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p66Shc-mediated hydrogen peroxide production impairs nephrogenesis causing reduction of number of glomeruli. Life Sci 2021; 279:119661. [PMID: 34087282 DOI: 10.1016/j.lfs.2021.119661] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 05/14/2021] [Accepted: 05/24/2021] [Indexed: 01/15/2023]
Abstract
AIMS Adaptor protein p66Shc, encoded by Shc1 gene, contributes to the pathogenesis of oxidative stress-related diseases. p66Shc ability to promote oxidative stress-related diseases requires phosphorylation of serine 36 residue (Ser36) and depends on translocation of p66Shc to the mitochondria. We tested the hypothesis that abnormal p66Shc-mediated reactive oxygen species (ROS) production could be critically involved in nephrons development during nephrogenesis. MAIN METHODS We have generated unique mutant rats (termed p66Shc-Del), which express endogenous p66Shc with a 9-amino acid deletion, and lack regulatory Ser36. H2O2 renal production was measured by enzymatic microelectrode biosensors. Nephron numbers in 3-5 weeks old p66Shc-Del rats were quantified using the acid maceration method. KEY FINDINGS p66Shc-Del rats, as wild type salt sensitive rats, display increased mean arterial blood pressure following chronic exposure to a high salt diet. In contrast to wild type rats, p66Shc-Del rats display increased H2O2 renal production and are characterized by a reduction in renal function. The number of glomeruli is significantly reduced in adult p66Shc-Del rats. SIGNIFICANCE Since low nephron number is an established risk factor for kidney disease and hypertension in humans and rodents, our data suggest that H2O2 renal production, caused by irregular signaling of p66Shc, could be critical in regulating nephrogenesis and that abnormal p66Shc signaling negatively impacts kidney development and renal function by increasing susceptibility to diabetic nephropathy and hypertension-induced nephropathy.
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Connor K, Murray DW, Jarzabek MA, Tran NL, White K, Dicker P, Sweeney KJ, O’Halloran PJ, MacCarthy B, Shiels LP, Lodi F, Lambrechts D, Sarkaria JN, Schiffelers RM, Symons M, Byrne AT. Targeting the RhoGEF βPIX/COOL-1 in Glioblastoma: Proof of Concept Studies. Cancers (Basel) 2020; 12:cancers12123531. [PMID: 33256106 PMCID: PMC7761123 DOI: 10.3390/cancers12123531] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 11/15/2020] [Accepted: 11/19/2020] [Indexed: 12/24/2022] Open
Abstract
Simple Summary Glioblastoma (GBM) is an incurable disease with a 14-month average life-expectancy following diagnosis, and clinical management has not improved in four decades. GBM mortality is due to rapid tumour growth and invasion into surrounding normal brain. Invasive cells make complete surgical removal of the tumour impossible, and result in disease relapse. Thus, it is imperative that any new treatment strategy takes these invading cells into consideration. Bevacizumab (Bev), which prevents the formation of new blood vessels, is an FDA approved therapy, but it has failed to increase overall survival in GBM and has even been shown to increase tumour invasion in some cases. Complementary anti-invasive therapies are therefore urgently required to enhance bevacizumab efficacy. We have identified βPIX/COOL-1, a RhoGEF protein which plays an important role in GBM cell invasion and angiogenesis and could be a useful target in this setting. Abstract Glioblastoma (GBM), a highly invasive and vascular malignancy is shown to rapidly develop resistance and evolve to a more invasive phenotype following bevacizumab (Bev) therapy. Rho Guanine Nucleotide Exchange Factor proteins (RhoGEFs) are mediators of key components in Bev resistance pathways, GBM and Bev-induced invasion. To identify GEFs with enhanced mRNA expression in the leading edge of GBM tumours, a cohort of GEFs was assessed using a clinical dataset. The GEF βPix/COOL-1 was identified, and the functional effect of gene depletion assessed using 3D-boyden chamber, proliferation, and colony formation assays in GBM cells. Anti-angiogenic effects were assessed in endothelial cells using tube formation and wound healing assays. In vivo effects of βPix/COOL-1-siRNA delivered via RGD-Nanoparticle in combination with Bev was studied in an invasive model of GBM. We found that siRNA-mediated knockdown of βPix/COOL-1 in vitro decreased cell invasion, proliferation and increased apoptosis in GBM cell lines. Moreover βPix/COOL-1 mediated endothelial cell migration in vitro. Mice treated with βPix/COOL-1 siRNA-loaded RGD-Nanoparticle and Bev demonstrated a trend towards improved median survival compared with Bev monotherapy. Our hypothesis generating study suggests that the RhoGEF βPix/COOL-1 may represent a target of vulnerability in GBM, in particular to improve Bev efficacy.
