Abstract: Adsorption and Bridging Adhesion of MBP with Cytoplasmic Model Myelin Membranes (2009 Annual Meeting)

Younjin Min, Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA

Kai Kristiansen, Department of Chemical Engineering, University of California at Santa Barbara, Santa Barbara, CA

Dongwoog Lee, Department of Chemical Engineering, University of California at Santa Barbara, Santa Barbara, CA

Joan M. Boggs, The Hospital for Sick Children, Molecular Structure and Function, Toronto, Canada

Cindy Husted, Neuroscience Research Institute, Biological Sciences 2, University of California, Santa Barbara, Santa Barbara, CA

Joesph A. Zasadzinski, Department of Chemical Engineering, University of California, Santa Barbara, CA

Jacob N. Israelachvili, Chemical Engineering, University of California at Santa Barbara, Santa Barbara, CA

The myelin sheath is a multilamellar membrane surrounding the axon of neurons in the nervous system. This sheath acts as an electrical insulator, which allows for faster and more efficient conduction of nerve impulses than unmyelinated nerves. The myelin consists of 8 kinds of lipid molecules on two alternating bilayers (cytoplasmic and extracellular faces of the cell membrane) together with various proteins. Myelin Basic Protein (MBP), which is mainly found on the cytoplasmic face, is believed to have an important role in maintaining myelin structure.

Myelin dysfunctions vary from deterioration of signal transduction to demyelinating diseases such as multiple sclerosis (MS). MS is characterized by the appearance of lesions, reflecting loss of membrane adhesion, swelling across the water gaps, vacuolization, vesiculation, and eventual disintegration of the myelin structure. We want to understand the molecular synergistic interaction responsible for a healthy myelin membrane structure [1].

We have performed Surface Force Apparatus (SFA) measurements on supported cytoplasmic myelin membrane [2], which show that as the bulk MBP concentration increases, the adhesion first increases, and then decreases. Simultaneously, and concurrently, the equilibrium spacing first decreases, and then increases. Thus, optimum adhesion coincides with minimum water gap thickness, which optimizes the electrical shielding properties of the myelin sheath. It appears that hydrophobic and electrostatic interactions are involved both in the adsorption of MBP and the inter-membrane interactions.

References:

[1] Y Hu, I Doudevski, D Wood, M Moscarello, C Husted, C Genain, J A Zasadzinski, and J Israelachvili, “Synergetic interactions of lipids and myelin basic protein”, Proceedings of National Academy of Sciences 101 (2004) 13466-13471.

[2] Y Min, K Kristiansen, J M Boggs, C Husted, J A Zasadzinski, and J Israelachvili, “Interaction forces and adhesion of supported myelin lipid bilayers modulated by myelin basic protein”, Proceedings of National Academy of Sciences 106 (2009) 3154-3159.

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See more of this Session: Biomolecules at Interfaces III
See more of this Group/Topical: Engineering Sciences and Fundamentals