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Montalbetti N, Dalghi MG, Parakala-Jain T, Clayton D, Apodaca G, Carattino MD. Antinociceptive effect of the calcitonin gene-related peptide receptor antagonist BIBN4096BS in mice with bacterial cystitis. Am J Physiol Renal Physiol 2023; 325:F779-F791. [PMID: 37823199 PMCID: PMC10878727 DOI: 10.1152/ajprenal.00217.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 09/25/2023] [Accepted: 10/09/2023] [Indexed: 10/13/2023] Open
Abstract
Patients with urinary tract infections (UTIs) suffer from urinary frequency, urgency, dysuria, and suprapubic pain, but the mechanisms by which bladder afferents sense the presence of uropathogens and encode this information is not well understood. Calcitonin gene-related peptide (CGRP) is a 37-mer neuropeptide found in a subset of bladder afferents that terminate primarily in the lamina propria. Here, we report that the CGRP receptor antagonist BIBN4096BS lessens lower urinary tract symptoms and prevents the development of pelvic allodynia in mice inoculated with uropathogenic Escherichia coli (UPEC) without altering urine bacterial loads or the host immune response to the infection. These findings indicate that CGRP facilitates the processing of noxious/inflammatory stimuli during UPEC infection. Using fluorescent in situ hybridization, we identified a population of suburothelial fibroblasts in the lamina propria, a region where afferent fibers containing CGRP terminate, that expresses the canonical CGRP receptor components Calcrl and Ramp1. We propose that these fibroblasts, in conjunction with CGRP+ afferents, form a circuit that senses substances released during the infection and transmit this noxious information to the central nervous system.NEW & NOTEWORTHY Afferent C fibers release neuropeptides including calcitonin gene-related peptide (CGRP). Here, we show that the specific CGRP receptor antagonist, BIBN409BS, ameliorates lower urinary tract symptoms and pelvic allodynia in mice inoculated with uropathogenic E. coli. Using fluorescent in situ hybridization, we identified a population of suburothelial fibroblasts in the lamina propria that expresses the canonical CGRP receptor. Our findings indicate that CGRP contributes to the transmission of nociceptive information arising from the bladder.
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Affiliation(s)
- Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Marianela G Dalghi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Tanmay Parakala-Jain
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Dennis Clayton
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Gerard Apodaca
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
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2
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Nickerson AJ, Mutchler SM, Sheng S, Cox NA, Ray EC, Kashlan OB, Carattino MD, Marciszyn AL, Winfrey A, Gingras S, Kirabo A, Hughey RP, Kleyman TR. Mice lacking γENaC palmitoylation sites maintain benzamil-sensitive Na+ transport despite reduced channel activity. JCI Insight 2023; 8:e172051. [PMID: 37707951 PMCID: PMC10721255 DOI: 10.1172/jci.insight.172051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 09/12/2023] [Indexed: 09/16/2023] Open
Abstract
Epithelial Na+ channels (ENaCs) control extracellular fluid volume by facilitating Na+ absorption across transporting epithelia. In vitro studies showed that Cys-palmitoylation of the γENaC subunit is a major regulator of channel activity. We tested whether γ subunit palmitoylation sites are necessary for channel function in vivo by generating mice lacking the palmitoylated cysteines (γC33A,C41A) using CRISPR/Cas9 technology. ENaCs in dissected kidney tubules from γC33A,C41A mice had reduced open probability compared with wild-type (WT) littermates maintained on either standard or Na+-deficient diets. Male mutant mice also had higher aldosterone levels than WT littermates following Na+ restriction. However, γC33A,C41A mice did not have reduced amiloride-sensitive Na+ currents in the distal colon or benzamil-induced natriuresis compared to WT mice. We identified a second, larger conductance cation channel in the distal nephron with biophysical properties distinct from ENaC. The activity of this channel was higher in Na+-restricted γC33A,C41A versus WT mice and was blocked by benzamil, providing a possible compensatory mechanism for reduced prototypic ENaC function. We conclude that γ subunit palmitoylation sites are required for prototypic ENaC activity in vivo but are not necessary for amiloride/benzamil-sensitive Na+ transport in the distal nephron or colon.
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Affiliation(s)
| | | | | | | | | | - Ossama B. Kashlan
- Department of Medicine
- Department of Computational and Systems Biology
| | | | | | | | - Sebastien Gingras
- Department of Immunology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Annet Kirabo
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | | | - Thomas R. Kleyman
- Department of Medicine
- Department of Cell Biology, and
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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3
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Dalghi MG, Montalbetti N, Wheeler TB, Apodaca G, Carattino MD. Real-Time Void Spot Assay. J Vis Exp 2023:10.3791/64621. [PMID: 36847378 PMCID: PMC10153432 DOI: 10.3791/64621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Abstract
Normal voiding behavior is the result of the coordinated function of the bladder, the urethra, and the urethral sphincters under the proper control of the nervous system. To study voluntary voiding behavior in mouse models, researchers have developed the void spot assay (VSA), a method that measures the number and area of urine spots deposited on a filter paper lining the floor of an animal's cage. Although technically simple and inexpensive, this assay has limitations when used as an end-point assay, including a lack of temporal resolution of voiding events and difficulties quantifying overlapping urine spots. To overcome these limitations, we developed a video-monitored VSA, which we call real-time VSA (RT-VSA), and which allows us to determine voiding frequency, assess voided volume and voiding patterns, and make measurements over 6 h time windows during both the dark and light phases of the day. The method described in this report can be applied to a wide variety of mouse-based studies that explore the physiological and neurobehavioral aspects of voluntary micturition in health and disease states.
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Affiliation(s)
- Marianela G Dalghi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh
| | - Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh
| | | | - Gerard Apodaca
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh; Department of Cell Biology, University of Pittsburgh;
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Ruiz WG, Clayton DR, Dalghi MG, Montalbetti N, Carattino MD, Apodaca G. Expression of Transgenes in Native Bladder Urothelium using Adenovirus-Mediated Transduction. J Vis Exp 2022:10.3791/64584. [PMID: 36282713 PMCID: PMC10108903 DOI: 10.3791/64584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In addition to forming a high-resistance barrier, the urothelium lining the renal pelvis, ureters, bladder, and proximal urethra is hypothesized to sense and transmit information about its environment to the underlying tissues, promoting voiding function and behavior. Disruption of the urothelial barrier, or its sensory/transducer function, can lead to disease. Studying these complex events is hampered by lack of simple strategies to alter gene and protein expression in the urothelium. Methods are described here that allow investigators to generate large amounts of high-titer adenovirus, which can then be used to transduce rodent urothelium with high efficiency, and in a relatively straightforward manner. Both cDNAs and small interfering RNAs can be expressed using adenoviral transduction, and the impact of transgene expression on urothelial function can be assessed 12 h to several days later. These methods have broad applicability to studies of normal and abnormal urothelial biology using mouse or rat animal models.
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Affiliation(s)
- Wily G Ruiz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine
| | - Dennis R Clayton
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine
| | - Marianela G Dalghi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine
| | - Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine
| | - Gerard Apodaca
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine;
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5
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Montalbetti N, Przepiorski AJ, Shi S, Sheng S, Baty CJ, Maggiore JC, Carattino MD, Vanichapol T, Davidson AJ, Hukriede NA, Kleyman TR. Functional characterization of ion channels expressed in kidney organoids derived from human induced pluripotent stem cells. Am J Physiol Renal Physiol 2022; 323:F479-F491. [PMID: 35979965 PMCID: PMC9529267 DOI: 10.1152/ajprenal.00365.2021] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 08/15/2022] [Accepted: 08/16/2022] [Indexed: 02/04/2023] Open
Abstract
Kidney organoids derived from human or rodent pluripotent stem cells have glomerular structures and differentiated/polarized nephron segments. Although there is an increasing understanding of the patterns of expression of transcripts and proteins within kidney organoids, there is a paucity of data regarding functional protein expression, in particular on transporters that mediate the vectorial transport of solutes. Using cells derived from kidney organoids, we examined the functional expression of key ion channels that are expressed in distal nephron segments: the large-conductance Ca2+-activated K+ (BKCa) channel, the renal outer medullary K+ (ROMK, Kir1.1) channel, and the epithelial Na+ channel (ENaC). RNA-sequencing analyses showed that genes encoding the pore-forming subunits of these transporters, and for BKCa channels, key accessory subunits, are expressed in kidney organoids. Expression and localization of selected ion channels was confirmed by immunofluorescence microscopy and immunoblot analysis. Electrophysiological analysis showed that BKCa and ROMK channels are expressed in different cell populations. These two cell populations also expressed other unidentified Ba2+-sensitive K+ channels. BKCa expression was confirmed at a single channel level, based on its high conductance and voltage dependence of activation. We also found a population of cells expressing amiloride-sensitive ENaC currents. In summary, our results show that human kidney organoids functionally produce key distal nephron K+ and Na+ channels.NEW & NOTEWORTHY Our results show that human kidney organoids express key K+ and Na+ channels that are expressed on the apical membranes of cells in the aldosterone-sensitive distal nephron, including the large-conductance Ca2+-activated K+ channel, renal outer medullary K+ channel, and epithelial Na+ channel.
