Proteins of peripheral myelin are associated with glycosphingolipid/cholesterol-enriched membranes.
A characteristic feature of the vertebrate nervous system is the ensheathment of axons by myelin, a multilamellar membrane specialization produced by polarized glial cells. Although the main protein and lipid components of the myelin sheath are well characterized, relatively little is known about the mechanisms of their intracellular distribution to the respective sites of assembly within the myelin sheath. To analyze whether peripheral myelin protein trafficking is mediated by glycosphingolipid/cholesterol-enriched membranes (GEMs), we studied the association of established myelin proteins, peripheral myelin protein 22 (PMP22), protein zero (P0), plasmolipin, and myelin basic protein (MBP), with these membrane microdomains. To examine the association of the selected peripheral myelin proteins with detergent-insoluble GEMs, purified myelin from sciatic nerve of adult rat was extracted with Triton X-100 at 4 degrees C and 37 degrees C and, in additional experiments, was pretreated with the cholesterol chelator methyl-beta-cyclodextrin. The material was then centrifuged to equilibrium in sucrose gradients, and fractions were analyzed by Western blotting. Here we demonstrate for the first time that PMP22, P0, and plasmolipin prepared from purified peripheral myelin are associated with GEMs. To characterize whether the association of these proteins is a specialized feature of myelinating Schwann cells, we studied the distribution of PMP22, P0, and plasmolipin in transiently transfected HeLa cells. These experiments confirm the specific association of these proteins with GEMs in both neural and nonneural cell types.
Molecular Neurobiology Laboratory, Department of Neurology, Heinrich-Heine-University, Düsseldorf, Germany.
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B
Hasse
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F
Bosse
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HW
Müller
D000818:Animals; D015153:Blotting, Western; D018929:Cell Culture Techniques; D021961:Cell Membrane Structures / Q000737:chemistry*; D002784:Cholesterol / Q000032:analysis*; D006028:Glycosphingolipids / Q000032:analysis*; D006367:HeLa Cells / Q000737:chemistry; D006801:Humans; D008565:Membrane Proteins; D004676:Myelin Basic Protein / Q000032:analysis; D018993:Myelin P0 Protein / Q000032:analysis; D009185:Myelin Proteins / Q000032:analysis*; D009186:Myelin Sheath / Q000737:chemistry*; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D009419:Nerve Tissue Proteins; D017933:Peripheral Nervous System; D011510:Proteolipids / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D012583:Schwann Cells / Q000737:chemistry; D012584:Sciatic Nerve
D006028:Glycosphingolipids; D008565:Membrane Proteins; D004676:Myelin Basic Protein; D018993:Myelin P0 Protein; D009185:Myelin Proteins; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D009419:Nerve Tissue Proteins; C048897:PLLP protein, human; C073687:PMP22 protein, human; C489076:Pllp protein, rat; C489546:Pmp22 protein, rat; D011510:Proteolipids; D002784:Cholesterol