Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Prostasin is a tryptic peptidase expressed in prostate, kidney, lung, and airway. Mammalian prostasins are related to Xenopus channel-activating protease, which stimulates epithelial Na+ channel (ENaC) activity in frogs. In human epithelia, prostasin is one of several membrane peptidases proposed to regulate ENaC. This study tests the hypothesis that prostasin can regulate ENaC in cystic fibrosis epithelia in which excessive Na+ uptake contributes to salt and water imbalance. We show that prostasin mRNA and protein are strongly expressed by human airway epithelial cell lines, including immortalized JME/CF15 nasal epithelial cells homozygous for the DeltaF508 cystic fibrosis mutation. Epithelial cells transfected with vectors encoding recombinant soluble prostasin secrete active, tryptic peptidase that is highly sensitive to inactivation by aprotinin. When studied as monolayers in Ussing chambers, JME/CF15 cells exhibit amiloride-sensitive, transepithelial Na+ currents that are markedly diminished by aprotinin, suggesting regulation by serine-class peptidases. Overproduction of membrane-anchored prostasin in transfected JME/CF15 cells does not augment Na+ currents, and trypsin-induced increases are small, suggesting that baseline serine peptidase-dependent ENaC activation is maximal in these cells. To probe prostasin's involvement in basal ENaC activity, we silenced expression of prostasin using short interfering RNA targeting of prostasin mRNA's 3'-untranslated region. This drops ENaC currents to 26 +/- 9% of baseline. These data predict that prostasin is a major regulator of ENaC-mediated Na+ current in DeltaF508 cystic fibrosis epithelia and suggest that airway prostasin is a target for therapeutic inhibition to normalize ion current in cystic fibrosis airway.
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PMID:Prostasin, a membrane-anchored serine peptidase, regulates sodium currents in JME/CF15 cells, a cystic fibrosis airway epithelial cell line. 1524 75

Human EFHC1 is a member of the EF-hand superfamily of Ca(2+)-binding proteins with three DM10 domains of unclear function. Point mutations in the EFHC1 gene are related to juvenile myoclonic epilepsy, a fairly common idiopathic generalized epilepsy. Here, we report the first structural and thermodynamic analyses of the EFHC1C-terminus (residues 403-640; named EFHC1C), comprising the last DM10 domain and the EF-hand motif. Circular dichroism spectroscopy revealed that the secondary structure of EFHC1C is composed by 34% of alpha-helices and 17% of beta-strands. Size exclusion chromatography and mass spectrometry showed that under oxidizing condition EFHC1C dimerizes through the formation of disulfide bond. Tandem mass spectrometry (MS/MS) analysis of peptides generated by trypsin digestion suggests that the Cys575 is involved in intermolecular S-S bond. In addition, DTNB assay showed that each reduced EFHC1C molecule has one accessible free thiol. Isothermal titration calorimetry (ITC) showed that while the interaction between Ca(2+) and EFHC1C is enthalpically driven (DeltaH=-58.6 to -67 kJ/mol and TDeltaS=-22.5 to -31 kJ/mol) the interaction between Mg(2+) and EFHC1C involves an entropic gain, and is approximately 5 times less enthalpically favorable (DeltaH=-11.7 to -14 kJ/mol and TDeltaS=21.9 to 19 kJ/mol) than for Ca(2+) binding. It was also found that under reducing condition Ca(2+) or Mg(2+) ions bind to EFHC1C in a 1/1 molar ratio, while under oxidizing condition this ratio is reduced, showing that EFHC1C dimerization blocks Ca(2+) and Mg(2+) binding.
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PMID:Characterization of the C-terminal half of human juvenile myoclonic epilepsy protein EFHC1: dimer formation blocks Ca2+ and Mg2+ binding to its functional EF-hand. 1859 66