Matthewman C , Johnson CK , Miller DM , Bianchi L .

R01 NS106951 NINDS NIH HHS

	Fig. 1. The finger domain contains the most divergent sequence. A: sequence alignment (Clustal Omega, https://www.ebi.ac.uk/Tools/msa/clustalo/) of human acid-sensing ion channel (ASIC) ASIC1a and Caenorhabditis elegans degenerin (DEG) channels MEC-4 and UNC-8. Shaded in gray are transmembrane domains TM1 and TM2; in yellow is the finger domain of MEC-4. B: schematic representation of a DEG/epithelial Na+ channel subunit. Cylinders and arrows represent α-helixes and β-sheets, respectively; lines depict loops. α-Helixes and β-sheets are numbered according to the primary protein sequence. In yellow, the finger domain with the degenerin-specific domains shown as dotted lines. Red dots represent hyperactive MEC-4 mutation A404T and UNC-8 mutation G387E; the gray dot represents mutation A387S in brain liver intestine Na+ channel (BLINaC) (56). Gray-shaded area represents the plasma membrane.
	Fig. 2. MEC-6 exerts its effects on current amplitude via the finger domain. Schematic representations of channel subunits expressed and comparison of mean current amplitudes recorded at −100 mV in physiologic solution (gray columns) and divalent-free solution (black columns). A: UNC-8(d), UNC-8(d) +MEC-2, and UNC-8(d) +MEC-2 +MEC-6. n = 11, 5, and 15 respectively in physiologic solution, and n = 9, 5, and 8 in divalent-free solution. B: MEC-4(d), MEC-4(d) + MEC-2, and MEC-4(d) + MEC-2 + MEC-6; n = 5, 12, and 14 respectively in physiologic solution, and n = 5, 4, and 8 in divalent-free solution. C: UNC-8/MEC-4 A404T (extracellular domain, ECD) chimera, UNC-8/MEC-4 A404T (ECD) + MEC-2, and UNC-8/MEC-4 A404T (ECD) + MEC-2 + MEC-6; n = 11, 11, and 8 respectively in physiologic solution, and n = 11, 14, and 8 in divalent-free solution. D: UNC-8/MEC-4 A404T (finger) chimera, UNC-8/MEC-4 A404T (finger) + MEC-2, and UNC-8/MEC-4 A404T (finger) + MEC-2 + MEC-6; n = 8, 8, and 10 respectively in physiologic solution, and n = 8, 8, and 10 in divalent-free solution. Data are expressed as mean ± SD. Statistical significance (by ANOVA with Bonferroni correction) between MEC-4(d) and MEC-4(d) coexpressed with MEC-2, and MEC-6 in physiologic solution and divalent-free solution and between UNC-8/ME-4 A404T (ECD) and UNC-8/MEC-4 A404T (finger) chimeras alone and coexpressed with MEC-6 is indicated by asterisks. P values are shown above the columns.
	Fig. 3. The finger domain establishes the cell death phenotype. A and B: micrographs of an intact healthy oocyte (noninjected) and a ruptured dead one [injected with UNC-8(G387E)] 3 days after injection. C: we scored cell death by counting the ratio of ruptured oocytes or oocytes with cytoplasmic protrusions over the course of 5 days, starting from day 2 after injection for oocytes injected with UNC-8(d) + MEC-2 + MEC-6 (black open circles, n of experiments was 5, with 10–15 oocytes injected per experiment), MEC-4(A404T) + MEC-2 + MEC-6 (black open squares, n = 2–4, with 10–15 oocytes injected per experiment), UNC-8/MEC-4 A404T (extracellular domain, ECD) + MEC-2 + MEC-6 (blue open triangles n = 2–3, with 10–15 oocytes injected per experiment), and UNC-8/MEC-4 A404T (finger) + MEC-2 + MEC-6 (pink asterisks, n = 2–4, with 10–15 oocytes injected per experiment). Data are expressed as mean ± SE.
	Fig. 4. UNC-8 Ca2+ block is conferred by the finger domain. A: representative whole cell currents recorded from an oocyte expressing UNC-8(d) + MEC-2 +MEC-6 perfused with a divalent cation-free NaCl solution containing 1 mM EGTA. The voltage protocol consisted of a holding potential of −30 mV and steps from −160 to + 100 mV in 20 mV increments. Right column currents represent same oocyte perfused with 500 µM Ca2+. B: same as in A for oocyte expressing MEC-4(A404T) +MEC-2 +MEC-6. Right column represents same oocyte perfused with 500 µM Ca2+. C: Same as in A and B for oocyte expressing UNC-8/MEC-4 (A404T) (finger) chimera +MEC-2 +MEC-6. Right column represents same oocyte perfused with 500 µM Ca2+. D: calcium dose-response curves for oocytes expressing UNC-8(d) +MEC-2 +MEC-6 (n = 10; black open circles, Ki = 7.4 µM), MEC-4 (A404T)+MEC-2+MEC-6 (n = 6) (pink open triangles, Ki = 1002 µM), UNC-8/MEC-4 (A404T) (extracellular, ECD) chimera + MEC-2+MEC-6 (n = 8) (blue open triangles, Ki = 944 µM), and UNC-8/MEC-4 (A404T) (finger) chimera+MEC-2+MEC-6 (n = 9; red asterisk, Ki = 766 µM). Data are expressed as mean ± SE and were fitted with a sigmoidal curve.
