scholarly journals Disrupting polycystin-2 EF hand Ca2+ affinity does not alter channel function or contribute to polycystic kidney disease

2020 ◽  
Vol 133 (24) ◽  
pp. jcs255562
Author(s):  
Thuy N. Vien ◽  
Leo C. T. Ng ◽  
Jessica M. Smith ◽  
Ke Dong ◽  
Matteus Krappitz ◽  
...  
Keyword(s):  
Kidney Disease ◽  
Polycystic Kidney Disease ◽  
Primary Cilia ◽  
Collecting Duct ◽  
Mouse Strains ◽  
Polycystic Kidney ◽  
Channel Function ◽  
Ef Hand ◽  
Voltage Dependent ◽  
Autosomal Dominant Polycystic Kidney

ABSTRACTApproximately 15% of autosomal dominant polycystic kidney disease (ADPKD) is caused by variants in PKD2. PKD2 encodes polycystin-2, which forms an ion channel in primary cilia and endoplasmic reticulum (ER) membranes of renal collecting duct cells. Elevated internal Ca2+ modulates polycystin-2 voltage-dependent gating and subsequent desensitization – two biophysical regulatory mechanisms that control its function at physiological membrane potentials. Here, we refute the hypothesis that Ca2+ occupancy of the polycystin-2 intracellular EF hand is responsible for these forms of channel regulation, and, if disrupted, results in ADPKD. We identify and introduce mutations that attenuate Ca2+-EF hand affinity but find channel function is unaltered in the primary cilia and ER membranes. We generated two new mouse strains that harbor distinct mutations that abolish Ca2+-EF hand association but do not result in a PKD phenotype. Our findings suggest that additional Ca2+-binding sites within polycystin-2 or Ca2+-dependent modifiers are responsible for regulating channel activity.

scholarly journals Molecular Pathways and Therapies in Autosomal-Dominant Polycystic Kidney Disease

Physiology ◽  
2015 ◽  
Vol 30 (3) ◽  
pp. 195-207 ◽  
Author(s):  
Takamitsu Saigusa ◽  
P. Darwin Bell
Keyword(s):  
Kidney Disease ◽  
Polycystic Kidney Disease ◽  
Primary Cilia ◽  
Autosomal Dominant ◽  
Molecular Pathways ◽  
Polycystic Kidney ◽  
Autosomal Dominant Polycystic Kidney ◽  
Multiple Cysts ◽  
Review Current

Autosomal-dominant polycystic kidney disease (ADPKD) is the most prevalent inherited renal disease, characterized by multiple cysts that can eventually lead to kidney failure. Studies investigating the role of primary cilia and polycystins have significantly advanced our understanding of the pathogenesis of PKD. This review will present clinical and basic aspects of ADPKD, review current concepts of PKD pathogenesis, evaluate potential therapeutic targets, and highlight challenges for future clinical studies.

scholarly journals Tubular STAT3 Limits Renal Inflammation in Autosomal Dominant Polycystic Kidney Disease

2020 ◽  
Vol 31 (5) ◽  
pp. 1035-1049 ◽  
Author(s):  
Amandine Viau ◽  
Maroua Baaziz ◽  
Amandine Aka ◽  
Manal Mazloum ◽  
Clément Nguyen ◽  
...  
Keyword(s):  
Kidney Disease ◽  
Polycystic Kidney Disease ◽  
Primary Cilia ◽  
Autosomal Dominant ◽  
Polycystic Kidney ◽  
Polycystic Kidneys ◽  
Renal Inflammation ◽  
Tubular Cells ◽  
Autosomal Dominant Polycystic Kidney ◽  
Cyst Growth

