β1-adrenergic receptor signaling activates the epithelial calcium channel, transient receptor potential vanilloid type 5(TRPV5), via the protein kinase a pathway

Abstract

Epinephrine and norepinephrine are present in the pro-urine. β-Adrenergic receptor (β-AR) blockers administered to counteract sympathetic overstimulation in patients with congestive heart failure have a negative inotropic effect, resulting in reduced cardiac contractility. Positive inotropes, β1-AR agonists, are used to improve cardiac functions. Active Ca2+ reabsorption in the late distal convoluted and connecting tubules (DCT2/CNT) is initiated by Ca2+ influx through the transient receptor potential vanilloid type 5 (TRPV5) Ca2+ channel. Although it was reported that β-ARs are present in the DCT2/CNT region, their role in active Ca2+ reabsorption remains elusive. Here we revealed that β1-AR, but not β2-AR, is localized with TRPV5 in DCT2/CNT. Subsequently, treatment of TRPV5-expressing mouse DCT2/CNT primary cell cultures with the β1-AR agonist dobutamine showed enhanced apicaltobasolateral transepithelial Ca2+ transport. In human embryonic kidney (HEK293) cells, dobutamine was shown to stimulate cAMP production, signifying functional β1-AR expression. Fura-2 experiments demonstrated increased activity of TRPV5 in response to dobutamine, which could be prevented by the PKAinhibitor H89. Moreover, nonphosphorylableT709A-TRPV5 and phosphorylation-mimicking T709D-TRPV5 mutants were unresponsive to dobutamine. Surface biotinylation showed that dobutamine did not affect plasma membrane abundance of TRPV5. In conclusion, activation of β1-AR stimulates active Ca2+ reabsorption in DCT2/CNT; an increase in TRPV5 activity via PKA phosphorylation of residue Thr-709 possibly plays an important role. These data explicate a calciotropic role in addition to the inotropic property of β1-AR. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.