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Van Sciver RE, Long AB, Katz HG, Gigante ED, Caspary T. Ciliary ARL13B inhibits developmental kidney cystogenesis in mouse. Dev Biol 2023; 500:1-9. [PMID: 37209936 PMCID: PMC10330881 DOI: 10.1016/j.ydbio.2023.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 05/15/2023] [Accepted: 05/17/2023] [Indexed: 05/22/2023]
Abstract
ARL13B is a small GTPase enriched in cilia. Deletion of Arl13b in mouse kidney results in renal cysts and an associated absence of primary cilia. Similarly, ablation of cilia leads to kidney cysts. To investigate whether ARL13B functions from within cilia to direct kidney development, we examined kidneys of mice expressing an engineered cilia-excluded ARL13B variant, ARL13BV358A. These mice retained renal cilia and developed cystic kidneys. Because ARL13B functions as a guanine nucleotide exchange factor (GEF) for ARL3, we examined kidneys of mice expressing an ARL13B variant that lacks ARL3 GEF activity, ARL13BR79Q. We found normal kidney development with no evidence of cysts in these mice. Taken together, our results show that ARL13B functions within cilia to inhibit renal cystogenesis during mouse development, and that this function does not depend on its role as a GEF for ARL3.
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Affiliation(s)
- Robert E Van Sciver
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA, 30322, USA.
| | - Alyssa B Long
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA, 30322, USA.
| | - Harrison G Katz
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA, 30322, USA; Department of Biology, Brown University, Providence, RI, 02912, USA.
| | - Eduardo D Gigante
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA, 30322, USA; Graduate Program in Neuroscience, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA, 30322, USA; Department of Biology, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
| | - Tamara Caspary
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA, 30322, USA.
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2
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Van Sciver RE, Long AB, Katz HG, Gigante ED, Caspary T. Ciliary ARL13B inhibits developmental kidney cystogenesis in mouse. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.08.527739. [PMID: 36798281 PMCID: PMC9934666 DOI: 10.1101/2023.02.08.527739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
ARL13B is a small GTPase enriched in cilia. Deletion of Arl13b in mouse kidney results in renal cysts and an associated absence of primary cilia. Similarly, ablation of cilia leads to kidney cysts. To investigate whether ARL13B functions from within cilia to direct kidney development, we examined kidneys of mice expressing an engineered cilia-excluded ARL13B variant, ARL13BV358A. These mice retained renal cilia and developed cystic kidneys. Because ARL13B functions as a guanine nucleotide exchange factor (GEF) for ARL3, we examined kidneys of mice expressing an ARL13B variant that lacks ARL3 GEF activity, ARL13BR79Q. We found normal kidney development with no evidence of cysts in these mice. Taken together, our results show that ARL13B functions within cilia to inhibit renal cystogenesis during mouse development, and that this function does not depend on its role as a GEF for ARL3.
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Affiliation(s)
- Robert E. Van Sciver
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA 30322, USA
| | - Alyssa B. Long
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA 30322, USA
| | - Harrison G. Katz
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA 30322, USA
- Present address: Department of Biology, Brown University, Providence, RI 02912, USA
| | - Eduardo D. Gigante
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA 30322, USA
- Graduate Program in Neuroscience, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA 30322, USA
- Present address: Department of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Tamara Caspary
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA 30322, USA
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3
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Marra AN, Li Y, Wingert RA. Antennas of organ morphogenesis: the roles of cilia in vertebrate kidney development. Genesis 2016; 54:457-69. [PMID: 27389733 PMCID: PMC5053263 DOI: 10.1002/dvg.22957] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 07/03/2016] [Accepted: 07/04/2016] [Indexed: 12/12/2022]
Abstract
Cilia arose early during eukaryotic evolution, and their structural components are highly conserved from the simplest protists to complex metazoan species. In recent years, the role of cilia in the ontogeny of vertebrate organs has received increasing attention due to a staggering correlation between human disease and dysfunctional cilia. In particular, the presence of cilia in both the developing and mature kidney has become a deep area of research due to ciliopathies common to the kidney, such as polycystic kidney disease (PKD). Interestingly, mutations in genes encoding proteins that localize to the cilia cause similar cystic phenotypes in kidneys of various vertebrates, suggesting an essential role for cilia in kidney organogenesis and homeostasis as well. Importantly, the genes so far identified in kidney disease have conserved functions across species, whose kidneys include both primary and motile cilia. Here, we aim to provide a comprehensive description of cilia and their role in kidney development, as well as highlight the usefulness of the zebrafish embryonic kidney as a model to further understand the function of cilia in kidney health.