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Affiliation(s)
| | - Aneta J Przepiorski
- Department of Developmental Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Shujie Shi
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Shaohu Sheng
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Catherine J Baty
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Joseph C Maggiore
- Department of Developmental Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Marcelo D Carattino
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Thitinee Vanichapol
- Department of Molecular Medicine and Pathology, School of Medical Sciences, University of Auckland, Auckland, New Zealand
| | - Alan J Davidson
- Department of Molecular Medicine and Pathology, School of Medical Sciences, University of Auckland, Auckland, New Zealand
| | - Neil A Hukriede
- Department of Developmental Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Thomas R Kleyman
- 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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Carattino MD, Ruiz WG, Apodaca G. Ex Vivo Analysis of Mechanically Activated Ca2+ Transients in Urothelial Cells. J Vis Exp 2022:10.3791/64532. [PMID: 36279534 PMCID: PMC10069332 DOI: 10.3791/64532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Mechanically activated ion channels are biological transducers that convert mechanical stimuli such as stretch or shear forces into electrical and biochemical signals. In mammals, mechanically activated channels are essential for the detection of external and internal stimuli in processes as diverse as touch sensation, hearing, red blood cell volume regulation, basal blood pressure regulation, and the sensation of urinary bladder fullness. While the function of mechanically activated ion channels has been extensively studied in the in vitro setting using the patch-clamp technique, assessing their function in their native environment remains a difficult task, often because of limited access to the sites of expression of these channels (e.g., afferent terminals, Merkel cells, baroreceptors, and kidney tubules) or difficulties applying the patch-clamp technique (e.g., the apical surfaces of urothelial umbrella cells). This protocol describes a procedure to assess mechanically evoked Ca2+ transients using the fluorescent sensor GCaMP5G in an ex vivo urothelial preparation, a technique that could be readily adapted for the study of mechanically evoked Ca2+ events in other native tissue preparations.
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Affiliation(s)
- Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh; Department of Cell Biology, University of Pittsburgh;
| | - Wily G Ruiz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh
| | - Gerard Apodaca
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh; Department of Cell Biology, University of Pittsburgh
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Clayton DR, Ruiz WG, Dalghi MG, Montalbetti N, Carattino MD, Apodaca G. Studies of ultrastructure, gene expression, and marker analysis reveal that mouse bladder PDGFRA + interstitial cells are fibroblasts. Am J Physiol Renal Physiol 2022; 323:F299-F321. [PMID: 35834272 PMCID: PMC9394772 DOI: 10.1152/ajprenal.00135.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 06/07/2022] [Accepted: 07/06/2022] [Indexed: 11/22/2022] Open
Abstract
Fibroblasts are crucial to normal and abnormal organ and tissue biology, yet we lack basic insights into the fibroblasts that populate the bladder wall. Candidates may include bladder interstitial cells (also referred to as myofibroblasts, telocytes, and interstitial cells of Cajal-like cells), which express the fibroblast-associated marker PDGFRA along with VIM and CD34 but whose form and function remain enigmatic. By applying the latest insights in fibroblast transcriptomics, coupled with studies of gene expression, ultrastructure, and marker analysis, we observe the following: 1) that mouse bladder PDGFRA+ cells exhibit all of the ultrastructural hallmarks of fibroblasts including spindle shape, lack of basement membrane, abundant endoplasmic reticulum and Golgi, and formation of homotypic cell-cell contacts (but not heterotypic ones); 2) that they express multiple canonical fibroblast markers (including Col1a2, CD34, LY6A, and PDGFRA) along with the universal fibroblast genes Col15a1 and Pi16 but they do not express Kit; and 3) that PDGFRA+ fibroblasts include suburothelial ones (which express ACTA2, CAR3, LY6A, MYH10, TNC, VIM, Col1a2, and Col15a1), outer lamina propria ones (which express CD34, LY6A, PI16, VIM, Col1a2, Col15a1, and Pi16), intermuscular ones (which express CD34, VIM, Col1a2, Col15a1, and Pi16), and serosal ones (which express CD34, PI16, VIM, Col1a2, Col15a1, and Pi16). Collectively, our study revealed that the ultrastructure of PDFRA+ interstitial cells combined with their expression of multiple canonical and universal fibroblast-associated gene products indicates that they are fibroblasts. We further propose that there are four regionally distinct populations of fibroblasts in the bladder wall, which likely contribute to bladder function and dysfunction.NEW & NOTEWORTHY We currently lack basic insights into the fibroblasts that populate the bladder wall. By exploring the ultrastructure of mouse bladder connective tissue cells, combined with analyses of their gene and protein expression, our study revealed that PDGRA+ interstitial cells (also referred to as myofibroblasts, telocytes, and interstitial cells of Cajal-like cells) are fibroblasts and that the bladder wall contains multiple, regionally distinct populations of these cells.
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Affiliation(s)
- Dennis R Clayton
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Wily G Ruiz
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Marianela G Dalghi
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | | | - Marcelo D Carattino
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Gerard Apodaca
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
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Montalbetti N, Dalghi MG, Bastacky SI, Clayton DR, Ruiz WG, Apodaca G, Carattino MD. Bladder infection with uropathogenic Escherichia coli increases the excitability of afferent neurons. Am J Physiol Renal Physiol 2022; 322:F1-F13. [PMID: 34779263 PMCID: PMC8698541 DOI: 10.1152/ajprenal.00167.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 11/05/2021] [Indexed: 01/03/2023] Open
Abstract
Urinary tract infections (UTIs) cause bladder hyperactivity and pelvic pain, but the underlying causes of these symptoms remain unknown. We investigated whether afferent sensitization contributes to the bladder overactivity and pain observed in mice suffering from experimentally induced bacterial cystitis. Inoculation of mouse bladders with the uropathogenic Escherichia coli strain UTI89 caused pelvic allodynia, increased voiding frequency, and prompted an acute inflammatory process marked by leukocytic infiltration and edema of the mucosa. Compared with controls, isolated bladder sensory neurons from UTI-treated mice exhibited a depolarized resting membrane potential, lower action potential threshold and rheobase, and increased firing in response to suprathreshold stimulation. To determine whether bacterial virulence factors can contribute to the sensitization of bladder afferents, neurons isolated from naïve mice were incubated with supernatants collected from bacterial cultures with or depleted of lipopolysaccharide (LPS). Supernatants containing LPS prompted the sensitization of bladder sensory neurons with both tetrodotoxin (TTX)-resistant and TTX-sensitive action potentials. However, bladder sensory neurons with TTX-sensitive action potentials were not affected by bacterial supernatants depleted of LPS. Unexpectedly, ultrapure LPS increased the excitability only of bladder sensory neurons with TTX-resistant action potentials, but the supplementation of supernatants depleted of LPS with ultrapure LPS resulted in the sensitization of both population of bladder sensory neurons. In summary, the results of our study indicate that multiple virulence factors released from UTI89 act on bladder sensory neurons to prompt their sensitization. These sensitized bladder sensory neurons mediate, at least in part, the bladder hyperactivity and pelvic pain seen in mice inoculated with UTI89.NEW & NOTEWORTHY Urinary tract infection (UTI) produced by uropathogenic Escherichia coli (UPEC) promotes sensitization of bladder afferent sensory neurons with tetrodotoxin-resistant and tetrodotoxin-sensitive action potentials. Lipopolysaccharide and other virulence factors produced by UPEC contribute to the sensitization of bladder afferents in UTI. In conclusion, sensitized afferents contribute to the voiding symptoms and pelvic pain present in mice bladder inoculated with UPEC.
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Affiliation(s)
- Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Marianela G Dalghi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Sheldon I Bastacky
- Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Dennis R Clayton
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Wily G Ruiz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Gerard Apodaca
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Cell Biology, 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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Montalbetti N, Carattino MD. Acid-sensing ion channels modulate bladder nociception. Am J Physiol Renal Physiol 2021; 321:F587-F599. [PMID: 34514879 PMCID: PMC8813206 DOI: 10.1152/ajprenal.00302.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 08/30/2021] [Accepted: 09/07/2021] [Indexed: 01/23/2023] Open
Abstract
Sensitization of neuronal pathways and persistent afferent drive are major contributors to somatic and visceral pain. However, the underlying mechanisms that govern whether afferent signaling will give rise to sensitization and pain are not fully understood. In the present report, we investigated the contribution of acid-sensing ion channels (ASICs) to bladder nociception in a model of chemical cystitis induced by cyclophosphamide (CYP). We found that the administration of CYP to mice lacking ASIC3, a subunit primarily expressed in sensory neurons, generates pelvic allodynia at a time point at which only modest changes in pelvic sensitivity are apparent in wild-type mice. The differences in mechanical pelvic sensitivity between wild-type and Asic3 knockout mice treated with CYP were ascribed to sensitized bladder C nociceptors. Deletion of Asic3 from bladder sensory neurons abolished their ability to discharge action potentials in response to extracellular acidification. Collectively, the results of our study support the notion that protons and their cognate ASIC receptors are part of a mechanism that operates at the nerve terminals to control nociceptor excitability and sensitization.NEW & NOTEWORTHY Our study indicates that protons and their cognate acid-sensing ion channel receptors are part of a mechanism that operates at bladder afferent terminals to control their function and that the loss of this regulatory mechanism results in hyperactivation of nociceptive pathways and the development of pain in the setting of chemical-induced cystitis.
