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Gerhards J, Maerz LD, Matthees ESF, Donow C, Moepps B, Premont RT, Burkhalter MD, Hoffmann C, Philipp M. Kinase Activity Is Not Required for G Protein-Coupled Receptor Kinase 4 Restraining mTOR Signaling during Cilia and Kidney Development. J Am Soc Nephrol 2023; 34:590-606. [PMID: 36810260 PMCID: PMC10103308 DOI: 10.1681/asn.0000000000000082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 11/27/2022] [Indexed: 01/28/2023] Open
Abstract
SIGNIFICANCE STATEMENT G protein-coupled receptor kinase 4 (GRK4) regulates renal sodium and water reabsorption. Although GRK4 variants with elevated kinase activity have been associated with salt-sensitive or essential hypertension, this association has been inconsistent among different study populations. In addition, studies elucidating how GRK4 may modulate cellular signaling are sparse. In an analysis of how GRK4 affects the developing kidney, the authors found that GRK4 modulates mammalian target of rapamycin (mTOR) signaling. Loss of GRK4 in embryonic zebrafish causes kidney dysfunction and glomerular cysts. Moreover, GRK4 depletion in zebrafish and cellular mammalian models results in elongated cilia. Rescue experiments suggest that hypertension in carriers of GRK4 variants may not be explained solely by kinase hyperactivity; instead, elevated mTOR signaling may be the underlying cause. BACKGROUND G protein-coupled receptor kinase 4 (GRK4) is considered a central regulator of blood pressure through phosphorylation of renal dopaminergic receptors and subsequent modulation of sodium excretion. Several nonsynonymous genetic variants of GRK4 have been only partially linked to hypertension, although these variants demonstrate elevated kinase activity. However, some evidence suggests that function of GRK4 variants may involve more than regulation of dopaminergic receptors alone. Little is known about the effects of GRK4 on cellular signaling, and it is also unclear whether or how altered GRK4 function might affect kidney development. METHODS To better understand the effect of GRK4 variants on the functionality of GRK4 and GRK4's actions in cellular signaling during kidney development, we studied zebrafish, human cells, and a murine kidney spheroid model. RESULTS Zebrafish depleted of Grk4 develop impaired glomerular filtration, generalized edema, glomerular cysts, pronephric dilatation, and expansion of kidney cilia. In human fibroblasts and in a kidney spheroid model, GRK4 knockdown produced elongated primary cilia. Reconstitution with human wild-type GRK4 partially rescues these phenotypes. We found that kinase activity is dispensable because kinase-dead GRK4 (altered GRK4 that cannot result in phosphorylation of the targeted protein) prevented cyst formation and restored normal ciliogenesis in all tested models. Hypertension-associated genetic variants of GRK4 fail to rescue any of the observed phenotypes, suggesting a receptor-independent mechanism. Instead, we discovered unrestrained mammalian target of rapamycin signaling as an underlying cause. CONCLUSIONS These findings identify GRK4 as novel regulator of cilia and of kidney development independent of GRK4's kinase function and provide evidence that the GRK4 variants believed to act as hyperactive kinases are dysfunctional for normal ciliogenesis.