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Affiliation(s)
- Amanda N Marra
- Department of Biological Sciences, Center for Stem Cells and Regenerative Medicine, Center for Zebrafish Research, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Yue Li
- Department of Biological Sciences, Center for Stem Cells and Regenerative Medicine, Center for Zebrafish Research, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Rebecca A Wingert
- Department of Biological Sciences, Center for Stem Cells and Regenerative Medicine, Center for Zebrafish Research, University of Notre Dame, Notre Dame, IN, 46556, USA.
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4
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Pan J, Seeger-Nukpezah T, Golemis EA. The role of the cilium in normal and abnormal cell cycles: emphasis on renal cystic pathologies. Cell Mol Life Sci 2012; 70:1849-74. [PMID: 22782110 DOI: 10.1007/s00018-012-1052-z] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Revised: 05/08/2012] [Accepted: 06/05/2012] [Indexed: 12/28/2022]
Abstract
The primary cilium protrudes from the cell surface and acts as a sensor for chemical and mechanical growth cues, with receptors for a number of growth factors (PDGFα, Hedgehog, Wnt, Notch) concentrated within the ciliary membrane. In normal tissues, the cilium assembles after cells exit mitosis and is resorbed as part of cell cycle re-entry. Although regulation of the cilium by cell cycle transitions has been appreciated for over 100 years, only recently have data emerged to indicate the cilium also exerts influence on the cell cycle. The resorption/protrusion cycle, regulated by proteins including Aurora-A, VHL, and GSK-3β, influences cell responsiveness to growth cues involving cilia-linked receptors; further, resorption liberates the ciliary basal body to differentiate into the centrosome, which performs discrete functions in S-, G2-, and M-phase. Besides these roles, the cilium provides a positional cue that regulates polarity of cell division, and thus directs cells towards fates of differentiation versus proliferation. In this review, we summarize the specific mechanisms mediating the cilia-cell cycle dialog. We then emphasize the examples of polycystic kidney disease (PKD), nephronopthisis (NPHP), and VHL-linked renal cysts as cases in which defects of ciliary function influence disease pathology, and may also condition response to treatment.
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Affiliation(s)
- Junmin Pan
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
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5
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In vitro investigation of renal epithelial injury suggests that primary cilium length is regulated by hypoxia-inducible mechanisms. Cell Biol Int 2012; 35:909-13. [PMID: 21241248 DOI: 10.1042/cbi20090154] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Primary cilia are non-motile sensory organelles that project from cells in many tissues. The role of renal primary cilium-based signalling in regulating epithelial cell proliferation and differentiation is highlighted by studies showing that defects of the cilium lead to epithelial de-differentiation, over proliferation and polycystic kidney disease. Recent studies show that renal primary cilia may also play a role in controlling epithelial differentiation during renal repair. After injury, renal cilium length increases dramatically and then undergoes a normalization that coincides with structural and functional repair in both human patients and mouse models of renal injury. These changes in cilium length are likely to modulate cilium-based signalling, but the injury-related factors that influence renal primary cilium length have yet to be determined. Here, we investigated the effect of three factors commonly associated with renal injury on renal cilium length in an in vitro setting. MDCK (Madin Darby canine kidney) cell cultures bearing primary cilia were treated with BSA to simulate albuminuria, cobalt chloride to simulate hypoxia and the inflammation-related cytokine tumour necrosis factor α. Primary cilium length was only increased in cultures treated with cobalt chloride. Our results suggest a role for hypoxia and the induction of HIF-1α (hypoxia-inducible factor 1α) in increasing renal primary cilium length following renal injury.
