Inward calcium current through the polycystin-2-dependent channels of renal primary cilia

2021 ◽  
Author(s):  
Steven J. Kleene ◽  
Nancy K. Kleene
Keyword(s):  
Primary Cilium ◽  
Calcium Current ◽  
Primary Cilia ◽  
Autosomal Dominant ◽  
Collecting Duct ◽  
Polycystic Kidney ◽  
Renal Epithelial Cells ◽  
Medullary Collecting Duct ◽  
The Mean ◽  
Autosomal Dominant Polycystic Kidney

In 15% of cases, autosomal dominant polycystic kidney disease (ADPKD) arises from defects in polycystin-2 (PC2). PC2 is a member of the TRPP subfamily of cation-conducting channels and is expressed in the endoplasmic reticulum and primary cilium of renal epithelial cells. PC2 opposes a pro-cystogenic influence of the cilium, and it has been proposed that this beneficial effect is mediated in part by a flow of Ca2+ through PC2 channels into the primary cilium. However, previous efforts to determine the permeability of PC2 channels to Ca2+ have yielded widely varying results. Here we report the mean macroscopic Ca2+ influx through native PC2 channels in the primary cilia of mIMCD-3 cells, which are derived from murine inner medullary collecting duct. Under conditions designed to isolate inward Ca2+ currents, a small inward Ca2+ current was detected in cilia with active PC2 channels, but not in cilia lacking those channels. The current was activated by addition of 10 µM internal Ca2+, which is known to activate ciliary PC2 channels. It was blocked by 10 µM isosakuranetin, which blocks the same channels. On average, the current amplitude was −1.8 pA at −190 mV; its conductance from −50 to −200 mV averaged 20 pS. Thus the native PC2 channels of renal primary cilium are able to conduct a small but detectable Ca2+ influx under the conditions tested. The possible consequences of this influx are discussed.

scholarly journals Ca2+-Dependent Regulation by the Cyclic AMP Pathway of Primary Cilium Length in LLC-PK1 Renal Epithelial Cells

2020 ◽  
Author(s):  
Noelia Scarinci ◽  
Paula L. Perez ◽  
María del Rocío Cantero ◽  
Horacio F. Cantiello
Keyword(s):  
Kidney Disease ◽  
Epithelial Cells ◽  
Primary Cilium ◽  
Primary Cilia ◽  
Autosomal Dominant ◽  
Cyst Formation ◽  
Polycystic Kidney ◽  
Renal Epithelial Cells ◽  
Autosomal Dominant Polycystic Kidney ◽  
Cilium Length

AbstractThe primary cilium is a sensory organelle projecting from the apical surface of renal epithelial cells. Dysfunctional cilia have been linked to a number of genetic diseases known as ciliopathies, which include autosomal dominant polycystic kidney disease (ADPKD). Previous studies have determined that renal epithelial primary cilia express both the polycystin-2 (PC2, TRPP2) channel and the type-2 vasopressin receptor (V2R), coupled to local cAMP production. However, little is known as to how Ca2+ and cAMP signals lead to changes in the length of the primary cilium. Here, we explored how cAMP signals regulate the length of the primary cilium in wild type LLC-PK1 renal epithelial cells. Primary cilia length was determined by immunocytochemical labeling of the ciliary axoneme. Treatment of cells with the cAMP analog 8-Br-cAMP (1 mM) in normal external Ca2+ (1.2 mM) produced a 25.3% increase (p < 0.0001) in the length of the primary cilium, a phenomenon also observed in cells exposed to high external Ca2+ (6.2 mM). However, exposure of cells to vasopressin (AVP, 10 μM), which also increases cAMP in primary cilia of LLC-PK1 cells, mimicked the effect of 8-Br-cAMP in normal, but not in high Ca2+. Further, specific gene silencing of PC2 expression further increased primary cilium length after 8-Br-cAMP treatment, in normal, but not high Ca2+. The encompassed data indicate a crosstalk between the cAMP and Ca2+ signals to modulate the length of the primary cilium, in a phenomenon that implicates the expression of PC2.Significance StatementMorphological changes in primary cilia have been linked to genetic disorders, including autosomal dominant polycystic kidney disease (ADPKD), a major cause of kidney disease. Both cAMP and Ca2+ are universal second messengers that regulate polycystin-2 (PC2, TRPP2), a Ca2+ permeable non-selective cation channel implicated in ADPKD, and expressed in the primary cilium of renal epithelial cells. Despite current interest, little is known as to how second messenger systems and how aberrant regulation of PC2 may link primary cilium structure with cyst formation in ADPKD. Here we determined that both the cAMP analog 8-Br-cAMP and vasopressin increase the length of the primary cilium in renal epithelial cells. However, this phenomenon depends of external Ca2+ and PKD2 gene silencing. Proper cAMP signaling may be essential in the control of the primary cilium of renal epithelial cells, and the onset of cyst formation in ADPKD.

scholarly journals Polycystin-2 (TRPP2) Regulates Primary Cilium Length in LLC-PK1 Renal Epithelial Cells

2020 ◽  
Author(s):  
Paula L. Perez ◽  
Noelia Scarinci ◽  
Horacio F. Cantiello ◽  
María del Rocío Cantero
Keyword(s):  
Epithelial Cells ◽  
Gene Silencing ◽  
Primary Cilium ◽  
Primary Cilia ◽  
Cyst Formation ◽  
Channel Blockers ◽  
Wild Type ◽  
Polycystic Kidney ◽  
Renal Epithelial Cells ◽  
Autosomal Dominant Polycystic Kidney

