The mode of anchorage to the cell surface determines both the function and the membrane location of Thy-1 glycoprotein.
The surface glycoprotein, Thy-1, when expressed by transfection in NG115/401L neural cells, inhibits their neurite outgrowth over astrocytes. We have investigated the role of the glycosylphosphatidylinositol anchor of Thy-1 in this inhibition. Hybrid molecules, in which the lipid anchor was replaced by polypeptide transmembrane domains, were expressed by transfection. Lines expressing Thy-1 with the transmembrane and full cytoplasmic domains of NCAM-140, or with the transmembrane and truncated cytoplasmic domain of CD8, were not inhibited in their ability to extend neurites over astrocytes. Truncation of the cytoplasmic domain of NCAM-140 to just two amino acids, however, produced a transmembrane form of Thy-1 that, when expressed at high levels, inhibited neurite outgrowth. All forms of Thy-1 were concentrated in clusters that occurred primarily on fine filopodia. In double transfectants expressing normal Thy-1 and Thy-1 with the full NCAM cytoplasmic tail, the clusters of each form were separate, with no instances of the transmembrane form being found within the clusters of lipid-anchored Thy-1. Thy-1 with the two-amino-acid cytoplasmic domain of NCAM also occurred in clusters separate from those occupied by lipid-anchored Thy-1, but substantial 'invasion' of the clusters of normal Thy-1 by this transmembrane construct occurred. We suggest that the ability of this hybrid protein to enter the lipid-anchored clusters enables it to activate the signalling pathways that normal Thy-1 uses. Thus the membrane anchor, in targetting Thy-1 to different microdomains on the cell surface, determines its ability to inhibit neurite outgrowth on astrocytes.
|Keywords||*Cell Adhesion, 0 (Antigens, Thy-1), 0 (Cell Adhesion Molecules, Neuronal), 0 (Glycosylphosphatidylinositols), 0 (Oligodeoxyribonucleotides), Amino Acid Sequence, Animals, Antigens, Thy-1/analysis/biosynthesis/*metabolism, Astrocytes/*physiology, Base Sequence, Cell Adhesion Molecules, Neuronal/analysis/biosynthesis/*metabolism, Cell Membrane/*physiology/ultrastructure, Glioma, Glycosylphosphatidylinositols/*metabolism, Hybrid Cells, Mice, Microscopy, Immunoelectron, Molecular Sequence Data, Mutagenesis, Site-Directed, Neurites/*physiology, Neuroblastoma, Oligodeoxyribonucleotides, Point Mutation, Polymerase Chain Reaction, Rats, Restriction Mapping, Support, Non-U.S. Gov't, Transfection|
|Journal||Journal of Cell Science|
Tiveron, M-C, Nosten-Bertrand, M, Jani, H, Garnett, D, Hirst, E.M.A, Grosveld, F.G, & Morris, R.J. (1994). The mode of anchorage to the cell surface determines both the function and the membrane location of Thy-1 glycoprotein. Journal of Cell Science, 107, 1783–1796. Retrieved from http://hdl.handle.net/1765/2493