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Abstract
The primary cilium is a microtubule-based nonmotile organelle that is found on most cells in the mammalian body. Once regarded as a vestigial organelle, it has been recently shown to play unforeseen roles in mammalian physiology and tissue homeostasis. In kidney epithelial cells, the primary cilium plays a fundamental role in tubule organization and function and it is now considered to serve as a versatile mechanosensor and chemosensor. Diseases related to kidney primary cilia include autosomal polycystic kidney disease, recessive polycystic kidney disease, Bardet-Biedl syndrome, and nephronophthisis. Multiple proteins whose functions are disrupted in cystic kidney diseases have been localized in the primary cilium. This review provides a general introduction to the cell biology and function of renal primary cilia and an overview of cilia-related kidney diseases.
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Hartman TR, Liu D, Zilfou JT, Robb V, Morrison T, Watnick T, Henske EP. The tuberous sclerosis proteins regulate formation of the primary cilium via a rapamycin-insensitive and polycystin 1-independent pathway. Hum Mol Genet 2008; 18:151-63. [PMID: 18845692 PMCID: PMC2644647 DOI: 10.1093/hmg/ddn325] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Tuberous sclerosis complex (TSC) is a tumor suppressor gene syndrome in which severe renal cystic disease can occur. Many renal cystic diseases, including autosomal dominant polycystic kidney disease (ADPKD), are associated with absence or dysfunction of the primary cilium. We report here that hamartin (TSC1) localizes to the basal body of the primary cilium, and that Tsc1−/− and Tsc2−/− mouse embryonic fibroblasts (MEFs) are significantly more likely to contain a primary cilium than wild-type controls. In addition, the cilia of Tsc1−/− and Tsc2−/− MEFs are 17–27% longer than cilia from wild-type MEFs. These data suggest a novel type of ciliary disruption in TSC, associated with enhanced cilia development. The TSC1 and TSC2 proteins function as a heterodimer to inhibit the activity of the mammalian target of rapamycin complex 1 (TORC1). The enhanced ciliary formation in the Tsc1−/− and Tsc2−/− MEFs was not abrogated by rapamycin, which indicates a TORC1-independent mechanism. Polycystin 1 (PC1), the product of the PKD1 gene, has been found to interact with TSC2, but Pkd1−/− MEFs did not have enhanced ciliary formation. Furthermore, while activation of mTOR has been observed in renal cysts from ADPKD patients, Pkd1−/− MEFs did not have evidence of constitutive mTOR activation, thereby underscoring the independent functions of the TSC proteins and PC1 in regulation of primary cilia and mTOR. Our data link the TSC proteins with the primary cilium and reveal a novel phenotype of enhanced ciliary formation in a cyst-associated disease.
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Affiliation(s)
- Tiffiney R Hartman
- Department of Medical Oncology, Fox Chase Cancer Center, Philadelphia, PA 19090, USA
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Tian Y, Kolb R, Hong JH, Carroll J, Li D, You J, Bronson R, Yaffe MB, Zhou J, Benjamin T. TAZ promotes PC2 degradation through a SCFbeta-Trcp E3 ligase complex. Mol Cell Biol 2007; 27:6383-95. [PMID: 17636028 PMCID: PMC2099608 DOI: 10.1128/mcb.00254-07] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Studies of a TAZ knockout mouse reveal a novel function of the transcriptional regulator TAZ, that is, as a binding partner of the F-box protein beta-Trcp. TAZ-/- mice develop polycystic kidney disease (PKD) and emphysema. The calcium-permeable cation channel protein polycystin 2 (PC2) is overexpressed in kidneys of TAZ-/- mice as a result of decreased degradation via an SCF(beta-Trcp) E3 ubiquitin ligase pathway. Replacements of serines in a phosphodegron motif in TAZ prevent beta-Trcp binding and PC2 degradation. Coexpression of a cytoplasmic fragment of polycystin 1 blocks the PC2-TAZ interaction and prevents TAZ-mediated degradation of PC2. Depletion of TAZ in zebrafish also results in a cystic kidney accompanied by overexpression of PC2. These results establish a common role of TAZ across vertebrate species in a protein degradation pathway regulated by phosphorylation and implicate deficiencies in this pathway in the development of PKD.