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Affiliation(s)
- Nicolas Montalbetti
- 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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10
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Dalghi MG, Ruiz WG, Clayton DR, Montalbetti N, Daugherty SL, Beckel JM, Carattino MD, Apodaca G. Functional roles for PIEZO1 and PIEZO2 in urothelial mechanotransduction and lower urinary tract interoception. JCI Insight 2021; 6:e152984. [PMID: 34464353 PMCID: PMC8525643 DOI: 10.1172/jci.insight.152984] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 08/12/2021] [Indexed: 11/17/2022] Open
Abstract
The mechanisms that link visceral mechanosensation to the perception of internal organ status (i.e., interoception) remain elusive. In response to bladder filling, the urothelium releases ATP, which is hypothesized to stimulate voiding function by communicating the degree of bladder fullness to subjacent tissues, including afferent nerve fibers. To determine if PIEZO channels function as mechanosensors in these events, we generated conditional urothelial Piezo1-, Piezo2-, and dual Piezo1/2-knockout (KO) mice. While functional PIEZO1 channels were expressed in all urothelial cell layers, Piezo1-KO mice had a limited phenotype. Piezo2 expression was limited to a small subset of superficial umbrella cells, yet male Piezo2-KO mice exhibited incontinence (i.e., leakage) when their voiding behavior was monitored during their active dark phase. Dual Piezo1/2-KO mice had the most affected phenotype, characterized by decreased urothelial responses to mechanical stimulation, diminished ATP release, bladder hypoactivity in anesthetized Piezo1/2-KO females but not males, and urinary incontinence in both male and female Piezo1/2-KO mice during their dark phase but not inactive light one. Our studies reveal that the urothelium functions in a sex- and circadian rhythm–dependent manner to link urothelial PIEZO1/2 channel–driven mechanotransduction to normal voiding function and behavior, and in the absence of these signals, bladder dysfunction ensues.
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Affiliation(s)
| | | | | | | | | | | | - Marcelo D Carattino
- Department of Medicine.,Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Gerard Apodaca
- Department of Medicine.,Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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11
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Dalghi MG, Montalbetti N, Carattino MD, Apodaca G. The Urothelium: Life in a Liquid Environment. Physiol Rev 2020; 100:1621-1705. [PMID: 32191559 PMCID: PMC7717127 DOI: 10.1152/physrev.00041.2019] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 03/02/2020] [Accepted: 03/14/2020] [Indexed: 02/08/2023] Open
Abstract
The urothelium, which lines the renal pelvis, ureters, urinary bladder, and proximal urethra, forms a high-resistance but adaptable barrier that surveils its mechanochemical environment and communicates changes to underlying tissues including afferent nerve fibers and the smooth muscle. The goal of this review is to summarize new insights into urothelial biology and function that have occurred in the past decade. After familiarizing the reader with key aspects of urothelial histology, we describe new insights into urothelial development and regeneration. This is followed by an extended discussion of urothelial barrier function, including information about the roles of the glycocalyx, ion and water transport, tight junctions, and the cellular and tissue shape changes and other adaptations that accompany expansion and contraction of the lower urinary tract. We also explore evidence that the urothelium can alter the water and solute composition of urine during normal physiology and in response to overdistension. We complete the review by providing an overview of our current knowledge about the urothelial environment, discussing the sensor and transducer functions of the urothelium, exploring the role of circadian rhythms in urothelial gene expression, and describing novel research tools that are likely to further advance our understanding of urothelial biology.
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Affiliation(s)
- Marianela G Dalghi
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Nicolas Montalbetti
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Marcelo D Carattino
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Gerard Apodaca
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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12
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Shi S, Montalbetti N, Wang X, Rush BM, Marciszyn AL, Baty CJ, Tan RJ, Carattino MD, Kleyman TR. Paraoxonase 3 functions as a chaperone to decrease functional expression of the epithelial sodium channel. J Biol Chem 2020; 295:4950-4962. [PMID: 32079677 DOI: 10.1074/jbc.ra119.011789] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 02/17/2020] [Indexed: 01/11/2023] Open
Abstract
The paraoxonase (PON) family comprises three highly conserved members: PON1, PON2, and PON3. They are orthologs of Caenorhabditis elegans MEC-6, an endoplasmic reticulum-resident chaperone that has a critical role in proper assembly and surface expression of the touch-sensing degenerin channel in nematodes. We have shown recently that MEC-6 and PON2 negatively regulate functional expression of the epithelial Na+ channel (ENaC), suggesting that the chaperone function is conserved within this family. We hypothesized that other PON family members also modulate ion channel expression. Pon3 is specifically expressed in the aldosterone-sensitive distal tubules in the mouse kidney. We found here that knocking down endogenous Pon3 in mouse cortical collecting duct cells enhanced Na+ transport, which was associated with increased γENaC abundance. We further examined Pon3 regulation of ENaC in two heterologous expression systems, Fisher rat thyroid cells and Xenopus oocytes. Pon3 coimmunoprecipitated with each of the three ENaC subunits in Fisher rat thyroid cells. As a result of this interaction, the whole-cell and surface abundance of ENaC α and γ subunits was reduced by Pon3. When expressed in oocytes, Pon3 inhibited ENaC-mediated amiloride-sensitive Na+ currents, in part by reducing the surface expression of ENaC. In contrast, Pon3 did not alter the response of ENaC to chymotrypsin-mediated proteolytic activation or [2-(trimethylammonium)ethyl]methanethiosulfonate-induced activation of αβS518Cγ, suggesting that Pon3 does not affect channel open probability. Together, our results suggest that PON3 regulates ENaC expression by inhibiting its biogenesis and/or trafficking.
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Affiliation(s)
- Shujie Shi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Xueqi Wang
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Nephrology, Second Xiangya Hospital of Central South University, Changsha 410011, Hunan, China
| | - Brittney M Rush
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Allison L Marciszyn
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Catherine J Baty
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Roderick J Tan
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Thomas R Kleyman
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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13
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Abstract
Acid-sensing ion channels (ASICs) are cation-permeable channels that in the periphery are primarily expressed in sensory neurons that innervate tissues and organs. Soon after the cloning of the ASIC subunits, almost 20 yr ago, investigators began to use genetically modified mice to assess the role of these channels in physiological processes. These studies provide critical insights about the participation of ASICs in sensory processes, including mechanotransduction, chemoreception, and nociception. Here, we provide an extensive assessment of these findings and discuss the current gaps in knowledge with regard to the functions of ASICs in the peripheral nervous system.
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Affiliation(s)
- Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
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14
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Dalghi MG, Clayton DR, Ruiz WG, Al-Bataineh MM, Satlin LM, Kleyman TR, Ricke WA, Carattino MD, Apodaca G. Expression and distribution of PIEZO1 in the mouse urinary tract. Am J Physiol Renal Physiol 2019; 317:F303-F321. [PMID: 31166705 PMCID: PMC6732449 DOI: 10.1152/ajprenal.00214.2019] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 05/29/2019] [Indexed: 01/09/2023] Open
Abstract
The proper function of the organs that make up the urinary tract (kidneys, ureters, bladder, and urethra) depends on their ability to sense and respond to mechanical forces, including shear stress and wall tension. However, we have limited understanding of the mechanosensors that function in these organs and the tissue sites in which these molecules are expressed. Possible candidates include stretch-activated PIEZO channels (PIEZO1 and PIEZO2), which have been implicated in mechanically regulated body functions including touch sensation, proprioception, lung inflation, and blood pressure regulation. Using reporter mice expressing a COOH-terminal fusion of Piezo1 with the sequence for the tandem-dimer Tomato gene, we found that PIEZO1 is expressed in the kidneys, ureters, bladder, and urethra as well as organs in close proximity, including the prostate, seminal vesicles and ducts, ejaculatory ducts, and the vagina. We further found that PIEZO1 expression is not limited to one cell type; it is observed in the endothelial and parietal cells of the renal corpuscle, the basolateral surfaces of many of the epithelial cells that line the urinary tract, the interstitial cells of the bladder and ureters, and populations of smooth and striated muscle cells. We propose that in the urinary tract, PIEZO1 likely functions as a mechanosensor that triggers responses to wall tension.