BackgroundThe inactivation of the ciliary proteins polycystin 1 or polycystin 2 leads to autosomal dominant polycystic kidney disease (ADPKD). Although signaling by primary cilia and interstitial inflammation both play a critical role in the disease, the reciprocal interactions between immune and tubular cells are not well characterized. The transcription factor STAT3, a component of the cilia proteome that is involved in crosstalk between immune and nonimmune cells in various tissues, has been suggested as a factor fueling ADPKD progression.MethodTo explore how STAT3 intersects with cilia signaling, renal inflammation, and cyst growth, we used conditional murine models involving postdevelopmental ablation of Pkd1, Stat3, and cilia, as well as cultures of cilia-deficient or STAT3-deficient tubular cell lines.ResultsOur findings indicate that, although primary cilia directly modulate STAT3 activation in vitro, the bulk of STAT3 activation in polycystic kidneys occurs through an indirect mechanism in which primary cilia trigger macrophage recruitment to the kidney, which in turn promotes Stat3 activation. Surprisingly, although inactivating Stat3 in Pkd1-deficient tubules slightly reduced cyst burden, it resulted in a massive infiltration of the cystic kidneys by macrophages and T cells, precluding any improvement of kidney function. We also found that Stat3 inactivation led to increased expression of the inflammatory chemokines CCL5 and CXCL10 in polycystic kidneys and cultured tubular cells.ConclusionsSTAT3 appears to repress the expression of proinflammatory cytokines and restrict immune cell infiltration in ADPKD. Our findings suggest that STAT3 is not a critical driver of cyst growth in ADPKD but rather plays a major role in the crosstalk between immune and tubular cells that shapes disease expression.

scholarly journals Exploring the Spectrum of Kidney Ciliopathies

Diagnostics ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1099
Author(s):  
Matteo Santoni ◽  
Francesco Piva ◽  
Alessia Cimadamore ◽  
Matteo Giulietti ◽  
Nicola Battelli ◽  
...  
Keyword(s):  
Kidney Disease ◽  
Signaling Pathways ◽  
Polycystic Kidney Disease ◽  
Primary Cilium ◽  
Primary Cilia ◽  
Kidney Diseases ◽  
Ubiquitin Proteasome System ◽  
Polycystic Kidney ◽  
Ubiquitin Proteasome ◽  
Autosomal Dominant Polycystic Kidney

Ciliopathies are a group of multi-organ diseases caused by the disruption of the primary cilium. This event leads to a variety of kidney disorders, including nephronophthisis, renal cystic dysplasia, and renal cell carcinoma (RCC). Primary cilium contributes to the regulation of the cell cycle and protein homeostasis, that is, the balance between protein synthesis and degradation by acting on the ubiquitin-proteasome system, autophagy, and mTOR signaling. Many proteins are involved in renal ciliopathies. In particular, fibrocystin (PKHD1) is involved in autosomal recessive polycystic kidney disease (ARPKD), while polycystin-1 (PKD1) and polycystin-2 (PKD2) are implicated in autosomal dominant polycystic kidney disease (ADPKD). Moreover, primary cilia are associated with essential signaling pathways, such as Hedgehog, Wnt, and Platelet-Derived Growth Factor (PDGF). In this review, we focused on the ciliopathies associated with kidney diseases, exploring genes and signaling pathways associated with primary cilium and the potential role of cilia as therapeutic targets in renal disorders.

scholarly journals Synergistic Genetic Interactions between Pkhd1 and Pkd1 Result in an ARPKD-Like Phenotype in Murine Models

2019 ◽  
Vol 30 (11) ◽  
pp. 2113-2127 ◽  
Author(s):  
Rory J. Olson ◽  
Katharina Hopp ◽  
Harrison Wells ◽  
Jessica M. Smith ◽  
Jessica Furtado ◽  
...  
Keyword(s):  
Kidney Disease ◽  
Polycystic Kidney Disease ◽  
Primary Cilia ◽  
Genetic Interaction ◽  
Protein Localization ◽  
Murine Models ◽  
Polycystic Kidney ◽  
Mild Phenotype ◽  
Length Changes ◽  
Autosomal Dominant Polycystic Kidney

BackgroundAutosomal recessive polycystic kidney disease (ARPKD) and autosomal dominant polycystic kidney disease (ADPKD) are genetically distinct, with ADPKD usually caused by the genes PKD1 or PKD2 (encoding polycystin-1 and polycystin-2, respectively) and ARPKD caused by PKHD1 (encoding fibrocystin/polyductin [FPC]). Primary cilia have been considered central to PKD pathogenesis due to protein localization and common cystic phenotypes in syndromic ciliopathies, but their relevance is questioned in the simple PKDs. ARPKD’s mild phenotype in murine models versus in humans has hampered investigating its pathogenesis.MethodsTo study the interaction between Pkhd1 and Pkd1, including dosage effects on the phenotype, we generated digenic mouse and rat models and characterized and compared digenic, monogenic, and wild-type phenotypes.ResultsThe genetic interaction was synergistic in both species, with digenic animals exhibiting phenotypes of rapidly progressive PKD and early lethality resembling classic ARPKD. Genetic interaction between Pkhd1 and Pkd1 depended on dosage in the digenic murine models, with no significant enhancement of the monogenic phenotype until a threshold of reduced expression at the second locus was breached. Pkhd1 loss did not alter expression, maturation, or localization of the ADPKD polycystin proteins, with no interaction detected between the ARPKD FPC protein and polycystins. RNA-seq analysis in the digenic and monogenic mouse models highlighted the ciliary compartment as a common dysregulated target, with enhanced ciliary expression and length changes in the digenic models.ConclusionsThese data indicate that FPC and the polycystins work independently, with separate disease-causing thresholds; however, a combined protein threshold triggers the synergistic, cystogenic response because of enhanced dysregulation of primary cilia. These insights into pathogenesis highlight possible common therapeutic targets.