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Affiliation(s)
- Yu Tian
- Department of Pathology, Harvard Medical School, Boston, MA 02115, USA
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9
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Cantiello HF, Montalbetti N, Li Q, Chen XZ. The Cytoskeletal Connection to Ion Channels as a Potential Mechanosensory Mechanism: Lessons from Polycystin-2 (TRPP2). CURRENT TOPICS IN MEMBRANES 2007; 59:233-96. [PMID: 25168140 DOI: 10.1016/s1063-5823(06)59010-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Mechanosensitivity of ion channels, or the ability to transfer mechanical forces into a gating mechanism of channel regulation, is split into two main working (not mutually exclusive) hypotheses. One is that elastic and/or structural changes in membrane properties act as a transducing mechanism of channel regulation. The other hypothesis involves tertiary elements, such as the cytoskeleton which, itself by dynamic interactions with the ion channel, may convey conformational changes, including those ascribed to mechanical forces. This hypothesis is supported by numerous instances of regulatory changes in channel behavior by alterations in cytoskeletal structures/interactions. However, only recently, the molecular nature of these interactions has slowly emerged. Recently, a surge of evidence has emerged to indicate that transient receptor potential (TRP) channels are key elements in the transduction of a variety of environmental signals. This chapter describes the molecular linkage and regulatory elements of polycystin-2 (PC2), a TRP-type (TRPP2) nonselective cation channel whose mutations cause autosomal dominant polycystic kidney disease (ADPKD). The chapter focuses on the involvement of cytoskeletal structures in the regulation of PC2 and discusses how these connections are the transducing mechanism of environmental signals to its channel function.
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Affiliation(s)
- Horacio F Cantiello
- Renal Unit, Massachusetts General Hospital East, Charlestown, Massachusetts 02129; Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115; Laboratorio de Canales Iónicos, Departamento de Fisicoquímica y Química Analítica, Facultad de Farmacia y Bioquímica, Buenos Aires 1113, Argentina
| | - Nicolás Montalbetti
- Laboratorio de Canales Iónicos, Departamento de Fisicoquímica y Química Analítica, Facultad de Farmacia y Bioquímica, Buenos Aires 1113, Argentina
| | - Qiang Li
- Department of Physiology, University of Alberta, Edmonton T6G 2H7, Canada
| | - Xing-Zhen Chen
- Department of Physiology, University of Alberta, Edmonton T6G 2H7, Canada
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Siroky BJ, Ferguson WB, Fuson AL, Xie Y, Fintha A, Komlosi P, Yoder BK, Schwiebert EM, Guay-Woodford LM, Bell PD. Loss of primary cilia results in deregulated and unabated apical calcium entry in ARPKD collecting duct cells. Am J Physiol Renal Physiol 2006; 290:F1320-8. [PMID: 16396941 DOI: 10.1152/ajprenal.00463.2005] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Recent genetic analysis has identified a pivotal role of primary cilia in the pathogenesis of polycystic kidney disease (PKD). However, little is known regarding how cilia loss/dysfunction contributes to cyst development. In epithelial cells, changes in apical fluid flow induce cilia-mediated Ca2+ entry via polycystin-2 (PC2), a cation channel. The Oak Ridge Polycystic Kidney (orpk) mouse contains a mutated Tg737 gene that disrupts expression of polaris, a protein required for ciliogenesis. These studies examine the effect of cilia malformation on Ca2+ entry in orpk cilia(-) collecting duct principal cells, and in orpk cells in which wild-type Tg737 was reintroduced, orpk cilia(+). [Ca2+]i was monitored in confluent cell monolayers using fluorescence microscopy. Intrinsic apical Ca2+ entry was measured by Mn2+ quenching and Ca2+ depletion/readdition under flow conditions below the threshold for stimulation. We found that unstimulated apical Ca2+ entry was markedly increased in cilia(-) cells and was sensitive to Gd3+, an inhibitor of PC2. Electrophysiological measurements demonstrate increased abundance of an apical channel, consistent with PC2, in cilia(-) cells. Immunofluorescence studies revealed that PC2, normally expressed on and at the base of cilia in orpk cilia(+) cells, was observed throughout the apical membrane in cilia(-) cells. Furthermore, cilia(-) cells displayed elevated subapical Ca2+ levels measured with the near-membrane Ca2+ indicator FFP-18. We propose that cilia exert a tonic regulatory influence on apical Ca2+ entry, and absence of cilia results in loss of spatial organization of PC2, causing unregulated Ca2+ entry and elevations in subapical [Ca2+], a factor which may contribute to cyst formation.
