FUNCTIONAL-CHARACTERIZATION OF BETA-ISOFORMS OF MURINE NA,K-ATPASE - THE ADHESION MOLECULE ON GLIA (AMOG BETA-2), BUT NOT BETA-1, PROMOTES NEURITE OUTGROWTH/

We have previously provided evidence for a dual function of the adhesi on molecule on glia (AMOG/beta2), the beta2 subunit of the murine Na,K -ATPase, both as neural recognition molecule mediating neuron-glia int eractions and as functional beta subunit of the sodium pump. To analyz e the functional role of AMOG/beta2 in neurite outgrowth, AMOG/beta2-e xpressing L-cells were generated by transfection and used as substrate s for neurite outgrowth of cerebellar and hippocampal neurons. AMOG/be ta2-transfected L-cells led to an increase in neurite length after 6 h , which was specifically inhibited by antibodies to AMOG/beta2 and a n euronal membrane fraction. Moreover, the extracellular domain of AMOG/ beta2 generated as a soluble recombinant protein in Chinese hamster ov ary cells partially inhibited the increase in neurite outgrowth on AMO G/beta2-transfected L-cells. L-cells transfected with the mouse beta1 subunit had no effect on neurite extension. Our observations show for the first time differences in functional properties for different beta isoforms of the Na,K-ATPase and suggest that AMOG/beta2 but not beta1 is able to interact with an unknown neuronal receptor leading to incr eased neurite outgrowth, most likely via signal transduction.