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Affiliation(s)
- Marianela G Dalghi
- Department of Medicine and George M. O'Brien Pittsburgh Center for Kidney Research, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
| | - Dennis R Clayton
- Department of Medicine and George M. O'Brien Pittsburgh Center for Kidney Research, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
| | - Wily G Ruiz
- Department of Medicine and George M. O'Brien Pittsburgh Center for Kidney Research, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
| | - Mohammad M Al-Bataineh
- Department of Medicine and George M. O'Brien Pittsburgh Center for Kidney Research, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
| | - Lisa M Satlin
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai , New York, New York
| | - Thomas R Kleyman
- Department of Medicine and George M. O'Brien Pittsburgh Center for Kidney Research, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
- Department of Cell Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
- Department of Chemical Biology and Pharmacology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
| | - William A Ricke
- Department of Urology and George M. O'Brien Center for Research Excellence, University of Wisconsin-Madison, Madison, Wisconsin
| | - Marcelo D Carattino
- Department of Medicine and George M. O'Brien Pittsburgh Center for Kidney Research, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
- Department of Cell Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
| | - Gerard Apodaca
- Department of Medicine and George M. O'Brien Pittsburgh Center for Kidney Research, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
- Department of Cell Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
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15
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Montalbetti N, Rooney JG, Rued AC, Carattino MD. Molecular determinants of afferent sensitization in a rat model of cystitis with urothelial barrier dysfunction. J Neurophysiol 2019; 122:1136-1146. [PMID: 31314637 DOI: 10.1152/jn.00306.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The internal surface of the urinary bladder is covered by the urothelium, a stratified epithelium that forms an impermeable barrier to urinary solutes. Increased urothelial permeability is thought to contribute to symptom generation in several forms of cystitis by sensitizing bladder afferents. In this report we investigate the physiological mechanisms that mediate bladder afferent hyperexcitability in a rat model of cystitis induced by overexpression in the urothelium of claudin-2 (Cldn2), a tight junction-associated protein upregulated in bladder biopsies from patients with interstitial cystitis/bladder pain syndrome. Patch-clamp studies showed that overexpression of Cldn2 in the urothelium sensitizes a population of isolectin GS-IB4-negative [IB4(-)] bladder sensory neurons with tetrodotoxin-sensitive (TTX-S) action potentials. Gene expression analysis revealed a significant increase in mRNA levels of the delayed-rectifier voltage-gated K+ channel (Kv)2.2 and the accessory subunit Kv9.1 in this population of bladder sensory neurons. Consistent with this finding, Kv2/Kv9.1 channel activity was greater in IB4(-) bladder sensory neurons from rats overexpressing Cldn2 in the urothelium than in control counterparts. Likewise, current density of TTX-S voltage-gated Na+ (Nav) channels was greater in sensitized neurons than in control counterparts. Significantly, guangxitoxin-1E (GxTX-1E), a selective blocker of Kv2 channels, blunted the repetitive firing of sensitized IB4(-) sensory neurons. In summary, our studies indicate that an increase in the activity of TTX-S Nav and Kv2/Kv9.1 channels mediates repetitive firing of sensitized bladder sensory neurons in rats with increased urothelial permeability.NEW & NOTEWORTHY Hyperexcitability of sensitized bladder sensory neurons in a rat model of interstitial cystitis/bladder pain syndrome (IC/BPS) results from increased activity of tetrodotoxin-sensitive voltage-gated Na+ and delayed-rectifier voltage-gated K+ (Kv)2/Kv9.1 channels. Of major significance, our studies indicate that Kv2/Kv9.1 channels play a major role in symptom generation in this model of IC/BPS by maintaining the sustained firing of the sensitized bladder sensory neurons.
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Affiliation(s)
- Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - James G Rooney
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Anna C Rued
- 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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16
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Wang XP, Im SJ, Balchak DM, Montalbetti N, Carattino MD, Ray EC, Kashlan OB. Murine epithelial sodium (Na +) channel regulation by biliary factors. J Biol Chem 2019; 294:10182-10193. [PMID: 31092599 PMCID: PMC6664190 DOI: 10.1074/jbc.ra119.007394] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 05/15/2019] [Indexed: 01/01/2023] Open
Abstract
The epithelial sodium channel (ENaC) mediates Na+ transport in several epithelia, including the aldosterone-sensitive distal nephron, distal colon, and biliary epithelium. Numerous factors regulate ENaC activity, including extracellular ligands, post-translational modifications, and membrane-resident lipids. However, ENaC regulation by bile acids and conjugated bilirubin, metabolites that are abundant in the biliary tree and intestinal tract and are sometimes elevated in the urine of individuals with advanced liver disease, remains poorly understood. Here, using a Xenopus oocyte-based system to express and functionally study ENaC, we found that, depending on the bile acid used, bile acids both activate and inhibit mouse ENaC. Whether bile acids were activating or inhibiting was contingent on the position and orientation of specific bile acid moieties. For example, a hydroxyl group at the 12-position and facing the hydrophilic side (12α-OH) was activating. Taurine-conjugated bile acids, which have reduced membrane permeability, affected ENaC activity more strongly than did their more membrane-permeant unconjugated counterparts, suggesting that bile acids regulate ENaC extracellularly. Bile acid-dependent activation was enhanced by amino acid substitutions in ENaC that depress open probability and was precluded by proteolytic cleavage that increases open probability, consistent with an effect of bile acids on ENaC open probability. Bile acids also regulated ENaC in a cortical collecting duct cell line, mirroring the results in Xenopus oocytes. We also show that bilirubin conjugates activate ENaC. These results indicate that ENaC responds to compounds abundant in bile and that their ability to regulate this channel depends on the presence of specific functional groups.
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Affiliation(s)
- Xue-Ping Wang
- From the Renal-Electrolyte Division, Department of Medicine
| | | | | | | | - Marcelo D Carattino
- From the Renal-Electrolyte Division, Department of Medicine
- the Department of Cell Biology and Molecular Physiology, and
| | - Evan C Ray
- From the Renal-Electrolyte Division, Department of Medicine
| | - Ossama B Kashlan
- From the Renal-Electrolyte Division, Department of Medicine,
- the Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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17
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Ong J, Kinsman BJ, Sved AF, Rush BM, Tan RJ, Carattino MD, Stocker SD. Renal sensory nerves increase sympathetic nerve activity and blood pressure in 2-kidney 1-clip hypertensive mice. J Neurophysiol 2019; 122:358-367. [PMID: 31091159 DOI: 10.1152/jn.00173.2019] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Renal denervation lowers arterial blood pressure (ABP) in multiple clinical trials and some experimental models of hypertension. These antihypertensive effects have been attributed to the removal of renal afferent nerves. The purpose of the present study was to define the function, anatomy, and contribution of mouse renal sensory neurons to a renal nerve-dependent model of hypertension. First, electrical stimulation of mouse renal afferent nerves produced frequency-dependent increases in ABP that were eliminated by ganglionic blockade. Stimulus-triggered averaging revealed renal afferent stimulation significantly increased splanchnic, renal, and lumbar sympathetic nerve activity (SNA). Second, kidney injection of wheat germ agglutinin into male C57Bl6 mice (12-14 wk; Jackson Laboratories) produced ipsilateral labeling in the T11-L2 dorsal root ganglia. Next, 2-kidney 1-clip (2K1C) hypertension was produced in male C57Bl6 mice (12-14 wk; Jackson Laboratories) by placement of a 0.5-mm length of polytetrafluoroethylene tubing around the left renal artery. 2K1C mice displayed an elevated ABP measured via telemetry and a greater fall in mean ABP to ganglionic blockade at day 14 or 21 vs. day 0. Renal afferent discharge was significantly higher in 2K1C-clipped vs. 2K1C-unclipped or sham kidneys. In addition, 2K1C-clipped vs. 2K1C-unclipped or sham kidneys had lower renal mass and higher mRNA levels of several proinflammatory cytokines. Finally, both ipsilateral renal denervation (10% phenol) or selective denervation of renal afferent nerves (periaxonal application of 33 mM capsaicin) at time of clipping resulted in lower ABP of 2K1C mice at day 14 or 21. These findings suggest mouse renal sensory neurons are activated to increase SNA and ABP in 2K1C hypertension. NEW & NOTEWORTHY This study documents the function, anatomy, and contribution of mouse renal sensory nerves to neurogenic hypertension produced by renal stenosis. Activation of renal afferents increased sympathetic nerve activity and blood pressure. Renal afferent activity was elevated in hypertensive mice, and renal afferent denervation lowered blood pressure. Clinically, patients with renal stenosis have been excluded from clinical trials for renal denervation, but this study highlights the potential therapeutic efficacy to target renal nerves in these patients.
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Affiliation(s)
- Jason Ong
- Division of Renal-Electrolyte, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Neuroscience, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Brian J Kinsman
- Division of Renal-Electrolyte, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Alan F Sved
- Department of Neuroscience, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Brittney M Rush
- Division of Renal-Electrolyte, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Roderick J Tan
- Division of Renal-Electrolyte, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Marcelo D Carattino
- Division of Renal-Electrolyte, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Sean D Stocker
- Division of Renal-Electrolyte, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
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18
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Montalbetti N, Stocker SD, Apodaca G, Bastacky SI, Carattino MD. Urinary K + promotes irritative voiding symptoms and pain in the face of urothelial barrier dysfunction. Sci Rep 2019; 9:5509. [PMID: 30940909 PMCID: PMC6445132 DOI: 10.1038/s41598-019-41971-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 03/12/2019] [Indexed: 12/22/2022] Open
Abstract
The internal surface of the bladder is lined by the urothelium, a stratified epithelium that forms an impermeable barrier to water and urine constituents. Abnormalities in the urothelial barrier have been described in certain forms of cystitis and were hypothesized to contribute to irritative voiding symptoms and pain by allowing the permeation of urinary K+ into suburothelial tissues, which then alters afferent signaling and smooth muscle function. Here, we examined the mechanisms underlying organ hyperactivity and pain in a model of cystitis caused by adenoviral-mediated expression of claudin-2 (Cldn2), a tight junction protein that forms paracellular pores and increases urothelial permeability. We found that in the presence of a leaky urothelium, intravesical K+ sensitizes bladder afferents and enhances their response to distension. Notably, dietary K+ restriction, a maneuver that reduces urinary K+, prevented the development of pelvic allodynia and inflammation seen in rats expressing Cldn2. Most importantly, intravesical K+ causes and is required to maintain bladder hyperactivity in rats with increased urothelial permeability. Our study demonstrates that in the face of a leaky urothelium, urinary K+ is the main determinant of afferent hyperexcitability, organ hyperactivity and pain. These findings support the notion that voiding symptoms and pain seen in forms of cystitis that coexist with urothelial barrier dysfunction could be alleviated by cutting urinary K+ levels.