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Affiliation(s)
- Brian J Siroky
- Department of Physiology, Univ. of Alabama at Birmingham, Birmingham, AL, USA
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11
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Schermer B, Höpker K, Omran H, Ghenoiu C, Fliegauf M, Fekete A, Horvath J, Köttgen M, Hackl M, Zschiedrich S, Huber TB, Kramer-Zucker A, Zentgraf H, Blaukat A, Walz G, Benzing T. Phosphorylation by casein kinase 2 induces PACS-1 binding of nephrocystin and targeting to cilia. EMBO J 2005; 24:4415-24. [PMID: 16308564 PMCID: PMC1356326 DOI: 10.1038/sj.emboj.7600885] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Accepted: 11/03/2005] [Indexed: 11/09/2022] Open
Abstract
Mutations in proteins localized to cilia and basal bodies have been implicated in a growing number of human diseases. Access of these proteins to the ciliary compartment requires targeting to the base of the cilia. However, the mechanisms involved in transport of cilia proteins to this transitional zone are elusive. Here we show that nephrocystin, a ciliary protein mutated in the most prevalent form of cystic kidney disease in childhood, is expressed in respiratory epithelial cells and accumulates at the base of cilia, overlapping with markers of the basal body area and the transition zone. Nephrocystin interacts with the phosphofurin acidic cluster sorting protein (PACS)-1. Casein kinase 2 (CK2)-mediated phosphorylation of three critical serine residues within a cluster of acidic amino acids in nephrocystin mediates PACS-1 binding, and is essential for colocalization of nephrocystin with PACS-1 at the base of cilia. Inhibition of CK2 activity abrogates this interaction and results in the loss of correct nephrocystin targeting. These data suggest that CK2-dependent transport processes represent a novel pathway of targeting proteins to the cilia.
