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Abstract
Extracellular proteases can activate the epithelial Na channel (ENaC) by cleavage of the γ subunit. Here, we investigated the cleavage state of the channel in the kidneys of mice and rats on a low-salt diet. We identified the cleaved species of channels expressed in Fisher rat thyroid cells by coexpressing the apical membrane-bound protease channel-activating protease 1 (CAP1; prostasin). To compare the peptides produced in the heterologous system with those in the mouse kidney, we treated both lysates with PNGaseF to remove N-linked glycosylation. The apparent molecular mass of the smallest COOH-terminal fragment of γENaC (52 kDa) was indistinguishable from that of the CAP1-induced species in Fisher rat thyroid cells. Similar cleaved peptides were observed in total and cell surface fractions of the rat kidney. This outcome suggests that most of the subunits at the surface have been processed by extracellular proteases. This was confirmed using nonreducing gels, in which the NH2- and COOH-terminal fragments of γENaC are linked by a disulfide bond. Under these conditions, the major cleaved form in the rat kidney had an apparent molecular mass of 56 kDa, ∼4 kDa lower than that of the full-length form, consistent with excision of a short peptide by two proteolytic events. We conclude that the most abundant γENaC species in the apical membrane of rat and mouse kidneys on a low-Na diet is the twice-cleaved, presumably activated form.NEW & NOTEWORTHY We have identified the major aldosterone-dependent cleaved form of the epithelial Na channel (ENaC) γ subunit in the kidney as a twice-cleaved peptide. This form appears to be identical in size with a subunit cleaved in vitro by the extracellular protease channel-activating protease 1 (prostasin). In the absence of reducing agents, it has an overall molecular mass less than that of the intact subunit, consistent with the excision of an inhibitory domain.
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Affiliation(s)
- Gustavo Frindt
- Department of Physiology and Biophysics, Weill Cornell School of Medicine, New York, New York
| | - Shujie Shi
- Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Thomas R Kleyman
- Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.,Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.,Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill Cornell School of Medicine, New York, New York
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Lu TJ, Kan WC, Yang SS, Jiang ST, Wu SN, Ling P, Bao BY, Lin CY, Yang ZY, Weng YP, Chan CH, Lu TL. MST3 is involved in ENaC-mediated hypertension. Am J Physiol Renal Physiol 2019; 317:F30-F42. [PMID: 30969802 DOI: 10.1152/ajprenal.00455.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Liddle syndrome is an inherited form of human hypertension caused by increasing epithelial Na+ channel (ENaC) expression. Increased Na+ retention through ENaC with subsequent volume expansion causes hypertension. In addition to ENaC, the Na+-K+-Cl- cotransporter (NKCC) and Na+-Cl- symporter (NCC) are responsible for Na+ reabsorption in the kidneys. Several Na+ transporters are evolutionarily regulated by the Ste20 kinase family. Ste20-related proline/alanine-rich kinase and oxidative stress-responsive kinase-1 phosphorylate downstream NKCC2 and NCC to maintain Na+ and blood pressure (BP) homeostasis. Mammalian Ste20 kinase 3 (MST3) is another member of the Ste20 family. We previously reported that reduced MST3 levels were found in the kidneys in spontaneously hypertensive rats and that MST3 was involved in Na+ regulation. To determine whether MST3 is involved in BP stability through Na+ regulation, we generated a MST3 hypomorphic mutation and designated MST3+/- and MST3-/- mice to examine BP and serum Na+ and K+ concentrations. MST3-/- mice exhibited hypernatremia, hypokalemia, and hypertension. The increased ENaC in the kidney played roles in hypernatremia. The reabsorption of more Na+ promoted more K+ secretion in the kidney and caused hypokalemia. The hypernatremia and hypokalemia in MST3-/- mice were significantly reversed by the ENaC inhibitor amiloride, indicating that MST3-/- mice reabsorbed more Na+ through ENaC. Furthermore, Madin-Darby canine kidney cells stably expressing kinase-dead MST3 displayed elevated ENaC currents. Both the in vivo and in vitro results indicated that MST3 maintained Na+ homeostasis through ENaC regulation. We are the first to report that MST3 maintains BP stability through ENaC regulation.
