Activation of epithelial sodium channels by prostasin in Xenopus oocytes.
Prostasin, a novel serine protease, was purified from seminal fluid, and its cDNA sequence was determined. Expression of prostasin was detected in human tissues, including prostate, kidney, and lung, as well as bodily fluids, including seminal fluid and urine. However, its physiologic role in the human body is not known. Recently, a novel regulatory mechanism by which serine proteases activate epithelial sodium channel in the Xenopus oocyte was identified. Therefore, it was hypothesized that prostasin could activate sodium currents, and a rat prostasin cDNA clone was isolated to investigate its physiologic function. Rat prostasin mRNA is expressed predominantly in kidney, and lower levels of expression were detected in prostate, lung, colon, stomach, and skin. These all are epithelial tissues in which the epithelial sodium channel (ENaC) is expressed. Coexpression of rat prostasin and rat ENaC in Xenopus oocytes increased the amiloride-sensitive sodium current by twofold. Preincubation of oocytes that expressed prostasin with aprotinin did not result in an increase in sodium current, compared with the control. The removal of aprotinin from the bath solution resulted in a twofold increase of the current only in oocytes that expressed prostasin, which indicates that protease activity of prostasin is required for the ENaC activation. Expression of rat prostasin had no effect on the potassium current when expressed with rat renal outer medulla K channel, which shows specificity of prostasin action for ENAC: These results indicate that prostasin acts as an extracellular regulator of ENAC:
Adachi
Masataka
M
Third Department of Internal Medicine, Kumamoto University School of Medicine, Kumamoto, Japan.
Kitamura
Kenichiro
K
Third Department of Internal Medicine, Kumamoto University School of Medicine, Kumamoto, Japan.
Miyoshi
Taku
T
Third Department of Internal Medicine, Kumamoto University School of Medicine, Kumamoto, Japan.
Narikiyo
Takefumi
T
Third Department of Internal Medicine, Kumamoto University School of Medicine, Kumamoto, Japan.
Iwashita
Kozo
K
Third Department of Internal Medicine, Kumamoto University School of Medicine, Kumamoto, Japan.
Shiraishi
Naoki
N
Third Department of Internal Medicine, Kumamoto University School of Medicine, Kumamoto, Japan.
Nonoguchi
Hiroshi
H
Third Department of Internal Medicine, Kumamoto University School of Medicine, Kumamoto, Japan.
Tomita
Kimio
K
Third Department of Internal Medicine, Kumamoto University School of Medicine, Kumamoto, Japan.
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D007611:Aprotinin / Q000494:pharmacology; D001483:Base Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D004594:Electrophysiology; D004848:Epithelium / Q000378:metabolism; D007684:Kidney Tubules / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying; D012313:RNA / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000378:metabolism / Q000502:physiology*; D015222:Sodium Channels / Q000378:metabolism*; D014981:Xenopus; D000099271:Prostasin
D000584:Amiloride; D007611:Aprotinin; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D012313:RNA; D012697:Serine Endopeptidases; D015222:Sodium Channels; D000099271:Prostasin; C510692:Kcnj1 protein, rat