles (GUVs) made of erythrocyte membrane lipids (erythro-GUVs) when exposed to the detergent Triton X-100 (TX-100). We clearly show that TX-100 has a restructuring action on biomembranes. Contact with TX-100 readily induces domain formation on the previously homogeneous membrane of erythro-GUVs at physiological and room temperatures. The shape and dynamics of the formed domains point to liquid-ordered/liquid-disordered (Lo/Ld) phase separation, typically found in raft-like ternary lipid mixtures. The Ld domains are then separated from the original vesicle and completely solubilized by TX-100. The insoluble vesicle left, in the Lo phase, represents around 2/3 of the original vesicle surface at room temperature and decreases to almost 1/2 at physiological temperature. This chain of events could be entirely reproduced with biomimetic GUVs of a simple ternary lipid mixture, 2:1:2 POPC/SM/chol (phosphatidylcholine/sphyngonnyelin/cholesterol), showing that this behavior will arise because of fundamental physicochemical properties of simple lipid mixtures. This work provides direct visualization of TX-100-induced domain formation followed by selective (Ld phase) solubilization in a model system with a complex biological lipid composition. (AU)

• FAPESP's process: 10/18516-5 - Caracterization of erythrocyte membrane domains obtained with or without detergent
• Grantee: Cleyton Crepaldi Domingues
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 12/10442-8 - Perturbations on charged lipid bilayers induced by electric pulses, antimicrobial peptides and vesicles with opposite charge
• Grantee: Karin Do Amaral Riske
• Support Opportunities: Regular Research Grants