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Affiliation(s)
- Te-Jung Lu
- Department of Medical Laboratory Science and Biotechnology, Chung Hwa University of Medical Technology , Tainan , Taiwan
| | - Wei-Chih Kan
- Department of Nephrology, Chi-Mei Medical Center , Tainan , Taiwan.,Department of Biological Science and Technology, Chung Hwa University of Medical Technology , Tainan , Taiwan
| | - Sung-Sen Yang
- Division of Nephrology, Department of Medicine, Tri-service General Hospital, Graduate Institute of Medical Sciences, National Defense Medical Center , Taipei , Taiwan
| | - Si-Tse Jiang
- Department of Research and Development, National Laboratory Animal Center, National Applied Research Laboratories , Tainan , Taiwan
| | - Sheng-Nan Wu
- Department of Physiology, College of Medicine, National Cheng Kung University , Tainan , Taiwan
| | - Pin Ling
- Department of Physiology, College of Medicine, National Cheng Kung University , Tainan , Taiwan.,Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University , Tainan , Taiwan
| | - Bo-Ying Bao
- School of Pharmacy, China Medical University , Taichung , Taiwan
| | - Chia-Yu Lin
- Department of Medical Laboratory Science and Biotechnology, China Medical University , Taichung , Taiwan
| | - Zin-Ya Yang
- Department of Medical Laboratory Science and Biotechnology, China Medical University , Taichung , Taiwan
| | - Yui-Ping Weng
- Department of Biological Science and Technology, Chung Hwa University of Medical Technology , Tainan , Taiwan
| | - Chee-Hong Chan
- Department of Nephrology, Chang Bing Show Chwan Memorial Hospital, Lukang, Changhua, Taiwan
| | - Te Ling Lu
- School of Pharmacy, China Medical University , Taichung , Taiwan
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Alli A, Yu L, Holzworth M, Richards J, Cheng KY, Lynch IJ, Wingo CS, Gumz ML. Direct and indirect inhibition of the circadian clock protein Per1: effects on ENaC and blood pressure. Am J Physiol Renal Physiol 2019; 316:F807-F813. [PMID: 30759025 DOI: 10.1152/ajprenal.00408.2018] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Circadian rhythms govern physiological functions and are important for overall health. The molecular circadian clock comprises several transcription factors that mediate circadian control of physiological function, in part, by regulating gene expression in a tissue-specific manner. These connections are well established, but the underlying mechanisms are incompletely understood. The overall goal of this study was to examine the connection among the circadian clock protein Period 1 (Per1), epithelial Na+ channel (ENaC), and blood pressure (BP) using a multipronged approach. Using global Per1 knockout mice on a 129/sv background in combination with a high-salt diet plus mineralocorticoid treatment, we demonstrated that loss of Per1 in this setting is associated with protection from hypertension. Next, we used the ENaC inhibitor benzamil to demonstrate a role for ENaC in BP regulation and urinary Na+ excretion in 129/sv mice. We targeted Per1 indirectly using pharmacological inhibition of Per1 nuclear entry in vivo to demonstrate altered expression of known Per1 target genes as well as a BP-lowering effect in 129/sv mice. Finally, we directly inhibited Per1 via genetic knockdown in amphibian distal nephron cells to demonstrate, for the first time, that reduced Per1 expression is associated with decreased ENaC activity at the single channel level.
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Affiliation(s)
- Abdel Alli
- Department of Physiology and Functional Genomics, University of Florida , Gainesville, Florida.,Division of Nephrology, Hypertension, and Renal Transplantation, Department of Medicine, University of Florida , Gainesville, Florida
| | - Ling Yu
- Department of Physiology and Functional Genomics, University of Florida , Gainesville, Florida.,College of Resources and Environmental Sciences, Nanjing Agricultural University , Nanjing , China
| | - Meaghan Holzworth
- Division of Nephrology, Hypertension, and Renal Transplantation, Department of Medicine, University of Florida , Gainesville, Florida
| | - Jacob Richards
- Division of Nephrology, Hypertension, and Renal Transplantation, Department of Medicine, University of Florida , Gainesville, Florida
| | - Kit-Yan Cheng
- Division of Nephrology, Hypertension, and Renal Transplantation, Department of Medicine, University of Florida , Gainesville, Florida.,North Florida/South Georgia Veterans Affairs Medical Center , Gainesville, Florida
| | - I Jeanette Lynch
- Division of Nephrology, Hypertension, and Renal Transplantation, Department of Medicine, University of Florida , Gainesville, Florida.,North Florida/South Georgia Veterans Affairs Medical Center , Gainesville, Florida
| | - Charles S Wingo
- Department of Physiology and Functional Genomics, University of Florida , Gainesville, Florida.,Division of Nephrology, Hypertension, and Renal Transplantation, Department of Medicine, University of Florida , Gainesville, Florida.,North Florida/South Georgia Veterans Affairs Medical Center , Gainesville, Florida
| | - Michelle L Gumz
- Division of Nephrology, Hypertension, and Renal Transplantation, Department of Medicine, University of Florida , Gainesville, Florida.,North Florida/South Georgia Veterans Affairs Medical Center , Gainesville, Florida.,Department of Biochemistry and Molecular Biology, University of Florida , Gainesville, Florida
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