The adhesion molecule on glia (AMOG) is a homologue of the beta subunit of the Na,K-ATPase.
AMOG (adhesion molecule on glia) is a Ca2(+)-independent adhesion molecule which mediates selective neuron-astrocyte interaction in vitro (Antonicek, H., E. Persohn, and M. Schachner. 1987. J. Cell Biol. 104:1587-1595). Here we report the structure of AMOG and its association with the Na,K-ATPase. The complete cDNA sequence of mouse AMOG revealed 40% amino acid identity with the previously cloned beta subunit of rat brain Na,K-ATPase. Immunoaffinity-purified AMOG and the beta subunit of detergent-purified brain Na,K-ATPase had identical apparent molecular weights, and were immunologically cross-reactive. Immunoaffinity-purified AMOG was associated with a protein of 100,000 Mr. Monoclonal antibodies revealed that this associated protein comprised the alpha 2 (and possibly alpha 3) isoforms of the Na,K-ATPase catalytic subunit, but not alpha 1. The monoclonal AMOG antibody that blocks adhesion was shown to interact with Na,K-ATPase in intact cultured astrocytes by its ability to increase ouabain-inhibitable 86Rb+ uptake. AMOG-mediated adhesion occurred, however, both at 4 degrees C and in the presence of ouabain, an inhibitor of the Na,K-ATPase. Both AMOG and the beta subunit are predicted to be extracellularly exposed glycoproteins with single transmembrane segments, quite different in structure from the Na,K-ATPase alpha subunit or any other ion pump. We hypothesize that AMOG or variants of the beta subunit of the Na,K-ATPase, tightly associated with an alpha subunit, are recognition elements for adhesion that subsequently link cell adhesion with ion transport.
Gloor
S
S
Department of Neurobiology, University of Heidelberg, Federal Republic of Germany.
Antonicek
H
H
Sweadner
K J
KJ
Pagliusi
S
S
Frank
R
R
Moos
M
M
Schachner
M
M
D000251:Adenosine Triphosphatases; D000595:Amino Acid Sequence; D000818:Animals; D001253:Astrocytes / Q000378:metabolism / Q000502:physiology; D001483:Base Sequence; D015153:Blotting, Western; D001921:Brain / Q000201:enzymology / Q000378:metabolism; D027682:Cation Transport Proteins; D002448:Cell Adhesion; D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D005455:Fluorescent Antibody Technique; D015723:Gene Library; D007700:Kinetics; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics*; D011487:Protein Conformation; D012413:Rubidium / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics*
C504191:Atp1b2 protein, mouse; C504192:Atp1b2 protein, rat; D027682:Cation Transport Proteins; D015816:Cell Adhesion Molecules, Neuronal; D046911:Macromolecular Substances; D009419:Nerve Tissue Proteins; D004247:DNA; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium