Probing orientational behavior of MHC class I protein and lipid probes in cell membranes by fluorescence polarization-resolved imaging

Area of Science:

• Cell biology
• Biophysics
• Molecular imaging

Background:

• Cell membranes are dynamic environments where proteins and lipids interact.
• The orientational order of membrane components provides insights into their function and interactions.
• Major histocompatibility complex class I (MHC I) proteins play crucial roles in immune responses.

Purpose of the Study:

• To analyze the molecular orientational order of MHC I proteins and lipid probes in living cell membranes.
• To investigate how cytoskeleton disruption affects the orientational order of these membrane components.
• To elucidate the relationship between protein-cytoskeleton interactions and lipid membrane morphology.

Main Methods:

• Utilized steady-state polarization-resolved fluorescence imaging to study molecular orientational order.
• Applied statistical analysis to quantify the angular distribution width of fluorescently labeled MHC I proteins and lipid probes.
• Examined cells with disrupted actin and microtubule networks.

Main Results:

• Observed distinct changes in the orientational order of MHC I proteins and lipid probes upon cytoskeleton disruption.
• Found opposite trends in orientational order for proteins and lipids in the plasma membrane after cytoskeletal treatments.
• Demonstrated that MHC I orientational order is linked to cytoskeleton interactions, while lipid order is influenced by membrane morphology.

Conclusions:

• MHC I protein orientational order in the plasma membrane is significantly influenced by interactions with the cytoskeleton.
• The orientational order of lipid probes in the plasma membrane is primarily governed by local cell membrane morphology.
• These findings highlight the distinct regulatory mechanisms governing protein and lipid organization within cell membranes.