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Pratt SJP, Plunkett CM, Kuzu G, Trinh T, Barbara J, Choconta P, Quackenbush D, Huynh T, Smith A, Barnes SW, New J, Pierce J, Walker JR, Mainquist J, King FJ, Elliott J, Hammack S, Decker RS. A high throughput cell stretch device for investigating mechanobiology in vitro. APL Bioeng 2024; 8:026129. [PMID: 38938688 PMCID: PMC11210978 DOI: 10.1063/5.0206852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Accepted: 05/31/2024] [Indexed: 06/29/2024] Open
Abstract
Mechanobiology is a rapidly advancing field, with growing evidence that mechanical signaling plays key roles in health and disease. To accelerate mechanobiology-based drug discovery, novel in vitro systems are needed that enable mechanical perturbation of cells in a format amenable to high throughput screening. Here, both a mechanical stretch device and 192-well silicone flexible linear stretch plate were designed and fabricated to meet high throughput technology needs for cell stretch-based applications. To demonstrate the utility of the stretch plate in automation and screening, cell dispensing, liquid handling, high content imaging, and high throughput sequencing platforms were employed. Using this system, an assay was developed as a biological validation and proof-of-concept readout for screening. A mechano-transcriptional stretch response was characterized using focused gene expression profiling measured by RNA-mediated oligonucleotide Annealing, Selection, and Ligation with Next-Gen sequencing. Using articular chondrocytes, a gene expression signature containing stretch responsive genes relevant to cartilage homeostasis and disease was identified. The possibility for integration of other stretch sensitive cell types (e.g., cardiovascular, airway, bladder, gut, and musculoskeletal), in combination with alternative phenotypic readouts (e.g., protein expression, proliferation, or spatial alignment), broadens the scope of high throughput stretch and allows for wider adoption by the research community. This high throughput mechanical stress device fills an unmet need in phenotypic screening technology to support drug discovery in mechanobiology-based disease areas.
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Affiliation(s)
- Stephen J. P. Pratt
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | | | - Guray Kuzu
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - Ton Trinh
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - Joshua Barbara
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - Paula Choconta
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - Doug Quackenbush
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - Truc Huynh
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - Anders Smith
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - S. Whitney Barnes
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - Joel New
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - James Pierce
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - John R. Walker
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - James Mainquist
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - Frederick J. King
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - Jimmy Elliott
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - Scott Hammack
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
| | - Rebekah S. Decker
- Novartis, Biomedical Research 10675 John Jay Hopkins Dr, San Diego, California 92121, USA
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Davis MJ, Zawieja SD. Pacemaking in the lymphatic system. J Physiol 2024. [PMID: 38520402 DOI: 10.1113/jp284752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 02/08/2024] [Indexed: 03/25/2024] Open
Abstract
Lymphatic collecting vessels exhibit spontaneous phasic contractions that are critical for lymph propulsion and tissue fluid homeostasis. This rhythmic activity is driven by action potentials conducted across the lymphatic muscle cell (LMC) layer to produce entrained contractions. The contraction frequency of a lymphatic collecting vessel displays exquisite mechanosensitivity, with a dynamic range from <1 to >20 contractions per minute. A myogenic pacemaker mechanism intrinsic to the LMCs was initially postulated to account for pressure-dependent chronotropy. Further interrogation into the cellular constituents of the lymphatic vessel wall identified non-muscle cell populations that shared some characteristics with interstitial cells of Cajal, which have pacemaker functions in the gastrointestinal and lower urinary tracts, thus raising the possibility of a non-muscle cell pacemaker. However, recent genetic knockout studies in mice support LMCs and a myogenic origin of the pacemaker activity. LMCs exhibit stochastic, but pressure-sensitive, sarcoplasmic reticulum calcium release (puffs and waves) from IP3R1 receptors, which couple to the calcium-activated chloride channel Anoctamin 1, causing depolarisation. The resulting electrical activity integrates across the highly coupled lymphatic muscle electrical syncytia through connexin 45 to modulate diastolic depolarisation. However, multiple other cation channels may also contribute to the ionic pacemaking cycle. Upon reaching threshold, a voltage-gated calcium channel-dependent action potential fires, resulting in a nearly synchronous calcium global calcium flash within the LMC layer to drive an entrained contraction. This review summarizes the key ion channels potentially responsible for the pressure-dependent chronotropy of lymphatic collecting vessels and various mechanisms of IP3R1 regulation that could contribute to frequency tuning.
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Affiliation(s)
- Michael J Davis
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, USA
| | - Scott D Zawieja
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, USA
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Tang J, Yu W, Lin L, Yang R, Li G, Jin M, Gu Y, Jiang B, Lu E. Role of αENaC in root resorption of adjacent teeth due to entirely impacted mandibular third molars. BMC Oral Health 2024; 24:360. [PMID: 38515079 PMCID: PMC10956368 DOI: 10.1186/s12903-024-04040-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Accepted: 02/17/2024] [Indexed: 03/23/2024] Open
Abstract
BACKGROUND Entirely impacted mandibular third molar (EIM3M) concerns the pathological external root resorption (ERR) of the adjacent mandibular second molar (M2M) and formation of granulation tissue between two molars. The study aimed to clarify the effect of αENaC, a mechano-sensitive molecule, to explore the mechanical mechanism in this scenario. METHODS The force EIM3M exerted on M2M was proved by finite element analysis. αENaC expressions were tested by real-time polymerase chain reaction (PCR), immunoblotting and immunofluorescence. Inflammatory and epithelial-mesenchymal transition (EMT)-related molecules expressions were also detected by real-time PCR. The correlation was analyzed by Spearman's correlation analysis, and receiver-operator characteristic (ROC) curve was further exhibited. RESULTS The force was concentrated in the ERR area. αENaC was upregulated, positively correlated with ERR degree and localized to the fibroblasts in ERR granulation tissues. Moreover, αENaC was respectively and positively associated with elevated TNF-α and N-cadherin in ERR granulation tissues. More importantly, ROC analysis verified αENaC as a novel indication of the incidence of this disease. CONCLUSIONS Our finding revealed the force from EIM3M causing ERR of M2M, and elucidated the expression and localization of αENaC and its positive correlation with inflammation, EMT and disease severity, suggesting a novel indication in this disease.
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Affiliation(s)
- Jiaqi Tang
- Department of Stomatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, 160 Pujian Road, Shanghai, 200127, China
| | - Weijun Yu
- Department of Stomatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, 160 Pujian Road, Shanghai, 200127, China
| | - Lu Lin
- Department of Stomatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, 160 Pujian Road, Shanghai, 200127, China
| | - Ruhan Yang
- Department of Stomatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, 160 Pujian Road, Shanghai, 200127, China
| | - Guanglong Li
- Department of Stomatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, 160 Pujian Road, Shanghai, 200127, China
| | - Min Jin
- Department of Stomatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, 160 Pujian Road, Shanghai, 200127, China
| | - Yuting Gu
- Department of Stomatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, 160 Pujian Road, Shanghai, 200127, China.
| | - Bin Jiang
- Department of Stomatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, 160 Pujian Road, Shanghai, 200127, China.
| | - Eryi Lu
- Department of Stomatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, 160 Pujian Road, Shanghai, 200127, China.
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Carrisoza-Gaytan R, Mutchler SM, Carattino F, Soong J, Dalghi MG, Wu P, Wang W, Apodaca G, Satlin LM, Kleyman TR. PIEZO1 is a distal nephron mechanosensor and is required for flow-induced K+ secretion. J Clin Invest 2024; 134:e174806. [PMID: 38426496 PMCID: PMC10904061 DOI: 10.1172/jci174806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 01/02/2024] [Indexed: 03/02/2024] Open
Abstract
Ca2+-activated BK channels in renal intercalated cells (ICs) mediate luminal flow-induced K+ secretion (FIKS), but how ICs sense increased flow remains uncertain. We examined whether PIEZO1, a mechanosensitive Ca2+-permeable channel expressed in the basolateral membranes of ICs, is required for FIKS. In isolated cortical collecting ducts (CCDs), the mechanosensitive cation-selective channel inhibitor GsMTx4 dampened flow-induced increases in intracellular Ca2+ concentration ([Ca2+]i), whereas the PIEZO1 activator Yoda1 increased [Ca2+]i and BK channel activity. CCDs from mice fed a high-K+ (HK) diet exhibited a greater Yoda1-dependent increase in [Ca2+]i than CCDs from mice fed a control K+ diet. ICs in CCDs isolated from mice with a targeted gene deletion of Piezo1 in ICs (IC-Piezo1-KO) exhibited a blunted [Ca2+]i response to Yoda1 or increased flow, with an associated loss of FIKS in CCDs. Male IC-Piezo1-KO mice selectively exhibited an increased blood [K+] in response to an oral K+ bolus and blunted urinary K+ excretion following a volume challenge. Whole-cell expression of BKα subunit was reduced in ICs of IC-Piezo1-KO mice fed an HK diet. We conclude that PIEZO1 mediates flow-induced basolateral Ca2+ entry into ICs, is upregulated in the CCD in response to an HK diet, and is necessary for FIKS.
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Affiliation(s)
| | | | - Francisco Carattino
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Joanne Soong
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Marianela G. Dalghi
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Peng Wu
- Department of Nephrology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - WenHui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York, USA
| | - Gerard Apodaca
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Cell Biology and
| | - Lisa M. Satlin
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Thomas R. Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Cell Biology and
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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Lemmens-Gruber R, Tzotzos S. The Epithelial Sodium Channel-An Underestimated Drug Target. Int J Mol Sci 2023; 24:ijms24097775. [PMID: 37175488 PMCID: PMC10178586 DOI: 10.3390/ijms24097775] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 04/14/2023] [Accepted: 04/15/2023] [Indexed: 05/15/2023] Open
Abstract
Epithelial sodium channels (ENaC) are part of a complex network of interacting biochemical pathways and as such are involved in several disease states. Dependent on site and type of mutation, gain- or loss-of-function generated symptoms occur which span from asymptomatic to life-threatening disorders such as Liddle syndrome, cystic fibrosis or generalized pseudohypoaldosteronism type 1. Variants of ENaC which are implicated in disease assist further understanding of their molecular mechanisms in order to create models for specific pharmacological targeting. Identification and characterization of ENaC modifiers not only furthers our basic understanding of how these regulatory processes interact, but also enables discovery of new therapeutic targets for the disease conditions caused by ENaC dysfunction. Numerous test compounds have revealed encouraging results in vitro and in animal models but less in clinical settings. The EMA- and FDA-designated orphan drug solnatide is currently being tested in phase 2 clinical trials in the setting of acute respiratory distress syndrome, and the NOX1/ NOX4 inhibitor setanaxib is undergoing clinical phase 2 and 3 trials for therapy of primary biliary cholangitis, liver stiffness, and carcinoma. The established ENaC blocker amiloride is mainly used as an add-on drug in the therapy of resistant hypertension and is being studied in ongoing clinical phase 3 and 4 trials for special applications. This review focuses on discussing some recent developments in the search for novel therapeutic agents.