Mechanoregulation of intracellular Ca2+ concentration is attenuated in collecting duct of monocilium-impaired orpk mice

2005 ◽  
Vol 289 (5) ◽  
pp. F978-F988 ◽  
Author(s):  
Wen Liu ◽  
Noel S. Murcia ◽  
Yi Duan ◽  
Sheldon Weinbaum ◽  
Bradley K. Yoder ◽  
...  
Keyword(s):  
Kidney Disease ◽  
Polycystic Kidney Disease ◽  
Primary Cilia ◽  
Collecting Duct ◽  
Polycystic Kidney ◽  
New Findings ◽  
Collecting Ducts ◽  
Before And After ◽  
Luminal Flow

Autosomal recessive polycystic kidney disease (ARPKD) is characterized by the progressive dilatation of collecting ducts, the nephron segments responsible for the final renal regulation of sodium, potassium, acid-base, and water balance. Murine models of ARPKD possess mutations in genes encoding cilia-associated proteins, including Tg737 in orpk mice. New findings implicate defects in structure/function of primary cilia as central to the development of polycystic kidney disease. Our group (Liu W, Xu S, Woda C, Kim P, Weinbaum S, and Satlin LM, Am J Physiol Renal Physiol 285: F998–F1012, 2003) recently reported that increases in luminal flow rate in rabbit collecting ducts increase intracellular Ca2+ concentration ([Ca2+]i) in cells therein. We thus hypothesized that fluid shear acting on the apical membrane or hydrodynamic bending moments acting on the cilium increase renal epithelial [Ca2+]i. To further explore this, we tested whether flow-induced [Ca2+]i transients in collecting ducts from mutant orpk mice, which possess structurally abnormal cilia, differ from those in controls. Isolated segments from 1- and 2-wk-old mice were microperfused in vitro and loaded with fura 2; [Ca2+]i was measured by digital ratio fluorometry before and after the rate of luminal flow was increased. All collecting ducts responded to an increase in flow with an increase in [Ca2+]i, a response that appeared to be dependent on luminal Ca2+ entry. However, the magnitude of the increase in [Ca2+]i in 2- but not 1-wk-old mutant orpk animals was blunted. We speculate that this defect in mechano-induced Ca2+ signaling in orpk mice leads to aberrant structure and function of the collecting duct in ARPKD.

scholarly journals Tubular STAT3 limits renal inflammation in autosomal dominant polycystic kidney disease

2019 ◽  
Author(s):  
Amandine Viau ◽  
Maroua Baziz ◽  
Amandine Aka ◽  
Clément Nguyen ◽  
E. Wolfgang Kuehn ◽  
...  
Keyword(s):  
Kidney Disease ◽  
Polycystic Kidney Disease ◽  
Primary Cilia ◽  
Autosomal Dominant ◽  
Polycystic Kidney ◽  
Polycystic Kidneys ◽  
Renal Inflammation ◽  
Tubular Cells ◽  
Autosomal Dominant Polycystic Kidney ◽  
Cyst Growth