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Affiliation(s)
- Julian Gerhards
- Section of Pharmacogenomics, Department of Experimental and Clinical Pharmacology and Pharmacogenomics, Eberhard-Karls-University Tübingen, Tübingen, Germany
| | - Lars D. Maerz
- Institute of Biochemistry and Molecular Biology, Ulm University, Ulm, Germany
| | - Edda S. F. Matthees
- Institute for Molecular Cell Biology, University Hospital Jena, Friedrich-Schiller University of Jena, Jena, Germany
| | - Cornelia Donow
- Institute of Biochemistry and Molecular Biology, Ulm University, Ulm, Germany
| | - Barbara Moepps
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
| | - Richard T. Premont
- Department of Medicine, Duke University Medical Center, Durham, North Carolina
| | - Martin D. Burkhalter
- Section of Pharmacogenomics, Department of Experimental and Clinical Pharmacology and Pharmacogenomics, Eberhard-Karls-University Tübingen, Tübingen, Germany
| | - Carsten Hoffmann
- Institute for Molecular Cell Biology, University Hospital Jena, Friedrich-Schiller University of Jena, Jena, Germany
| | - Melanie Philipp
- Section of Pharmacogenomics, Department of Experimental and Clinical Pharmacology and Pharmacogenomics, Eberhard-Karls-University Tübingen, Tübingen, Germany
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Serifi I, Besta S, Karetsou Z, Giardoglou P, Beis D, Niewiadomski P, Papamarcaki T. Targeting of SET/I2PP2A oncoprotein inhibits Gli1 transcription revealing a new modulator of Hedgehog signaling. Sci Rep 2021; 11:13940. [PMID: 34230583 PMCID: PMC8260731 DOI: 10.1038/s41598-021-93440-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 06/18/2021] [Indexed: 01/17/2023] Open
Abstract
The Hedgehog (Hh)/Gli signaling pathway controls cell proliferation and differentiation, is critical for the development of nearly every tissue and organ in vertebrates and is also involved in tumorigenesis. In this study, we characterize the oncoprotein SET/I2PP2A as a novel regulator of Hh signaling. Our previous work has shown that the zebrafish homologs of SET are expressed during early development and localized in the ciliated organs. In the present work, we show that CRISPR/Cas9-mediated knockdown of setb gene in zebrafish embryos resulted in cyclopia, a characteristic patterning defect previously reported in Hh mutants. Consistent with these findings, targeting setb gene using CRISPR/Cas9 or a setb morpholino, reduced Gli1-dependent mCherry expression in the Hedgehog reporter zebrafish line Tg(12xGliBS:mCherry-NLS). Likewise, SET loss of function by means of pharmacological inhibition and gene knockdown prevented the increase of Gli1 expression in mammalian cells in vitro. Conversely, overexpression of SET resulted in an increase of the expression of a Gli-dependent luciferase reporter, an effect likely attributable to the relief of the Sufu-mediated inhibition of Gli1. Collectively, our data support the involvement of SET in Gli1-mediated transcription and suggest the oncoprotein SET/I2PP2A as a new modulator of Hedgehog signaling.
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Affiliation(s)
- Iliana Serifi
- Laboratory of Biological Chemistry, Medical Department, School of Health Sciences, University of Ioannina, 451 10, Ioannina, Greece.,Department of Biomedical Research, Foundation for Research and Technology-Hellas, Institute of Molecular Biology and Biotechnology, 451 10, Ioannina, Greece
| | - Simoni Besta
- Laboratory of Biological Chemistry, Medical Department, School of Health Sciences, University of Ioannina, 451 10, Ioannina, Greece
| | - Zoe Karetsou
- Laboratory of Biological Chemistry, Medical Department, School of Health Sciences, University of Ioannina, 451 10, Ioannina, Greece
| | - Panagiota Giardoglou
- Developmental Biology, Center for Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation Academy of Athens, 115 27, Athens, Greece
| | - Dimitris Beis
- Developmental Biology, Center for Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation Academy of Athens, 115 27, Athens, Greece
| | | | - Thomais Papamarcaki
- Laboratory of Biological Chemistry, Medical Department, School of Health Sciences, University of Ioannina, 451 10, Ioannina, Greece. .,Department of Biomedical Research, Foundation for Research and Technology-Hellas, Institute of Molecular Biology and Biotechnology, 451 10, Ioannina, Greece.