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Affiliation(s)
- Rosa Lemmens-Gruber
- Department of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, University of Vienna, A-1090 Vienna, Austria
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6
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Davis MJ, Earley S, Li YS, Chien S. Vascular mechanotransduction. Physiol Rev 2023; 103:1247-1421. [PMID: 36603156 PMCID: PMC9942936 DOI: 10.1152/physrev.00053.2021] [Citation(s) in RCA: 43] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 09/26/2022] [Accepted: 10/04/2022] [Indexed: 01/07/2023] Open
Abstract
This review aims to survey the current state of mechanotransduction in vascular smooth muscle cells (VSMCs) and endothelial cells (ECs), including their sensing of mechanical stimuli and transduction of mechanical signals that result in the acute functional modulation and longer-term transcriptomic and epigenetic regulation of blood vessels. The mechanosensors discussed include ion channels, plasma membrane-associated structures and receptors, and junction proteins. The mechanosignaling pathways presented include the cytoskeleton, integrins, extracellular matrix, and intracellular signaling molecules. These are followed by discussions on mechanical regulation of transcriptome and epigenetics, relevance of mechanotransduction to health and disease, and interactions between VSMCs and ECs. Throughout this review, we offer suggestions for specific topics that require further understanding. In the closing section on conclusions and perspectives, we summarize what is known and point out the need to treat the vasculature as a system, including not only VSMCs and ECs but also the extracellular matrix and other types of cells such as resident macrophages and pericytes, so that we can fully understand the physiology and pathophysiology of the blood vessel as a whole, thus enhancing the comprehension, diagnosis, treatment, and prevention of vascular diseases.
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Affiliation(s)
- Michael J Davis
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri
| | - Scott Earley
- Department of Pharmacology, University of Nevada, Reno, Nevada
| | - Yi-Shuan Li
- Department of Bioengineering, University of California, San Diego, California
- Institute of Engineering in Medicine, University of California, San Diego, California
| | - Shu Chien
- Department of Bioengineering, University of California, San Diego, California
- Institute of Engineering in Medicine, University of California, San Diego, California
- Department of Medicine, University of California, San Diego, California
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7
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Rapid shear stress-dependent ENaC membrane insertion is mediated by the endothelial glycocalyx and the mineralocorticoid receptor. Cell Mol Life Sci 2022; 79:235. [PMID: 35397686 PMCID: PMC8995297 DOI: 10.1007/s00018-022-04260-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 03/02/2022] [Accepted: 03/18/2022] [Indexed: 02/08/2023]
Abstract
The contribution of the shear stress-sensitive epithelial Na+ channel (ENaC) to the mechanical properties of the endothelial cell surface under (patho)physiological conditions is unclear. This issue was addressed in in vivo and in vitro models for endothelial dysfunction. Cultured human umbilical vein endothelial cells (HUVEC) were exposed to laminar (LSS) or non-laminar shear stress (NLSS). ENaC membrane insertion was quantified using Quantum-dot-based immunofluorescence staining and the mechanical properties of the cell surface were probed with the Atomic Force Microscope (AFM) in vitro and ex vivo in isolated aortae of C57BL/6 and ApoE/LDLR-/- mice. Flow- and acetylcholine-mediated vasodilation was measured in vivo using magnetic resonance imaging. Acute LSS led to a rapid mineralocorticoid receptor (MR)-dependent membrane insertion of ENaC and subsequent stiffening of the endothelial cortex caused by actin polymerization. Of note, NLSS stress further augmented the cortical stiffness of the cells. These effects strongly depend on the presence of the endothelial glycocalyx (eGC) and could be prevented by functional inhibition of ENaC and MR in vitro endothelial cells and ex vivo endothelial cells derived from C57BL/6, but not ApoE/LDLR-/- vessel. In vivo In C57BL/6 vessels, ENaC- and MR inhibition blunted flow- and acetylcholine-mediated vasodilation, while in the dysfunctional ApoE/LDLR-/- vessels, this effect was absent. In conclusion, under physiological conditions, endothelial ENaC, together with the glycocalyx, was identified as an important shear stress sensor and mediator of endothelium-dependent vasodilation. In contrast, in pathophysiological conditions, ENaC-mediated mechanotransduction and endothelium-dependent vasodilation were lost, contributing to sustained endothelial stiffening and dysfunction.
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8
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Fronius M. Epithelial Na+ channel and the glycocalyx: a sweet and salty relationship for arterial shear stress sensing. Curr Opin Nephrol Hypertens 2022; 31:142-150. [PMID: 34966089 DOI: 10.1097/mnh.0000000000000779] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW The ability of endothelial cells to sense mechanical force, and shear stress in particular, is crucial for normal vascular function. This relies on an intact endothelial glycocalyx that facilitates the production of nitric oxide (NO). An emerging arterial shear stress sensor is the epithelial Na+ channel (ENaC). This review highlights existing and new evidence for the interdependent activity of the glycocalyx and ENaC and its implications for vascular function. RECENT FINDINGS New evidence suggests that the glycocalyx and ENaC are physically connected and that this is important for shear stress sensing. The connection relies on N-glycans attached to glycosylated asparagines of α-ENaC. Removal of specific N-glycans reduced ENaC's shear stress response. Similar effects were observed following degradation of the glycocalyx. Endothelial specific viral transduction of α-ENaC increased blood pressure (∼40 mmHg). This increase was attenuated in animals transduced with an α-ENaC version lacking N-glycans. SUMMARY These observations indicate that ENaC is connected to the glycocalyx and their activity is interdependent to facilitate arterial shear stress sensation. Future research focusing on how N-glycans mediate this interaction can provide new insights for the understanding of vascular function in health and disease.
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Affiliation(s)
- Martin Fronius
- Department of Physiology, School of Biomedical Sciences
- HeartOtago, University of Otago, Dunedin
- Healthy Hearts Aotearoa New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, Centre of Research Excellence, Auckland, New Zealand
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9
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Jia Q, Yang Y, Chen X, Yao S, Hu Z. Emerging roles of mechanosensitive ion channels in acute lung injury/acute respiratory distress syndrome. Respir Res 2022; 23:366. [PMID: 36539808 PMCID: PMC9764320 DOI: 10.1186/s12931-022-02303-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 12/16/2022] [Indexed: 12/24/2022] Open
Abstract
Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a devastating respiratory disorder with high rates of mortality and morbidity, but the detailed underlying mechanisms of ALI/ARDS remain largely unknown. Mechanosensitive ion channels (MSCs), including epithelial sodium channel (ENaC), Piezo channels, transient receptor potential channels (TRPs), and two-pore domain potassium ion (K2P) channels, are highly expressed in lung tissues, and the activity of these MSCs can be modulated by mechanical forces (e.g., mechanical ventilation) and other stimuli (e.g., LPS, hyperoxia). Dysfunction of MSCs has been found in various types of ALI/ARDS, and MSCs play a key role in regulating alveolar fluid clearance, alveolar epithelial/endothelial barrier function, the inflammatory response and surfactant secretion in ALI/ARDS lungs. Targeting MSCs exerts therapeutic effects in the treatment of ALI/ARDS. In this review, we summarize the structure and functions of several well-recognized MSCs, the role of MSCs in the pathogenesis of ALI/ARDS and recent advances in the pharmacological and molecular modulation of MSCs in the treatment of ALI/ARDS. According to the current literature, targeting MSCs might be a very promising therapeutic approach against ALI/ARDS.
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Affiliation(s)
- Qi Jia
- grid.33199.310000 0004 0368 7223Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yiyi Yang
- grid.33199.310000 0004 0368 7223Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xiangdong Chen
- grid.33199.310000 0004 0368 7223Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Shanglong Yao
- grid.33199.310000 0004 0368 7223Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhiqiang Hu
- grid.33199.310000 0004 0368 7223Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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10
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Gettings SM, Maxeiner S, Tzika M, Cobain MRD, Ruf I, Benseler F, Brose N, Krasteva-Christ G, Vande Velde G, Schönberger M, Althaus M. Two functional epithelial sodium channel isoforms are present in rodents despite pronounced evolutionary pseudogenisation and exon fusion. Mol Biol Evol 2021; 38:5704-5725. [PMID: 34491346 PMCID: PMC8662647 DOI: 10.1093/molbev/msab271] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The epithelial sodium channel (ENaC) plays a key role in salt and water homeostasis in
tetrapod vertebrates. There are four ENaC subunits (α, β, γ, δ), forming heterotrimeric
αβγ- or δβγ-ENaCs. Although the physiology of αβγ-ENaC is well understood, for decades the
field has stalled with respect to δβγ-ENaC due to the lack of mammalian model organisms.
The SCNN1D gene coding for δ-ENaC was previously believed to be absent in
rodents, hindering studies using standard laboratory animals. We analyzed all currently
available rodent genomes and discovered that SCNN1D is present in rodents
but was independently lost in five rodent lineages, including the Muridae (mice and rats).
The independent loss of SCNN1D in rodent lineages may be constrained by
phylogeny and taxon-specific adaptation to dry habitats, however habitat aridity does not
provide a selection pressure for maintenance of SCNN1D across Rodentia. A
fusion of two exons coding for a structurally flexible region in the extracellular domain
of δ-ENaC appeared in the Hystricognathi (a group that includes guinea pigs). This
conserved pattern evolved at least 41 Ma and represents a new autapomorphic feature for
this clade. Exon fusion does not impair functionality of guinea pig (Cavia
porcellus) δβγ-ENaC expressed in Xenopus oocytes.
Electrophysiological characterization at the whole-cell and single-channel level revealed
conserved biophysical features and mechanisms controlling guinea pig αβγ- and δβγ-ENaC
function as compared with human orthologs. Guinea pigs therefore represent commercially
available mammalian model animals that will help shed light on the physiological function
of δ-ENaC.
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Affiliation(s)
- Sean M Gettings
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom.,Biomedical Imaging, Department of Imaging and Pathology, Faculty of Medicine, KU Leuven, Belgium
| | - Stephan Maxeiner
- Institute for Anatomy and Cell Biology, Saarland University School of Medicine, Homburg, Germany
| | - Maria Tzika
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Matthew R D Cobain
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Irina Ruf
- Division of Messel Research and Mammalogy, Senckenberg Research Institute and Natural History Museum Frankfurt, Frankfurt am Main, Germany
| | - Fritz Benseler
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Gabriela Krasteva-Christ
- Institute for Anatomy and Cell Biology, Saarland University School of Medicine, Homburg, Germany
| | - Greetje Vande Velde
- Biomedical Imaging, Department of Imaging and Pathology, Faculty of Medicine, KU Leuven, Belgium
| | - Matthias Schönberger
- Biomedical Imaging, Department of Imaging and Pathology, Faculty of Medicine, KU Leuven, Belgium
| | - Mike Althaus
- Institute for Functional Gene Analytics, Department of Natural Sciences, Bonn-Rhein-Sieg University of Applied Sciences, Rheinbach, Germany
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11
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Roy Choudhury A, Großhans J, Kong D. Ion Channels in Epithelial Dynamics and Morphogenesis. Cells 2021; 10:cells10092280. [PMID: 34571929 PMCID: PMC8465836 DOI: 10.3390/cells10092280] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 08/22/2021] [Accepted: 08/30/2021] [Indexed: 01/21/2023] Open
Abstract
Mechanosensitive ion channels mediate the neuronal sensation of mechanical signals such as sound, touch, and pain. Recent studies point to a function of these channel proteins in cell types and tissues in addition to the nervous system, such as epithelia, where they have been little studied, and their role has remained elusive. Dynamic epithelia are intrinsically exposed to mechanical forces. A response to pull and push is assumed to constitute an essential part of morphogenetic movements of epithelial tissues, for example. Mechano-gated channels may participate in sensing and responding to such forces. In this review, focusing on Drosophila, we highlight recent results that will guide further investigations concerned with the mechanistic role of these ion channels in epithelial cells.
