Asymmetric Phosphoinositide Lipid Bilayers Generated by Spontaneous Lipid Insertion

Area of Science:

• Biochemistry
• Cell Biology
• Membrane Biophysics

Background:

• Phosphatidylinositol phosphate (PIP) lipids regulate cellular processes via protein interactions, particularly actin assembly.
• Supported lipid bilayers (SLBs) model these interactions, but creating fluid, asymmetric PIP-containing SLBs remains challenging.

Purpose of the Study:

• To develop a robust method for generating asymmetric SLBs with mobile and functional phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) lipids.
• To investigate the recruitment and activity of actin-binding proteins on these engineered membranes.

Main Methods:

• Dissolving PI(4,5)P2 below its critical micelle concentration (CMC) for spontaneous insertion into SLB upper leaflets.
• Utilizing fluorescence recovery after photobleaching (FRAP) to confirm PI(4,5)P2 mobility.
• Assessing protein recruitment and actin filament sliding by ezrin and myosin 1 motors.

Main Results:

• A simple, reproducible method for creating asymmetric SLBs with tunable PI(4,5)P2 content was established.
• PI(4,5)P2 lipids demonstrated mobility within the SLB.
• Recruited proteins, including ezrin and myosin 1, exhibited functional activity, such as sliding actin filaments.

Conclusions:

• The developed method provides a straightforward strategy for generating functional, asymmetric PI(4,5)P2-containing SLBs.
• This approach is applicable to other lipid species with high CMC values, advancing membrane biophysics research.