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Affiliation(s)
- Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Sean D Stocker
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Gerard Apodaca
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Sheldon I Bastacky
- Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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19
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Wang X, Im SJ, Ertem M, Balchak DM, Montalbetti N, Carattino MD, Ray EC, Kashlan OB. ENaC activation by bile acids depends on specific moieties, but not on membrane permeability. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.751.16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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20
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Ong J, Sved AF, Tan RJ, Rush BM, Carattino MD, Stocker SD. Abstract 081: Renal Sensory Nerves Increase Blood Pressure and Sympathetic Nerve Activity in 2-Kidney 1-Clip Hypertensive Mice. Hypertension 2018. [DOI: 10.1161/hyp.72.suppl_1.081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Renal denervation lowers arterial blood pressure (ABP) in multiple clinical trials and some experimental models of hypertension. These antihypertensive effects have been attributed to the removal of renal afferent nerves. The purpose of the present study was to determine whether renal sensory nerves contributed to the 2-Kidney-1-Clip (2K1C) model of hypertension. 2K1C hypertension was produced in male C57Bl6 mice (12-14 weeks, Jackson Laboratories) by placement of a 0.5mm length of PTFE tubing (ID: 0.008” x OD: 0.014”) around the left renal artery. 2K1C mice (n=6) displayed an elevated ABP measured via telemetry (Day 0: 96±4mmHg vs Day 14: 115±3mmHg, P<0.05). Ganglionic blockade with hexamethonium (30mg/kg, ip) produced a greater fall in mean ABP at Day 14 vs Day 0 (Day 0: -38±4mmHg vs Day 14: -51±4mmHg, P<0.05). Ipsilateral vs contralateral kidneys of 2K1C mice had lower mass (0.072±0.01g vs 0.163±0.02g, respectively; P<0.05) and higher mRNA levels of several pro-inflammatory cytokines (IL1B, IL2, IL10, TNFa; P<0.05). Both total renal denervation (10% phenol) or selective denervation of renal afferent nerves (periaxonal application of 33mM capsaicin) at time of clipping resulted in a lower ABP than 2K1C mice at Day 14 (2K1C: 115±3mmHg, phenol: 104±2mmHg, capsaicin: 105±3mmHg; P<0.05). Direct recording of renal afferent nerve activity showed significantly greater discharge in 2K1C versus control mice (control: 2.2±1.3Hz vs 2K1C: 61±12Hz, n=3/group; P<0.05). Furthermore, electrical stimulation of renal afferent nerves in control mice produced a frequency-dependent increase in ABP (5Hz: 3±1mmHg, 10Hz: 7±1mmHg, 20Hz: 12±2mmHg, n=4/group; P<0.05). These responses were eliminated after ganglionic blockade with 5mg/kg chlorisondamine (5Hz: 1±1mmHg, 10Hz: 1±1mmHg, 20Hz: 1±1mmHg; P<0.05). Stimulus-triggered averaging of SNA during stimulation of renal afferent nerves (1 Hz, 200uA) revealed significant (P<0.05, n=4/group) increases in splanchnic (221±28%), renal (195+15%), and lumbar (234±32%) SNA. Interestingly, the latency to the peak SNA (142±10ms) suggests supraspinal pathways mediate the sympathoexcitatory response. These findings suggest 2K1C hypertension depends on renal sensory nerves and elevated SNA via supraspinal pathways.
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21
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Krauson AJ, Rooney JG, Carattino MD. Molecular basis of inhibition of acid sensing ion channel 1A by diminazene. PLoS One 2018; 13:e0196894. [PMID: 29782492 PMCID: PMC5962070 DOI: 10.1371/journal.pone.0196894] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 04/20/2018] [Indexed: 11/18/2022] Open
Abstract
Acid-sensing ion channels (ASICs) are trimeric proton-gated cation permeable ion channels expressed primarily in neurons. Here we employed site-directed mutagenesis and electrophysiology to investigate the mechanism of inhibition of ASIC1a by diminazene. This compound inhibits mouse ASIC1a with a half-maximal inhibitory concentration (IC50) of 2.4 μM. At first, we examined whether neutralizing mutations of Glu79 and Glu416 alter diminazene block. These residues form a hexagonal array in the lower palm domain that was previously shown to contribute to pore opening in response to extracellular acidification. Significantly, single Gln substitutions at positions 79 and 416 in ASIC1a reduced diminazene apparent affinity by 6-7 fold. This result suggests that diminazene inhibits ASIC1a in part by limiting conformational rearrangement in the lower palm domain. Because diminazene is charged at physiological pHs, we assessed whether it inhibits ASIC1a by blocking the ion channel pore. Consistent with the notion that diminazene binds to a site within the membrane electric field, diminazene block showed a strong dependence with the membrane potential. Moreover, a Gly to Ala mutation at position 438, in the ion conduction pathway of ASIC1a, increased diminazene IC50 by one order of magnitude and eliminated the voltage dependence of block. Taken together, our results indicate that the inhibition of ASIC1a by diminazene involves both allosteric modulation and blocking of ion flow through the conduction pathway. Our findings provide a foundation for the development of more selective and potent ASIC pore blockers.
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Affiliation(s)
- Aram J Krauson
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - James G Rooney
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
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22
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Abstract
Acid-sensing ion channels (ASICs) are trimeric proton-activated, cation-selective neuronal channels that are considered to play important roles in mechanosensation and nociception. Here we investigated the role of ASIC3, a subunit primarily expressed in sensory neurons, in bladder sensory signaling and function. We found that extracellular acidification evokes a transient increase in current, consistent with the kinetics of activation and desensitization of ASICs, in ~25% of the bladder sensory neurons harvested from both wild-type (WT) and ASIC3 knockout (KO) mice. The absence of ASIC3 increased the magnitude of the peak evoked by extracellular acidification and reduced the rate of decay of the ASIC-like currents. These findings suggest that ASICs are assembled as heteromers and that the absence of ASIC3 alters the composition of these channels in bladder sensory neurons. Consistent with the notion that ASIC3 serves as a proton sensor, 59% of the bladder sensory neurons harvested from WT, but none from ASIC3 KO mice, fired action potentials in response to extracellular acidification. Studies of bladder function revealed that ASIC3 deletion reduces voiding volume and the pressure required to trigger micturition. In summary, our findings indicate that ASIC3 plays a role in the control of bladder function by modulating the response of afferents to filling.
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Affiliation(s)
- Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - James G Rooney
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Allison L Marciszyn
- 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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23
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Bhattacharyya S, Jean-Alphonse FG, Raghavan V, McGarvey JC, Rbaibi Y, Vilardaga JP, Carattino MD, Weisz OA. Cdc42 activation couples fluid shear stress to apical endocytosis in proximal tubule cells. Physiol Rep 2017; 5:5/19/e13460. [PMID: 29038362 PMCID: PMC5641940 DOI: 10.14814/phy2.13460] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 08/30/2017] [Accepted: 09/04/2017] [Indexed: 11/24/2022] Open
Abstract
Cells lining the kidney proximal tubule (PT) respond to acute changes in glomerular filtration rate and the accompanying fluid shear stress (FSS) to regulate reabsorption of ions, glucose, and other filtered molecules and maintain glomerulotubular balance. Recently, we discovered that exposure of PT cells to FSS also stimulates an increase in apical endocytic capacity (Raghavan et al. PNAS, 111:8506–8511, 2014). We found that FSS triggered an increase in intracellular Ca2+ concentration ([Ca2+]i) that required release of extracellular ATP and the presence of primary cilia. In this study, we elucidate steps downstream of the increase in [Ca2+]i that link FSS‐induced calcium increase to increased apical endocytic capacity. Using an intramolecular FRET probe, we show that activation of Cdc42 is a necessary step in the FSS‐stimulated apical endocytosis cascade. Cdc42 activation requires the primary cilia and the FSS‐mediated increase in [Ca2+]i. Moreover, Cdc42 activity and FSS‐stimulated endocytosis are coordinately modulated by activators and inhibitors of calmodulin. Together, these data suggest a mechanism by which PT cell exposure to FSS is translated into enhanced endocytic uptake of filtered molecules.