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12
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Zhang J, Yuan HK, Chen S, Zhang ZR. Detrimental or beneficial: Role of endothelial ENaC in vascular function. J Cell Physiol 2021; 237:29-48. [PMID: 34279047 DOI: 10.1002/jcp.30505] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 06/29/2021] [Accepted: 07/01/2021] [Indexed: 12/19/2022]
Abstract
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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Affiliation(s)
- Jun Zhang
- School of Biomedical Sciences and Li Ka Shing Institute of Health Science, The Chinese University of Hong Kong, Hong Kong, China
| | - Hui-Kai Yuan
- Department of General Surgery, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Shuo Chen
- Department of Biopharmaceutical Sciences, School of Pharmacy, Harbin Medical University (Daqing), Daqing, China
| | - Zhi-Ren Zhang
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang Key Laboratory for Metabolic Disorder & Cancer Related Cardiovascular Diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
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13
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Bewick GS, Banks RW. Mechanotransduction channels in proprioceptive sensory nerve terminals: still an open question? CURRENT OPINION IN PHYSIOLOGY 2021. [DOI: 10.1016/j.cophys.2020.11.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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14
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Barth D, Knoepp F, Fronius M. Enhanced Shear Force Responsiveness of Epithelial Na + Channel's (ENaC) δ Subunit Following the Insertion of N-Glycosylation Motifs Relies on the Extracellular Matrix. Int J Mol Sci 2021; 22:2500. [PMID: 33801449 PMCID: PMC7958617 DOI: 10.3390/ijms22052500] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 02/23/2021] [Accepted: 02/23/2021] [Indexed: 12/15/2022] Open
Abstract
Members of the Degenerin/epithelial Na+ channel (ENaC) protein family and the extracellular cell matrix (ECM) form a mechanosensitive complex. A core feature of this complex are tethers, which connect the channel with the ECM, however, knowledge about the nature of these tethers is scarce. N-glycans of α ENaC were recently identified as potential tethers but whether N-glycans serve as a ubiquitous feature for mechanosensation processes remains unresolved. The purpose of this study was to reveal whether the addition of N-glycans to δ ENaC-which is less responsive to shear force (SF)-increases its SF-responsiveness and whether this relies on a linkage to the ECM. Therefore, N-glycosylation motifs were introduced via site-directed mutagenesis, the resulting proteins expressed with β and γ ENaC in Xenopus oocytes, and SF-activated currents measured by two-electrode voltage-clamp. The insertion of N-glycosylation motifs increases δ ENaC's SF responsiveness. The inclusion of a glycosylated asparagine (N) at position 487 did increase the molecular mass and provided a channel whose SF response was abolished following ECM degradation via hyaluronidase. This indicates that the addition of N-glycans improves SF-responsiveness and that this effect relies on an intact ECM. These findings further support the role of N-glycans as tethers for mechanotransduction.
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Affiliation(s)
- Daniel Barth
- Institute of Physiology, Rheinisch-Westfälische Technische Hochschule Aachen, 52074 Aachen, Germany;
| | - Fenja Knoepp
- Excellence-Cluster Cardio-Pulmonary Institute, Universities of Giessen and Marburg Lung Center, Member of the German Center for Lung Research, Justus-Liebig University Giessen, 35392 Giessen, Germany;
| | - Martin Fronius
- Department of Physiology and HeartOtago, University of Otago, 9054 Dunedin, New Zealand
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15
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Ware AW, Harris JJ, Slatter TL, Cunliffe HE, McDonald FJ. The epithelial sodium channel has a role in breast cancer cell proliferation. Breast Cancer Res Treat 2021; 187:31-43. [PMID: 33630195 DOI: 10.1007/s10549-021-06133-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Accepted: 02/05/2021] [Indexed: 01/22/2023]
Abstract
PURPOSE Breast cancer is the most common cancer affecting women worldwide with half a million associated deaths annually. Despite a huge global effort, the pathways of breast cancer progression are not fully elucidated. Ion channels have recently emerged as novel regulators of cancer cell proliferation and metastasis. The epithelial sodium channel, ENaC, made up of α, β and γ subunits is well known for its role in Na+ reabsorption in epithelia, but a number of novel roles for ENaC have been described, including potential roles in cancer. A role for ENaC in breast cancer, however, has yet to be described. Therefore, the effects of ENaC level and activity on breast cancer proliferation were investigated. METHODS Through the publicly available SCAN-B dataset associations between αENaC mRNA expression and breast cancer subtypes, proliferation markers and epithelial-mesenchymal transition markers (EMT) were assessed. αENaC expression, through overexpression or siRNA-mediated knockdown, and activity, through the ENaC-specific inhibitor amiloride, were altered in MCF7, T47D, BT549, and MDAMB231 breast cancer cells. MTT and EdU cell proliferation assays were used to determine the effect of these manipulations on breast cancer cell proliferation. RESULTS High αENaC mRNA expression was associated with less aggressive and less proliferative breast cancer subtypes and with reduced expression of proliferation markers. Decreased αENaC expression or activity, in the mesenchymal breast cancer cell lines BT549 and MDAMB231, increased breast cancer cell proliferation. Conversely, increased αENaC expression decreased breast cancer cell proliferation. CONCLUSION αENaC expression is associated with a poor prognosis in breast cancer and is a novel regulator of breast cancer cell proliferation. Taken together, these results identify ENaC as a potential future therapeutic target.
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Affiliation(s)
- Adam W Ware
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Joshua J Harris
- Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Tania L Slatter
- Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Heather E Cunliffe
- Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Fiona J McDonald
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.
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16
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Foote AG, Thibeault SL. Sensory Innervation of the Larynx and the Search for Mucosal Mechanoreceptors. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2021; 64:371-391. [PMID: 33465318 PMCID: PMC8632506 DOI: 10.1044/2020_jslhr-20-00350] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 09/19/2020] [Accepted: 10/28/2020] [Indexed: 05/03/2023]
Abstract
Purpose The larynx is a uniquely situated organ, juxtaposed between the gastrointestinal and respiratory tracts, and endures considerable immunological challenges while providing reflexogenic responses via putative mucosal mechanoreceptor afferents. Laryngeal afferents mediate precise monitoring of sensory events by relay to the internal branch of the superior laryngeal nerve (iSLN). Exposure to a variety of stimuli (e.g., mechanical, chemical, thermal) at the mucosa-airway interface has likely evolved a diverse array of specialized sensory afferents for rapid laryngeal control. Accordingly, mucosal mechanoreceptors in demarcated laryngeal territories have been hypothesized as primary sources of sensory input. The purpose of this article is to provide a tutorial on current evidence for laryngeal afferent receptors in mucosa, the role of mechano-gated ion channels within airway epithelia and mechanisms for mechanoreceptors implicated in laryngeal health and disease. Method An overview was conducted on the distribution and identity of iSLN-mediated afferent receptors in the larynx, with specific focus on mechanoreceptors and their functional roles in airway mucosa. Results/Conclusions Laryngeal somatosensation at the cell and molecular level is still largely unexplored. This tutorial consolidates various animal and human researches, with translational emphasis provided for the importance of mucosal mechanoreceptors to normal and abnormal laryngeal function. Information presented in this tutorial has relevance to both clinical and research arenas. Improved understanding of iSLN innervation and corresponding mechanotransduction events will help shed light upon a variety of pathological reflex responses, including persistent cough, dysphonia, and laryngospasm.
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Affiliation(s)
- Alexander G. Foote
- Division of Otolaryngology–Head and Neck Surgery, University of Wisconsin–Madison
| | - Susan L. Thibeault
- Division of Otolaryngology–Head and Neck Surgery, University of Wisconsin–Madison
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17
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Paudel P, McDonald FJ, Fronius M. The δ subunit of epithelial sodium channel in humans-a potential player in vascular physiology. Am J Physiol Heart Circ Physiol 2020; 320:H487-H493. [PMID: 33275523 DOI: 10.1152/ajpheart.00800.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Vascular epithelial sodium channels (ENaCs) made up of canonical α, β, and γ subunits have attracted more attention recently owing to their physiological role in vascular health and disease. A fourth subunit, δ-ENaC, is expressed in various mammalian species, except mice and rats, which are common animal models for cardiovascular research. Accordingly, δ-ENaC is the least understood subunit. However, the recent discovery of δ subunit in human vascular cells indicates that this subunit may play a significant role in normal/pathological vascular physiology in humans. Channels containing the δ subunit have different biophysical and pharmacological properties compared with channels containing the α subunit, with the potential to alter the vascular function of ENaC in health and disease. Hence, it is important to investigate the expression and function of δ-ENaC in the vasculature to identify whether δ-ENaC is a potential new drug target for the treatment of cardiovascular disease. In this review, we will focus on the existing knowledge of δ-ENaC and implications for vascular physiology and pathophysiology in humans.
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Affiliation(s)
- Puja Paudel
- Department of Physiology, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
| | - Fiona J McDonald
- Department of Physiology, University of Otago, Dunedin, New Zealand
| | - Martin Fronius
- Department of Physiology, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
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18
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Hill MA, Jaisser F, Sowers JR. Role of the vascular endothelial sodium channel activation in the genesis of pathologically increased cardiovascular stiffness. Cardiovasc Res 2020; 118:130-140. [PMID: 33188592 DOI: 10.1093/cvr/cvaa326] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 09/10/2020] [Accepted: 10/26/2020] [Indexed: 12/24/2022] Open
Abstract
Cardiovascular (CV) stiffening represents a complex series of events evolving from pathological changes in individual cells of the vasculature and heart which leads to overt tissue fibrosis. While vascular stiffening occurs naturally with ageing it is accelerated in states of insulin (INS) resistance, such as obesity and type 2 diabetes. CV stiffening is clinically manifested as increased arterial pulse wave velocity and myocardial fibrosis-induced diastolic dysfunction. A key question that remains is how are these events mechanistically linked. In this regard, heightened activation of vascular mineralocorticoid receptors (MR) and hyperinsulinaemia occur in obesity and INS resistance states. Further, a downstream mediator of MR and INS receptor activation, the endothelial cell Na+ channel (EnNaC), has recently been identified as a key molecular determinant of endothelial dysfunction and CV fibrosis and stiffening. Increased activity of the EnNaC results in a number of negative consequences including stiffening of the cortical actin cytoskeleton in endothelial cells, impaired endothelial NO release, increased oxidative stress-meditated NO destruction, increased vascular permeability, and stimulation of an inflammatory environment. Such endothelial alterations impact vascular function and stiffening through regulation of vascular tone and stimulation of tissue remodelling including fibrosis. In the case of the heart, obesity and INS resistance are associated with coronary vascular endothelial stiffening and associated reductions in bioavailable NO leading to heart failure with preserved systolic function (HFpEF). After a brief discussion on mechanisms leading to vascular stiffness per se, this review then focuses on recent findings regarding the role of INS and aldosterone to enhance EnNaC activity and associated CV stiffness in obesity/INS resistance states. Finally, we discuss how coronary artery-mediated EnNaC activation may lead to cardiac fibrosis and HFpEF, a condition that is especially pronounced in obese and diabetic females.
