Critique of a Radically New Model for Plasma Membrane Bilayer Organization

Area of Science:

• Cell Biology
• Biochemistry
• Membrane Biophysics

Background:

• The molecular organization of the plasma membrane bilayer is a fundamental concept in cell biology.
• A novel model proposes an asymmetric distribution of phospholipids and cholesterol within the erythrocyte membrane bilayer.

Purpose of the Study:

• To critically evaluate a new model for plasma membrane organization.
• To address discrepancies between the proposed model and established literature.

Main Methods:

• Analysis of phospholipase A2 hydrolysis of phosphatidylcholine in erythrocytes.
• Review of ultrastructural data on erythrocyte membrane composition.
• Assessment of cholesterol distribution using molecular probes.

Main Results:

• Incomplete phosphatidylcholine hydrolysis by phospholipase A2 can be attributed to product inhibition, not endofacial localization.
• Ultrastructural analysis confirms phosphatidylcholine predominantly resides in the outer leaflet of the erythrocyte bilayer.
• Predicted high outer leaflet cholesterol concentrations are not supported by probe-based detection.

Conclusions:

• The proposed model of plasma membrane organization is inconsistent with existing experimental evidence.
• The model's reliance on incomplete hydrolysis data and its conflict with ultrastructural and probe data render it insecure.