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Duong Phu M, Bross S, Burkhalter MD, Philipp M. Limitations and opportunities in the pharmacotherapy of ciliopathies. Pharmacol Ther 2021; 225:107841. [PMID: 33771583 DOI: 10.1016/j.pharmthera.2021.107841] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 03/11/2021] [Indexed: 01/10/2023]
Abstract
Ciliopathies are a family of rather diverse conditions, which have been grouped based on the finding of altered or dysfunctional cilia, potentially motile, small cellular antennae extending from the surface of postmitotic cells. Cilia-related disorders include embryonically arising conditions such as Joubert, Usher or Kartagener syndrome, but also afflictions with a postnatal or even adult onset phenotype, i.e. autosomal dominant polycystic kidney disease. The majority of ciliopathies are syndromic rather than affecting only a single organ due to cilia being found on almost any cell in the human body. Overall ciliopathies are considered rare diseases. Despite that, pharmacological research and the strive to help these patients has led to enormous therapeutic advances in the last decade. In this review we discuss new treatment options for certain ciliopathies, give an outlook on promising future therapeutic strategies, but also highlight the limitations in the development of therapeutic approaches of ciliopathies.
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Affiliation(s)
- Max Duong Phu
- Department of Experimental and Clinical Pharmacology and Pharmacogenomics, Section of Pharmacogenomics, Eberhard-Karls-University of Tübingen, 72074 Tübingen, Germany
| | - Stefan Bross
- Department of Experimental and Clinical Pharmacology and Pharmacogenomics, Section of Pharmacogenomics, Eberhard-Karls-University of Tübingen, 72074 Tübingen, Germany
| | - Martin D Burkhalter
- Department of Experimental and Clinical Pharmacology and Pharmacogenomics, Section of Pharmacogenomics, Eberhard-Karls-University of Tübingen, 72074 Tübingen, Germany
| | - Melanie Philipp
- Department of Experimental and Clinical Pharmacology and Pharmacogenomics, Section of Pharmacogenomics, Eberhard-Karls-University of Tübingen, 72074 Tübingen, Germany.
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Casar Tena T, Maerz LD, Szafranski K, Groth M, Blätte TJ, Donow C, Matysik S, Walther P, Jeggo PA, Burkhalter MD, Philipp M. Resting cells rely on the DNA helicase component MCM2 to build cilia. Nucleic Acids Res 2019; 47:134-151. [PMID: 30329080 PMCID: PMC6326816 DOI: 10.1093/nar/gky945] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Accepted: 10/04/2018] [Indexed: 12/24/2022] Open
Abstract
Minichromosome maintenance (MCM) proteins facilitate replication by licensing origins and unwinding the DNA double strand. Interestingly, the number of MCM hexamers greatly exceeds the number of firing origins suggesting additional roles of MCMs. Here we show a hitherto unanticipated function of MCM2 in cilia formation in human cells and zebrafish that is uncoupled from replication. Zebrafish depleted of MCM2 develop ciliopathy-phenotypes including microcephaly and aberrant heart looping due to malformed cilia. In non-cycling human fibroblasts, loss of MCM2 promotes transcription of a subset of genes, which cause cilia shortening and centriole overduplication. Chromatin immunoprecipitation experiments show that MCM2 binds to transcription start sites of cilia inhibiting genes. We propose that such binding may block RNA polymerase II-mediated transcription. Depletion of a second MCM (MCM7), which functions in complex with MCM2 during its canonical functions, reveals an overlapping cilia-deficiency phenotype likely unconnected to replication, although MCM7 appears to regulate a distinct subset of genes and pathways. Our data suggests that MCM2 and 7 exert a role in ciliogenesis in post-mitotic tissues.
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Affiliation(s)
- Teresa Casar Tena
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
| | - Lars D Maerz
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
| | - Karol Szafranski
- Leibniz Institute on Aging, Fritz Lipmann Institute, 07745 Jena, Germany
| | - Marco Groth
- Leibniz Institute on Aging, Fritz Lipmann Institute, 07745 Jena, Germany
| | - Tamara J Blätte
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
| | - Cornelia Donow
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
| | - Sabrina Matysik
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
| | - Paul Walther
- Central Facility for Electron Microscopy, Ulm University, 89081 Ulm, Germany
| | - Penelope A Jeggo
- Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, UK
| | - Martin D Burkhalter
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
| | - Melanie Philipp
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
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