AbstractPolycystin-2 (PC2, TRPP2) is a Ca2+ permeable non-selective cation channel whose dysfunction generates autosomal dominant polycystic kidney disease (ADPKD). PC2 is present in different cell locations, including the primary cilium of renal epithelial cells. Little is known, however, as to whether PC2 contributes to the structure of the primary cilium. Here, we explored the effect(s) of external Ca2+, PC2 channel blockers, and PKD2 gene silencing on the length of primary cilia in wild type LLC-PK1 renal epithelial cells. To identify primary cilia and measure their length, confluent cell monolayers were fixed and immuno-labeled with an anti-acetylated α-tubulin antibody. Although primary cilia length measurements did not follow a Normal distribution, data were normalized by Box-Cox transformation rendering statistical difference under all experimental conditions. Cells exposed to high external Ca2+ (6.2 mM) decreased a 13.5% (p < 0.001) primary cilia length as compared to controls (1.2 mM Ca2+). In contrast, the PC2 inhibitors amiloride (200 μM) and LiCl (10 mM), both increased primary ciliary length by 33.2% (p < 0.001), and 17.4% (p < 0.001), respectively. PKD2 gene silencing by siRNA also elicited a statistically significant, 10.3% (p < 0.001) increase in primary cilia length, as compared to their respective scrambled RNA transfected cells. The data indicate that maneuvers that either regulate PC2 function or gene expression, modify the length of primary cilia in renal epithelial cells. Proper regulation of PC2 function in the primary cilium may be essential in the onset of mechanisms that trigger cyst formation in ADPKD.Significance StatementPolycystin-2 (PC2, TRPP2) is a Ca2+ permeable non-selective cation channel causing the autosomal dominant polycystic kidney disease (ADPKD). The importance of intact cilia and of fully functional polycystins in the onset of ADPKD cyst formation, point to yet unknown signaling mechanisms occurring within this organelle. We determined that the extracellular Ca2+ concentration, PC2 channel blockers, and PKD2 gene silencing, all contribute to the length of primary cilia in wild type LLC-PK1 renal epithelial cells. The data indicate that proper regulation of PC2 function in the primary cilium may be essential in the onset of mechanisms that trigger cyst formation in ADPKD.

scholarly journals Extracellular vesicles and exosomes generated from cystic renal epithelial cells promote cyst growth in autosomal dominant polycystic kidney disease

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hao Ding ◽  
Linda Xiaoyan Li ◽  
Peter C. Harris ◽  
Junwei Yang ◽  
Xiaogang Li
Keyword(s):  
Kidney Disease ◽  
Epithelial Cells ◽  
Polycystic Kidney Disease ◽  
Extracellular Vesicles ◽  
Autosomal Dominant ◽  
Therapeutic Potential ◽  
Polycystic Kidney ◽  
Renal Epithelial Cells ◽  
Autosomal Dominant Polycystic Kidney ◽  
Cyst Growth

AbstractAutosomal dominant polycystic kidney disease (ADPKD) is caused by germline mutations of PKD1 or PKD2 on one allele and a somatic mutation inactivating the remaining normal allele. However, if and how null ADPKD gene renal epithelial cells affect the biology and function of neighboring cells, including heterozygous renal epithelial cells, fibroblasts and macrophages during cyst initiation and expansion remains unknown. Here we address this question with a “cystic extracellular vesicles/exosomes theory”. We show that cystic cell derived extracellular vesicles and urinary exosomes derived from ADPKD patients promote cyst growth in Pkd1 mutant kidneys and in 3D cultures. This is achieved by: 1) downregulation of Pkd1 gene expression and upregulation of specific miRNAs, resulting in the activation of PKD associated signaling pathways in recipient renal epithelial cells and tissues; 2) the activation of fibroblasts; and 3) the induction of cytokine expression and the recruitment of macrophages to increase renal inflammation in cystic kidneys. Inhibition of exosome biogenesis/release with GW4869 significantly delays cyst growth in aggressive and milder ADPKD mouse models, suggesting that targeting exosome secretion has therapeutic potential for ADPKD.

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 The Natural Course of Total Kidney Volume in Patients with Autosomal Dominant Polycystic Kidney Disease undergoing Hemodialysis

2021 ◽  
Vol 36 (2) ◽  
pp. 109-115
Author(s):  
Ye Na Kim ◽  
Yeonsoon Jung ◽  
Ho Sik Shin ◽  
Hark Rim ◽  
Jung Gu Park ◽  
...  
Keyword(s):  
Autosomal Dominant ◽  
Kidney Volume ◽  
Polycystic Kidney ◽  
Total Kidney Volume ◽  
Change Rate ◽  
The Mean ◽  
Autosomal Dominant Polycystic Kidney ◽  
Group 2 ◽  
Group 1

Objectives: The natural course of native kidneys after hemodialysis initiation in patients with autosomal dominant polycystic kidney disease (ADPKD) remains poorly understood.Methods: We measured the total volumes of native kidneys in 12 patients who had at least one enhanced computed tomography (CT) image both before and after initiation of hemodialysis (group 1) and in 18 patients who had no image before dialysis but more than two images after dialysis (group 2). In patients with images, the last image was used for analysis only after dialysis.Results: The mean total kidney volume (TKV) (± SD) before hemodialysis initiation was 3132 ± 1413 mL and the mean TKV of the last image was 3047 ± 1323 mL in group 1. The mean TKV change rate (%) was - 5.2 ± 27.4% (P > 0.05) during follow-up of 3.9 ± 1.9 years in group 1. The mean TKV change rate was 2.8 ± 34.4% (P > 0.05) in group 2. The follow-up period after dialysis initiation ranged from 4.2 ± 4.7 to 8.0 ± 5.2 years.Conclusions: The results suggest that the TKV of native polycystic kidneys decreases substantially after hemodialysis initiation. This reduction occurs mainly during the early post-hemodialysis period and followed by a slow enlargement of TKV.

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.

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