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Affiliation(s)
- Kate Connor
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland; (K.C.); (D.W.M.); (M.A.J.); (K.W.); (K.J.S.); (P.J.O.); (B.M.); (L.P.S.)
| | - David W. Murray
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland; (K.C.); (D.W.M.); (M.A.J.); (K.W.); (K.J.S.); (P.J.O.); (B.M.); (L.P.S.)
| | - Monika A. Jarzabek
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland; (K.C.); (D.W.M.); (M.A.J.); (K.W.); (K.J.S.); (P.J.O.); (B.M.); (L.P.S.)
| | - Nhan L. Tran
- Department of Cancer Biology and Neurological Surgery, Mayo Clinic Arizona, Scottsdale, AZ 85054, USA;
| | - Kieron White
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland; (K.C.); (D.W.M.); (M.A.J.); (K.W.); (K.J.S.); (P.J.O.); (B.M.); (L.P.S.)
| | - Patrick Dicker
- Epidemiology & Public Health, Royal College of Surgeons in Ireland, Dublin 2, Ireland;
| | - Kieron J. Sweeney
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland; (K.C.); (D.W.M.); (M.A.J.); (K.W.); (K.J.S.); (P.J.O.); (B.M.); (L.P.S.)
- National Neurosurgical Department, Beaumont Hospital, Dublin 9, Ireland
| | - Philip J. O’Halloran
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland; (K.C.); (D.W.M.); (M.A.J.); (K.W.); (K.J.S.); (P.J.O.); (B.M.); (L.P.S.)
- National Neurosurgical Department, Beaumont Hospital, Dublin 9, Ireland
| | - Brian MacCarthy
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland; (K.C.); (D.W.M.); (M.A.J.); (K.W.); (K.J.S.); (P.J.O.); (B.M.); (L.P.S.)
| | - Liam P. Shiels
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland; (K.C.); (D.W.M.); (M.A.J.); (K.W.); (K.J.S.); (P.J.O.); (B.M.); (L.P.S.)
| | - Francesca Lodi
- Center for Cancer Biology, Laboratory for Translational Genetics, Vlaams Instituut voor Biotechnologie (VIB), B-3000 Leuven, Belgium; (F.L.); (D.L.)
| | - Diether Lambrechts
- Center for Cancer Biology, Laboratory for Translational Genetics, Vlaams Instituut voor Biotechnologie (VIB), B-3000 Leuven, Belgium; (F.L.); (D.L.)
| | - Jann N. Sarkaria
- Department of Radiation Oncology, Mayo Clinic, Rochester, MN 55905, USA;
| | - Raymond M. Schiffelers
- Department of Clinical Chemistry and Haematology, University Medical Center Utrecht, 100 3584 Utrecht, The Netherlands;
| | - Marc Symons
- Department of Oncology & Cell Biology, Feinstein Institute for Medical Research at North Shore-LIJ, Manhasset, NY 11030, USA;
| | - Annette T. Byrne
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland; (K.C.); (D.W.M.); (M.A.J.); (K.W.); (K.J.S.); (P.J.O.); (B.M.); (L.P.S.)
- Correspondence: ; Tel.: +353-1-402-8673
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Matsuda J, Maier M, Aoudjit L, Baldwin C, Takano T. ARHGEF7 ( β-PIX) Is Required for the Maintenance of Podocyte Architecture and Glomerular Function. J Am Soc Nephrol 2020; 31:996-1008. [PMID: 32188698 DOI: 10.1681/asn.2019090982] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Accepted: 02/09/2020] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND Previous studies showed that Cdc42, a member of the prototypical Rho family of small GTPases and a regulator of the actin cytoskeleton, is critical for the normal development and health of podocytes. However, upstream regulatory mechanisms for Cdc42 activity in podocytes are largely unknown. METHODS We used a proximity-based ligation assay, BioID, to identify guanine nucleotide exchange factors that activate Cdc42 in immortalized human podocytes. We generated podocyte-specific ARHGEF7 (commonly known as β-PIX) knockout mice by crossing β-PIX floxed mice with Podocin-Cre mice. Using shRNA, we established cultured mouse podocytes with β-PIX knockdown and their controls. RESULTS We identified β-PIX as a predominant guanine nucleotide exchange factor that interacts with Cdc42 in human podocytes. Podocyte-specific β-PIX knockout mice developed progressive proteinuria and kidney failure with global or segmental glomerulosclerosis in adulthood. Glomerular podocyte density gradually decreased in podocyte-specific β-PIX knockout mice, indicating podocyte loss. Compared with controls, glomeruli from podocyte-specific β-PIX knockout mice and cultured mouse podocytes with β-PIX knockdown exhibited significant reduction in Cdc42 activity. Loss of β-PIX promoted podocyte apoptosis, which was mediated by the reduced activity of the prosurvival transcriptional regulator Yes-associated protein. CONCLUSIONS These findings indicate that β-PIX is required for the maintenance of podocyte architecture and glomerular function via Cdc42 and its downstream Yes-associated protein activities. This appears to be the first evidence that a Rho-guanine nucleotide exchange factor plays a critical role in podocytes.
