A microbial TRP-like polycystic-kidney-disease-related ion channel gene.
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ABSTRACT:
SUBMITTER: Palmer CP
PROVIDER: S-EPMC1134949 | biostudies-other | 2005 Apr
REPOSITORIES: biostudies-other
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Project description:PKD2L1, also termed TRPP3 from the TRPP subfamily (polycystic TRP channels), is involved in the sour sensation and other pH-dependent processes. PKD2L1 is believed to be a nonselective cation channel that can be regulated by voltage, protons, and calcium. Despite its considerable importance, the molecular mechanisms underlying PKD2L1 regulations are largely unknown. Here, we determine the PKD2L1 atomic structure at 3.38?Å resolution by cryo-electron microscopy, whereby side chains of nearly all residues are assigned. Unlike its ortholog PKD2, the pore helix (PH) and transmembrane segment 6 (S6) of PKD2L1, which are involved in upper and lower-gate opening, adopt an open conformation. Structural comparisons of PKD2L1 with a PKD2-based homologous model indicate that the pore domain dilation is coupled to conformational changes of voltage-sensing domains (VSDs) via a series of ?-? interactions, suggesting a potential PKD2L1 gating mechanism.
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Project description:BackgroundA major difference between autosomal recessive polycystic kidney disease (ARPKD) and autosomal dominant polycystic kidney disease (ADPKD) lies in the pattern of inheritance, and the resultant timing and focality of cyst formation. In both diseases, cysts form in the kidney and liver as a consequence of the cellular recessive genotype of the respective disease gene, but this occurs by germline inheritance in ARPKD and somatic second hit mutations to the one normal allele in ADPKD. The fibrocystic liver phenotype in ARPKD is attributed to abnormal ductal plate formation because of the absence of PKHD1 expression during embryogenesis and organ development. The finding of polycystic liver disease in a subset of adult PKHD1 heterozygous carriers raises the question of whether somatic second hit mutations in PKHD1 in adults may also result in bile duct-derived cyst formation.MethodsWe used an adult-inducible Pkhd1 mouse model to examine whether Pkhd1 has a functional role in maintaining bile duct homeostasis after normal liver development.ResultsInactivation of Pkhd1 beginning at 4 weeks of age resulted in a polycystic liver phenotype with minimal fibrosis at 17 weeks. Increased biliary epithelium, which lines these liver cysts, was most pronounced in female mice. We assessed genetic interaction of this phenotype with either reduced or increased copies of Pkd1, and found no significant effects on the Pkhd1 phenotype in the liver or kidney from altered Pkd1 expression.ConclusionsSomatic adult inactivation of Pkhd1 results in a polycystic liver phenotype. Pkhd1 is a required gene in adulthood for biliary structural homeostasis independent of Pkd1. This suggests that PKHD1 heterozygous carrier patients can develop liver cysts after somatic mutations in their normal copy of PKHD1.
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Project description:The Polycystic Kidney Disease 2 (Pkd2) gene is mutated in autosomal dominant polycystic kidney disease (ADPKD), one of the most common human monogenic disorders. Here, we present the cryo-EM structure of PKD2 in lipid bilayers at 3.0 Å resolution, which establishes PKD2 as a homotetrameric ion channel and provides insight into potential mechanisms for its activation. The PKD2 voltage-sensor domain retains two of four gating charges commonly found in those of voltage-gated ion channels. The PKD2 ion permeation pathway is constricted at the selectivity filter and near the cytoplasmic end of S6, suggesting that two gates regulate ion conduction. The extracellular domain of PKD2, a hotspot for ADPKD pathogenic mutations, contributes to channel assembly and strategically interacts with the transmembrane core, likely serving as a physical substrate for extracellular stimuli to allosterically gate the channel. Finally, our structure establishes the molecular basis for the majority of pathogenic mutations in Pkd2-related ADPKD.
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Project description:A number of inherited disorders result in renal cyst development. The most common form, autosomal dominant polycystic kidney disease (ADPKD), is a disorder most often diagnosed in adults and caused by mutation in PKD1 or PKD2. The PKD1 protein, polycystin-1, is a large receptor-like protein, whereas polycystin-2 is a transient receptor potential channel. The polycystin complex localizes to primary cilia and may act as a mechanosensor essential for maintaining the differentiated state of epithelia lining tubules in the kidney and biliary tract. Elucidation of defective cellular processes has highlighted potential therapies, some of which are now being tested in clinical trials. ARPKD is the neonatal form of PKD and is associated with enlarged kidneys and biliary dysgenesis. The disease phenotype is highly variable, ranging from neonatal death to later presentation with minimal kidney disease. ARPKD is caused by mutation in PKHD1, and two truncating mutations are associated with neonatal lethality. The ARPKD protein, fibrocystin, is localized to cilia/basal body and complexes with polycystin-2. Rare, syndromic forms of PKD also include defects of the eye, central nervous system, digits, and/or neural tube and highlight the role of cilia and pathways such as Wnt and Hh in their pathogenesis.
