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Polycystin-2 is regulated by endoplasmic reticulum-associated degradation

Membrane Protein Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
Human Molecular Genetics (Impact Factor: 6.68). 05/2008; 17(8):1109-19. DOI: 10.1093/hmg/ddm383
Source: PubMed

ABSTRACT Endoplasmic reticulum(ER)-associated degradation (ERAD) is an essential process for cell homeostasis and remains not well understood. During ERAD, misfolded proteins are recognized, ubiquitinated on ER and subsequently retro-translocated/dislocated from ER to the 26S proteasome in the cytosol for proteolytic elimination. Polycystin-2 (PC2), a member of the transient receptor potential superfamily of cation channels, is a Ca channel mainly located on ER and primary cilium membranes of cells. Mutations in PC2 are associated with autosomal dominant polycystic kidney disease (ADPKD). The cellular and molecular mechanisms underlying the PC2-associated pathogenesis remain unclear. Here we show that PC2 degradation is regulated by the ERAD pathway through the ubiquitin-proteasome system. PC2 interacted with ATPase p97, a well-known ERAD component extracting substrates from ER, and immobilized it in perinuclear regions. PC2 also interacted with Herp, an ubiquitin-like protein implicated in regulation of ERAD. We found that Herp is required for and promotes PC2 degradation. ER stress accelerates the retro-translocation of PC2 for cytosolic degradation, at least in part through increasing the Herp expression. Thus, PC2 is a novel ERAD substrate. Herp also promoted, to varied degrees, the degradation of PC2 truncation mutants, including two pathogenic mutants R872X and E837X, as long as they interact with Herp. In contrast, Herp did not interact with, and has no effect on the degradation of, PC2 mutant missing both the N- and C-termini. The ERAD machinery may thus be important for ADPKD pathogenesis because the regulation of PC2 expression by the ERAD pathway is altered by mutations in PC2.