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Affiliation(s)
- Sohinee Bhattacharyya
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Frédéric G Jean-Alphonse
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Venkatesan Raghavan
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Jennifer C McGarvey
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Youssef Rbaibi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Jean-Pierre Vilardaga
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Ora A Weisz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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24
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Mukherjee A, Wang Z, Kinlough CL, Poland PA, Marciszyn AL, Montalbetti N, Carattino MD, Butterworth MB, Kleyman TR, Hughey RP. Specific Palmitoyltransferases Associate with and Activate the Epithelial Sodium Channel. J Biol Chem 2017; 292:4152-4163. [PMID: 28154191 DOI: 10.1074/jbc.m117.776146] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Indexed: 11/06/2022] Open
Abstract
The epithelial sodium channel (ENaC) has an important role in regulating extracellular fluid volume and blood pressure, as well as airway surface liquid volume and mucociliary clearance. ENaC is a trimer of three homologous subunits (α, β, and γ). We previously reported that cytoplasmic residues on the β (βCys-43 and βCys-557) and γ (γCys-33 and γCys-41) subunits are palmitoylated. Mutation of Cys that blocked ENaC palmitoylation also reduced channel open probability. Furthermore, γ subunit palmitoylation had a dominant role over β subunit palmitoylation in regulating ENaC. To determine which palmitoyltransferases (termed DHHCs) regulate the channel, mouse ENaCs were co-expressed in Xenopus oocytes with each of the 23 mouse DHHCs. ENaC activity was significantly increased by DHHCs 1, 2, 3, 7, and 14. ENaC activation by DHHCs was lost when γ subunit palmitoylation sites were mutated, whereas DHHCs 1, 2, and 14 still activated ENaC lacking β subunit palmitoylation sites. β subunit palmitoylation was increased by ENaC co-expression with DHHC 7. Both wild type ENaC and channels lacking β and γ palmitoylation sites co-immunoprecipitated with the five activating DHHCs, suggesting that ENaC forms a complex with multiple DHHCs. RT-PCR revealed that transcripts for the five activating DHHCs were present in cultured mCCDcl1 cells, and DHHC 3 was expressed in aquaporin 2-positive principal cells of mouse aldosterone-sensitive distal nephron where ENaC is localized. Treatment of polarized mCCDcl1 cells with a general inhibitor of palmitoylation reduced ENaC-mediated Na+ currents within minutes. Our results indicate that specific DHHCs have a role in regulating ENaC.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Thomas R Kleyman
- From the Departments of Medicine, .,Cell Biology, and.,Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
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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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26
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Abstract
Acid-sensing ion channels (ASICs) are cation-selective proton-gated channels expressed in neurons that participate in diverse physiological processes, including nociception, synaptic plasticity, learning, and memory. ASIC subunits contain intracellular N and C termini, two transmembrane domains that constitute the pore, and a large extracellular loop with defined domains termed the finger, β-ball, thumb, palm, and knuckle. Here we examined the contribution of the finger, β-ball, and thumb domains to activation and desensitization through the analysis of chimeras and the assessment of the effect of covalent modification of introduced Cys at the domain-domain interfaces. Our studies with ASIC1a-ASIC2a chimeras showed that swapping the thumb domain between subunits results in faster channel desensitization. Likewise, the covalent modification of Cys residues at selected positions in the β-ball-thumb interface accelerates the desensitization of the mutant channels. Studies of accessibility with thiol-reactive reagents revealed that the β-ball and thumb domains reside apart in the resting state but that they become closer to each other in response to extracellular acidification. We propose that the thumb domain moves upon continuous exposure to an acidic extracellular milieu, assisting with the closing of the pore during channel desensitization.
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Affiliation(s)
- Aram J Krauson
- From the Renal-Electrolyte Division, Department of Medicine, and
| | - Marcelo D Carattino
- From the Renal-Electrolyte Division, Department of Medicine, and Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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27
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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28
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Webb TN, Carrisoza-Gaytan R, Montalbetti N, Rued A, Roy A, Socovich AM, Subramanya AR, Satlin LM, Kleyman TR, Carattino MD. Cell-specific regulation of L-WNK1 by dietary K. Am J Physiol Renal Physiol 2015; 310:F15-26. [PMID: 26662201 DOI: 10.1152/ajprenal.00226.2015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 10/11/2015] [Indexed: 12/31/2022] Open
Abstract
Flow-induced K(+) secretion in the aldosterone-sensitive distal nephron is mediated by high-conductance Ca(2+)-activated K(+) (BK) channels. Familial hyperkalemic hypertension (pseudohypoaldosteronism type II) is an inherited form of hypertension with decreased K(+) secretion and increased Na(+) reabsorption. This disorder is linked to mutations in genes encoding with-no-lysine kinase 1 (WNK1), WNK4, and Kelch-like 3/Cullin 3, two components of an E3 ubiquitin ligase complex that degrades WNKs. We examined whether the full-length (or "long") form of WNK1 (L-WNK1) affected the expression of BK α-subunits in HEK cells. Overexpression of L-WNK1 promoted a significant increase in BK α-subunit whole cell abundance and functional channel expression. BK α-subunit abundance also increased with coexpression of a kinase dead L-WNK1 mutant (K233M) and with kidney-specific WNK1 (KS-WNK1), suggesting that the catalytic activity of L-WNK1 was not required to increase BK expression. We examined whether dietary K(+) intake affected L-WNK1 expression in the aldosterone-sensitive distal nephron. We found a paucity of L-WNK1 labeling in cortical collecting ducts (CCDs) from rabbits on a low-K(+) diet but observed robust staining for L-WNK1 primarily in intercalated cells when rabbits were fed a high-K(+) diet. Our results and previous findings suggest that L-WNK1 exerts different effects on renal K(+) secretory channels, inhibiting renal outer medullary K(+) channels and activating BK channels. A high-K(+) diet induced an increase in L-WNK1 expression selectively in intercalated cells and may contribute to enhanced BK channel expression and K(+) secretion in CCDs.
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Affiliation(s)
- Tennille N Webb
- Department of Pediatrics, University of Pittsburgh, Pittsburgh, Pennsylvania
| | | | | | - Anna Rued
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Ankita Roy
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | | | - Arohan R Subramanya
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania; Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, Pennsylvania
| | - Lisa M Satlin
- Department of Pediatrics, The Icahn School of Medicine at Mount Sinai, New York, New York; and
| | - Thomas R Kleyman
- 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;
| | - Marcelo D Carattino
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
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29
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Montalbetti N, Rued AC, Clayton DR, Ruiz WG, Bastacky SI, Prakasam HS, Eaton AF, Kullmann FA, Apodaca G, Carattino MD. Increased urothelial paracellular transport promotes cystitis. Am J Physiol Renal Physiol 2015; 309:F1070-81. [PMID: 26423859 DOI: 10.1152/ajprenal.00200.2015] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 09/24/2015] [Indexed: 12/11/2022] Open
Abstract
Changes in the urothelial barrier are observed in patients with cystitis, but whether this leads to inflammation or occurs in response to it is currently unknown. To determine whether urothelial barrier dysfunction is sufficient to promote cystitis, we employed in situ adenoviral transduction to selectively overexpress the pore-forming tight junction-associated protein claudin-2 (CLDN-2). As expected, the expression of CLDN-2 in the umbrella cells increased the permeability of the paracellular route toward ions, but not to large organic molecules. In vivo studies of bladder function revealed higher intravesical basal pressures, reduced compliance, and increased voiding frequency in rats transduced with CLDN-2 vs. controls transduced with green fluorescent protein. While the integrity of the urothelial barrier was preserved in the rats transduced with CLDN-2, we found that the expression of this protein in the umbrella cells initiated an inflammatory process in the urinary bladder characterized by edema and the presence of a lymphocytic infiltrate. Taken together, these results are consistent with the notion that urothelial barrier dysfunction may be sufficient to trigger bladder inflammation and to alter bladder function.
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Affiliation(s)
- Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Anna C Rued
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Dennis R Clayton
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Wily G Ruiz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Sheldon I Bastacky
- Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - H Sandeep Prakasam
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Amity F Eaton
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - F Aura Kullmann
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Gerard Apodaca
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania; and
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30
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Heidrich E, Carattino MD, Hughey RP, Pilewski JM, Kleyman TR, Myerburg MM. Intracellular Na+ regulates epithelial Na+ channel maturation. J Biol Chem 2015; 290:11569-77. [PMID: 25767115 DOI: 10.1074/jbc.m115.640763] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Indexed: 12/28/2022] Open
Abstract
Epithelial Na(+) channel (ENaC) function is regulated by the intracellular Na(+) concentration ([Na(+)]i) through a process known as Na(+) feedback inhibition. Although this process is known to decrease the expression of proteolytically processed active channels on the cell surface, it is unknown how [Na(+)]i alters ENaC cleavage. We show here that [Na(+)]i regulates the posttranslational processing of ENaC subunits during channel biogenesis. At times when [Na(+)]i is low, ENaC subunits develop mature N-glycans and are processed by proteases. Conversely, glycan maturation and sensitivity to proteolysis are reduced when [Na(+)]i is relatively high. Surface channels with immature N-glycans were not processed by endogenous channel activating proteases, nor were they sensitive to cleavage by exogenous trypsin. Biotin chase experiments revealed that the immature surface channels were not converted into mature cleaved channels following a reduction in [Na(+)]i. The hypothesis that [Na(+)]i regulates ENaC maturation within the biosynthetic pathways is further supported by the finding that Brefeldin A prevented the accumulation of processed surface channels following a reduction in [Na(+)]i. Therefore, increased [Na(+)]i interferes with ENaC N-glycan maturation and prevents the channel from entering a state that allows proteolytic processing.
