Overlapping and diverse distribution of Na-K ATPase isozymes in neurons and glia.

The Na-K ATPase is the plasma membrane enzyme that catalyzes the active uptake of K+ and extrusion of Na+, thereby establishing ion concentration gradients between the inside and outside of the cell. It consumes a large fraction of the energy used in the brain. The enzyme is present in both neurons and glia. Studies of ion flux and of the properties of membrane-associated ATPase activity have suggested that there is more than one functional type of Na-K ATPase in the central nervous system. Molecular cloning has demonstrated that there are three different genes encoding catalytic (alpha) subunits and at least two genes encoding glycoprotein (beta) subunits; all are expressed in the brain. This brief review summarizes the current understanding of Na-K ATPase isozyme distribution and properties. Both neurons and glia can express different isoforms in a cell-specific manner.