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Affiliation(s)
- Jun Matsuda
- Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada
| | - Mirela Maier
- Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada
| | - Lamine Aoudjit
- Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada
| | - Cindy Baldwin
- Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada
| | - Tomoko Takano
- Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada
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Ho PY, Li H, Cheng L, Bhalla V, Fenton RA, Hallows KR. AMPK phosphorylation of the β 1Pix exchange factor regulates the assembly and function of an ENaC inhibitory complex in kidney epithelial cells. Am J Physiol Renal Physiol 2019; 317:F1513-F1525. [PMID: 31566435 DOI: 10.1152/ajprenal.00592.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The metabolic sensor AMP-activated protein kinase (AMPK) inhibits the epithelial Na+ channel (ENaC), a key regulator of salt reabsorption by the kidney and thus total body volume and blood pressure. Recent studies have suggested that AMPK promotes the association of p21-activated kinase-interacting exchange factor-β1 β1Pix, 14-3-3 proteins, and the ubiquitin ligase neural precursor cell expressed developmentally downregulated protein (Nedd)4-2 into a complex that inhibits ENaC by enhancing Nedd4-2 binding to ENaC and ENaC degradation. Functional β1Pix is required for ENaC inhibition by AMPK and promotes Nedd4-2 phosphorylation and stability in mouse kidney cortical collecting duct cells. Here, we report that AMPK directly phosphorylates β1Pix in vitro. Among several AMPK phosphorylation sites on β1Pix detected by mass spectrometry, Ser71 was validated as functionally significant. Compared with wild-type β1Pix, overexpression of a phosphorylation-deficient β1Pix-S71A mutant attenuated ENaC inhibition and the AMPK-activated interaction of both β1Pix and Nedd4-2 to 14-3-3 proteins in cortical collecting duct cells. Similarly, overexpression of a β1Pix-Δ602-611 deletion tract mutant unable to bind 14-3-3 proteins decreased the interaction between Nedd4-2 and 14-3-3 proteins, suggesting that 14-3-3 binding to β1Pix is critical for the formation of a β1Pix/Nedd4-2/14-3-3 complex. With expression of a general peptide inhibitor of 14-3-3-target protein interactions (R18), binding of both β1Pix and Nedd4-2 to 14-3-3 proteins was reduced, and AMPK-dependent ENaC inhibition was also attenuated. Altogether, our results demonstrate the importance of AMPK-mediated phosphorylation of β1Pix at Ser71, which promotes 14-3-3 interactions with β1Pix and Nedd4-2 to form a tripartite ENaC inhibitory complex, in the mechanism of ENaC regulation by AMPK.
