Na+, K+-ATPase Isozyme Diversity; Comparative Biochemistry and Physiological Implications of Novel Functional Interactions

Na+, K+-ATPase is ubiquitously expressed in the plasma membrane ofall animal cells where it serves as the principal regulator of intracellularion homeostasis. Na+, K+-ATPase is responsible for generating andmaintaining transmembrane ionic gradients that are of vital importance forcellular function and subservient activities such as volume regulation, pHmaintenance, and generation of action potentials and secondary activetransport. The diversity of Na+, K+-ATPase subunit isoforms andtheir complex spatial and temporal patterns of cellular expression suggestthat Na+, K+-ATPase isozymes perform specialized physiologicalfunctions. Recent studies have shown that the α subunit isoformspossess considerably different kinetic properties and modes of regulationand the β subunit isoforms modulate the activity, expression and plasmamembrane targeting of Na+, K+-ATPase isozymes. This review focuseson recent developments in Na+, K+-ATPase research, and in particular reportsof expression of isoforms in various tissues and experiments aimed atelucidating the intrinsic structural features of isoforms important forNa+, K+-ATPase function.