scholarly journals Plasmin and chymotrypsin have distinct preferences for channel activating cleavage sites in the γ subunit of the human epithelial sodium channel

2012 ◽  
Vol 140 (4) ◽  
pp. 375-389 ◽  
Author(s):  
Silke Haerteis ◽  
Matteus Krappitz ◽  
Alexei Diakov ◽  
Annabel Krappitz ◽  
Robert Rauh ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Cleavage Site ◽  
Double Mutant ◽  
Epithelial Sodium Channel ◽  
Xenopus Laevis Oocytes ◽  
Cleavage Sites ◽  
Channel Activation ◽  
Proteolytic Activation ◽  
Double Mutation ◽  
Γ Subunit

Proteolytic activation of the epithelial sodium channel (ENaC) involves cleavage of its γ subunit in a critical region targeted by several proteases. Our aim was to identify cleavage sites in this region that are functionally important for activation of human ENaC by plasmin and chymotrypsin. Sequence alignment revealed a putative plasmin cleavage site in human γENaC (K189) that corresponds to a plasmin cleavage site (K194) in mouse γENaC. We mutated this site to alanine (K189A) and expressed human wild-type (wt) αβγENaC and αβγK189AENaC in Xenopus laevis oocytes. The γK189A mutation reduced but did not abolish activation of ENaC whole cell currents by plasmin. Mutating a putative prostasin site (γRKRK178AAAA) had no effect on the stimulatory response to plasmin. In contrast, a double mutation (γRKRK178AAAA;K189A) prevented the stimulatory effect of plasmin. We conclude that in addition to the preferential plasmin cleavage site K189, the putative prostasin cleavage site RKRK178 may serve as an alternative site for proteolytic channel activation by plasmin. Interestingly, the double mutation delayed but did not abolish ENaC activation by chymotrypsin. The time-dependent appearance of cleavage products at the cell surface nicely correlated with the stimulatory effect of chymotrypsin on ENaC currents in oocytes expressing wt or double mutant ENaC. Delayed proteolytic activation of the double mutant channel with a stepwise recruitment of so-called near-silent channels was confirmed in single-channel recordings from outside-out patches. Mutating two phenylalanines (FF174) in the vicinity of the prostasin cleavage site prevented proteolytic activation by chymotrypsin. This indicates that chymotrypsin preferentially cleaves at FF174. The close proximity of FF174 to the prostasin site may explain why mutating the prostasin site impedes channel activation by chymotrypsin. In conclusion, this study supports the concept that different proteases have distinct preferences for certain cleavage sites in γENaC, which may be relevant for tissue-specific proteolytic ENaC activation.

scholarly journals TMPRSS4-dependent activation of the epithelial sodium channel requires cleavage of the γ-subunit distal to the furin cleavage site

2012 ◽  
Vol 302 (1) ◽  
pp. F1-F8 ◽  
Author(s):  
Christopher J. Passero ◽  
Gunhild M. Mueller ◽  
Michael M. Myerburg ◽  
Marcelo D. Carattino ◽  
Rebecca P. Hughey ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Cleavage Site ◽  
Epithelial Sodium Channel ◽  
Cleavage Sites ◽  
Furin Cleavage ◽  
Channel Activation ◽  
Α Subunit ◽  
Γ Subunit ◽  
Furin Cleavage Site ◽  
Unique Mechanism

The epithelial sodium channel (ENaC) is activated by a unique mechanism, whereby inhibitory tracts are released by proteolytic cleavage within the extracellular loops of two of its three homologous subunits. While cleavage by furin within the biosynthetic pathway releases one inhibitory tract from the α-subunit and moderately activates the channel, full activation through release of a second inhibitory tract from the γ-subunit requires cleavage once by furin and then at a distal site by a second protease, such as prostasin, plasmin, or elastase. We now report that coexpression of mouse transmembrane protease serine 4 (TMPRSS4) with mouse ENaC in Xenopus oocytes was associated with a two- to threefold increase in channel activity and production of a unique ∼70-kDa carboxyl-terminal fragment of the γ-subunit, similar to the ∼70-kDa γ-subunit fragment that we previously observed with prostasin-dependent channel activation. TMPRSS4-dependent channel activation and production of the ∼70-kDa fragment were partially blocked by mutation of the prostasin-dependent cleavage site (γRKRK186QQQQ). Complete inhibition of TMPRSS4-dependent activation of ENaC and γ-subunit cleavage was observed when three basic residues between the furin and prostasin cleavage sites were mutated (γK173Q, γK175Q, and γR177Q), in addition to γRKRK186QQQQ. Mutation of the four basic residues associated with the furin cleavage site (γRKRR143QQQQ) also prevented TMPRSS4-dependent channel activation. We conclude that TMPRSS4 primarily activates ENaC by cleaving basic residues within the tract γK173-K186 distal to the furin cleavage site, thereby releasing a previously defined key inhibitory tract encompassing γR158-F168 from the γ-subunit.

