Expression of Myelin Basic Protein Isoforms in Nonglial Cells

• Published in: The Journal of cell biology Vol. 110; no. 5; pp. 1719 - 1727
• Main Authors: Staugaitis, Susan M., Smith, P. R., Colman, David R.
• Format: Journal Article
• Language: English
• Published: New York, NY Rockefeller University Press 01.05.1990; The Rockefeller University Press
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Brain - metabolism; Cell membranes; Cells; Complementary DNA; Exons; Fluorescence; Fluorescent Antibody Technique; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - genetics; HeLa Cells; Humans; Intracellular Membranes - metabolism; Messenger RNA; Microscopy, Fluorescence; Miscellaneous; Molecular Sequence Data; Myelin; Myelin Basic Protein - biosynthesis; Myelin Basic Protein - genetics; Myelin basic proteins; Protein isoforms; Proteins; Sequence Homology, Nucleic Acid; Subcellular Fractions - metabolism; Transfection; Human; In vitro transcription; Brain; Confocal system; In vitro translation; Myelin; Rodentia; Hela cell line; Vertebrata; Mammalia; Transfection; Complementary DNA; Oligodendrocyte; Mouse; Basic protein; Isoform; Immunofluorescence; Localization; Fluorescence microscopy
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.110.5.1719

The myelin basic proteins (MBPs) mediate the cytoplasmic apposition of the oligodendrocyte plasma membrane to form the major dense line of central nervous system myelin. Four major isoforms of murine MBP, obtained by alternative splicing of seven exons from a single primary transcript, display distinct developmental profiles. We expressed these major MBPs individually in HeLa cells and mapped their distributions by immunofluorescence and confocal microscopy. The 14- and 18.5-kD MBPs that are the predominant forms in compact myelin distributed primarily in the perinuclear regions of the cell in configurations highly suggestive of close association with membranes. We infer that these MBP isoforms possess strong, nonspecific membrane-binding properties that have been adapted by the oligodendrocyte to mediate compaction of the sheaths of plasma membrane that form myelin. In contrast, the 17- and 21.5- kD isoforms distributed diffusely in both the cytoplasm and the nucleoplasm and often accumulated within the nucleus. This distribution can be correlated with the presence of the peptide segment encoded by exon II, which is unique to these isoforms. The physiological significance of the nuclear targeting displayed by the 17- and 21.5-kD MBP isoforms in HeLa cells remains to be determined.