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Affiliation(s)
- Michael A Hill
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, USA.,Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, 134 Research Park Drive, Columbia, MO 65212, USA
| | - Frederic Jaisser
- Centre de Recherche des Cordeliers, Sorbonne Université, INSERM, Université de Paris, F-75006 Paris, France
| | - James R Sowers
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, USA.,Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, 134 Research Park Drive, Columbia, MO 65212, USA.,Diabetes and Cardiovascular Center, University of Missouri School of Medicine, Columbia, MO 65212, USA.,Department of Medicine, University of Missouri School of Medicine, Columbia, MO 65212, USA
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19
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Carr JMJR, Hoiland RL, Caldwell HG, Coombs GB, Howe CA, Tremblay JC, Green DJ, Ainslie PN. Internal carotid and brachial artery shear‐dependent vasodilator function in young healthy humans. J Physiol 2020; 598:5333-5350. [DOI: 10.1113/jp280369] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 09/07/2020] [Indexed: 12/12/2022] Open
Affiliation(s)
- Jay M. J. R. Carr
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia – Okanagan Campus Kelowna British Columbia Canada
| | - Ryan L. Hoiland
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia – Okanagan Campus Kelowna British Columbia Canada
- Department of Anesthesiology Pharmacology and Therapeutics Vancouver General Hospital University of British Columbia Vancouver British Columbia Canada
| | - Hannah G. Caldwell
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia – Okanagan Campus Kelowna British Columbia Canada
| | - Geoff B. Coombs
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia – Okanagan Campus Kelowna British Columbia Canada
| | - Connor A. Howe
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia – Okanagan Campus Kelowna British Columbia Canada
| | - Joshua C. Tremblay
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia – Okanagan Campus Kelowna British Columbia Canada
| | - Daniel J. Green
- School of Human Sciences (Sport and Exercise Sciences) The University of Western Australia Crawley Western Australia Australia
| | - Philip N. Ainslie
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia – Okanagan Campus Kelowna British Columbia Canada
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20
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Wichmann L, Althaus M. Evolution of epithelial sodium channels: current concepts and hypotheses. Am J Physiol Regul Integr Comp Physiol 2020; 319:R387-R400. [PMID: 32783689 DOI: 10.1152/ajpregu.00144.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The conquest of freshwater and terrestrial habitats was a key event during vertebrate evolution. Occupation of low-salinity and dry environments required significant osmoregulatory adaptations enabling stable ion and water homeostasis. Sodium is one of the most important ions within the extracellular liquid of vertebrates, and molecular machinery for urinary reabsorption of this electrolyte is critical for the maintenance of body osmoregulation. Key ion channels involved in the fine-tuning of sodium homeostasis in tetrapod vertebrates are epithelial sodium channels (ENaCs), which allow the selective influx of sodium ions across the apical membrane of epithelial cells lining the distal nephron or the colon. Furthermore, ENaC-mediated sodium absorption across tetrapod lung epithelia is crucial for the control of liquid volumes lining the pulmonary surfaces. ENaCs are vertebrate-specific members of the degenerin/ENaC family of cation channels; however, there is limited knowledge on the evolution of ENaC within this ion channel family. This review outlines current concepts and hypotheses on ENaC phylogeny and discusses the emergence of regulation-defining sequence motifs in the context of osmoregulatory adaptations during tetrapod terrestrialization. In light of the distinct regulation and expression of ENaC isoforms in tetrapod vertebrates, we discuss the potential significance of ENaC orthologs in osmoregulation of fishes as well as the putative fates of atypical channel isoforms in mammals. We hypothesize that ancestral proton-sensitive ENaC orthologs might have aided the osmoregulatory adaptation to freshwater environments whereas channel regulation by proteases evolved as a molecular adaptation to lung liquid homeostasis in terrestrial tetrapods.
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Affiliation(s)
- Lukas Wichmann
- Institute for Animal Physiology, Justus Liebig University, Giessen, Germany
| | - Mike Althaus
- Department of Natural Sciences, Bonn-Rhein-Sieg University of Applied Sciences, Rheinbach, Germany
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21
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Baldin JP, Barth D, Fronius M. Epithelial Na + Channel (ENaC) Formed by One or Two Subunits Forms Functional Channels That Respond to Shear Force. Front Physiol 2020; 11:141. [PMID: 32256376 PMCID: PMC7090232 DOI: 10.3389/fphys.2020.00141] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 02/11/2020] [Indexed: 12/19/2022] Open
Abstract
Canonical epithelial sodium channels (ENaCs) are heterotrimers formed by α, β, and γ ENaC subunits in vertebrates and belong to the Degenerin/ENaC family of proteins. Proteins from this family form mechanosensitive channels throughout the animal kingdom. Activity of canonical ENaC is regulated by shear force (SF) mediating Na+ absorption in the kidney and vascular tone of arteries. Expression analysis suggests that non-canonical ENaC, formed by single or only two subunits, exist in certain tissues, but it is unknown if these channels respond to SF. α, β, γ, and δ ENaC subunits were expressed either alone or in combinations of two subunits in Xenopus oocytes. Amiloride-sensitive currents and the responses to SF were assessed using two-electrode voltage clamp recordings. With the exception of γ ENaC, all homomeric channels provided amiloride-sensitive currents and responded to SF applied via a fluid stream directed onto the oocytes. Channels containing two subunits were also activated by SF. Here, the presence of the γ ENaC subunit when co-expressed with α or δ augmented the SF response in comparison to the αβγ/δβγ ENaC. Overall, we provide evidence that non-canonical ENaC can form channels that respond to SF. This supports a potential function of non-canonical ENaC as mechanosensors in epithelial, vascular, and sensory cells.
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Affiliation(s)
- Jan-Peter Baldin
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Daniel Barth
- Institute of Physiology, Rheinisch-Westfälische Technische Hochschule Aachen University, Aachen, Germany
| | - Martin Fronius
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
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22
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Verschuren EHJ, Castenmiller C, Peters DJM, Arjona FJ, Bindels RJM, Hoenderop JGJ. Sensing of tubular flow and renal electrolyte transport. Nat Rev Nephrol 2020; 16:337-351. [DOI: 10.1038/s41581-020-0259-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/06/2020] [Indexed: 02/06/2023]
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23
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Shear force sensing of epithelial Na + channel (ENaC) relies on N-glycosylated asparagines in the palm and knuckle domains of αENaC. Proc Natl Acad Sci U S A 2019; 117:717-726. [PMID: 31871197 PMCID: PMC6955349 DOI: 10.1073/pnas.1911243117] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The ability to sense mechanical forces is essential for all living organisms. Extracellular tethers have been proposed to mediate mechanical activation of channels belonging to the epithelial Na+ channel (ENaC)/degenerin protein family. The nature and architecture of the tethers that link the channel protein with the extracellular matrix are unknown. Our study provides experimental evidence that glycosylated asparagines and their N-glycans are part of tethers for mechanical activation of ENaC by shear force. The identified asparagines are also important for arterial blood pressure regulation in vivo. These findings provide insights into how mechanical forces are sensed by mechanosensitive ENaC channels to regulate blood pressure. Mechanosensitive ion channels are crucial for normal cell function and facilitate physiological function, such as blood pressure regulation. So far little is known about the molecular mechanisms of how channels sense mechanical force. Canonical vertebrate epithelial Na+ channel (ENaC) formed by α-, β-, and γ-subunits is a shear force (SF) sensor and a member of the ENaC/degenerin protein family. ENaC activity in epithelial cells contributes to electrolyte/fluid-homeostasis and blood pressure regulation. Furthermore, ENaC in endothelial cells mediates vascular responsiveness to regulate blood pressure. Here, we provide evidence that ENaC’s ability to mediate SF responsiveness relies on the “force-from-filament” principle involving extracellular tethers and the extracellular matrix (ECM). Two glycosylated asparagines, respectively their N-glycans localized in the palm and knuckle domains of αENaC, were identified as potential tethers. Decreased SF-induced ENaC currents were observed following removal of the ECM/glycocalyx, replacement of these glycosylated asparagines, or removal of N-glycans. Endothelial-specific overexpression of αENaC in mice induced hypertension. In contrast, expression of αENaC lacking these glycosylated asparagines blunted this effect. In summary, glycosylated asparagines in the palm and knuckle domains of αENaC are important for SF sensing. In accordance with the force-from-filament principle, they may provide a connection to the ECM that facilitates vascular responsiveness contributing to blood pressure regulation.
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24
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Li Q, Fung E. Multifaceted Functions of Epithelial Na + Channel in Modulating Blood Pressure. Hypertension 2019; 73:273-281. [PMID: 30580685 DOI: 10.1161/hypertensionaha.118.12330] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Qi Li
- From the Division of Cardiology, Department of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong (Q.L., E.F.).,Laboratory for Heart Failure and Circulation Research, Li Ka Shing Institute of Health Sciences, Prince of Wales Hospital, Hong Kong SAR (Q.L., E.F.)
| | - Erik Fung
- From the Division of Cardiology, Department of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong (Q.L., E.F.).,Gerald Choa Cardiac Research Centre, Faculty of Medicine, The Chinese University of Hong Kong (E.F.).,Lui Che Woo Institute of Innovative Medicine, Faculty of Medicine, The Chinese University of Hong Kong (E.F.).,Laboratory for Heart Failure and Circulation Research, Li Ka Shing Institute of Health Sciences, Prince of Wales Hospital, Hong Kong SAR (Q.L., E.F.)
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25
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Leiphart RJ, Chen D, Peredo AP, Loneker AE, Janmey PA. Mechanosensing at Cellular Interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:7509-7519. [PMID: 30346180 DOI: 10.1021/acs.langmuir.8b02841] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
At the plasma membrane interface, cells use various adhesions to sense their extracellular environment. These adhesions facilitate the transmission of mechanical signals that dictate cell behavior. This review discusses the mechanisms by which these mechanical signals are transduced through cell-matrix and cell-cell adhesions and how this mechanotransduction influences cell processes. Cell-matrix adhesions require the activation of and communication between various transmembrane protein complexes such as integrins. These links at the plasma membrane affect how a cell senses and responds to its matrix environment. Cells also communicate with each other through cell-cell adhesions, which further regulate cell behavior on a single- and multicellular scale. Coordination and competition between cell-cell and cell-matrix adhesions in multicellular aggregates can, to a significant extent, be modeled by differential adhesion analyses between the different interfaces even without knowing the details of cellular signaling. In addition, cell-matrix and cell-cell adhesions are connected by an intracellular cytoskeletal network that allows for direct communication between these distinct adhesions and activation of specific signaling pathways. Other membrane-embedded protein complexes, such as growth factor receptors and ion channels, play additional roles in mechanotransduction. Overall, these mechanoactive elements show the dynamic interplay between the cell, its matrix, and neighboring cells and how these relationships affect cellular function.
