Oligodendrocytes in brain and optic nerve express the beta 3 subunit isoform of Na,K-ATPase

The Na,K-ATPase, which catalyzes the active transport of Na+ and K+, has tw o principal subunits (alpha and beta) that have several genetically distinc t isoforms. Most of these isoforms are expressed in the nervous system, but certain ones are preferentially expressed in glia and others in neurons. O f the beta isoforms, beta 1 predominates in neurons and beta 2 in astrocyte s, although there are some exceptions. Here we demonstrate that beta 3 is e xpressed in rat and mouse white matter oligodendrocytes. Immunofluorescence microscopy identified beta 3 in oligodendrocytes of rat brain white matter in typical linear arrays of cell bodies between fascicles of axons. The in tensity of stain peaked at 20 postnatal days. beta 3 was identified in cort ical oligodendrocytes grown in culture, where it was expressed in processes and colocalized with antibody to galactocerebroside, In the mouse and rat optic nerve, beta 3 stain was seen in oligodendrocytes, where it colocalize d with carbonic anhydrase II. For comparison, optic nerve was stained for t he beta 1 and beta 2 subunits, showing distinct patterns of labelling of ax ons (beta 1) and astrocytes (beta 2). The C6 glioma cell line was also foun d to express the beta 3 isoform preferentially. Since beta 3 was not found at detectable levels in astrocytes, this suggests that 06 is closer to olig odendrocytes than astrocytes in the glial cell lineage. (C) 2000 Wiley-Liss , Inc.