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Affiliation(s)
- Pei-Yin Ho
- Division of Nephrology and Hypertension, Department of Medicine and USC/UKRO Kidney Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Hui Li
- Division of Nephrology and Hypertension, Department of Medicine and USC/UKRO Kidney Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Lei Cheng
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Vivek Bhalla
- Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California
| | - Robert A Fenton
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Kenneth R Hallows
- Division of Nephrology and Hypertension, Department of Medicine and USC/UKRO Kidney Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California
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Ho PY, Li H, Pavlov TS, Tuerk RD, Tabares D, Brunisholz R, Neumann D, Staruschenko A, Hallows KR. β 1Pix exchange factor stabilizes the ubiquitin ligase Nedd4-2 and plays a critical role in ENaC regulation by AMPK in kidney epithelial cells. J Biol Chem 2018; 293:11612-11624. [PMID: 29858246 DOI: 10.1074/jbc.ra118.003082] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 05/22/2018] [Indexed: 12/22/2022] Open
Abstract
Our previous work has established that the metabolic sensor AMP-activated protein kinase (AMPK) inhibits the epithelial Na+ channel (ENaC) by promoting its binding to neural precursor cell-expressed, developmentally down-regulated 4-2, E3 ubiquitin protein ligase (Nedd4-2). Here, using MS analysis and in vitro phosphorylation, we show that AMPK phosphorylates Nedd4-2 at the Ser-444 (Xenopus Nedd4-2) site critical for Nedd4-2 stability. We further demonstrate that the Pak-interacting exchange factor β1Pix is required for AMPK-mediated inhibition of ENaC-dependent currents in both CHO and murine kidney cortical collecting duct (CCD) cells. Short hairpin RNA-mediated knockdown of β1Pix expression in CCD cells attenuated the inhibitory effect of AMPK activators on ENaC currents. Moreover, overexpression of a β1Pix dimerization-deficient mutant unable to bind 14-3-3 proteins (Δ602-611) increased ENaC currents in CCD cells, whereas overexpression of WT β1Pix had the opposite effect. Using additional immunoblotting and co-immunoprecipitation experiments, we found that treatment with AMPK activators promoted the binding of β1Pix to 14-3-3 proteins in CCD cells. However, the association between Nedd4-2 and 14-3-3 proteins was not consistently affected by AMPK activation, β1Pix knockdown, or overexpression of WT β1Pix or the β1Pix-Δ602-611 mutant. Moreover, we found that β1Pix is important for phosphorylation of the aforementioned Nedd4-2 site critical for its stability. Overall, these findings elucidate novel molecular mechanisms by which AMPK regulates ENaC. Specifically, they indicate that AMPK promotes the assembly of β1Pix, 14-3-3 proteins, and Nedd4-2 into a complex that inhibits ENaC by enhancing Nedd4-2 binding to ENaC and its degradation.
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Affiliation(s)
- Pei-Yin Ho
- Division of Nephrology and Hypertension, Department of Medicine and USC/UKRO Kidney Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Hui Li
- Division of Nephrology and Hypertension, Department of Medicine and USC/UKRO Kidney Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Tengis S Pavlov
- the Division of Hypertension and Vascular Research, Henry Ford Health System, Detroit, Michigan 48202; Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Roland D Tuerk
- Department of Biology, Institute of Cell Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Diego Tabares
- Division of Nephrology and Hypertension, Department of Medicine and USC/UKRO Kidney Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - René Brunisholz
- Functional Genomics Center, ETH Zurich, 8097 Zurich, Switzerland
| | - Dietbert Neumann
- Department of Biology, Institute of Cell Biology, ETH Zurich, 8093 Zurich, Switzerland; Department of Pathology, School for Cardiovascular Diseases, Maastricht University, 6200 MD Maastricht, The Netherlands
| | | | - Kenneth R Hallows
- Division of Nephrology and Hypertension, Department of Medicine and USC/UKRO Kidney Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California 90033.
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Kaito Y, Kataoka R, Mihara T, Takechi K, Takahira A, Watanabe S, Han F, Tamura M. Phosphorylation of Ser-525 in βPix impairs Nox1-activating ability in Caco-2 cells. Arch Biochem Biophys 2018; 638:58-65. [PMID: 29242061 DOI: 10.1016/j.abb.2017.12.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Revised: 12/01/2017] [Accepted: 12/09/2017] [Indexed: 10/18/2022]
Abstract
βPix activates Nox1, an O2--generating NADPH oxidase, through Rac activation. In this study, we found that S525E mutation of βPix eliminated its Nox1-activating ability in transfected Caco-2 cells. Unexpectedly, affinity for Rac was not diminished but rather enhanced by S525E mutation, and guanine nucleotide exchange factor (GEF) activity was not altered. The N-terminal fragment (amino acids 1-400) showed similar Rac-binding and GEF activity to wild-type βPix. In contrast, the C-terminal fragment (amino acids 408-646) had higher Rac-binding activity, particularly for Rac-GTP, than wild-type βPix, and showed no GEF activity. These data suggest that a second Rac-binding site within the C-terminal region is opened by phosphorylation of Ser-525. The site may bind not only Rac-GDP but also Rac-GTP released from the N-terminal catalytic region, which interrupts Rac-GTP translocation to the membrane where Nox1 resides. If one considers that S340E mutation enhances Nox1 activation (Kaito et al., 2014), the present study suggests that βPix can also play an inhibitory role in O2- production, depending on the sites of phosphorylation.