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Affiliation(s)
- Ryan J Leiphart
- Department of Bioengineering , University of Pennsylvania , 210 S 33rd St , Philadelphia , Pennsylvania 19104 , United States
- McKay Orthopedic Research Laboratory , University of Pennsylvania , Philadelphia , Pennsylvania , United States
| | - Dongning Chen
- Department of Bioengineering , University of Pennsylvania , 210 S 33rd St , Philadelphia , Pennsylvania 19104 , United States
- Center for Engineering Mechanobiology , University of Pennsylvania , Philadelphia , Pennsylvania , United States
| | - Ana P Peredo
- Department of Bioengineering , University of Pennsylvania , 210 S 33rd St , Philadelphia , Pennsylvania 19104 , United States
- McKay Orthopedic Research Laboratory , University of Pennsylvania , Philadelphia , Pennsylvania , United States
| | - Abigail E Loneker
- Department of Bioengineering , University of Pennsylvania , 210 S 33rd St , Philadelphia , Pennsylvania 19104 , United States
- Center for Engineering Mechanobiology , University of Pennsylvania , Philadelphia , Pennsylvania , United States
| | - Paul A Janmey
- Department of Bioengineering , University of Pennsylvania , 210 S 33rd St , Philadelphia , Pennsylvania 19104 , United States
- Institute for Medicine and Engineering, Department of Physiology , University of Pennsylvania , 3340 Smith Walk , Philadelphia , Pennsylvania 19104 , United States
- Center for Engineering Mechanobiology , University of Pennsylvania , Philadelphia , Pennsylvania , United States
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26
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Shear force modulates the activity of acid-sensing ion channels at low pH or in the presence of non-proton ligands. Sci Rep 2019; 9:6781. [PMID: 31043630 PMCID: PMC6494901 DOI: 10.1038/s41598-019-43097-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 04/16/2019] [Indexed: 12/17/2022] Open
Abstract
Acid-sensing ion channels (ASICs) belong to the degenerin/epithelial sodium channel protein family that form mechanosensitive ion channels. Evidence as to whether or not ASICs activity is directly modulated by mechanical force is lacking. Human ASICs (hASIC1V3, hASIC2a and hASIC3a) were heterologously expressed as homomeric channels in Xenopus oocytes and two-electrode voltage-clamp recordings were performed. hASIC3a was expressed in HEK-293 cells and currents measured by whole-cell patch-clamp recordings. ASIC currents in response to shear force (SF) were measured at pH 7.4, acidic pH, or in the presence of non-proton ligands at pH 7.4. SF was applied via a fluid stream generated through a pressurized perfusion system. No effect was observed at pH 7.4. Increased transient currents for each homomeric channel were observed when elevated SF was applied in conjunction with acidic pH (6.0-4.0). The sustained current was not (hASIC2a) or only slightly increased (hASIC1V3 and hASIC3a). SF-induced effects were not seen in water injected oocytes and were blocked by amiloride. Non-proton ligands activated a persistent current in hASIC1V3 and cASIC1 (MitTx) and hASIC3a (GMQ) at pH 7.4. Here SF caused a further current increase. Results suggest that ASICs do have an intrinsic ability to respond to mechanical force, supporting their role as mechanosensors in certain local environments.
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Fels J, Kusche-Vihrog K. Endothelial Nanomechanics in the Context of Endothelial (Dys)function and Inflammation. Antioxid Redox Signal 2019; 30:945-959. [PMID: 29433330 PMCID: PMC6354603 DOI: 10.1089/ars.2017.7327] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 08/31/2017] [Indexed: 12/31/2022]
Abstract
SIGNIFICANCE Stiffness of endothelial cells is closely linked to the function of the vasculature as it regulates the release of vasoactive substances such as nitric oxide (NO) and reactive oxygen species. The outer layer of endothelial cells, consisting of the glycocalyx above and the cortical zone beneath the plasma membrane, is a vulnerable compartment able to adapt its nanomechanical properties to any changes of forces exerted by the adjacent blood stream. Sustained stiffening of this layer contributes to the development of endothelial dysfunction and vascular pathologies. Recent Advances: The development of specific techniques to quantify the mechanical properties of cells enables the detailed investigation of the mechanistic link between structure and function of cells. CRITICAL ISSUES Challenging the mechanical stiffness of cells, for instance, by inflammatory mediators can lead to the development of endothelial dysfunction. Prevention of sustained stiffening of the outer layer of endothelial cells in turn improves endothelial function. FUTURE DIRECTIONS The mechanical properties of cells can be used as critical marker and test system for the proper function of the vascular system. Pharmacological substances, which are able to improve endothelial nanomechanics and function, could take a new importance in the prevention and treatment of vascular diseases. Thus, detailed knowledge acquisition about the structure/function relationship of endothelial cells and the underlying signaling pathways should be promoted.
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Affiliation(s)
- Johannes Fels
- Institute of Cell Dynamics and Imaging, University of Münster, Münster, Germany
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28
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Cheung TT, Ismail NAS, Moir R, Arora N, McDonald FJ, Condliffe SB. Annexin II Light Chain p11 Interacts With ENaC to Increase Functional Activity at the Membrane. Front Physiol 2019; 10:7. [PMID: 30800070 PMCID: PMC6375906 DOI: 10.3389/fphys.2019.00007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Accepted: 01/07/2019] [Indexed: 11/13/2022] Open
Abstract
The epithelial Na+ channel (ENaC) provides for Na+ absorption in various types of epithelia including the kidney, lung, and colon where ENaC is localized to the apical membrane to enable Na+ entry into the cell. The degree of Na+ entry via ENaC largely depends on the number of active channels localized to the cell membrane, and is tightly controlled by interactions with ubiquitin ligases, kinases, and G-proteins. While regulation of ENaC endocytosis has been well-studied, relatively little is understood of the proteins that govern ENaC exocytosis. We hypothesized that the annexin II light chain, p11, could participate in the transport of ENaC along the exocytic pathway. Our results demonstrate that all three ENaC channel subunits interacted with p11 in an in vitro binding assay. Furthermore, p11 was able to immunoprecipitate ENaC in epithelial cells. Quantitative mass spectrometry of affinity-purified ENaC-p11 complexes recovered several other trafficking proteins including HSP-90 and annexin A6. We also report that p11 exhibits a robust protein expression in cortical collecting duct epithelial cells. However, the expression of p11 in these cells was not influenced by either short-term or long-term exposure to aldosterone. To determine whether the p11 interaction affected ENaC function, we measured amiloride sensitive Na+ currents in Xenopus oocytes or mammalian epithelia co-expressing ENaC and p11 or a siRNA to p11. Results from these experiments showed that p11 significantly augmented ENaC current, whereas knockdown of p11 decreased current. Further, knockdown of p11 reduced ENaC cell surface population suggesting p11 promotes membrane insertion of ENaC. Overall, our findings reveal a novel protein interaction that controls the number of ENaC channels inserted at the membrane via the exocytic pathway.
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Affiliation(s)
- Tanya T Cheung
- Department of Physiology, University of Otago, Dunedin, New Zealand
| | - Noor A S Ismail
- Department of Physiology, University of Otago, Dunedin, New Zealand.,Biochemistry Department, Faculty of Medicine, Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia
| | - Rachel Moir
- Department of Physiology, University of Otago, Dunedin, New Zealand
| | - Nikhil Arora
- Department of Physiology, University of Otago, Dunedin, New Zealand
| | - Fiona J McDonald
- Department of Physiology, University of Otago, Dunedin, New Zealand
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29
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Kamel KS, Schreiber M, Halperin ML. Renal potassium physiology: integration of the renal response to dietary potassium depletion. Kidney Int 2018; 93:41-53. [PMID: 29102372 DOI: 10.1016/j.kint.2017.08.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 07/31/2017] [Accepted: 08/03/2017] [Indexed: 01/30/2023]
Abstract
We summarize the current understanding of the physiology of the renal handling of potassium (K+), and present an integrative view of the renal response to K+ depletion caused by dietary K+ restriction. This renal response involves contributions from different nephron segments, and aims to diminish the rate of excretion of K+ as a result of: decreasing the rate of electrogenic (and increasing the rate of electroneutral) reabsorption of sodium in the aldosterone-sensitive distal nephron (ASDN), decreasing the abundance of renal outer medullary K+ channels in the luminal membrane of principal cells in the ASDN, decreasing the flow rate in the ASDN, and increasing the reabsorption of K+ in the cortical and medullary collecting ducts. The implications of this physiology for the association between K+ depletion and hypertension, and K+ depletion and formation of calcium kidney stones are discussed.
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Affiliation(s)
- Kamel S Kamel
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada; Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
| | - Martin Schreiber
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Mitchell L Halperin
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada; Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
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30
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Kandel C, Schmidt P, Perniss A, Keshavarz M, Scholz P, Osterloh S, Althaus M, Kummer W, Deckmann K. ENaC in Cholinergic Brush Cells. Front Cell Dev Biol 2018; 6:89. [PMID: 30159312 PMCID: PMC6103785 DOI: 10.3389/fcell.2018.00089] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 07/25/2018] [Indexed: 12/17/2022] Open
Abstract
Cholinergic polymodal chemosensory cells in the mammalian urethra (urethral brush cells = UBC) functionally express the canonical bitter and umami taste transduction signaling cascade. Here, we aimed to determine whether UBC are functionally equipped for the perception of salt through ENaC (epithelial sodium channel). Cholinergic UBC were isolated from ChAT-eGFP reporter mice (ChAT = choline acetyltransferase). RT-PCR showed mRNA expression of ENaC subunits Scnn1a, Scnn1b, and Scnn1g in urethral epithelium and isolated UBC. Scnn1a could also be detected by next generation sequencing in 4/6 (66%) single UBC, two of them also expressed the bitter receptor Tas2R108. Strong expression of Scnn1a was seen in some urothelial umbrella cells and in 65% of UBC (30/46 cells) in a Scnn1a reporter mouse strain. Intracellular [Ca2+] was recorded in isolated UBC stimulated with the bitter substance denatonium benzoate (25 mM), ATP (0.5 mM) and NaCl (50 mM, on top of 145 mM Na+ and 153 mM Cl− baseline in buffer); mannitol (150 mM) served as osmolarity control. NaCl, but not mannitol, evoked an increase in intracellular [Ca2+] in 70% of the tested UBC. The NaCl-induced effect was blocked by the ENaC inhibitor amiloride (IC50 = 0.47 μM). When responses to both NaCl and denatonium were tested, all three possible positive response patterns occurred in a balanced distribution: 42% NaCl only, 33% denatonium only, 25% to both stimuli. A similar reaction pattern was observed with ATP and NaCl as test stimuli. About 22% of the UBC reacted to all three stimuli. Thus, NaCl evokes calcium responses in several UBC, likely involving an amiloride-sensitive channel containing α-ENaC. This feature does not define a new subpopulation of UBC, but rather emphasizes their polymodal character. The actual function of α-ENaC in cholinergic UBC—salt perception, homeostatic ion transport, mechanoreception—remains to be determined.
