The Lectin-like Domain of TNF Increases ENaC Open Probability through a Novel Site at the Interface between the Second Transmembrane and C-terminal Domains of the α-Subunit

Lucas, Rudolf; Yue, Qiang; Alli, Abdel A.; Duke, Billie Jeanne; Al‐Khalili, Otor; Thai, Tiffany L.; Hamacher, Jürg; Sridhar, Supriya; Lebedyeva, Iryna; Su, Huabo; Tzotzos, Susan; Fischer, Bernhard; Gameiro, Armanda Formigao; Loose, Maria; Chakraborty, Trinad; Shabbir, Waheed; Aufy, Mohammed; Lemmens‐Gruber, Rosa; Eaton, Douglas C.; Czikora, István

doi:10.1074/jbc.m116.718163

Cited by 20 publications

(56 citation statements)

References 55 publications

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“…The TIP peptide specifically binds to the a subunit of ENaC, but not to the b and g subunits. 20,22 Because depletion of ENaC-a abrogated the protective effects of the TIP peptide in barrier function in toxin-treated human lung microvascular endothelial cell 25 as well as in TNF-induced p38 activation and PGE 2 generation in glomerular endothelial cells (this study), we hypothesize that ENaC-a is the specific receptor for the peptide, although the existence of alternative receptors cannot be fully excluded.…”

Section: Discussionmentioning

confidence: 78%

“…Because our results above indicated that TIP peptide, which binds to ENaC-a, 20,22 reduced local glomerular inflammation in NTN, we asked whether there was an ENaC-mediated effect in intrinsic GEC. As shown in Figure 6a Because TIP peptide activates ENaC by binding to its a subunit and because ENaC-mediated Na þ reabsorption in the collecting duct can be involved in the development of hypertension, 41 we investigated whether it can alter MAP.…”

Section: Tip Peptide Induces Enac Activation In Glomerular Endotheliamentioning

confidence: 99%

“…[11][12][13][14][15] We have shown that different functional domains of TNF, that is, the receptor binding region versus the lectinlike domain, 16,17 can have opposing effects on tissue injury and barrier dysfunction. [18][19][20][21][22][23] Mutations in the lectin-like domain did not impair TNF's antibacterial activities in a murine model of septic peritonitis. 24 This finding provided a unique opportunity to evaluate a TNF-derived circular peptide mimicking the lectin-like domain of TNF, the TIP peptide 17 (sequence: CGQRETPEGAEAKPWYC), to resolve ongoing inflammation during the course of NTN, without interfering with the cytokine's role in immune defense.…”

mentioning

confidence: 93%

“…24 This finding provided a unique opportunity to evaluate a TNF-derived circular peptide mimicking the lectin-like domain of TNF, the TIP peptide 17 (sequence: CGQRETPEGAEAKPWYC), to resolve ongoing inflammation during the course of NTN, without interfering with the cytokine's role in immune defense. We demonstrated that the TIP peptide binds to the a subunit of the epithelial sodium channel (ENaC), 20,22 which can be expressed in both epithelial and endothelial cells. 25,26 Support for this experimental direction is provided by the finding that inhaled TIP peptide (a.k.a.…”

mentioning

confidence: 99%

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The TNF-derived TIP peptide activates the epithelial sodium channel and ameliorates experimental nephrotoxic serum nephritis

Madaio

Czikora

Kvirkvelia

et al. 2019

Kidney International

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In mice, the initial stage of nephrotoxic serum-induced nephritis (NTN) mimics antibody-mediated human glomerulonephritis. Local immune deposits generate tumor necrosis factor (TNF), which activates pro-inflammatory pathways in glomerular endothelial cells (GECs) and podocytes. Because TNF receptors mediate antibacterial defense, existing anti-TNF therapies can promote infection; however, we have previously demonstrated that different functional domains of TNF may have opposing effects. The TIP peptide mimics the lectin-like domain of TNF, and has been shown to blunt inflammation in acute lung injury without impairing TNF receptor-mediated antibacterial activity. We evaluated the impact of TIP peptide in NTN. Intraperitoneal administration of TIP peptide reduced inflammation, proteinuria, and blood urea nitrogen. The protective effect was blocked by the cyclooxygenase inhibitor indomethacin, indicating involvement of prostaglandins. Targeted glomerular delivery of TIP peptide improved pathology in moderate NTN and reduced mortality in severe NTN, indicating a local protective effect. We show that TIP peptide activates the epithelial sodium channel(ENaC), which is expressed by GEC, upon binding to the channel's a subunit. In vitro, TNF treatment of GEC activated pro-inflammatory pathways and decreased the generation of prostaglandin E2 and nitric oxide, which promote recovery from NTN. TIP peptide counteracted these effects. Despite the capacity of TIP peptide to activate ENaC, it did not increase mean arterial blood pressure in mice. In the later autologous phase of NTN, TIP peptide blunted the infiltration of Th17 cells. By countering the deleterious effects of TNF through direct actions in GEC, TIP peptide could provide a novel strategy to treat glomerular inflammation.Kidney International (2019) 95, 1359-1372; https://doi.