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Project description:Polycystic Kidney Disease (PKD) is a genetic disease of the kidney characterized by the gradual replacement of normal kidney parenchyma by fluid-filled cysts and fibrotic tissue. Autosomal Dominant Polycystic Kidney Disease (ADPKD) is caused by mutations in the PKD1 or PKD2 gene. Here we present an RNASeq experiment designed to investigate the effect of a kidney specific and Tamoxifen inducible knockout of the Pkd1 gene in mice. The Pkd1cko mice were harvested at different time points 2-weeks, 3-weeks, 5-weeks, 10.5-weeks, 11-weeks and 15-weeks after gene inactivation.
2019-12-24 | E-MTAB-8086 | biostudies-arrayexpress
Project description:PKD2 and PKD1 genes are mutated in human autosomal dominant polycystic kidney disease. PKD2 can form either a homomeric cation channel or a heteromeric complex with the PKD1 receptor, presumed to respond to ligand(s) and/or mechanical stimuli. Here, we identify a two-residue hydrophobic gate in PKD2L1, and a single-residue hydrophobic gate in PKD2. We find that a PKD2 gain-of-function gate mutant effectively rescues PKD2 knockdown-induced phenotypes in embryonic zebrafish. The structure of a PKD2 activating mutant F604P by cryo-electron microscopy reveals a ?- to ?-helix transition within the pore-lining helix S6 that leads to repositioning of the gate residue and channel activation. Overall the results identify hydrophobic gates and a gating mechanism of PKD2 and PKD2L1.
| S-EPMC5998024 | biostudies-literature
Project description:Background: Autosomal dominant polycystic kidney disease (PKD) is characterized by extensive cyst formation and progressive fibrosis. However, the molecular mechanisms whereby the loss/loss-of-function of polycystin 1 or 2 (PC1/2) provokes fibrosis are largely unknown. The small GTPase RhoA has been implicated in cystogenesis, while we have shown that the RhoA/cytoskeleton/myocardin-related transcription factor (MRTF) pathway is a key inducer of epithelium-induced fibrogenesis. Therefore, we hypothesized that MRTF 1) is activated by PC1/2 loss, and 2) plays a critical role in fibrogenic repogramming of the epithelium and the subsequent induction of fibrosis. Methods: PC1/2 loss was achieved by gene silencing in tubular cells (in vitro) and in PKD1 (RC/RC) and PKD2 (ws25/-) mice (in vivo). RhoA activation was measured by pull-down assays and immunofluorescence. MRTF localization (nuclear/cytosolic ratio, intensity) was quantified in large cell populations and in renal tissue using automated image analysis. PC1/PC2 loss-promoted, MRTF-dependent gene expression was followed by qPCR, RNAseq and RNAscope. MRTF-dependent paracrine effects were assessed by a bioassay. Results: Loss of PC1 or PC2 activated RhoA in vitro and in vivo, resulting in cytoskeletal remodelling and robust nuclear MRTF translocation, accompanied by increased MRTF expression. Nuclear translocation occurred predominantly in dilated tubules, while overexpression in the cyst-lining epithelium. A large cohort of PC1/PC2 downregulation-induced genes was MRTF-dependent, including cytoskeletal, integrin-related, and matricellular/fibrogenic proteins. Epithelial MRTF was necessary for paracrine priming of fibroblast-myofibroblast transition. Conclusion: The Rho/MRTF pathway is a critical novel mediator of PC1/2 loss-induced acquisition of the profibrotic epithelial phenotype and the ensuing fibrosis.
2024-05-01 | GSE252716 | GEO
Project description:Understanding the complex interactions between the various pathways disrupted in polycystic kidney and liver disease is essential to identify and optimize therapies for these disorders. Studies published in the past year have demonstrated a functional interaction between the main proteins implicated in these diseases and identified novel therapeutic approaches.
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Project description:In order to identify candidate cation channels important for retinal physiology, 28 TRP channel genes were surveyed for expression in the mouse retina. Transcripts for all TRP channels were detected by RT-PCR and sequencing. Northern blotting revealed that mRNAs for 12 TRP channel genes are enriched in the retina. The strongest signals were observed for TRPC1, TRPC3, TRPM1, TRPM3, and TRPML1, and clear signals were obtained for TRPC4, TRPM7, TRPP2, TRPV2, and TRPV4. In situ hybridization and immunofluorescence revealed widespread expression throughout multiple retinal layers for TRPC1, TRPC3, TRPC4, TRPML1, PKD1, and TRPP2. Striking localization of enhanced mRNA expression was observed for TRPC1 in the photoreceptor inner segment layer, for TRPM1 in the inner nuclear layer (INL), for TRPM3 in the INL, and for TRPML1 in the outer plexiform and nuclear layers. Strong immunofluorescence signal in cone outer segments was observed for TRPM7 and TRPP2. TRPC5 immunostaining was largely confined to INL cells immediately adjacent to the inner plexiform layer. TRPV2 antibodies stained photoreceptor axons in the outer plexiform layer. Expression of TRPM1 splice variants was strong in the ciliary body, whereas TRPM3 was strongly expressed in the retinal pigmented epithelium.
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