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Affiliation(s)
- Chrissy Kandel
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Patricia Schmidt
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Alexander Perniss
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Maryam Keshavarz
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Paul Scholz
- Department of Cell Physiology, Ruhr-University Bochum, Bochum, Germany
| | - Sabrina Osterloh
- Department of Cell Physiology, Ruhr-University Bochum, Bochum, Germany
| | - Mike Althaus
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Wolfgang Kummer
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Klaus Deckmann
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
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31
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Petrik D, Myoga MH, Grade S, Gerkau NJ, Pusch M, Rose CR, Grothe B, Götz M. Epithelial Sodium Channel Regulates Adult Neural Stem Cell Proliferation in a Flow-Dependent Manner. Cell Stem Cell 2018; 22:865-878.e8. [DOI: 10.1016/j.stem.2018.04.016] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 02/16/2018] [Accepted: 04/17/2018] [Indexed: 12/22/2022]
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32
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Shi S, Mutchler SM, Blobner BM, Kashlan OB, Kleyman TR. Pore-lining residues of MEC-4 and MEC-10 channel subunits tune the Caenorhabditis elegans degenerin channel's response to shear stress. J Biol Chem 2018; 293:10757-10766. [PMID: 29743244 DOI: 10.1074/jbc.ra118.002499] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/08/2018] [Indexed: 12/20/2022] Open
Abstract
The Caenorhabditis elegans MEC-4/MEC-10 channel mediates the worm's response to gentle body touch and is activated by laminar shear stress (LSS) when expressed in Xenopus oocytes. Substitutions at multiple sites within the second transmembrane domain (TM2) of MEC-4 or MEC-10 abolish the gentle touch response in worms, but the roles of these residues in mechanosensing are unclear. The present study therefore examined the role of specific MEC-4 and MEC-10 TM2 residues in the channel's response to LSS. We found that introducing mutations within the TM2 of MEC-4 or MEC-10 not only altered channel activity, but also affected the channel's response to LSS. This response was enhanced by Cys substitutions at selected MEC-4 sites (Phe715, Gly716, Gln718, and Leu719) between the degenerin and the putative amiloride-binding sites in this subunit. In contrast, the LSS response was largely blunted in MEC-10 variants bearing single Cys substitutions in the regions preceding and following the amiloride-binding site (Gly677-Leu681), as well as with four MEC-10 touch-deficient mutations that introduced charged residues into the TM2 domain. An enhanced response to LSS was observed with a MEC-10 mutation in the putative selectivity filter. Overall, MEC-4 or MEC-10 mutants that altered the channel's LSS response are primarily clustered between the degenerin site and the selectivity filter, a region that probably forms the narrowest portion of the channel pore. Our results suggest that pore-lining residues of MEC-4 and MEC-10 have important yet different roles in tuning the channel's response to mechanical forces.
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Affiliation(s)
- Shujie Shi
- From the Renal-Electrolyte Division, Department of Medicine
| | - Stephanie M Mutchler
- From the Renal-Electrolyte Division, Department of Medicine.,Department of Pharmacology and Chemical Biology, and
| | | | - Ossama B Kashlan
- From the Renal-Electrolyte Division, Department of Medicine.,Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Thomas R Kleyman
- From the Renal-Electrolyte Division, Department of Medicine, .,Department of Pharmacology and Chemical Biology, and.,Department of Cell Biology
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33
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Ashley Z, Barth D, Baldin JP, Fronius M. N‐Glycan and Heparan Sulphate Components of the Extracellular Matrix are Essential for Laminar Shear Stress Response of the Epithelial Sodium Channel (ENaC). FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.868.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Zoe Ashley
- Department of PhysiologyUniversity of OtagoDunedinNew Zealand
| | - Daniel Barth
- Department of PhysiologyUniversity of OtagoDunedinNew Zealand
| | | | - Martin Fronius
- Department of PhysiologyUniversity of OtagoDunedinNew Zealand
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34
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Wichmann L, Vowinkel KS, Perniss A, Manzini I, Althaus M. Incorporation of the δ-subunit into the epithelial sodium channel (ENaC) generates protease-resistant ENaCs in Xenopus laevis. J Biol Chem 2018; 293:6647-6658. [PMID: 29576549 DOI: 10.1074/jbc.ra118.002543] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 03/14/2018] [Indexed: 11/06/2022] Open
Abstract
The epithelial sodium channel (ENaC) is a critical regulator of vertebrate electrolyte homeostasis. ENaC is the only constitutively open ion channel in the degenerin/ENaC protein family, and its expression, membrane abundance, and open probability therefore are tightly controlled. The canonical ENaC is composed of three subunits (α, β, and γ), but a fourth δ-subunit may replace α and form atypical δβγ-ENaCs. Using Xenopus laevis as a model, here we found that mRNAs of the α- and δ-subunits are differentially expressed in different tissues and that δ-ENaC predominantly is present in the urogenital tract. Using whole-cell and single-channel electrophysiology of oocytes expressing Xenopus αβγ- or δβγ-ENaC, we demonstrate that the presence of the δ-subunit enhances the amount of current generated by ENaC due to an increased open probability, but also changes current into a transient form. Activity of canonical ENaCs is critically dependent on proteolytic processing of the α- and γ-subunits, and immunoblotting with epitope-tagged ENaC subunits indicated that, unlike α-ENaC, the δ-subunit does not undergo proteolytic maturation by the endogenous protease furin. Furthermore, currents generated by δβγ-ENaC were insensitive to activation by extracellular chymotrypsin, and presence of the δ-subunit prevented cleavage of γ-ENaC at the cell surface. Our findings suggest that subunit composition constitutes an additional level of ENaC regulation, and we propose that the Xenopus δ-ENaC subunit represents a functional example that demonstrates the importance of proteolytic maturation during ENaC evolution.
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Affiliation(s)
- Lukas Wichmann
- From the School of Natural and Environmental Sciences, Newcastle University, Ridley Building 2, Newcastle upon Tyne NE1 7RU, United Kingdom and.,the Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus-Liebig University, 35392 Giessen, Germany
| | - Kirsty Sophia Vowinkel
- the Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus-Liebig University, 35392 Giessen, Germany
| | - Alexander Perniss
- the Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus-Liebig University, 35392 Giessen, Germany
| | - Ivan Manzini
- the Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus-Liebig University, 35392 Giessen, Germany
| | - Mike Althaus
- From the School of Natural and Environmental Sciences, Newcastle University, Ridley Building 2, Newcastle upon Tyne NE1 7RU, United Kingdom and
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35
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Ashley Z, Mugloo S, McDonald FJ, Fronius M. Epithelial Na + channel differentially contributes to shear stress-mediated vascular responsiveness in carotid and mesenteric arteries from mice. Am J Physiol Heart Circ Physiol 2018; 314:H1022-H1032. [PMID: 29373035 DOI: 10.1152/ajpheart.00506.2017] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A potential "new player" in arteries for mediating shear stress responses is the epithelial Na+ channel (ENaC). The contribution of ENaC as shear sensor in intact arteries, and particularly different types of arteries (conduit and resistance), is unknown. We investigated the role of ENaC in both conduit (carotid) and resistance (third-order mesenteric) arteries isolated from C57Bl/6J mice. Vessel characteristics were determined at baseline (60 mmHg, no flow) and in response to increased intraluminal pressure and shear stress using a pressure myograph. These protocols were performed in the absence and presence of the ENaC inhibitor amiloride (10 µM) and after inhibition of endothelial nitric oxide synthase (eNOS) by Nω-nitro-l-arginine methyl ester (l-NAME; 100 µM). Under no-flow conditions, amiloride increased internal and external diameters of carotid (13 ± 2%, P < 0.05) but not mesenteric (0.5 ± 0.9%, P > 0.05) arteries. In response to increased intraluminal pressure, amiloride had no effect on the internal diameter of either type of artery. However, amiloride affected the stress-strain curves of mesenteric arteries. With increased shear stress, ENaC-dependent effects were observed in both arteries. In carotid arteries, amiloride augmented flow-mediated dilation (9.2 ± 5.3%) compared with control (no amiloride, 6.2 ± 3.3%, P < 0.05). In mesenteric arteries, amiloride induced a flow-mediated constriction (-11.5 ± 6.6%) compared with control (-2.2 ± 4.5%, P < 0.05). l-NAME mimicked the effect of ENaC inhibition and prevented further amiloride effects in both types of arteries. These observations indicate that ENaC contributes to shear sensing in conduit and resistance arteries. ENaC-mediated effects were associated with NO production but may involve different (artery-dependent) downstream signaling pathways. NEW & NOTEWORTHY The epithelial Na+ channel (ENaC) contributes to shear sensing in conduit and resistance arteries. In conduit arteries ENaC has a role as a vasoconstrictor, whereas in resistance arteries ENaC contributes to vasodilation. Interaction of ENaC with endothelial nitric oxide synthase/nitric oxide signaling to mediate the effects is supported; however, cross talk with other shear stress-dependent signaling pathways cannot be excluded.
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Affiliation(s)
- Zoe Ashley
- Department of Physiology, University of Otago , Dunedin , New Zealand.,HeartOtago, University of Otago , Dunedin , New Zealand
| | - Sama Mugloo
- Department of Physiology, University of Otago , Dunedin , New Zealand.,HeartOtago, University of Otago , Dunedin , New Zealand
| | - Fiona J McDonald
- Department of Physiology, University of Otago , Dunedin , New Zealand
| | - Martin Fronius
- Department of Physiology, University of Otago , Dunedin , New Zealand.,HeartOtago, University of Otago , Dunedin , New Zealand
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36
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Kashlan OB, Kinlough CL, Myerburg MM, Shi S, Chen J, Blobner BM, Buck TM, Brodsky JL, Hughey RP, Kleyman TR. N-linked glycans are required on epithelial Na + channel subunits for maturation and surface expression. Am J Physiol Renal Physiol 2017; 314:F483-F492. [PMID: 29187368 DOI: 10.1152/ajprenal.00195.2017] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Epithelial Na+ channel (ENaC) subunits undergo N-linked glycosylation in the endoplasmic reticulum where they assemble into an αβγ complex. Six, 13, and 5 consensus sites (Asn-X-Ser/Thr) for N-glycosylation reside in the extracellular domains of the mouse α-, β-, and γ-subunits, respectively. Because the importance of ENaC N-linked glycans has not been fully addressed, we examined the effect of preventing N-glycosylation of specific subunits on channel function, expression, maturation, and folding. Heterologous expression in Xenopus oocytes or Fischer rat thyroid cells with αβγ-ENaC lacking N-linked glycans on a single subunit reduced ENaC activity as well as the inhibitory response to extracellular Na+. The lack of N-linked glycans on the β-subunit also precluded channel activation by trypsin. However, channel activation by shear stress was N-linked glycan independent, regardless of which subunit was modified. We also discovered that the lack of N-linked glycans on any one subunit reduced the total and surface levels of cognate subunits. The lack of N-linked glycans on the β-subunit had the largest effect on total levels, with the lack of N-linked glycans on the γ- and α-subunits having intermediate and modest effects, respectively. Finally, channels with wild-type β-subunits were more sensitive to limited trypsin proteolysis than channels lacking N-linked glycans on the β-subunit. Our results indicate that N-linked glycans on each subunit are required for proper folding, maturation, surface expression, and function of the channel.
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Affiliation(s)
- Ossama B Kashlan
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Computational and Systems Biology, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Carol L Kinlough
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Michael M Myerburg
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Shujie Shi
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Jingxin Chen
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Brandon M Blobner
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Teresa M Buck
- Department of Biological Sciences, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Rebecca P Hughey
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Cell Biology, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Thomas R Kleyman
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Cell Biology, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Pharmacology and Chemical Biology, University of Pittsburgh , Pittsburgh, Pennsylvania
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37
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Wu D, Boucher RC, Button B, Elston T, Lin CL. An integrated mathematical epithelial cell model for airway surface liquid regulation by mechanical forces. J Theor Biol 2017; 438:34-45. [PMID: 29154907 DOI: 10.1016/j.jtbi.2017.11.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 11/09/2017] [Accepted: 11/14/2017] [Indexed: 01/17/2023]
Abstract
A robust method based on reverse engineering was utilized to construct the ion-channel conductance functions for airway epithelial sodium channels (ENaC), the cystic fibrosis transmembrane conductance regulator (CFTR), and calcium-activated chloride channels (CaCC). The ion-channel conductance models for both normal (NL) and cystic fibrosis (CF) airway epithelia were developed and then coupled to an adenosine triphosphate (ATP) metabolism model and a fluid transport model (collectively called the integrated cell model) to investigate airway surface liquid (ASL) volume regulation and hence mucus concentration, by mechanical forces in NL and CF human airways. The epithelial cell models for NL and CF required differences in Cl- secretion (decreased in CF) and Na+ absorption (raised in CF) to reproduce behaviors similar to in vitro epithelial cells exposed to mechanical forces (cyclic shear stress, cyclic compressive pressure and cilial strain) and selected modulators of ion channels and ATP release. The epithelial cell models were then used to investigate the effects of mechanical forces and evaporative flux on ASL and mucus homeostasis in both NL and CF airway epithelia. Because of reduced CF ASL volumes, CF mucus concentrations increased and produced a greater dependence of ASL volume regulation on cilia-mucus-ATP release interactions in CF than NL epithelial nodules. Similarly, the CF model was less tolerant to evaporation induced ASL volume reduction at all ATP release rates than the NL model. Consequently, this reverse engineered model appears to provide a robust tool for investigating CF pathophysiology and novel therapies.
