Dopamine acutely stimulates Na+/H+ exchanger (NHE3) endocytosis via clathrin-coated vesicles - Dependence on protein kinase A-mediated NHE3 phosphorylation

Dopamine (DA) is a key hormone in mammalian sodium homeostasis. DA induces natriuresis via acute inhibition of the renal proximal tubule apical membra ne Na+/H+ exchanger NHE3. We examined the mechanism by which DA inhibits MH E3 in a renal cell line. DA acutely decreases surface NHE3 antigen in dose- and time-dependent fashion without altering total cellular NHE3. Although DA, receptor agonist alone decreases surface NHE3, simultaneous DA, agonist synergistically enhances the effect of DA,, Decreased surface NHE3 antigen , caused by stimulation of NHE3 endocytosis, is dependent on intact functio ning of the GTPase dynamin and involves increased binding of NHE3 to the ad aptor protein AP2, DA-stimulated NHE3 endocytosis can be blocked by pharmac ologic or genetic protein kinase A inhibition or by mutation of two protein kinase A target serines (Ser-560 and Ser-613) on NRE3, We conclude that on e mechanism by which DA induces natriuresis is via protein kinase A-mediate d phosphorylation of proximal tubule NHE3 leading to endocytosis of NHE3 vi a clathrin-coated vesicles.