Regulation of prostasin by aldosterone in the kidney

Abstract

Prostasin is a serine protease present in mammalian urine that increases the activity of the epithelial sodium channel (ENaC) when the two are coexpressed in Xenopus oocytes. To determine if aldosterone, one of the principal regulators of urinary Na reabsorption by the distal nephron, affects prostasin expression, we examined prostasin mRNA and protein in a cultured mouse cortical collecting duct cell line (M-1), whole rats, and patients with primary aldosteronism. Aldosterone treatment of M-1 cells substantially increased prostasin expression and stimulated 22 Na uptake. Urinary excretion of prostasin in rats that were infused with aldosterone likwise increased by ∼4-fold when compared with the vehicle-infused rats. Finally, urinary excretion of prostasin in patients with primary aldosteronism was substantially increased when compared with normal patients. Adrenalectomy reduced urinary prostasin excretion to control levels, whereas urinary prostasin levels were not altered in patients undergoing surgery for other reasons. In patients with primary aldosteronism, reduction in the urinary excretion of prostasin correlated with the increase in the urinary Na/K ratio. These findings, together with our previous report that prostasin activates the amiloride-sensitive Na currents through ENaC, demonstrate that prostasin regulates Na balance in vivo by virtue of its heightened expression in the presence of aldosterone.

Regulation of sodium transport by ENaC in the kidney

“…Initial clinical studies indicated that urinary prostasin is elevated in patients with hyperaldosteronism [48]. Recent clinical studies have suggested more generally that urinary prostasin may serve as an in vivo marker of activation of ENaC [49], correlate with urinary aldosterone [50], and increase with pressure natriuresis [51].…”

Inhibition of prostasin expression by TGF-β1 in renal epithelial cells

“…Prostasin/CAP-1 stimulates the activity of ENaC when they are coexpressed in Xenopus oocytes [6][7][8]. In addition, we showed that aldosterone increases the expression of prostasin in both in vitro and in vivo conditions [9]. These results indicate that prostasin is an important physiologic regulator of sodium reabsorption in the kidney through EnaC, and suggest the possibility that prostasin is involved in the development of salt-sensitive hypertension.…”

“…The resulting antisera were affinity-purified against the immunizing peptide. The specificity of the antibody was evaluated by comparing the blots with previously reported antibody [9,19].…”

“…The activities of ENaC in M-1 cells were determined by measurement of amiloride-sensitive 22 Na up-take, as previously described [9]. Briefly, after incubation under experimental conditions, cells on 6-well plates were rinsed twice and preincubated for 15 minutes at 37 • C in an Na-free solution composed of (in mmol/L) 137 N-methylglucamine (NMDG), 5.4 KCl, 1.2 MgSO 4 , 2.8 CaCl 2 , and 15 HEPES (pH 7.4).…”

“…We used M-1 cells to characterize the transcriptional activity of the rat prostasin promoter because prostasin is endogenously expressed in M-1 cells [9], and because no rat CCD cell line is commercially available to our knowledge. M-1 cells were transfected with pGL3-basic alone, the full-length rat prostasin promoter in pGL3basic, or the rat prostasin promoter in reverse orientation in pGL3-basic.…”