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Affiliation(s)
- Dan Wu
- Marsico Lung Institute/University of North Carolina Cystic Fibrosis Center, School of Medicine, 7008 Marsico Hall, Chapel Hill, NC 27599-7248, United States; Department of Mechanical and Industrial Engineering, The University of Iowa, 2406 Seamans Center for the Engineering Arts and Sciences, Iowa City, IA 52242, United States
| | - Richard C Boucher
- Marsico Lung Institute/University of North Carolina Cystic Fibrosis Center, School of Medicine, 7008 Marsico Hall, Chapel Hill, NC 27599-7248, United States.
| | - Brian Button
- Marsico Lung Institute/University of North Carolina Cystic Fibrosis Center, School of Medicine, 7008 Marsico Hall, Chapel Hill, NC 27599-7248, United States
| | - Timothy Elston
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill 27599, United States
| | - Ching-Long Lin
- Department of Mechanical and Industrial Engineering, The University of Iowa, 2406 Seamans Center for the Engineering Arts and Sciences, Iowa City, IA 52242, United States.
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38
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Kleyman TR, Kashlan OB, Hughey RP. Epithelial Na + Channel Regulation by Extracellular and Intracellular Factors. Annu Rev Physiol 2017; 80:263-281. [PMID: 29120692 DOI: 10.1146/annurev-physiol-021317-121143] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Epithelial Na+ channels (ENaCs) are members of the ENaC/degenerin family of ion channels that evolved to respond to extracellular factors. In addition to being expressed in the distal aspects of the nephron, where ENaCs couple the absorption of filtered Na+ to K+ secretion, these channels are found in other epithelia as well as nonepithelial tissues. This review addresses mechanisms by which ENaC activity is regulated by extracellular factors, including proteases, Na+, and shear stress. It also addresses other factors, including acidic phospholipids and modification of ENaC cytoplasmic cysteine residues by palmitoylation, which enhance channel activity by altering interactions of the channel with the plasma membrane.
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Affiliation(s)
- Thomas R Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA; .,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA
| | - Ossama B Kashlan
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA; .,Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - Rebecca P Hughey
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA; .,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.,Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15219, USA
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Ernandez T, Udwan K, Chassot A, Martin PY, Feraille E. Uninephrectomy and apical fluid shear stress decrease ENaC abundance in collecting duct principal cells. Am J Physiol Renal Physiol 2017; 314:F763-F772. [PMID: 28877879 DOI: 10.1152/ajprenal.00200.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Acute nephron reduction such as after living kidney donation may increase the risk of hypertension. Uninephrectomy induces major hemodynamic changes in the remaining kidney, resulting in rapid increase of single-nephron glomerular filtration rate (GFR) and fluid delivery in the distal nephron. Decreased sodium (Na) fractional reabsorption after the distal tubule has been reported after uninephrectomy in animals preserving volume homeostasis. In the present study, we thought to specifically explore the effect of unilateral nephrectomy on epithelial Na channel (ENaC) subunit expression in mice. We show that γ-ENaC subunit surface expression was specifically downregulated after uninephrectomy, whereas the expression of the aldosterone-sensitive α-ENaC and α1-Na-K-ATPase subunits as well as of kidney-specific Na-K-Cl cotransporter isoform and Na-Cl cotransporter were not significantly altered. Because acute nephron reduction induces a rapid increase of single-nephron GFR, resulting in a higher tubular fluid flow, we speculated that local mechanical factors such as fluid shear stress (FSS) were involved in Na reabsorption regulation after uninephrectomy. We further explore such hypothesis in an in vitro model of FSS applied on highly differentiated collecting duct principal cells. We found that FSS specifically downregulates β-ENaC and γ-ENaC subunits at the transcriptional level through an unidentified heat-insensitive paracrine basolateral factor. The primary cilium as a potential mechanosensor was not required. In contrast, protein kinase A and calcium-sensitive cytosolic phospholipase A2 were involved, but we could not demonstrate a role for cyclooxygenase or epoxygenase metabolites.
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Affiliation(s)
- T Ernandez
- Service of Nephrology, University Hospital of Geneva , Geneva , Switzerland.,Department of Cell Physiology and Metabolism, University Medical Center , Geneva , Switzerland
| | - K Udwan
- Department of Cell Physiology and Metabolism, University Medical Center , Geneva , Switzerland
| | - A Chassot
- Department of Cell Physiology and Metabolism, University Medical Center , Geneva , Switzerland
| | - P-Y Martin
- Service of Nephrology, University Hospital of Geneva , Geneva , Switzerland
| | - E Feraille
- Department of Cell Physiology and Metabolism, University Medical Center , Geneva , Switzerland
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Shi S, Buck TM, Kinlough CL, Marciszyn AL, Hughey RP, Chalfie M, Brodsky JL, Kleyman TR. Regulation of the epithelial Na + channel by paraoxonase-2. J Biol Chem 2017; 292:15927-15938. [PMID: 28768768 DOI: 10.1074/jbc.m117.785253] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 07/14/2017] [Indexed: 01/11/2023] Open
Abstract
Paraoxonase-2 (PON-2) is a membrane-bound lactonase with unique anti-oxidative and anti-atherosclerotic properties. PON-2 shares key structural elements with MEC-6, an endoplasmic reticulum-resident molecular chaperone in Caenorhabditis elegans MEC-6 modulates the expression of a mechanotransductive ion channel comprising MEC-4 and MEC-10 in touch-receptor neurons. Because pon-2 mRNA resides in multiple rat nephron segments, including the aldosterone-sensitive distal nephron where the epithelial Na+ channel (ENaC) is expressed, we hypothesized that PON-2 would similarly regulate ENaC expression. We observed PON-2 expression in aquaporin 2-positive principal cells of the distal nephron of adult human kidney. PON-2 also co-immunoprecipitated with ENaC when co-expressed in HEK293 cells. When PON-2 was co-expressed with ENaC in Xenopus oocytes, ENaC activity was reduced, reflecting a reduction in ENaC surface expression. MEC-6 also reduced ENaC activity when co-expressed in Xenopus oocytes. The PON-2 inhibitory effect was ENaC-specific, as PON-2 had no effect on functional expression of the renal outer medullary potassium channel. PON-2 did not alter the response of ENaC to extracellular Na+, mechanical shear stress, or α-chymotrypsin-mediated proteolysis, suggesting that PON-2 did not alter the regulation of ENaC by these factors. Together, our data suggest that PON-2 regulates ENaC activity by modulating its intracellular trafficking and surface expression.
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Affiliation(s)
- Shujie Shi
- From the Renal-Electrolyte Division, Department of Medicine
| | | | | | | | - Rebecca P Hughey
- From the Renal-Electrolyte Division, Department of Medicine.,Department of Cell Biology.,Department of Microbiology and Molecular Genetics, and
| | - Martin Chalfie
- the Department of Biological Sciences, Columbia University, New York, New York 10027
| | | | - Thomas R Kleyman
- From the Renal-Electrolyte Division, Department of Medicine, .,Department of Cell Biology.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261 and
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Knoepp F, Bettmer J, Fronius M. Gadolinium released by the linear gadolinium-based contrast-agent Gd-DTPA decreases the activity of human epithelial Na + channels (ENaCs). BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1040-1048. [PMID: 28257815 DOI: 10.1016/j.bbamem.2017.02.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 02/16/2017] [Accepted: 02/27/2017] [Indexed: 02/05/2023]
Abstract
BACKGROUND Gadolinium-based-contrast-agents (GBCAs) are used for magnetic-resonance-imaging and associated with renal and cardiovascular adverse reactions caused by released Gd3+ ions. Gd3+ is also a modulator of mechano-gated ion channels, including the epithelial Na+ channel (ENaC) that is expressed in kidney epithelium and the vasculature. ENaC is important for salt-/water homeostasis and blood pressure regulation and a likely target of released Gd3+ from GBCAs causing the above-mentioned adverse reactions. Therefore this study examined the effect of Gd3+ and GBCAs on ENaC's activity. METHODS Human αβγENaC was expressed in Xenopus laevis oocytes and exposed to Gd3+, linear (Gd-DTPA, Magnevist) or cyclic (Dotarem) GBCAs. Transmembrane ion-currents (IM) were recorded by the two-electrode-voltage-clamp technique and Gd3+-release by Gd-DTPA was confirmed by inductively coupled plasma-mass spectrometry. RESULTS Gd3+ exerts biphasic effects on ENaC's activity: ≤0.3mmol/l decreased IM which was preventable by DEPC (modifies histidines). Strikingly Gd3+≥0.4mmol/l increased IM and this effect was prevented by cysteine-modifying MTSEA. Linear Gd-DTPA and Magnevist mimicked the effect of ≤0.3mmol/l Gd3+, whereas the chelator DTPA showed no effect. Gd3+ and Gd-DTPA increased the IC50 for amiloride, but did not affect ENaC's self-inhibition. Interestingly, cyclic Gd-DOTA (Dotarem) increased IM to a similar extent as its chelator DOTA, suggesting that the chelator rather than released Gd3+ is responsible for this effect. CONCLUSION These results confirm Gd3+-release from linear Gd-DTPA and indicate that the released Gd3+ amount is sufficient to interfere with ENaC's activity to provide putative explanations for GBCA-related adverse effects.
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Affiliation(s)
- Fenja Knoepp
- Excellence Cluster Cardio-Pulmonary System, Justus-Liebig-University Giessen, Aulweg 130, 35392 Giessen, Germany
| | - Joerg Bettmer
- Department of Physical and Analytical Chemistry, University of Oviedo, C/ Julián Clavería 8, 33006 Oviedo, Spain
| | - Martin Fronius
- Department of Physiology, University of Otago, PO Box 913, Dunedin 9054, New Zealand.
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Abstract
Microfluidics is an interdisciplinary field intersecting many areas in engineering. Utilizing a combination of physics, chemistry, biology, and biotechnology, along with practical applications for designing devices that use low volumes of fluids to achieve high-throughput screening, is a major goal in microfluidics. Microfluidic approaches allow the study of cells growth and differentiation using a variety of conditions including control of fluid flow that generates shear stress. Recently, Piezo1 channels were shown to respond to fluid shear stress and are crucial for vascular development. This channel is ideal for studying fluid shear stress applied to cells using microfluidic devices. We have developed an approach that allows us to analyze the role of Piezo channels on any given cell and serves as a high-throughput screen for drug discovery. We show that this approach can provide detailed information about the inhibitors of Piezo channels.