Experimental nephrotic syndrome leads to proteolytic activation of the epithelial sodium channel (ENaC) in the mouse kidney

2021 ◽  
Author(s):  
Bernhard N. Bohnert ◽  
Daniel Essigke ◽  
Andrea Janessa ◽  
Jonas C Schneider ◽  
Matthias Wörn ◽  
...  
Keyword(s):  
Nephrotic Syndrome ◽  
Sodium Channel ◽  
Serine Protease ◽  
Cleavage Site ◽  
Mineralocorticoid Receptor ◽  
Epithelial Sodium Channel ◽  
Sodium Retention ◽  
Cleavage Sites ◽  
Proteolytic Activation ◽  
Epithelial Sodium Channel Enac

Proteolytic activation of the renal epithelial sodium channel ENaC involves cleavage events in its α- and γ-subunits and is thought to mediate sodium retention in nephrotic syndrome (NS). However, detection of proteolytically processed ENaC in kidney tissue from nephrotic mice has been elusive so far. We used a refined Western blot technique to reliably discriminate full-length α- and γ-ENaC and their cleavage products after proteolysis at their proximal and distal cleavage sites (designated from the N-terminus), respectively. Proteolytic ENaC activation was investigated in kidneys from mice with experimental NS induced by doxorubicin or inducible podocin deficiency with or without treatment with the serine protease inhibitor aprotinin. Nephrotic mice developed sodium retention and increased expression of fragments of α- and γ-ENaC cleaved at both the proximal and more prominently at the distal cleavage site, respectively. Treatment with aprotinin but not with the mineralocorticoid receptor antagonist canrenoate prevented sodium retention and upregulation of the cleavage products in nephrotic mice. Increased expression of cleavage products of α- and γ-ENaC was similarly found in healthy mice treated with a low salt diet, sensitive to mineralocorticoid receptor blockade. In human nephrectomy specimens, γ-ENaC was found in the full-length form and predominantly cleaved at its distal cleavage site. In conclusion, murine experimental NS leads to aprotinin-sensitive proteolytic activation of ENaC at both proximal and more prominently distal cleavage sites of its α- and γ-subunit, most likely by urinary serine protease activity or proteasuria.

scholarly journals Defining an inhibitory domain in the gamma subunit of the epithelial sodium channel

2010 ◽  
Vol 299 (4) ◽  
pp. F854-F861 ◽  
Author(s):  
Christopher J. Passero ◽  
Marcelo D. Carattino ◽  
Ossama B. Kashlan ◽  
Mike M. Myerburg ◽  
Rebecca P. Hughey ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Epithelial Sodium Channel ◽  
Xenopus Laevis Oocytes ◽  
Airway Epithelia ◽  
Gamma Subunit ◽  
Γ Subunit ◽  
Inhibitory Region ◽  
Inhibitory Domain ◽  
Complete Deletion ◽  
Epithelial Sodium Channel Enac

Proteases activate the epithelial sodium channel (ENaC) by cleaving the large extracellular domains of the α- and γ-subunits and releasing peptides with inhibitory properties. Furin and prostasin activate mouse ENaC by cleaving the γ-subunit at sites flanking a 43 residue inhibitory tract (γE144-K186). To determine whether there is a minimal inhibitory region within this 43 residue tract, we generated serial deletions in the inhibitory tract of the γ-subunit in channels resistant to cleavage by furin and prostasin. We found that partial or complete deletion of a short segment in the γ-subunit, R158-N171, enhanced channel activity. Synthetic peptides overlapping this segment in the γ-subunit further identified a key 11-mer tract, R158-F168 (RFLNLIPLLVF), which inhibited wild-type ENaC expressed in Xenopus laevis oocytes, and endogenous channels in mpkCCD cells and human airway epithelia. Further studies with amino acid-substituted peptides defined residues that are required for inhibition in this key 11-mer tract. The presence of the native γ inhibitory tract in ENaC weakened the intrinsic binding constant of the 11-mer peptide inhibitor, suggesting that the γ inhibitory tract and the 11-mer peptide interact at overlapping sites within the channel.