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Affiliation(s)
- Elisa Heidrich
- From the Division of Pulmonary, Allergy, and Critical Care Medicine
| | - Marcelo D Carattino
- Renal-Electrolyte Division, and Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Rebecca P Hughey
- From the Division of Pulmonary, Allergy, and Critical Care Medicine, Renal-Electrolyte Division, and
| | - Joseph M Pilewski
- From the Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Thomas R Kleyman
- Renal-Electrolyte Division, and Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Mike M Myerburg
- From the Division of Pulmonary, Allergy, and Critical Care Medicine,
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31
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Krauson AJ, Carattino MD. Functional Coupling between the Finger and Thumb Domains of ASIC1A. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.1572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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32
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Carattino MD, Mueller GM, Palmer LG, Frindt G, Rued AC, Hughey RP, Kleyman TR. Prostasin interacts with the epithelial Na+ channel and facilitates cleavage of the γ-subunit by a second protease. Am J Physiol Renal Physiol 2014; 307:F1080-7. [PMID: 25209858 DOI: 10.1152/ajprenal.00157.2014] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
During maturation, the α- and γ-subunits of the epithelial Na+ channel (ENaC) undergo proteolytic processing by furin. Cleavage of the γ-subunit by furin at the consensus site γRKRR143 and subsequent cleavage by a second protease at a distal site strongly activate the channel. For example, coexpression of prostasin with ENaC increases both channel function and cleavage at the γRKRK186 site. We generated a polyclonal antibody that recognizes the region 144-186 in the γ-subunit (anti-γ43) to determine whether prostasin promotes the release of the intervening tract between the putative furin and γRKRK186 cleavage sites. Anti-γ43 precipitated both full-length (93 kDa) and furin-processed (83 kDa) γ-subunits from extracts obtained from oocytes expressing αβHA-γ-V5 channels, but only the full-length (93 kDa) γ-subunit from oocytes expressing αβHA-γ-V5 channels and either wild-type or a catalytically inactive prostasin. Although both wild-type and catalytically inactive prostasin activated ENaCs in an aprotinin-sensitive manner, only wild-type prostasin bound to aprotinin beads, suggesting that catalytically inactive prostasin facilitates the cleavage of the γ-subunit by an endogenous protease in Xenopus oocytes. As dietary salt restriction increases cleavage of the renal γ-subunit, we assessed release of the 43-mer inhibitory tract on rats fed a low-Na+ diet. We found that a low-Na+ diet increased γ-subunit cleavage detected with the anti-γ antibody and dramatically reduced the fraction precipitated with the anti-γ43 antibody. Our results suggest that the inhibitory tract dissociates from the γ-subunit in kidneys from rats on a low-Na+ diet.
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Affiliation(s)
- Marcelo D Carattino
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; Department Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Gunhild M Mueller
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York
| | - Gustavo Frindt
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York
| | - Anna C Rued
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Rebecca P Hughey
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; Department Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Thomas R Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; Department Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania; and
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33
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Krauson AJ, Carattino MD. Finger-Thumb Interdomain Interactions Influence ASIC1a Proton Activation. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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34
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Abstract
Acid-sensing ion channels (ASICs) are a group of trimeric cation permeable channels gated by extracellular protons that are mainly expressed in the nervous system. Despite the structural information available for ASIC1, there is limited understanding of the molecular mechanism that allows these channels to sense and respond to drops in extracellular pH. In this report, we employed the substituted cysteine accessibility method and site-directed mutagenesis to examine the mechanism of activation of ASIC1a by extracellular protons. We found that the modification of E238C and D345C channels by MTSET reduced proton apparent affinity for activation. Furthermore, the introduction of positively charged residues at position 345 rendered shifted biphasic proton activation curves. Likewise, channels bearing mutations at positions 79 and 416 in the palm domain of the channel showed reduced proton apparent affinity and biphasic proton activation curves. Of significance, the effect of the mutations at positions 79 and 345 on channel activation was additive. E79K-D345K required a change to a pH lower than 2 for maximal activation. In summary, this study provides direct evidence for the presence of two distinct proton coordination sites in the extracellular region of ASIC1a, which jointly facilitate pore opening in response to extracellular acidification.
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Affiliation(s)
- Aram J Krauson
- From the Division of Renal Electrolytes, Department of Medicine, and
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35
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Carattino MD, Prakasam HS, Ruiz WG, Clayton DR, McGuire M, Gallo LI, Apodaca G. Bladder filling and voiding affect umbrella cell tight junction organization and function. Am J Physiol Renal Physiol 2013; 305:F1158-68. [PMID: 23884145 DOI: 10.1152/ajprenal.00282.2013] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Epithelial cells are continuously exposed to mechanical forces including shear stress and stretch, although the effect these forces have on tight junction (TJ) organization and function are poorly understood. Umbrella cells form the outermost layer of the stratified uroepithelium and undergo large cell shape and surface area changes during the bladder cycle. Here we investigated the effects of bladder filling and voiding on the umbrella cell TJ. We found that bladder filling promoted a significant increase in the length of the TJ ring, which was quickly reversed within 5 min of voiding. Interestingly, when isolated uroepithelial tissue was mounted in Ussing chambers and exposed to physiological stretch, we observed a 10-fold drop in both transepithelial electrical resistance (TER) and the umbrella cell junctional resistance. The effects of stretch on TER were reversible and dependent on the applied force. Furthermore, the integrity of the umbrella cell TJ was maintained in the stretched uroepithelium, as suggested by the limited permeability of biotin, fluorescein, and ruthenium red. Finally, we found that depletion of extracellular Ca(2+) by EGTA completely disrupted the TER of unstretched, but not of stretched uroepithelium. Taken together, our studies indicate that the umbrella cell TJ undergoes major structural and functional reorganization during the bladder cycle. The impact of these changes on bladder function is discussed.
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36
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Wang Z, Subramanya AR, Satlin LM, Pastor-Soler NM, Carattino MD, Kleyman TR. Regulation of large-conductance Ca2+-activated K+ channels by WNK4 kinase. Am J Physiol Cell Physiol 2013; 305:C846-53. [PMID: 23885063 DOI: 10.1152/ajpcell.00133.2013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Large-conductance, Ca(2+)-activated K(+) channels, commonly referred to as BK channels, have a major role in flow-induced K(+) secretion in the distal nephron. With-no-lysine kinase 4 (WNK4) is a serine-threonine kinase expressed in the distal nephron that inhibits ROMK activity and renal K(+) secretion. WNK4 mutations have been described in individuals with familial hyperkalemic hypertension (FHHt), a Mendelian disorder characterized by low-renin hypertension and hyperkalemia. As BK channels also have an important role in renal K(+) secretion, we examined whether they are regulated by WNK4 in a manner similar to ROMK. BK channel activity was inhibited in a rabbit intercalated cell line transfected with WNK4 or a WNK4 mutant found in individuals with FHHt. Coexpression of an epitope-tagged BK α-subunit with WNK4 or the WNK4 mutant in HEK293 cells reduced BK α-subunit plasma membrane and whole cell expression. A region within WNK4 encompassing the autoinhibitory domain and a coiled coil domain was required for WNK4 to inhibit BK α-subunit expression. The relative fraction of BK α-subunit that was ubiquitinated was significantly increased in cells expressing WNK4, compared with controls. Our results suggest that WNK4 inhibits BK channel activity, in part, by increasing channel degradation through an ubiquitin-dependent pathway. Based on these results, we propose that WNK4 provides a cellular mechanism for the coordinated regulation of two key secretory K(+) channels in the distal nephron, ROMK and BK.
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Affiliation(s)
- Zhijian Wang
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
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37
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Shi S, Carattino MD, Hughey RP, Kleyman TR. ENaC Regulation by Proteases and Shear Stress. Curr Mol Pharmacol 2013; 6:28-34. [DOI: 10.2174/18744672112059990027] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 08/24/2012] [Accepted: 02/24/2013] [Indexed: 11/22/2022]
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38
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Abstract
Acid-sensing ion channels (ASICs) are trimeric cation-selective proton-gated ion channels expressed in the central and peripheral nervous systems. The pore-forming transmembrane helices in these channels are linked by short loops to the palm domain in the extracellular region. Here, we explore the contribution to proton gating and desensitization of Glu-79 and Glu-416 in the palm domain of ASIC1a. Engineered Cys, Lys, and Gln substitutions at these positions shifted apparent proton affinity toward more acidic values. Double mutant cycle analysis indicated that Glu-79 and Glu-416 cooperatively facilitated pore opening in response to extracellular acidification. Channels bearing Cys at position 79 or 416 were irreversibly modified by thiol-reactive reagents in a state-dependent manner. Glu-79 and Glu-416 are located in β-strands 1 and 12, respectively. The covalent modification by (2-(trimethylammonium)ethyl) methanethiosulfonate bromide of Cys at position 79 impacted conformational changes associated with pore closing during desensitization, whereas the modification of Cys at position 416 affected conformational changes associated with proton gating. These results suggest that β-strands 1 and 12 contribute antagonistically to activation and desensitization of ASIC1a. Site-directed mutagenesis experiments indicated that the lower palm domain contracts in response to extracellular acidification. Taken together, our studies suggest that the lower palm domain mediates conformational movements that drive pore opening and closing events.
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Affiliation(s)
- Margaret C Della Vecchia
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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39
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Krauson AJ, Carattino MD. Bulky Substitutions in the Thumb Domain of ASIC1a Restrict Proton-Gating. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.1515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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40
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Della Vecchia MC, Carattino MD. An Acidic Ring in the Palm Domain of ASIC1a Facilitates Pore opening. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.1517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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41
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Abstract
The epithelial Na(+) channel (ENaC) is regulated by a variety of external factors that alter channel activity by inducing conformational changes within its large extracellular region that are transmitted to the gate. The wrist domain consists of small linkers connecting the extracellular region to the transmembrane domains, where the channel pore and gate reside. We employed site-directed mutagenesis combined with two-electrode voltage clamp to investigate the role of the wrist domain in channel gating in response to extracellular factors. Channel inhibition by external Na(+) was reduced by selected mutations within the wrist domain of the α subunit, likely reflecting an increase in channel open probability. The most robust changes were observed when Cys was introduced at αPro-138 and αSer-568, sites immediately adjacent to the palm domain. In addition, one of these Cys mutants exhibited an enhanced response to shear stress. In the context of channels that have a low open probability due to retention of an inhibitory tract, the response to external Na(+) was reduced by Cys substitutions at both αPro-138 and αSer-568. We observed a significant correlation between changes in channel inhibition by external Na(+) and the relative response to shear stress for the α subunit mutants that were examined. Mutants that exhibited reduced inhibition by external Na(+) also showed an enhanced response to shear stress. Together, our data suggest that the wrist domain has a role in modulating the channel's response to external stimuli.
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Affiliation(s)
- Shujie Shi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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42
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Carattino MD. Cation transport goes with the flow. Am J Physiol Renal Physiol 2012; 303:F630-1. [DOI: 10.1152/ajprenal.00331.2012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Marcelo D. Carattino
- Department of Medicine Renal-Electrolyte Division and Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
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43
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Kashlan OB, Blobner BM, Zuzek Z, Carattino MD, Kleyman TR. Inhibitory tract traps the epithelial Na+ channel in a low activity conformation. J Biol Chem 2012; 287:20720-6. [PMID: 22511777 DOI: 10.1074/jbc.m112.358218] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proteolysis plays an important role in the maturation and activation of epithelial Na(+) channels (ENaCs). Non-cleaved channels are inactive at high extracellular Na(+) concentrations and fully cleaved channels are constitutively active. Cleavage of the α and γ subunits at multiple sites activates the channel through the release of imbedded inhibitory tracts. Peptides derived from these released tracts are also inhibitory, likely through binding at the inhibitory tract sites. We recently reported a model of the α subunit. We have now cross-linked Cys derivatives of the inhibitory peptide to the channel, using our model to predict sites at a domain interface of the α subunit that is in proximity to the N terminus of the peptide. Furthermore, peptide inhibition was mimicked in the absence of peptide by cross-linking the channel across the domain interface. Our results suggest a dynamic domain interface that can be exploited by inhibitory peptides and provides a mechanism for peptide inhibition and proteolytic activation.
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Affiliation(s)
- Ossama B Kashlan
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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44
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Carattino MD, Mueller GM, Palmer LG, Frindt G, Hughey RP, Kleyman TR. Dietary Na
+
restriction promotes release of an inhibitory tract from the γ ENaC subunit. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.1068.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Lawrence G Palmer
- Dept. of Physiology and BiophysicsWeill Medical College of Cornell U.New YorkNY
| | - Gustavo Frindt
- Dept. of Physiology and BiophysicsWeill Medical College of Cornell U.New YorkNY
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45
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Carattino MD, Prakasam HS, Ruiz WG, Apodaca G. Modulation of urinary bladder paracellular permeability by stretch. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.885.23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Wily G Ruiz
- MedicineUniversity of PittsburghPittsburghPA
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46
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Abstract
Acid-sensing ion channels (ASICs) are proton-gated cation-selective channels expressed in the peripheral and central nervous systems. The ion permeation pathway of ASIC1a is defined by residues 426-450 in the second transmembrane (TM2) segment. The gate, formed by the intersection of the TM2 segments, localizes near the extracellular boundary of the plasma membrane. We explored the contribution to ion permeation and selectivity of residues in the TM2 segment of ASIC1a. Studies of accessibility with positively charged methanethiosulfonate reagents suggest that the permeation pathway in the open state constricts below the gate, restricting the passage to large ions. Substitution of residues in the intracellular vestibule at positions 437, 438, 443, or 446 significantly increased the permeability to K(+) versus Na(+). ASIC1a shows a selectivity sequence for alkali metals of Na(+)>Li(+)>K(+)≫Rb(+)>Cs(+). Alanine and cysteine substitutions at position 438 increased, to different extents, the relative permeability to Li(+), K(+), Rb(+), and Cs(+). For these mutants, ion permeation was not a function of the diameter of the nonhydrated ion, suggesting that Gly-438 encompasses an ion coordination site that is essential for ion selectivity. M437C and A443C mutants showed slightly increased permeability to K(+), Rb(+), and Cs(+), suggesting that substitutions at these positions influence ion discrimination by altering molecular sieving. Our results indicate that ion selectivity is accomplished by the contribution of multiple sites in the pore of ASIC1a.
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Affiliation(s)
- Marcelo D Carattino
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
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47
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Passero CJ, Mueller GM, Myerburg MM, Carattino MD, Hughey RP, Kleyman TR. TMPRSS4-dependent activation of the epithelial sodium channel requires cleavage of the γ-subunit distal to the furin cleavage site. Am J Physiol Renal Physiol 2011; 302:F1-8. [PMID: 21993886 DOI: 10.1152/ajprenal.00330.2011] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The epithelial sodium channel (ENaC) is activated by a unique mechanism, whereby inhibitory tracts are released by proteolytic cleavage within the extracellular loops of two of its three homologous subunits. While cleavage by furin within the biosynthetic pathway releases one inhibitory tract from the α-subunit and moderately activates the channel, full activation through release of a second inhibitory tract from the γ-subunit requires cleavage once by furin and then at a distal site by a second protease, such as prostasin, plasmin, or elastase. We now report that coexpression of mouse transmembrane protease serine 4 (TMPRSS4) with mouse ENaC in Xenopus oocytes was associated with a two- to threefold increase in channel activity and production of a unique ∼70-kDa carboxyl-terminal fragment of the γ-subunit, similar to the ∼70-kDa γ-subunit fragment that we previously observed with prostasin-dependent channel activation. TMPRSS4-dependent channel activation and production of the ∼70-kDa fragment were partially blocked by mutation of the prostasin-dependent cleavage site (γRKRK186QQQQ). Complete inhibition of TMPRSS4-dependent activation of ENaC and γ-subunit cleavage was observed when three basic residues between the furin and prostasin cleavage sites were mutated (γK173Q, γK175Q, and γR177Q), in addition to γRKRK186QQQQ. Mutation of the four basic residues associated with the furin cleavage site (γRKRR143QQQQ) also prevented TMPRSS4-dependent channel activation. We conclude that TMPRSS4 primarily activates ENaC by cleaving basic residues within the tract γK173-K186 distal to the furin cleavage site, thereby releasing a previously defined key inhibitory tract encompassing γR158-F168 from the γ-subunit.
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Affiliation(s)
- Christopher J Passero
- Renal-Electrolyte Division, Dept. of Medicine, S933 Scaife Hall, 3550 Terrace St., Pittsburgh, PA 15261, USA
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48
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Shi S, Kashlan OB, Carattino MD, Kleyman TR. Mutations in the finger domain of the epithelial sodium channel alter the shear stress response. FASEB J 2011. [DOI: 10.1096/fasebj.25.1_supplement.1041.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Shujie Shi
- Renal‐Electrolyte DivisionDepartment of MedicineUniversity of PittsburghPittsburghPA
| | - Ossama B. Kashlan
- Renal‐Electrolyte DivisionDepartment of MedicineUniversity of PittsburghPittsburghPA
| | - Marcelo D. Carattino
- Renal‐Electrolyte DivisionDepartment of MedicineUniversity of PittsburghPittsburghPA
| | - Thomas R. Kleyman
- Renal‐Electrolyte DivisionDepartment of MedicineUniversity of PittsburghPittsburghPA
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49
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Abstract
Acid-sensing ion channels (ASICs) are trimeric cation channels that undergo activation and desensitization in response to extracellular acidification. The underlying mechanism coupling proton binding in the extracellular region to pore gating is unknown. Here we probed the reactivity toward methanethiosulfonate (MTS) reagents of channels with cysteine-substituted residues in the outer vestibule of the pore of ASIC1a. We found that positively-charged MTS reagents trigger pore opening of G428C. Scanning mutagenesis of residues in the region preceding the second transmembrane spanning domain indicated that the MTSET-modified side chain of Cys at position 428 interacts with Tyr-424. This interaction was confirmed by double-mutant cycle analysis. Strikingly, Y424C-G428C monomers were associated by intersubunit disulfide bonds and were insensitive to MTSET. Despite the spatial constraints introduced by these intersubunit disulfide bonds in the outer vestibule of the pore, Y424C-G428C transitions between the resting, open, and desensitized states in response to extracellular acidification. This finding suggests that the opening of the ion conductive pathway involves coordinated rotation of the second transmembrane-spanning domains.
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Affiliation(s)
- Lindsey A Tolino
- Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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50
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Shi S, Ghosh DD, Okumura S, Carattino MD, Kashlan OB, Sheng S, Kleyman TR. Base of the thumb domain modulates epithelial sodium channel gating. J Biol Chem 2011; 286:14753-61. [PMID: 21367859 DOI: 10.1074/jbc.m110.191734] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activity of the epithelial sodium channel (ENaC) is modulated by multiple external factors, including proteases, cations, anions and shear stress. The resolved crystal structure of acid-sensing ion channel 1 (ASIC1), a structurally related ion channel, and mutagenesis studies suggest that the large extracellular region is involved in recognizing external signals that regulate channel gating. The thumb domain in the extracellular region of ASIC1 has a cylinder-like structure with a loop at its base that is in proximity to the tract connecting the extracellular region to the transmembrane domains. This loop has been proposed to have a role in transmitting proton-induced conformational changes within the extracellular region to the gate. We examined whether loops at the base of the thumb domains within ENaC subunits have a similar role in transmitting conformational changes induced by external Na(+) and shear stress. Mutations at selected sites within this loop in each of the subunits altered channel responses to both external Na(+) and shear stress. The most robust changes were observed at the site adjacent to a conserved Tyr residue. In the context of channels that have a low open probability due to retention of an inhibitory tract, mutations in the loop activated channels in a subunit-specific manner. Our data suggest that this loop has a role in modulating channel gating in response to external stimuli, and are consistent with the hypothesis that external signals trigger movements within the extracellular regions of ENaC subunits that are transmitted to the channel gate.
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Affiliation(s)
- Shujie Shi
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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