Analysis of Na+,K+-ATPase Motion and Incorporation into the Plasma Membrane in Response to G Protein–coupled Receptor Signals in Living Cells

Abstract

Dopamine (DA) increases Na⁺,K⁺-ATPase activity in lung alveolar epithelial cells. This effect is associated with an increase in Na⁺,K⁺-ATPase molecules within the plasma membrane (Ridge et al., 2002). Analysis of Na⁺,K⁺-ATPase motion was performed in real-time in alveolar cells stably expressing Na⁺,K⁺-ATPase molecules carrying a fluorescent tag (green fluorescent protein) in the α-subunit. The data demonstrate a distinct (random walk) pattern of basal movement of Na⁺,K⁺-ATPase–containing vesicles in nontreated cells. DA increased the directional movement (by 3.5 fold) of the vesicles and an increase in their velocity (by 25%) that consequently promoted the incorporation of vesicles into the plasma membrane. The movement of Na⁺,K⁺-ATPase–containing vesicles and incorporation into the plasma membrane were microtubule dependent, and disruption of this network perturbed vesicle motion toward the plasma membrane and prevented the increase in the Na⁺,K⁺-ATPase activity induced by DA. Thus, recruitment of new Na⁺,K⁺-ATPase molecules into the plasma membrane appears to be a major mechanism by which dopamine increases total cell Na⁺,K⁺-ATPase activity.