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Shi S, Carattino MD. Expression and Analysis of Flow-regulated Ion Channels in Xenopus Oocytes. Bio Protoc 2017; 7:e2224. [PMID: 28670605 DOI: 10.21769/bioprotoc.2224] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
Mechanically-gated ion channels play key roles in mechanotransduction, a process that translates physical forces into biological signals. Epithelial and endothelial cells are exposed to laminar shear stress (LSS), a tangential force exerted by flowing fluids against the wall of vessels and epithelia. The protocol outlined herein has been used to examine the response of ion channels expressed in Xenopus oocytes to LSS (Hoger et al., 2002; Carattino et al., 2004; Shi et al., 2006). The Xenopus oocyte is a reliable system that allows for the expression and chemical modification of ion channels and regulatory proteins (George et al., 1989; Palmer et al., 1990; Sheng et al., 2001; Carattino et al., 2003). Therefore, this technique is suitable for studying the molecular mechanisms that allow flow-activated channels to respond to LSS.
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Affiliation(s)
- Shujie Shi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
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Schwingshackl A. The role of stretch-activated ion channels in acute respiratory distress syndrome: finally a new target? Am J Physiol Lung Cell Mol Physiol 2016; 311:L639-52. [PMID: 27521425 DOI: 10.1152/ajplung.00458.2015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 08/05/2016] [Indexed: 02/06/2023] Open
Abstract
Mechanical ventilation (MV) and oxygen therapy (hyperoxia; HO) comprise the cornerstones of life-saving interventions for patients with acute respiratory distress syndrome (ARDS). Unfortunately, the side effects of MV and HO include exacerbation of lung injury by barotrauma, volutrauma, and propagation of lung inflammation. Despite significant improvements in ventilator technologies and a heightened awareness of oxygen toxicity, besides low tidal volume ventilation few if any medical interventions have improved ARDS outcomes over the past two decades. We are lacking a comprehensive understanding of mechanotransduction processes in the healthy lung and know little about the interactions between simultaneously activated stretch-, HO-, and cytokine-induced signaling cascades in ARDS. Nevertheless, as we are unraveling these mechanisms we are gathering increasing evidence for the importance of stretch-activated ion channels (SACs) in the activation of lung-resident and inflammatory cells. In addition to the discovery of new SAC families in the lung, e.g., two-pore domain potassium channels, we are increasingly assigning mechanosensing properties to already known Na(+), Ca(2+), K(+), and Cl(-) channels. Better insights into the mechanotransduction mechanisms of SACs will improve our understanding of the pathways leading to ventilator-induced lung injury and lead to much needed novel therapeutic approaches against ARDS by specifically targeting SACs. This review 1) summarizes the reasons why the time has come to seriously consider SACs as new therapeutic targets against ARDS, 2) critically analyzes the physiological and experimental factors that currently limit our knowledge about SACs, and 3) outlines the most important questions future research studies need to address.
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45
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Shi S, Luke CJ, Miedel MT, Silverman GA, Kleyman TR. Activation of the Caenorhabditis elegans Degenerin Channel by Shear Stress Requires the MEC-10 Subunit. J Biol Chem 2016; 291:14012-14022. [PMID: 27189943 DOI: 10.1074/jbc.m116.718031] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Indexed: 01/12/2023] Open
Abstract
Mechanotransduction in Caenorhabditis elegans touch receptor neurons is mediated by an ion channel formed by MEC-4, MEC-10, and accessory proteins. To define the role of these subunits in the channel's response to mechanical force, we expressed degenerin channels comprising MEC-4 and MEC-10 in Xenopus oocytes and examined their response to laminar shear stress (LSS). Shear stress evoked a rapid increase in whole cell currents in oocytes expressing degenerin channels as well as channels with a MEC-4 degenerin mutation (MEC-4d), suggesting that C. elegans degenerin channels are sensitive to LSS. MEC-10 is required for a robust LSS response as the response was largely blunted in oocytes expressing homomeric MEC-4 or MEC-4d channels. We examined a series of MEC-10/MEC-4 chimeras to identify specific domains (amino terminus, first transmembrane domain, and extracellular domain) and sites (residues 130-132 and 134-137) within MEC-10 that are required for a robust response to shear stress. In addition, the LSS response was largely abolished by MEC-10 mutations encoded by a touch-insensitive mec-10 allele, providing a correlation between the channel's responses to two different mechanical forces. Our findings suggest that MEC-10 has an important role in the channel's response to mechanical forces.
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Affiliation(s)
- Shujie Shi
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Cliff J Luke
- Department of Pediatrics, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Mark T Miedel
- Department of Pediatrics, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Gary A Silverman
- Department of Pediatrics, University of Pittsburgh, Pittsburgh, Pennsylvania 15261; Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Thomas R Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261; Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261; Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.
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Cornelius RJ, Wang B, Wang-France J, Sansom SC. Maintaining K + balance on the low-Na +, high-K + diet. Am J Physiol Renal Physiol 2016; 310:F581-F595. [PMID: 26739887 DOI: 10.1152/ajprenal.00330.2015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 12/29/2015] [Indexed: 02/07/2023] Open
Abstract
A low-Na+, high-K+ diet (LNaHK) is considered a healthier alternative to the "Western" high-Na+ diet. Because the mechanism for K+ secretion involves Na+ reabsorptive exchange for secreted K+ in the distal nephron, it is not understood how K+ is eliminated with such low Na+ intake. Animals on a LNaHK diet produce an alkaline load, high urinary flows, and markedly elevated plasma ANG II and aldosterone levels to maintain their K+ balance. Recent studies have revealed a potential mechanism involving the actions of alkalosis, urinary flow, elevated ANG II, and aldosterone on two types of K+ channels, renal outer medullary K+ and large-conductance K+ channels, located in principal and intercalated cells. Here, we review these recent advances.
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Affiliation(s)
- Ryan J Cornelius
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon; and
| | - Bangchen Wang
- Department of Cellular/Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska
| | - Jun Wang-France
- Department of Cellular/Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska
| | - Steven C Sansom
- Department of Cellular/Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska
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Carrisoza-Gaytan R, Carattino MD, Kleyman TR, Satlin LM. An unexpected journey: conceptual evolution of mechanoregulated potassium transport in the distal nephron. Am J Physiol Cell Physiol 2015; 310:C243-59. [PMID: 26632600 DOI: 10.1152/ajpcell.00328.2015] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Flow-induced K secretion (FIKS) in the aldosterone-sensitive distal nephron (ASDN) is mediated by large-conductance, Ca(2+)/stretch-activated BK channels composed of pore-forming α-subunits (BKα) and accessory β-subunits. This channel also plays a critical role in the renal adaptation to dietary K loading. Within the ASDN, the cortical collecting duct (CCD) is a major site for the final renal regulation of K homeostasis. Principal cells in the ASDN possess a single apical cilium whereas the surfaces of adjacent intercalated cells, devoid of cilia, are decorated with abundant microvilli and microplicae. Increases in tubular (urinary) flow rate, induced by volume expansion, diuretics, or a high K diet, subject CCD cells to hydrodynamic forces (fluid shear stress, circumferential stretch, and drag/torque on apical cilia and presumably microvilli/microplicae) that are transduced into increases in principal (PC) and intercalated (IC) cell cytoplasmic Ca(2+) concentration that activate apical voltage-, stretch- and Ca(2+)-activated BK channels, which mediate FIKS. This review summarizes studies by ourselves and others that have led to the evolving picture that the BK channel is localized in a macromolecular complex at the apical membrane, composed of mechanosensitive apical Ca(2+) channels and a variety of kinases/phosphatases as well as other signaling molecules anchored to the cytoskeleton, and that an increase in tubular fluid flow rate leads to IC- and PC-specific responses determined, in large part, by the cell-specific composition of the BK channels.
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Affiliation(s)
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, Pittsburgh, Pennsylvania
| | - Thomas R Kleyman
- Renal-Electrolyte Division, Department of Medicine, Pittsburgh, Pennsylvania
| | - Lisa M Satlin
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, New York; and
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Vitzthum C, Clauss WG, Fronius M. Mechanosensitive activation of CFTR by increased cell volume and hydrostatic pressure but not shear stress. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:2942-51. [PMID: 26357939 DOI: 10.1016/j.bbamem.2015.09.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 09/03/2015] [Accepted: 09/05/2015] [Indexed: 12/20/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a Cl(-) channel that is essential for electrolyte and fluid homeostasis. Preliminary evidence indicates that CFTR is a mechanosensitive channel. In lung epithelia, CFTR is exposed to different mechanical forces such as shear stress (Ss) and membrane distention. The present study questioned whether Ss and/or stretch influence CFTR activity (wild type, ∆F508, G551D). Human CFTR (hCFTR) was heterologously expressed in Xenopus oocytes and the response to the mechanical stimulus and forskolin/IBMX (FI) was measured by two-electrode voltage-clamp experiments. Ss had no influence on hCFTR activity. Injection of an intracellular analogous solution to increase cell volume alone did not affect hCFTR activity. However, hCFTR activity was augmented by injection after pre-stimulation with FI. The response to injection was similar in channels carrying the common mutations ∆F508 and G551D compared to wild type hCFTR. Stretch-induced CFTR activation was further assessed in Ussing chamber measurements using Xenopus lung preparations. Under control conditions increased hydrostatic pressure (HP) decreased the measured ion current including activation of a Cl(-) secretion that was unmasked by the CFTR inhibitor GlyH-101. These data demonstrate activation of CFTR in vitro and in a native pulmonary epithelium in response to mechanical stress. Mechanosensitive regulation of CFTR is highly relevant for pulmonary physiology that relies on ion transport processes facilitated by pulmonary epithelial cells.
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Affiliation(s)
- Constanze Vitzthum
- Institute of Animal Physiology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Wolfgang G Clauss
- Institute of Animal Physiology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Martin Fronius
- Department of Physiology, University of Otago, Dunedin, New Zealand.
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Mustafa SB, Isaac J, Seidner SR, Dixon PS, Henson BM, DiGeronimo RJ. Mechanical stretch induces lung α-epithelial Na(+) channel expression. Exp Lung Res 2014; 40:380-91. [PMID: 25058750 DOI: 10.3109/01902148.2014.934410] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACT During fetal development physiological stretching helps drive lung growth and maturation. At birth, the α-subunit of the alveolar epithelial sodium channel (α-ENaC) is a critical factor in helping to facilitate clearance of lung fluid during the perinatal period. The effects of stretch, however, on α-ENaC expression in the fetal lung have yet to be elucidated. In an effort to explore this question, we used both an in vitro cell culture model that exposes cells to repetitive cyclic stretch (CS) as well as an in vivo preterm animal model of mechanical ventilation (MV). We found that murine lung epithelial (MLE-12) cells exposed to repetitive CS showed a significant rise in α-ENaC mRNA expression. Total and cell-surface protein abundance of α-ENaC were also elevated after 24 h of CS. Stretch-induced increases in α-ENaC expression were suppressed in the presence of either actinomycin D or cycloheximide. Pharmacological inhibition of the extracellular signal-regulated protein kinase (ERK1/2) did not attenuate stretch-induced increases in α-ENaC protein, whereas inhibition of p38 MAPK or c-Jun NH2-terminal kinase (JNK) did. In 29-day preterm rabbits, alveolar stretching secondary to postnatal MV markedly elevated fetal lung α-ENaC expression compared to spontaneously breathing counterparts. In summary, our findings indicate that mechanical stretch promotes α-ENaC expression.
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Affiliation(s)
- Shamimunisa B Mustafa
- 1Department of Pediatrics, University of Texas Health Science Center , San Antonio Texas , USA
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