	Fig. 5. Block of UNC-8(d) by Mg2+ conferred by the extracellular domain (ECD). A: representative whole cell currents recorded from an oocyte expressing UNC-8(d) perfused with a divalent cation-free NaCl solution. Right column currents represent same oocyte perfused with 500 µM Mg2+. B and C: Same as in A for an oocyte expressing MEC-4(A404T) +MEC-2 +MEC-6 and one expressing UNC-8/MEC-4(A404T) (finger) chimera +MEC-2 +MEC-6. Next column represents same oocytes perfused with 500 µM Mg2+. D: average current remaining at −100 mV after perfusion with 500 µM Mg2+ for UNC-8(d) (n = 6), UNC-8(d) + MEC-2 + MEC-6 (n = 6), MEC-4(d)+MEC-2+MEC-6 (n = 9), MEC-4 (A404T) + MEC-2 + MEC-6 (n = 5), UNC-8/MEC-4 A404T (ECD) chimera + MEC-2 + MEC-6 (n = 4), and UNC-8/MEC-4(A404T) (finger) chimera + MEC-2 + MEC-6 (n = 7). Data are expressed as mean ± SE. Statistical significance (one-way ANOVA with Bonferroni multiple comparison test) between UNC-8(d) or UNC-8(d) + MEC-2 + MEC-6, and all the other experimental groups is indicated by the asterisk. P values are shown above the columns.

Aviram, Paraoxonase inhibits high-density lipoprotein oxidation and preserves its functions. A possible peroxidative role for paraoxonase. 1998, Pubmed

Aviram, Paraoxonase inhibits high-density lipoprotein oxidation and preserves its functions. A possible peroxidative role for paraoxonase. 1998, Pubmed
Baron, Zn2+ and H+ are coactivators of acid-sensing ion channels. 2001, Pubmed , Xenbase
Besler, Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease. 2011, Pubmed
Bianchi, The neurotoxic MEC-4(d) DEG/ENaC sodium channel conducts calcium: implications for necrosis initiation. 2004, Pubmed , Xenbase
Brand, A stomatin dimer modulates the activity of acid-sensing ion channels. 2012, Pubmed
Brown, MEC-2 and MEC-6 in the Caenorhabditis elegans sensory mechanotransduction complex: auxiliary subunits that enable channel activity. 2008, Pubmed , Xenbase
Canessa, Epithelial sodium channel related to proteins involved in neurodegeneration. 1993, Pubmed , Xenbase
Chalfie, The identification and suppression of inherited neurodegeneration in Caenorhabditis elegans. 1990, Pubmed
Champigny, Mutations causing neurodegeneration in Caenorhabditis elegans drastically alter the pH sensitivity and inactivation of the mammalian H+-gated Na+ channel MDEG1. 1998, Pubmed , Xenbase
Chelur, The mechanosensory protein MEC-6 is a subunit of the C. elegans touch-cell degenerin channel. 2002, Pubmed , Xenbase
Chen, Subunit composition of a DEG/ENaC mechanosensory channel of Caenorhabditis elegans. 2015, Pubmed , Xenbase
Chen, Caenorhabditis elegans paraoxonase-like proteins control the functional expression of DEG/ENaC mechanosensory proteins. 2016, Pubmed , Xenbase
Chu, Subunit-dependent high-affinity zinc inhibition of acid-sensing ion channels. 2004, Pubmed
Davies, The effect of the human serum paraoxonase polymorphism is reversed with diazoxon, soman and sarin. 1996, Pubmed
Devarajan, Paraoxonase 2 deficiency alters mitochondrial function and exacerbates the development of atherosclerosis. 2011, Pubmed
Draganov, Rabbit serum paraoxonase 3 (PON3) is a high density lipoprotein-associated lactonase and protects low density lipoprotein against oxidation. 2000, Pubmed
Driscoll, The mec-4 gene is a member of a family of Caenorhabditis elegans genes that can mutate to induce neuronal degeneration. 1991, Pubmed
Fricke, Epithelial Na+ channels and stomatin are expressed in rat trigeminal mechanosensory neurons. 2000, Pubmed
García-Añoveros, Regulation of Caenorhabditis elegans degenerin proteins by a putative extracellular domain. 1995, Pubmed
García-Añoveros, The nematode degenerin UNC-105 forms ion channels that are activated by degeneration- or hypercontraction-causing mutations. 1998, Pubmed , Xenbase
Gessmann, Molecular modeling of mechanosensory ion channel structural and functional features. 2010, Pubmed
Goodman, MEC-2 regulates C. elegans DEG/ENaC channels needed for mechanosensation. 2002, Pubmed , Xenbase
Gu, Genetic interactions affecting touch sensitivity in Caenorhabditis elegans. 1996, Pubmed
Harbinder, Genetically targeted cell disruption in Caenorhabditis elegans. 1997, Pubmed
