Cell Biology

Myelin Gatekeeper

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Science  07 Oct 2011:
Vol. 334, Issue 6052, pp. 17
DOI: 10.1126/science.334.6052.17-a

The myelin membrane that wraps around axons is essential for the speedy transmission of electrical signals in the nervous system. Myelin is produced by oligodendrocytes and differs from most cellular membranes because of its unusually high lipid content and exclusion of large proteins: a composition that is optimized for the transmission of nerve impulses. Using an in vitro culture system, Aggarwal et al. studied how oligodendrocytes are able to create these specialized membranes. The membrane sheets are so thin that most cellular organelles cannot encroach, keeping them restricted to the fatter parts of the cell body. With vesicle transport excluded as a mechanism, the authors found that the composition of the membranes is regulated within the membrane domain, by myelin basic protein (MBP), which acts as a regulator of diffusion. In the absence of MBP, the exclusion of proteins with an overlarge cytoplasmic domain from the membrane was disrupted. Thus MBP, which appears to be spread throughout the myelin sheet, is critical for restricting access so that only a few, primarily small proteins are integrated into the myelin sheet.

Dev. Cell 21, 445 (2011).

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