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Affiliation(s)
- Yuuki Kaito
- Department of Applied Chemistry, Graduate School of Science and Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Ryosuke Kataoka
- Department of Applied Chemistry, Graduate School of Science and Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Tatsuya Mihara
- Department of Applied Chemistry, Graduate School of Science and Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Kento Takechi
- Department of Applied Chemistry, Graduate School of Science and Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Akira Takahira
- Department of Applied Chemistry, Graduate School of Science and Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Shuhei Watanabe
- Department of Applied Chemistry, Graduate School of Science and Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Fei Han
- Department of Applied Chemistry, Graduate School of Science and Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Minoru Tamura
- Department of Applied Chemistry, Graduate School of Science and Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan.
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7
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Wright KD, Staruschenko A, Sorokin A. Role of adaptor protein p66Shc in renal pathologies. Am J Physiol Renal Physiol 2017; 314:F143-F153. [PMID: 28978535 DOI: 10.1152/ajprenal.00414.2017] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
p66Shc is one of the three adaptor proteins encoded by the Shc1 gene, which are expressed in many organs, including the kidney. Recent studies shed new light on several key questions concerning the signaling mechanisms mediated by p66Shc. The central goal of this review article is to summarize recent findings on p66Shc and the role it plays in kidney physiology and pathology. This article provides a review of the various mechanisms whereby p66Shc has been shown to function within the kidney through a wide range of actions. The mitochondrial and cytoplasmic signaling of p66Shc, as it relates to production of reactive oxygen species (ROS) and renal pathologies, is further discussed.
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Affiliation(s)
- Kevin D Wright
- Cardiovascular Center, Medical College of Wisconsin , Milwaukee, Wisconsin.,Department of Medicine, Medical College of Wisconsin , Milwaukee, Wisconsin
| | - Alexander Staruschenko
- Cardiovascular Center, Medical College of Wisconsin , Milwaukee, Wisconsin.,Department of Physiology, Medical College of Wisconsin , Milwaukee, Wisconsin
| | - Andrey Sorokin
- Cardiovascular Center, Medical College of Wisconsin , Milwaukee, Wisconsin.,Department of Medicine, Medical College of Wisconsin , Milwaukee, Wisconsin
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Abstract
Endothelin-1 (ET-1) is a 21-amino acid peptide with mitogenic and powerful vasoconstricting properties. Under healthy conditions, ET-1 is expressed constitutively in all cells of the glomerulus and participates in homeostasis of glomerular structure and filtration function. Under disease conditions, increases in ET-1 are critically involved in initiating and maintaining glomerular inflammation, glomerular basement membrane hypertrophy, and injury of podocytes (visceral epithelial cells), thereby promoting proteinuria and glomerulosclerosis. Here, we review the role of ET-1 in the function of glomerular endothelial cells, visceral (podocytes) and parietal epithelial cells, mesangial cells, the glomerular basement membrane, stromal cells, inflammatory cells, and mesenchymal stem cells. We also discuss molecular mechanisms by which ET-1, predominantly through activation of the ETA receptor, contributes to injury to glomerular cells, and review preclinical and clinical evidence supporting its pathogenic role in glomerular injury in chronic renal disease. Finally, the therapeutic rationale for endothelin antagonists as a new class of antiproteinuric drugs is discussed.
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Affiliation(s)
- Matthias Barton
- Molecular Internal Medicine, University of Zurich, Zurich, Switzerland.
| | - Andrey Sorokin
- Department of Medicine, Kidney Disease Center, Division of Nephrology, Medical College of Wisconsin, Milwaukee, WI
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Abstract
The amiloride-sensitive epithelial Na(+) channel (ENaC) is a key player in the regulation of Na(+) homeostasis. Its functional activity is under continuous control by a variety of signaling molecules, including bioactive peptides of endothelin family. Since ENaC dysfunction is causative for disturbances in total body Na(+) levels associated with the abnormal regulation of blood volume, blood pressure, and lung fluid balance, uncovering the molecular mechanisms of inhibitory modulation or inappropriate activation of ENaC is crucial for the successful treatment of a variety of human diseases including hypertension. The precise regulation of ENaC is particularly important for normal Na(+) and fluid homeostasis in organs where endothelins are known to act: the kidneys, lung, and colon. Inhibition of ENaC by endothelin-1 (ET-1) has been established in renal cells, and several molecular mechanisms of inhibition of ENaC by ET-1 are proposed and will be reviewed in this chapter.
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Affiliation(s)
- Andrey Sorokin
- Division of Nephrology, Department of Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
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Heidary Arash E, Song KM, Song S, Shiban A, Attisano L. Arhgef7 promotes activation of the Hippo pathway core kinase Lats. EMBO J 2014; 33:2997-3011. [PMID: 25425573 DOI: 10.15252/embj.201490230] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The Hippo pathway regulates tissue growth and organ size, and inactivation contributes to cancer. Signals flow through Mst/Lats kinases, which phosphorylate and promote cytoplasmic localization of the transcriptional regulators Yap and Taz to inhibit transcription. Here, we identify the multidomain-containing guanine nucleotide exchange factor (GEF) Arhgef7, or βPix, as a positive Hippo pathway regulator. We show that βPix, which localizes to the cytoplasm, binds both Lats and Yap/Taz and thereby promotes Lats-mediated phosphorylation of Yap/Taz in a GEF-independent manner. βPix is required downstream of both cell density sensing and actin cytoskeletal rearrangements, and we demonstrate that loss of βPix expression in normal mammary epithelial cells strongly reduces Yap/Taz phosphorylation, promotes nuclear localization and increases target gene expression. Conversely, increased expression of βPIX in breast cancer cell lines re-couples the Hippo kinase cassette to Yap/Taz, promoting localization of Yap/Taz to the cytoplasm and inhibiting cell migration and proliferation. These studies thus define βPix as a key component that links the Hippo kinase cassette to Yap/Taz in response to multiple upstream Hippo pathway activators.
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Affiliation(s)
- Emad Heidary Arash
- Department of Biochemistry and Donnelly Centre, University of Toronto, Toronto, ON, Canada
| | - Ki Myung Song
- Department of Biochemistry and Donnelly Centre, University of Toronto, Toronto, ON, Canada
| | - Siyuan Song
- Department of Biochemistry and Donnelly Centre, University of Toronto, Toronto, ON, Canada
| | - Ahmed Shiban
- Department of Biochemistry and Donnelly Centre, University of Toronto, Toronto, ON, Canada
| | - Liliana Attisano
- Department of Biochemistry and Donnelly Centre, University of Toronto, Toronto, ON, Canada
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11
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Pavlov TS, Levchenko V, Staruschenko A. Role of Rho GDP dissociation inhibitor α in control of epithelial sodium channel (ENaC)-mediated sodium reabsorption. J Biol Chem 2014; 289:28651-9. [PMID: 25164814 DOI: 10.1074/jbc.m114.558262] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The epithelial sodium channel (ENaC) is expressed in the aldosterone-sensitive distal nephron where it performs sodium reabsorption from the lumen. We have recently shown that ENaC activity contributes to the development of salt-induced hypertension as a result of deficiency of EGF level. Previous studies revealed that Rho GDP-dissociation inhibitor α (RhoGDIα) is involved in the control of salt-sensitive hypertension and renal injury via Rac1, which is one of the small GTPases activating ENaC. Here we investigated the intracellular mechanism mediating the involvement of the RhoGDIα/Rac1 axis in the control of ENaC and the effect of EGF on ENaC in this pathway. We demonstrated that RhoGDIα is highly expressed in the cortical collecting ducts of mice and rats, and its expression is down-regulated in Dahl salt-sensitive rats fed a high salt diet. Knockdown of RhoGDIα in cultured cortical collecting duct principal cells increased ENaC subunits expression and ENaC-mediated sodium reabsorption. Furthermore, RhoGDIα deficiency causes enhanced response to EGF treatment. Patch clamp analysis reveals that RhoGDIα significantly decreases ENaC current density and prevents its up-regulation by RhoA and Rac1. Inhibition of Rho kinase with Y27632 had no effects on ENaC response to EGF either in control or RhoGDIα knocked down cells. However, EGF treatment increased levels of active Rac1, which was further enhanced in RhoGDIα-deficient cells. We conclude that changes in the RhoGDIα-dependent pathway have a permissive role in the Rac1-mediated enhancement of ENaC activity observed in salt-induced hypertension.
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Affiliation(s)
- Tengis S Pavlov
- From the Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Vladislav Levchenko
- From the Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Alexander Staruschenko
- From the Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
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