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Affiliation(s)
| | - Katja Höpker
- Renal Division, University Hospital Freiburg, Freiburg, Germany
| | - Heymut Omran
- Childrens Hospital, University Hospital Freiburg, Freiburg, Germany
| | | | - Manfred Fliegauf
- Childrens Hospital, University Hospital Freiburg, Freiburg, Germany
| | - Andrea Fekete
- Childrens Hospital, University Hospital Freiburg, Freiburg, Germany
| | - Judit Horvath
- Childrens Hospital, University Hospital Freiburg, Freiburg, Germany
| | - Michael Köttgen
- Renal Division, University Hospital Freiburg, Freiburg, Germany
| | - Matthias Hackl
- Renal Division, University Hospital Freiburg, Freiburg, Germany
| | | | - Tobias B Huber
- Renal Division, University Hospital Freiburg, Freiburg, Germany
| | | | | | - Andree Blaukat
- Department of Pharmacology, University of Heidelberg, Heidelberg, Germany
| | - Gerd Walz
- Renal Division, University Hospital Freiburg, Freiburg, Germany
| | - Thomas Benzing
- Renal Division, University Hospital Freiburg, Freiburg, Germany
- Renal Division, University Hospital, Hugstetterstrasse 55, 79106 Freiburg, Germany. Tel.: +49 761 270 3559; Fax: +49 761 270 3270; E-mail:
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Ma R, Li WP, Rundle D, Kong J, Akbarali HI, Tsiokas L. PKD2 functions as an epidermal growth factor-activated plasma membrane channel. Mol Cell Biol 2005; 25:8285-98. [PMID: 16135816 PMCID: PMC1234340 DOI: 10.1128/mcb.25.18.8285-8298.2005] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
PKD2, or polycystin 2, the product of the gene mutated in type 2 autosomal dominant polycystic kidney disease, belongs to the transient receptor potential channel superfamily and has been shown to function as a nonselective cation channel in the plasma membrane. However, the mechanism of PKD2 activation remains elusive. We show that PKD2 overexpression increases epidermal growth factor (EGF)-induced inward currents in LLC-PK(1) kidney epithelial cells, while the knockdown of endogenous PKD2 by RNA interference or the expression of a pathogenic missense variant, PKD2-D511V, blunts the EGF-induced response. Pharmacological experiments indicate that the EGF-induced activation of PKD2 occurs independently of store depletion but requires the activity of phospholipase C (PLC) and phosphoinositide 3-kinase (PI3K). Pipette infusion of purified phosphatidylinositol-4,5-bisphosphate (PIP(2)) suppresses the PKD2-mediated effect on EGF-induced conductance, while pipette infusion of phosphatidylinositol-3,4,5-trisphosphate (PIP(3)) does not have any effect on this conductance. Overexpression of type Ialpha phosphatidylinositol-4-phosphate 5-kinase [PIP(5)Kalpha], which catalyzes the formation of PIP(2), suppresses EGF-induced currents. Biochemical experiments show that PKD2 physically interacts with PLC-gamma2 and EGF receptor (EGFR) in transfected HEK293T cells and colocalizes with EGFR and PIP(2) in the primary cilium of LLC-PK(1) cells. We propose that plasma membrane PKD2 is under negative regulation by PIP(2). EGF may reduce the threshold of PKD2 activation by mechanical and other stimuli by releasing it from PIP(2)-mediated inhibition.
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Affiliation(s)
- Rong Ma
- Department of Cell Biology, University of Oklahoma Health Sciences Center, 941 Stanton L. Young Boulevard, Oklahoma City, OK 73104, USA
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13
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Whitfield JF. The neuronal primary cilium--an extrasynaptic signaling device. Cell Signal 2004; 16:763-7. [PMID: 15115655 DOI: 10.1016/j.cellsig.2003.12.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2003] [Revised: 10/28/2003] [Accepted: 12/01/2003] [Indexed: 10/26/2022]
Abstract
Many, but likely most, neurons in the central nervous system have a nonmotile "primary" cilium extending like an antenna or finger from one of the pair of centrioles in the cell's centrosome into the extracellular space. Since their discovery over 100 years ago, these organelles have been either dismissed as functionless relicts of a bygone era or more often simply ignored. However, it has long been known that the photoreceptor-bearing outer segments of retinal rods and cones are modified primary cilia and it has recently been found that kidney cells' primary cilia are sensitive flowmeters the disabling of which causes polycystic kidney disease. It has also been recently shown that somatostatin sst3 receptors and serotonin 5-HT(6) receptors are selectively sited on neurons in various parts of the rat brain. It seems likely that these selectively receptored neuronal primary cilia will turn out to be the forerunners of a family of cell-signaling devices that help drive various brain functions by sending signals into their own cells and into adjacent cells through gap junctions and via conventional chemical synapses.
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Affiliation(s)
- J F Whitfield
- Institute for Biological Sciences, National Research Council of Canada, Building M-54, Montreal Road Campus, Ottawa, Ontario, Canada.
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14
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Masyuk TV, Huang BQ, Ward CJ, Masyuk AI, Yuan D, Splinter PL, Punyashthiti R, Ritman EL, Torres VE, Harris PC, LaRusso NF. Defects in cholangiocyte fibrocystin expression and ciliary structure in the PCK rat. Gastroenterology 2003; 125:1303-10. [PMID: 14598246 DOI: 10.1016/j.gastro.2003.09.001] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND & AIMS Recent studies have showed that proteins associated with polycystic kidney disease (PKD) are expressed in cilia, linking this organelle and cyst formation in the kidney, but involvement of cilia in PKD-related biliary cystogenesis has not been shown. We investigated: (1) the expression of fibrocystin (a product of PKHD1, the autosomal-recessive PKD [ARPKD] gene) in cholangiocyte cilia; (2) biliary cyst formation in an orthologous rat model, PCK; and (3) the effect of Pkhd1 mutation on ciliary structure. METHODS Biliary cystogenesis was assessed by microcomputed tomography. Fibrocystin expression in cholangiocytes of isolated intrahepatic bile ducts (IBDUs) and liver cysts was analyzed by confocal and immunoelectron microscopy, and ciliary structure and length by scanning and transmission electron microscopy. Small interfering RNAs (siRNA) were used to examine the effect of fibrocystin loss on ciliary structure. RESULTS The biliary tree in the PCK rat was distorted markedly, showing multiple bile duct dilatation and focal budding. In normal IBDUs, each cholangiocyte had a single cilium that expressed fibrocystin. In contrast, cilia in the PCK rat were abnormal with bulbous extensions and diminished length, and were devoid of fibrocystin. In cholangiocytes of normal IBDUs, specific siRNA reduced Pkhd1 messenger RNA by 80%, the length of cilia by 41%, and fibrocystin ciliary expression to an undetectable level. CONCLUSIONS Our results indicate that fibrocystin is expressed in cholangiocyte cilia and that disruption of Pkhd1 by a germ line mutation in the PCK rat or by siRNA in IBDUs results in abnormalities in ciliary morphology and possibly biliary cystogenesis.
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MESH Headings
- Animals
- Bile Ducts/metabolism
- Bile Ducts/pathology
- Bile Ducts, Intrahepatic/metabolism
- Blotting, Western
- Cilia/metabolism
- Cilia/ultrastructure
- Disease Models, Animal
- Fluorescent Antibody Technique
- Gene Silencing
- Germ-Line Mutation
- Microscopy, Electron
- Microscopy, Electron, Scanning
- Microscopy, Immunoelectron
- Polycystic Kidney, Autosomal Recessive/genetics
- Polycystic Kidney, Autosomal Recessive/metabolism
- Polycystic Kidney, Autosomal Recessive/pathology
- RNA, Small Interfering/metabolism
- Rats
- Rats, Mutant Strains
- Receptors, Cell Surface/deficiency
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
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Affiliation(s)
- Tatyana V Masyuk
- Division of Gastroenterology and Hepatology, Mayo Medical School, Clinic and Foundation, 200 First Street SW, Rochester, MN 55905, USA
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15
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Hostetter CL, Sullivan-Brown JL, Burdine RD. Zebrafish pronephros: A model for understanding cystic kidney disease. Dev Dyn 2003; 228:514-22. [PMID: 14579389 DOI: 10.1002/dvdy.10371] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The embryonic kidney of the zebrafish is the pronephros. The ease of genetic analysis and experimentation in zebrafish, coupled with the simplicity of the pronephros, make the zebrafish an ideal model system for studying kidney development and function. Several mutations have been isolated in zebrafish genetic screens that result in cyst formation in the pronephros. Cloning and characterization of these mutations will provide insight into kidney development but may also provide understanding of the molecular basis of cystic kidney diseases. In this review, we focus on the zebrafish as a model for understanding cystic kidney disease and the links between cystic kidney disease and left-right patterning.
