Abstract
Na,K-ATPase is a membrane-bound protein that maintains intracellular ionic concentrations, i.e., low Na+ and high K+, using the energy from hydrolysis of ATP. We have now observed a rapid recruitment of Na,K-ATPase to the cell surface in responce to extracellular low calcium concentration in the parathyroid cell that releases PTH in responce to low calcium. Using isotope-labelled ouabain that is a specific ligand for Na,K-ATPase, we observed that the recruitment occurs in a few minutes. Biotinylation of the cell-surface proteins revealed that a considerable amount of Na,K-ATPase is present in intracellular region and bound to a specific protein. In analysis of the protein-deficient mice, the molecular association is required for a novel mechanism of rapid recruitment of Na,K-ATPase. This rapid recruitment is essential for PTH release that is the first step of calcium regulation of the whole body. This indicates the importance of NA,K-ATPase in the calcium homeostasis. [J Physiol Sci. 2006;56 Suppl:S111]
