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Plasmin activates human epithelial sodium channels in oocytes
Author(s) -
Bhattarai Deepa,
Su Xuefeng,
Ji HongLong
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1042.5
Subject(s) - plasmin , epithelial sodium channel , heterologous , chemistry , microbiology and biotechnology , biochemistry , biophysics , sodium , biology , enzyme , gene , organic chemistry
Salt absorption via epithelial sodium channels (ENaC) is a rate limiting process that is driven by basolaterally located Na/K‐ATPase in epithelial cells. In injured lungs, plasminogen activator inhibitor (PAI‐1) level is extremely high, possibly eliminating plasmin content in lung edema fluid. Plasmin cleaved heterologous mouse γ ENaC ( Passero CJ, et.al JBC 283:36586–36591, 2008 ). To examine the regulation of human ENaC by plasmin expressed in oocytes, we incubated oocytes with plasmin and evaluated ENaC activity using dual‐electrode voltage clamp technique. We found that plasmin (10μg/ml for 1 hour) stimulates ENaC currents up to 13 fold (from −1656.58 ± 127 nA to – 21711.189 ± 1797 nA, N=8, P<0.05). Plasmin activates αβγ ENaC activity in a time‐dependent manner with maximal activation in one hour. To identify the potential proteolytic domains in α and γ subunits, we applied plasmin to six deletion mutants, termed, α Δ173–178, α Δ201–204, α Δ432–444, γ Δ131–138, γ Δ178–193 and γ Δ410–422 . Interestingly, four deletion mutations (α Δ432–444, γ Δ131–138, γ Δ178–193 and γ Δ410–422 ) lost their responses to plasmin. Furthermore, several critical amino acid residues are able to reduce the stimulatory effects of plasmin on ENaC, including γ R135M , γ R137M, γ K179M and γ k181M . Our results suggest that plasmin may up‐regulate heterologous human αβγ ENaC channels via multiple proteolytic domains in both α and γ subunits. Supported by NIH grants HL87017 and HL95435.