Effect of Rigidifying and Fluidizing Agents on Membrane Raft Stability

Open Access
Chiang, Homer H.
Graduate Program:
Master of Science
Document Type:
Master Thesis
Date of Defense:
Committee Members:
  • Peter J Butler, Thesis Advisor
  • plasma membrane
  • membrane rafts
  • tocopherol
  • model membranes
  • triton-X
Partitioning of plasma membrane lipids into membrane rafts in cells is thought to serve as scaffolds for many signaling processes. Formation of rafts is driven by line tensions between phase boundaries caused by a lipid chain-region hydrophobic mismatch. While the composition and structure of membrane rafts have been intensely studied, the mechanisms that drive spontaneous raft formation and maintain raft stability are unknown. Here, we show for the first time that membrane raft partitioning in model membranes can be reversibly disrupted by addition of membrane rigidifying and fluidizing agents. Membrane-specific fluorescent markers were demonstrated to selectively label the liquid-ordered and liquid-disordered regions of ternary mixture giant unilamellar vesicles with varying amounts of cholesterol. Upon addition of the rigidifying agent α-tocopherol, partitioning of distinct phases was no longer observed. Phase partitioning was restored by addition of the detergent Triton-X100. These results confirm the view that membrane raft dynamics and regulation are critical to plasma membrane homeostasis. In addition, the dissolution and reformation of rafts in model membranes could serve as a platform for further raft manipulation studies.