Presence of the plasma membrane proteolipid (plasmolipin) in myelin.
Plasma membrane proteolipid (plasmolipin), which was originally isolated from kidney membranes, has also been shown to be present in brain. In this study, we examined the distribution of plasmolipin in brain regions, myelin, and oligodendroglial membranes. Immunoblot analysis of different brain regions revealed that plasmolipin levels were higher in regions rich in white matter. Plasmolipin was also detected in myelin, myelin subfractions, and oligodendroglial membranes. Immunocytochemical analysis of the cerebellum revealed that plasmolipin was localized in the myelinated tracts. Plasmolipin levels in myelin were enriched during five successive cycles of myelin purification, similar to the enrichment of myelin proteolipid apoprotein (PLP) and myelin basic protein (MBP). In contrast, levels of Na+,K(+)-ATPase and a 70-kDa protein were decreased. When myelin or white matter was extracted with chloroform/methanol, it contained, in addition to PLP, a significant amount of plasmolipin. Quantitative immunoblot analysis suggested that plasmolipin constitutes in the range of 2.2-4.8% of total myelin protein. Plasmolipin, purified from kidney membranes, was detected by silver stain on gels at 18 kDa and did not show immunological cross-reactivity with either PLP or MBP. Thus, it is concluded that plasmolipin is present in myelin, possibly as a component of the oligodendroglial plasma membrane, but is structurally and immunologically different from the previously characterized myelin proteolipids.
Cochary
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EF
Department of Biochemistry, Eunice Kennedy Shriver Center, Waltham, MA 02254.
Bizzozero
O A
OA
Sapirstein
V S
VS
Nolan
C E
CE
Fischer
I
I
D000818:Animals; D001059:Apoproteins / Q000032:analysis; D001923:Brain Chemistry; D002417:Cattle; D002462:Cell Membrane / Q000032:analysis; D002499:Centrifugation, Density Gradient; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D007668:Kidney / Q000032:analysis; D008565:Membrane Proteins; D051379:Mice; D004676:Myelin Basic Protein / Q000032:analysis; D009185:Myelin Proteins / Q000032:analysis; D018991:Myelin Proteolipid Protein; D009186:Myelin Sheath / Q000032:analysis*; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D009419:Nerve Tissue Proteins; D009836:Oligodendroglia / Q000032:analysis; D011510:Proteolipids / Q000032:analysis*; D051381:Rats; D012756:Sheep; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014018:Tissue Distribution
D001059:Apoproteins; D008565:Membrane Proteins; D004676:Myelin Basic Protein; D009185:Myelin Proteins; D018991:Myelin Proteolipid Protein; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D009419:Nerve Tissue Proteins; C048897:PLLP protein, human; C489075:Pllp protein, mouse; C489076:Pllp protein, rat; D011510:Proteolipids; D000254:Sodium-Potassium-Exchanging ATPase