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Section: Discussionmentioning

confidence: 78%

Section: Tip Peptide Induces Enac Activation In Glomerular Endotheliamentioning

confidence: 99%

mentioning

confidence: 93%

mentioning

confidence: 99%

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The TNF-derived TIP peptide activates the epithelial sodium channel and ameliorates experimental nephrotoxic serum nephritis

Madaio

Czikora

Kvirkvelia

et al. 2019

Kidney International

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“…The macroscopic amiloride-sensitive Na + currents of all investigated α-ENaC frameshift PHA1B mutants were significantly ( p < 0.001, for number of experiments see Table 3) decreased compared to WT control level (Figure 4A). Remarkably, solnatide was able to activate the reduced current in all studied frameshift mutants up to or even higher than WT control current in absence of solnatide (Figure 4B), even though these mutants lack the carboxyl-terminal domain of α-ENaC previously postulated to be the site of interaction of solnatide with ENaC (19, 31). A maximum level of concentration-dependent current activation was reached at 200 nM with EC 50 values as indicated in Table 3.…”

Section: Resultsmentioning

confidence: 80%

TNF Lectin-Like Domain Restores Epithelial Sodium Channel Function in Frameshift Mutants Associated with Pseudohypoaldosteronism Type 1B

et al. 2017

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Previous in vitro studies have indicated that tumor necrosis factor (TNF) activates amiloride-sensitive epithelial sodium channel (ENaC) current through its lectin-like (TIP) domain, since cyclic peptides mimicking the TIP domain (e.g., solnatide), showed ENaC-activating properties. In the current study, the effects of TNF and solnatide on individual ENaC subunits or ENaC carrying mutated glycosylation sites in the α-ENaC subunit were compared, revealing a similar mode of action for TNF and solnatide and corroborating the previous assumption that the lectin-like domain of TNF is the relevant molecular structure for ENaC activation. Accordingly, TNF enhanced ENaC current by increasing open probability of the glycosylated channel, position N511 in the α-ENaC subunit being identified as the most important glycosylation site. TNF significantly increased Na+ current through ENaC comprising only the pore forming subunits α or δ, was less active in ENaC comprising only β-subunits, and showed no effect on ENaC comprising γ-subunits. TNF did not increase the membrane abundance of ENaC subunits to the extent observed with solnatide. Since the α-subunit is believed to play a prominent role in the ENaC current activating effect of TNF and TIP, we investigated whether TNF and solnatide can enhance αβγ-ENaC current in α-ENaC loss-of-function frameshift mutants. The efficacy of solnatide has been already proven in pathological conditions involving ENaC in phase II clinical trials. The frameshift mutations αI68fs, αT169fs, αP197fs, αE272fs, αF435fs, αR438fs, αY447fs, αR448fs, αS452fs, and αT482fs have been reported to cause pseudohypoaldosteronism type 1B (PHA1B), a rare, life-threatening, salt-wasting disease, which hitherto has been treated only symptomatically. In a heterologous expression system, all frameshift mutants showed significantly reduced amiloride-sensitive whole-cell current compared to wild type αβγ-ENaC, whereas membrane abundance varied between mutants. Solnatide restored function in α-ENaC frameshift mutants to current density levels of wild type ENaC or higher despite their lacking a binding site for solnatide, previously located to the region between TM2 and the C-terminus of the α-subunit. TNF similarly restored current density to wild type levels in the mutant αR448fs. Activation of βγ-ENaC may contribute to this moderate current enhancement, but whatever the mechanism, experimental data indicate that solnatide could be a new strategy to treat PHA1B.

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Detrimental or beneficial: Role of endothelial ENaC in vascular function

Zhang

Yuan

Chen

et al. 2021

Journal Cellular Physiology

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In the past, it was believed that the expression of the epithelial sodium channel (ENaC) was restricted to epithelial tissues, such as the distal nephron, airway, sweat glands, and colon, where it is critical for sodium homeostasis. Over the past two decades, this paradigm has shifted due to the finding that ENaC is also expressed in various nonepithelial tissues, notably in vascular endothelial cells. In this review, the recent findings of the expression, regulation, and function of the endothelial ENaC (EnNaC) are discussed.The expression of EnNaC subunits is reported in a variety of endothelial cell lines and vasculatures, but this is controversial across different species and vessels and is not a universal finding in all vascular beds. The expression density of EnNaC is very faint compared to ENaC in the epithelium. To date, little is known about the regulatory mechanism of EnNaC. Through it can be regulated by aldosterone, the detailed downstream signaling remains elusive. EnNaC responds to increased extracellular sodium with the feedforward activation mechanism, which is quite different from the Na + self-inhibition mechanism of ENaC. Functionally, EnNaC was shown to be a determinant of cellular mechanics and vascular tone as it can sense shear stress, and its activation or insertion into plasma membrane causes endothelial stiffness and reduced nitric oxide production. However, in some blood vessels, EnNaC is essential for maintaining the integrity of endothelial barrier function. In this context, we discuss the possible reasons for the distinct role of EnNaC in vasculatures.

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The Lectin-like Domain of TNF Increases ENaC Open Probability through a Novel Site at the Interface between the Second Transmembrane and C-terminal Domains of the α-Subunit

Cited by 20 publications

References 55 publications

The TNF-derived TIP peptide activates the epithelial sodium channel and ameliorates experimental nephrotoxic serum nephritis

The TNF-derived TIP peptide activates the epithelial sodium channel and ameliorates experimental nephrotoxic serum nephritis

TNF Lectin-Like Domain Restores Epithelial Sodium Channel Function in Frameshift Mutants Associated with Pseudohypoaldosteronism Type 1B

Detrimental or beneficial: Role of endothelial ENaC in vascular function

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