Abstract. 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. . 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 409; amino acid identity with the previously cloned subunit of rat brain Na,K-ATPase. Immunoaflinitypurified AMOG and the/$ 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 or2 (and possibly ix3) isoforms of the Na,K-ATPase catalytic subunit, but not a l. The monoclonal AMOG antibody that blocks adhesion was shown to interact with Na,KATPase in intact cultured astrocytes by its ability to increase ouabain-inhibitable S6Rb+ uptake. AMOGmediated adhesion occurred, however, both at 4°C and in the presence of ouabain, an inhibitor of the Na,KATPase. Both AMOG and the I$ subunit are predicted to be extracellulady exposed glycoproteins with single transmembrane segments, quite different in structure from the Na,K-ATPase ot subunit or any other ion pump. We hypothesize that AMOG or variants of the B subunit of the Na,K-ATPase, tightly associated with an ot subunit, are recognition elements for adhesion that subsequently link cell adhesion with ion transport.
Abstract.Adhesion molecule on glia (AMOG) is a novel neural cell adhesion molecule that mediates neuron-astrocyte interaction in vitro. In situ AMOG is expressed in the cerebellum by glial cells at the critical developmental stages of granule neuron migration. Granule neuron migration that is guided by surface contacts between migrating neurons and astroglial processes is inhibited by monoclonal AMOG antibody, probably by disturbing neuron-glia adhesion. AMOG is an integral cell surface glycoprotein of 45-50-kD molecular weight with a carbohydrate content of at least 30%. It does not belong to the L2/HNK-1 family of neural cell adhesion molecules but expresses another carbohydrate epitope that is shared with the adhesion molecules L1 and myelin-associated glycoprotein, but is not present on N-CAM or J1.
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