Hicks, The evolution of function in strictosidine synthase-like proteins. 2011, Pubmed
Horke, Paraoxonase-2 reduces oxidative stress in vascular cells and decreases endoplasmic reticulum stress-induced caspase activation. 2007, Pubmed
Huang, A stomatin-like protein necessary for mechanosensation in C. elegans. 1995, Pubmed
Huang, Gene interactions affecting mechanosensory transduction in Caenorhabditis elegans. 1994, Pubmed
Huber, Podocin and MEC-2 bind cholesterol to regulate the activity of associated ion channels. 2006, Pubmed
Immke, Protons open acid-sensing ion channels by catalyzing relief of Ca2+ blockade. 2003, Pubmed
Jasti, Structure of acid-sensing ion channel 1 at 1.9 A resolution and low pH. 2007, Pubmed
Jiang, Cysteine 149 in the extracellular finger domain of acid-sensing ion channel 1b subunit is critical for zinc-mediated inhibition. 2011, Pubmed
Lapatsina, Regulation of ASIC channels by a stomatin/STOML3 complex located in a mobile vesicle pool in sensory neurons. 2012, Pubmed
Mackness, Multiple forms of sheep serum A-esterase activity associated with the high-density lipoprotein. 1988, Pubmed
Matthewman, Ca2+ permeability and Na+ conductance in cellular toxicity caused by hyperactive DEG/ENaC channels. 2016, Pubmed , Xenbase
Miller-Fleming, The DEG/ENaC cation channel protein UNC-8 drives activity-dependent synapse removal in remodeling GABAergic neurons. 2016, Pubmed
Ng, Paraoxonase-2 is a ubiquitously expressed protein with antioxidant properties and is capable of preventing cell-mediated oxidative modification of low density lipoprotein. 2001, Pubmed
O'Hagan, The MEC-4 DEG/ENaC channel of Caenorhabditis elegans touch receptor neurons transduces mechanical signals. 2005, Pubmed
Paukert, Identification of the Ca2+ blocking site of acid-sensing ion channel (ASIC) 1: implications for channel gating. 2004, Pubmed , Xenbase
Price, Stomatin modulates gating of acid-sensing ion channels. 2004, Pubmed
Reddy, Human paraoxonase-3 is an HDL-associated enzyme with biological activity similar to paraoxonase-1 protein but is not regulated by oxidized lipids. 2001, Pubmed
Rothem, Paraoxonases are associated with intestinal inflammatory diseases and intracellularly localized to the endoplasmic reticulum. 2007, Pubmed
Schoenmakers, CHELATOR: an improved method for computing metal ion concentrations in physiological solutions. 1992, Pubmed
Shi, Regulation of the epithelial Na+ channel by paraoxonase-2. 2017, Pubmed , Xenbase
Shih, Mice lacking serum paraoxonase are susceptible to organophosphate toxicity and atherosclerosis. 1998, Pubmed
Shreffler, The unc-8 and sup-40 genes regulate ion channel function in Caenorhabditis elegans motorneurons. 1995, Pubmed
Shreffler, Genes controlling ion permeability in both motorneurons and muscle. 1997, Pubmed
Smolen, Characteristics of the genetically determined allozymic forms of human serum paraoxonase/arylesterase. 1991, Pubmed
Stevens, Engineered recombinant human paraoxonase 1 (rHuPON1) purified from Escherichia coli protects against organophosphate poisoning. 2008, Pubmed
Waldmann, The mammalian degenerin MDEG, an amiloride-sensitive cation channel activated by mutations causing neurodegeneration in Caenorhabditis elegans. 1996, Pubmed
Waldmann, A proton-gated cation channel involved in acid-sensing. 1997, Pubmed , Xenbase
Waldmann, H(+)-gated cation channels: neuronal acid sensors in the NaC/DEG family of ion channels. 1998, Pubmed
Wang, Insights into the molecular determinants of proton inhibition in an acid-inactivated degenerins and mammalian epithelial Na(+) channel. 2009, Pubmed , Xenbase
Wang, Neurotoxic unc-8 mutants encode constitutively active DEG/ENaC channels that are blocked by divalent cations. 2013, Pubmed , Xenbase
Wiemuth, A single amino acid tunes Ca2+ inhibition of brain liver intestine Na+ channel (BLINaC). 2010, Pubmed , Xenbase
Zhang, MEC-2 is recruited to the putative mechanosensory complex in C. elegans touch receptor neurons through its stomatin-like domain. 2004, Pubmed , Xenbase
Zhang, Gating of acid-sensitive ion channel-1: release of Ca2+ block vs. allosteric mechanism. 2006, Pubmed , Xenbase
de Weille, Identification, functional expression and chromosomal localisation of a sustained human proton-gated cation channel. 1998, Pubmed