Studies of lipid flip-flop in symmetric bilayers

• Grant number: 24/00346-9
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: March 01, 2024
• End date: February 28, 2025
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Thais Azevedo Enoki Liarte
• Grantee: Maria Luana Bueno Sá
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 22/04046-4 - Investigating the asymmetry of the plasma membrane: model membranes mimicking healthy and tumor cells, and anti-tumor therapeutic strategies, AP.JP

Abstract

The plasma membrane is asymmetric, meaning each leaflet has a distinct lipid composition and phase behavior. The loss of membrane asymmetry might be a crucial difference between health and disease. Cancer cells exhibit phosphatidylserine (PS) asymmetry loss, meaning that PS lipids, found in healthy cells on the PM inner leaflet, are exposed to the exoplasmic leaflet, signaling apoptosis (1, 2). Here, we plan to investigate the molecular principles related to spontaneous lipid flip-flop and when the flip-flop is speeded by a transmembrane peptide, e.g., gramicidin A and antimicrobial peptides. Different from many studies of lipid flip-flop, we aim to investigate PS flip-flop varying the salt concentration in the solution and to apply a small and controlled osmotic pressure between the medium inside and outside of large unilamellar vesicles (LUVs). It should be noted that the concentrations of every type of cation inside and outside the cell are different, and the PS in the inner leaflet is likely bound by Mg2+ (3). Here, we plan to use two main strategies to determine the flip-flop rates of phospholipids by using i) fluorescence and fluorescence quencher experiments and ii) FRET experiments.