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    • "n et al . 2007 ) , as well as with RP2 , a protein mutated in retinitis pigmentosa ( Hurd et al . 2010 ) , and Id2 , a negative transcription factor that regulates the cell cycle ( Li et al . 2005 ) . Various processes can lead to the degradation of proteins . PC1 associates with Siah - 1 ( Kim et al . 2004 ) , and PC2 associates with ATPase p97 ( Liang et al . 2008a ) , PERK and eIF2α ( Liang et al . 2008b ) , which are components of these degradation processes ."
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    ABSTRACT: Mutations of the two polycystins, PC1 and PC2, lead to polycystic kidney disease. Polycystins are able to form complexes with numerous families of proteins that have been suggested to participate in mechanical sensing. The proposed role of polycystins and their partners in the kidney primary cilium is to sense urine flow. A role for polycystins in mechanosensing has also been shown in other cell types such as vascular smooth muscle cells and cardiac myocytes. At the plasma membrane, polycystins interact with diverse ion channels of the TRP family and with stretch-activated channels (Piezos, TREKs). The actin cytoskeleton and its interacting proteins, such as filaminA, have been shown to be essential for these interactions. Numerous proteins involved in cell-cell and cell-extracellular matrix junctions interact with PC1 and/or PC2. These multimeric protein complexes are important for cell structure integrity, the transmission of force, as well as for mechanosensing and mechanotransduction. A group of polycystin partners are also involved in subcellular trafficking mechanisms. Finally, PC1 and especially PC2 interact with elements of the endoplasmic reticulum and are essential components of calcium homeostasis. In conclusion, we propose that both PC1 and PC2 act as conductors to tune the overall cellular mechanosensitivity.
    The Journal of Physiology 03/2014; 592(12). DOI:10.1113/jphysiol.2014.271346 · 4.54 Impact Factor
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    • "TRPP2 is known to form homo-and hetero-multimers (Tsiokas et al., 1999; Newby et al., 2002; Bai et al., 2008; Zhang et al., 2009) and associates with polycistin-1 protein (PC1), the canonical TRP channels e.g. TRPC1 and TRPV4 (Tsiokas et al., 1999; Kottgen et al., 2008), type I inositol 1,4,5- triphosphate receptor (IP3R) (Li et al., 2005c), epidermal growth factor receptor (Liang et al., 2008a), ER membrane protein and regulators of ER-associated degradation pathways. Although a highly conserved sequence identity between porcine and murine PKD2 has been reported (Torres et al., 2001) and similarity between the porcine and human TRPP2 protein has been demonstrated in the porcine kidney cells (LLC–PK1) (Koulen et al., 2002; Rundle et al., 2004), detailed information about porcine PKD2 gene remains lacking. "
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    ABSTRACT: Mutations in the PKD2 gene cause autosomal dominant polycystic kidney disease (ADPKD), a common, inherited disease that frequently leads to end-stage renal disease (ESRD). Swine show substantial similarity to humans physiologically and anatomically, and are therefore a good model system in which to decipher the structure and function of the PKD2 gene and to identify potential therapeutic targets. Here we report the cloning and characterization of the porcine PKD2 cDNA showing that the full-length gene (3370 bases) is highly expressed in kidney, with minimal expression in the liver. RNA interference (RNAi) is a promising tool to enable identification of the essential components necessary for exploitation of the pathway involved in cellular processes. We therefore designed four shRNAs and nine siRNAs targeting the region of the porcine PKD2 gene from exons 3 to 9, which is supposed to be a critical region contributing to the severity of ADPKD. The results from HeLa cells with the dual-luciferase reporter system and porcine kidney cells (LLC-PK1) showed that sh12 could efficiently knock down the PKD2 gene with an efficiency of 51% and P1 and P2 were the most effective siRNAs inhibiting 85% and 77% respectively of PKD2 expression compared with untreated controls. A subsequent functional study of the transient receptor potential polycystic (TRPP) 2 channel protein indicated that the decreased expression of TRPP2 induced by siRNA P1 and P2 could release the arrest of the cell cycle from G0/G1 promoting progression to S and G2 phases. Our data, therefore, provides evidence of potential knock-down target sites in the PKD2 gene and paves the way for the future generation of transgenic ADPKD knock-down animal models.
    Gene 05/2011; 476(1-2):38-45. DOI:10.1016/j.gene.2011.01.017 · 2.08 Impact Factor
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    • "Mutations in two genes were linked to ADPKD: PKD1 codes for polycystin 1 (PC1), a plasma membrane resident receptor [2], and PKD2 codes for polycystin 2 (PC2) or TRPP2, a member of the transient receptor potential (TRP) family that resides in the endoplasmic reticulum (ER) and the plasma membrane [3] [4] [5]. The two polycystins interact in the plasma membrane and may form a signaling complex [5] [6] [7] [8]. Recent research on ADPKD suggests PKD mutations result in problems in downstream signaling-as well as cell–cell adhesion-components, most notably b-catenin, and that these problems cause alterations in planar cell polarity and tubular morphogenesis that, eventually, result in cyst formation (summarized in [1]). "
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    ABSTRACT: The formation of multiple cysts in one or several organs is a characteristic of several human inherited diseases. Recent research suggests that problems in planar cell polarity may be the common denominator in polycystic diseases. Mutations in at least two genes are linked to autosomal dominant polycystic liver disease (PCLD), PRKCSH and SEC63. A recent study linked PRKCSH to the signaling- and cytoskeletal adaptor-component β-catenin. In a yeast two hybrid screen we identified the cytosolic protein nucleoredoxin (NRX) as an interaction partner of human Sec63. Since NRX is involved in the Wnt signaling pathways, we characterized this interaction. Thus, Sec63 is linked to the Wnt signaling pathways and this interaction may be the reason why mutations in SEC63 can lead to PCLD.
    FEBS letters 02/2011; 585(4):596-600. DOI:10.1016/j.febslet.2011.01.024 · 3.34 Impact Factor
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