Orientation of myelin proteolipid protein in the oligodendrocyte cell membrane

The orientation of proteins within a cell membrane can often be difficult to determine. A number of models have been proposed for the orientation of the myelin protein, proteolipid protein (PLP), each of which includes exposed domains on the intracellular and extracellular membrane faces. Immunolabeling experiments have localized the C-terminus and the region spanning amino acids 103–116 to the cytoplasmic face of the membrane, but no well characterized antibodies have been available that label extracellular PLP domains. In this report, we describe the generation and characterization of mouse monoclonal antibodies (mAb) against putative extramembrane domains. Three of the mAb, specific for PLP peptides 40–59, 178–191, or 215–232, immunostain live oligodendrocytes, indicating that these regions of the molecule are exposed on the external surface of the cell. In addition, we have used these mAb to study the time-course of incorporation of PLP into the oligodendrocyte membrane. These studies increase our knowledge of the orientation of PLP in the lipid bilayer and are relevant for understanding myelin function. Special issue dedicated to Dr. Marion E. Smith. Marion has filled many roles in my life (M. Lees): She has been a long time colleague, personal friend, meeting roommate, and traveling companion. Even our husbands have become good friends. Further, Marion’s scientific contributions in multiple aspects of neurochemistry have made her a role model for all scientists, and particularly for young women. It should be noted that all of the authors of this paper just happen to be women.