ABSTRACTThe inactivation of the ciliary proteins polycystin 1 or 2 leads to autosomal dominant polycystic kidney disease (ADPKD), the leading genetic cause of chronic kidney disease. Both cilia signaling and interstitial inflammation play a critical role in the disease. Yet, the reciprocal interactions between immune and tubular cells are not well characterized. The transcription factor STAT3, which is suspected to fuel ADPKD progression, is involved in crosstalks between immune and non-immune cells in various tissues and is a component of the cilia proteome. Here, we explore how STAT3 intersects with cilia signaling, renal inflammation and cyst growth using conditional murine models of post-developmental Pkd1, Stat3 and cilia ablation. Our results indicate that, although primary cilia directly modulate STAT3 activation in vitro, the bulk of STAT3 activation in polycystic kidneys occurs through an indirect mechanism in which primary cilia trigger macrophage recruitment to the kidney, which in turn promotes STAT3 activation. Surprisingly, while disrupting Stat3 in Pkd1 deficient tubules slightly reduced cyst burden, it resulted in a massive infiltration of the cystic kidneys by macrophages and T cells, precluding any improvement of kidney function. Mechanistically, STAT3 represses the expression of the inflammatory chemokines CCL5 and CXCL10 in polycystic kidneys and cultured tubular cells. These results demonstrate that STAT3 is not a critical driver of cyst growth in ADPKD but plays a major role in the crosstalk between immune and tubular cells that shapes disease expression.

scholarly journals Loss of polycystins suppresses deciliation via the activation of the centrosomal integrity pathway

2020 ◽  
Vol 3 (9) ◽  
pp. e202000750 ◽  
Author(s):  
Vasileios Gerakopoulos ◽  
Peter Ngo ◽  
Leonidas Tsiokas
Keyword(s):  
Cell Cycle ◽  
Kidney Disease ◽  
Signaling Pathways ◽  
Polycystic Kidney Disease ◽  
Primary Cilia ◽  
Autosomal Dominant ◽  
Polycystic Kidney ◽  
Cyclic Pattern ◽  
Autosomal Dominant Polycystic Kidney ◽  
Cystic Growth

The primary cilium is a microtubule-based, antenna-like organelle housing several signaling pathways. It follows a cyclic pattern of assembly and deciliation (disassembly and/or shedding), as cells exit and re-enter the cell cycle, respectively. In general, primary cilia loss leads to kidney cystogenesis. However, in animal models of autosomal dominant polycystic kidney disease, a major disease caused by mutations in the polycystin genes (Pkd1 or Pkd2), primary cilia ablation or acceleration of deciliation suppresses cystic growth, whereas deceleration of deciliation enhances cystogenesis. Here, we show that deciliation is delayed in the cystic epithelium of a mouse model of postnatal deletion of Pkd1 and in Pkd1- or Pkd2-null cells in culture. Mechanistic experiments show that PKD1 depletion activates the centrosomal integrity/mitotic surveillance pathway involving 53BP1, USP28, and p53 leading to a delay in deciliation. Reduced deciliation rate causes prolonged activation of cilia-based signaling pathways that could promote cystic growth. Our study links polycystins to cilia dynamics, identifies cellular deciliation downstream of the centrosomal integrity pathway, and helps explain pro-cystic effects of primary cilia in autosomal dominant polycystic kidney disease.

The role of DNA damage as a therapeutic target in autosomal dominant polycystic kidney disease

2019 ◽  
Vol 21 ◽  
Author(s):  
Jennifer Q. J. Zhang ◽  
Sayanthooran Saravanabavan ◽  
Alexandra Munt ◽  
Annette T. Y. Wong ◽  
David C. Harris ◽  
...  
Keyword(s):  
Dna Damage ◽  
Kidney Disease ◽  
Polycystic Kidney Disease ◽  
Autosomal Dominant ◽  
Germ Line ◽  
Collecting Duct ◽  
Cyst Formation ◽  
Polycystic Kidney ◽  
Advantages And Disadvantages ◽  
Autosomal Dominant Polycystic Kidney

Abstract Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic kidney disease and is caused by heterozygous germ-line mutations in either PKD1 (85%) or PKD2 (15%). It is characterised by the formation of numerous fluid-filled renal cysts and leads to adult-onset kidney failure in ~50% of patients by 60 years. Kidney cysts in ADPKD are focal and sporadic, arising from the clonal proliferation of collecting-duct principal cells, but in only 1–2% of nephrons for reasons that are not clear. Previous studies have demonstrated that further postnatal reductions in PKD1 (or PKD2) dose are required for kidney cyst formation, but the exact triggering factors are not clear. A growing body of evidence suggests that DNA damage, and activation of the DNA damage response pathway, are altered in ciliopathies. The aims of this review are to: (i) analyse the evidence linking DNA damage and renal cyst formation in ADPKD; (ii) evaluate the advantages and disadvantages of biomarkers to assess DNA damage in ADPKD and finally, (iii) evaluate the potential effects of current clinical treatments on modifying DNA damage in ADPKD. These studies will address the significance of DNA damage and may lead to a new therapeutic approach in ADPKD.

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