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Differential intracellular sorting of the myelin‐associated glycoprotein isoforms
Author(s) -
Minuk J.,
Braun P.E.
Publication year - 1996
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/(sici)1097-4547(19960601)44:5<411::aid-jnr1>3.0.co;2-i
Subject(s) - gene isoform , transfection , myelin associated glycoprotein , biology , cytoplasm , microbiology and biotechnology , transmembrane protein , glycoprotein , epithelial polarity , extracellular , cell culture , myelin , cell , biochemistry , receptor , gene , central nervous system , genetics , neuroscience
Myelin‐associated glycoprotein (MAG), a myelin‐specific protein, is expressed as two isoforms, designated as L‐MAG and S‐MAG. Both share identical extracellular and transmembrane domains but differ in their cytoplasmic domains. L‐MAG is expressed earlier during myelination than S‐MAG. These features, as well as others, suggest that the isoforms have different functions. To confirm this hypothesis, both isoforms were expressed transiently and stably in Madin‐Darby canine kidney (MDCK) epithelial cells, and the localization of the isoforms was studied. In both transiently and stably transfected cells, L‐MAG sorted primarily to the basolateral membrane. In single transfected cells, S‐MAG sorted primarily to the apical membrane. When groups of adjacent cells became transiently transfected, S‐MAG accumulated at areas of cell‐cell contact within the basolateral membrane. In stably transfected cells S‐MAG sorted to the basolateral membrane. The data suggest that L‐MAG contains an invariable basolateral sorting signal, but that the sorting of S‐MAG is dependent upon extrinsic factors, such as coexpression by adjacent (contacting) cells. As MDCK cells sort the MAG isoforms differently, these data support the hypothesis that the MAG isoforms do perform different functions. © 1996 Wiley‐Liss, Inc.