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Affiliation(s)
- Christine L Hostetter
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08540, USA
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16
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Paul SM, Ternet M, Salvaterra PM, Beitel GJ. The Na+/K+ ATPase is required for septate junction function and epithelial tube-size control in the Drosophila tracheal system. Development 2003; 130:4963-74. [PMID: 12930776 DOI: 10.1242/dev.00691] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Although the correct architecture of epithelial tubes is crucial for the function of organs such as the lung, kidney and vascular system, little is known about the molecular mechanisms that control tube size. We show that mutations in the ATPalpha alpha and nrv2 beta subunits of the Na+/K+ ATPase cause Drosophila tracheal tubes to have increased lengths and expanded diameters. ATPalpha and nrv2 mutations also disrupt stable formation of septate junctions, structures with some functional and molecular similarities to vertebrate tight junctions. The Nrv2 beta subunit isoforms have unique tube size and junctional functions because Nrv2, but not other Drosophila Na+/K+ ATPase beta subunits, can rescue nrv2 mutant phenotypes. Mutations in known septate junctions genes cause the same tracheal tube-size defects as ATPalpha and nrv2 mutations, indicating that septate junctions have a previously unidentified role in epithelial tube-size control. Double mutant analyses suggest that tube-size control by septate junctions is mediated by at least two discernable pathways, although the paracellular diffusion barrier function does not appear to involved because tube-size control and diffusion barrier function are genetically separable. Together, our results demonstrate that specific isoforms of the Na+/K+ ATPase play a crucial role in septate junction function and that septate junctions have multiple distinct functions that regulate paracellular transport and epithelial tube size.
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Affiliation(s)
- Sarah M Paul
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208, USA
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17
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Abstract
With few exceptions, the non-cycling cells in a vast range of animals including humans have a non-motile primary cilium that extends from the mother centriole of the pair of centrioles in their centrosomes located between their Golgi apparatuses and nuclei. It has very recently been shown that the primary cilium of a dog or a mouse embryonic kidney cell is a fluid flowmeter studded with heterodimeric complexes of mechanoreceptors linked to Ca(2+)-permeable cation channels that when the cilium is bent can send Ca(2+) signals into the cell and beyond to neighboring cells through gap junctions. More than 30 years ago, osteocytes were reported also to have primary cilia, but this was promptly ignored or forgotten. Osteocytes are the bones' strain sensors, which measure skeletal activity from the effects of currents of extracellular fluid caused by their bones being bent and squeezed during various activities such as walking and running. Since bending a kidney cell's primary cilium can send a Ca(2+) wave surging through itself and its neighbors, the bending of an osteocyte's primary cilium by sloshing extracellular fluid is likely to do the same thing and thus be involved in measuring and responding to bone strain.
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Affiliation(s)
- James F Whitfield
- Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario, Canada.
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18
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Calvet JP. New insights into ciliary function: kidney cysts and photoreceptors. Proc Natl Acad Sci U S A 2003; 100:5583-5. [PMID: 12732727 PMCID: PMC156242 DOI: 10.1073/pnas.1031799100] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- James P Calvet
- Department of Biochemistry and Molecular Biology and the Kidney Institute, University of Kansas Medical Center, Kansas City 66160-7421, USA.
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19
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Abstract
Many organs are composed of epithelial tubes that transport vital fluids. Such tubular organs develop in many different ways and generate tubes of widely varying sizes and structures, but always with the apical epithelial surface lining the lumen. We describe recent progress in several diverse cell culture and genetic models of tube morphogenesis, which suggest apical membrane biogenesis, vesicle fusion, and secretion play central roles in tube formation and growth. We propose a unifying mechanism of tube morphogenesis that has been modified to create tube diversity and describe how defects in the tube size-sensing step can lead to polycystic kidney disease.
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Affiliation(s)
- Barry Lubarsky
- Howard Hughes Medical Institute, Department of Biochemistry, Stanford University, School of Medicine, Stanford, CA 94305, USA
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