scholarly journals Proteolytic activation of the human epithelial sodium channel by trypsin and trypsin IV involves distinct cleavage sites (1181.2)

2014 ◽  
Vol 28 (S1) ◽  
Author(s):  
Silke Haerteis ◽  
Annabel Krappitz ◽  
Matteus Krappitz ◽  
Jane Murphy ◽  
Wolfgang Knecht ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Epithelial Sodium Channel ◽  
Cleavage Sites ◽  
Proteolytic Activation

scholarly journals Proteolytic Activation of the Human Epithelial Sodium Channel by Trypsin IV and Trypsin I Involves Distinct Cleavage Sites

2014 ◽  
Vol 289 (27) ◽  
pp. 19067-19078 ◽  
Author(s):  
Silke Haerteis ◽  
Annabel Krappitz ◽  
Matteus Krappitz ◽  
Jane E. Murphy ◽  
Marko Bertog ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Epithelial Sodium Channel ◽  
Cleavage Sites ◽  
Proteolytic Activation

scholarly journals Cleavage in the γ-subunit of the epithelial sodium channel (ENaC) plays an important role in the proteolytic activation of near-silent channels

2008 ◽  
Vol 586 (19) ◽  
pp. 4587-4608 ◽  
Author(s):  
Alexei Diakov ◽  
Katarzyna Bera ◽  
Marianna Mokrushina ◽  
Bettina Krueger ◽  
Christoph Korbmacher
Keyword(s):  
Sodium Channel ◽  
Epithelial Sodium Channel ◽  
Proteolytic Activation ◽  
Γ Subunit ◽  
Epithelial Sodium Channel Enac

Differential Regulation of the Epithelial Sodium Channel (ENaC) in Rat Kidney, Lung and Distal Colon in Response to Aldosterone.

Hypertension ◽  
2000 ◽  
Vol 36 (suppl_1) ◽  
pp. 724-724
Author(s):  
Shyama M E Masilamani ◽  
Gheun-Ho Kim ◽  
Mark A Knepper
Keyword(s):  
Sodium Channel ◽  
Epithelial Sodium Channel ◽  
Distal Colon ◽  
Β Subunit ◽  
Dietary Salt ◽  
Α Subunit ◽  
Salt Restriction ◽  
Γ Subunit ◽  
Dietary Salt Restriction ◽  
Epithelial Sodium Channel Enac

P170 The mineralocorticoid hormone, aldosterone increases renal tubule Na absorption via increases in the protein abundances of the α-subunit of the epithelial sodium channel (ENaC) and the 70 kDa form of the γ- subunit of ENaC (JCI 104:R19-R23). This study assesses the affect of dietary salt restriction on the regulation of the epithelial sodium channel (ENaC) in the lung and distal colon, in addition to kidney, using semiquantitative immunoblotting. Rats were placed initially on either a control Na intake (0.02 meq/day), or a low Na intake (0.2 meq/day) for 10 days. The low salt treated rats demonstrated an increase in plasma aldosterone levels at day 10 (control = 0.78 + 0.32 nM; Na restricted = 3.50 + 1.30 nM). In kidney homogenates, there were marked increases in the band density of the α-subunit of ENaC (286 % of control) and the 70 kDa form of γ-subunit of ENaC (262 % of control), but no increase in the abundance of the β-subunit of ENaC. In lung homogenates, there was no significant change in the band densities of the α, β, or γ subunits of ENaC. In distal colon, there was an increase in the band density of the β-subunit of ENaC (311 % of control) and an increase in both the 85 kDa (2355% of control) and 70 kDa (843 % of control) form of the γ subunit of ENaC in response to dietary Na restriction. However, there was no significant difference in the band density of the α-subunit of ENaC. These findings demonstrate tissue specific regulation of the three subunits of ENaC in response to dietary salt restriction.

Liddle's syndrome associated with a point mutation in the extracellular domain of the epithelial sodium channel γ subunit

2002 ◽  
Vol 20 (12) ◽  
pp. 2383-2390 ◽  
Author(s):  
Timo P Hiltunen ◽  
Tuula Hannila-Handelberg ◽  
Noora Petäjäniemi ◽  
Ilkka Kantola ◽  
Ilkka Tikkanen ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Point Mutation ◽  
Epithelial Sodium Channel ◽  
Extracellular Domain ◽  
Γ Subunit ◽  
Liddle’S Syndrome ◽  
Liddle's Syndrome
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