Disease relevance of PKD2

• Mutations of either PKD1 or PKD2 cause autosomal dominant polycystic kidney disease, a syndrome characterized by extensive formation of renal cysts and progressive renal failure [1].
• A spectrum of mutations in the polycystic kidney disease-2 (PKD2) gene from eight Canadian kindreds [2].
• A spectrum of mutations was found in approximately 73% (8 of 11) of the families screened, with no difference in the detection rate between the PKD2-linked families and the families with late-onset ESRD [2].
• Intracranial aneurysms have been reported in PKD2, as well as in PKD1 families [3].
• Finally, in situ hybridization studies localize this novel gene to 4q22, where PKD2, the second most common locus for ADPKD, is known to map [4].

High impact information on PKD2

• PKD2, mutations in which cause autosomal dominant polycystic kidney disease (ADPKD), encodes an integral membrane glycoprotein with similarity to calcium channel subunits [5].
• Somatic loss of Pkd2 expression is both necessary and sufficient for renal cyst formation in ADPKD, suggesting that PKD2 occurs by a cellular recessive mechanism [6].
• Germline mutations in PKD2 cause autosomal dominant polycystic kidney disease [6].
• We also show that polycystin-2 is localized in the cell in the absence of polycystin-1, but is translocated to the plasma membrane in its presence [7].
• PKD2, a gene for polycystic kidney disease that encodes an integral membrane protein [8].

Chemical compound and disease context of PKD2

• A novel frameshift mutation induced by an adenosine insertion in the polycystic kidney disease 2 (PKD2) gene [9].
• Other genes related to and interacting with the trp family include the Grc gene, which codes for a growth factor-regulated channel protein, and PKD1/PKD2, involved in polycystic kidney disease [10].
• The polycystic kidney disease 2 (PKD2) gene, encoding a 968-amino acid integral membrane protein with six predicted membrane-spanning domains and intracellular NH2 and COOH termini, is mutated in approximately 15% of the cases of autosomal dominant polycystic kidney disease (ADPKD), a common genetic disease frequently resulting in renal failure [11].

Biological context of PKD2

• Alternative splicing has been documented for the 'PKD2-like' genes as a naturally occurring event and for PKD2 in pathologic context [12].
• Alternatively, PKD2 channel activity may be important in the cell division process or in cell fate decisions after division [13].
• These results suggest that if a two-hit mechanism is required for cyst formation in PKD2 there is a high rate of somatic missense mutation [14].
• We investigated the expression pattern of PKD1 and PKD2 transcripts and proteins during human embryogenesis and kidney development, using Northern blot analysis, in situ hybridization, and immunohistochemical methods [15].
• RNA interference experiments reveal that endogenous mDia1 knockdown in HeLa cells results in the loss of PKD2 from mitotic spindles and alters intracellular Ca(2+) release [13].

Anatomical context of PKD2

• Systematic scanning of PKD2/Pkd2 cDNAs obtained through RT-PCR from murine tissues and human cell lines revealed alternative splice forms that were sequenced and checked for translation [12].
• Using antisera raised to the human PKD2 protein, polycystin-2, we describe for the first time its distribution in human fetal tissues, as well as its expression in adult kidney and polycystic PKD2 tissues [14].
• PKD1 and PKD2 are thought to function together as part of a multiprotein receptor/ion-channel complex or independently and may be involved in transducing Ca(2+)-dependent mechanosensitive signals in response to cilia bending in renal epithelial cells and endodermally derived cells [16].
• Distinct subcellular expression of endogenous polycystin-2 in the plasma membrane and Golgi apparatus of MDCK cells [17].
• In addition, the in vivo interaction between endogenous PC2 and alpha-actinins was demonstrated by co-immunoprecipitation in human embryonic kidney 293 and Madin-Darby canine kidney (MDCK) cells, rat kidney and heart tissues and human syncytiotrophoblast (hST) apical membrane vesicles [18].

Associations of PKD2 with chemical compounds

• Thereafter, PKD2 is diffusely expressed at all stages of nephron development, whereas high PKD1 expression first appears in differentiated proximal tubules [15].
• This mutation occurred in the polyadenosine tract (nt2152-2159) of exon 11 and is predicted to result in a frameshift with premature translation termination of the PKD2 product, polycystin 22, immediately after codon 723 [9].
• The plasma membrane staining disappeared following extraction with a buffer containing Triton X-100, whereas signals for polycystin-1 and E-cadherin remained visible, suggesting that polycystin-2 is neither tightly bound to the Triton X-100 insoluble cytoskeleton, nor to these proteins [17].
• The PC2-alpha-actinin association was confirmed by in vitro glutathione S-transferase pull-down and dot blot overlay assays [18].
• Weak immunoreactivity for polycystin-2, which was markedly enhanced by protease digestion, was detected in formaldehyde-fixed normal human elastic and intracranial arteries [3].

Physical interactions of PKD2

• One domain involves a minimal region of 73 amino acids in the C-terminal cytoplasmic tail of PKD2 shown previously to constitute an interacting domain with PKD1 [19].
• We conclude that endogenous polycystin-2 is transported via the Golgi apparatus to the plasma membrane and has a broader membrane localization than polycystin-1 [17].
• Using the yeast two-hybrid assay, we found that PC2 interacts with the microtubule-dependent motor kinesin-2 subunit KIF3A, a protein involved in polycystic kidney disease [20].
• In-frame deletions in the first extracellular loop and C-terminal phosphofurin acidic cluster sorting protein-1 (PACS-1) binding sites in the cytoplasmic tail caused Polycystin-2 mislocalization to the apical cell surface [21].

Co-localisations of PKD2

• In cultured renal cells, the PKHD1 gene product colocalized with polycystin-2, the gene product of autosomal dominant polycystic disease type 2, at the basal bodies of primary cilia [22].
• In addition to the expected mitochondria localization, ATP-2 and other ATP synthase components colocalize with LOV-1 and PKD-2 in cilia [23].

Regulatory relationships of PKD2

• Here, we used single-strand conformation polymorphism (SSCP) analysis to screen the entire coding sequence of PKD1 and PKD2 in 85 healthy controls and 72 Han Chinese from 24 ADPKD pedigrees [24].
• Identification of an N-terminal glycogen synthase kinase 3 phosphorylation site which regulates the functional localization of polycystin-2 in vivo and in vitro [25].

Other interactions of PKD2

• PKD1 is thought to encode a membrane protein, polycystin-1, involved in cell-cell or cell-matrix interactions, whereas the PKD2 gene product, polycystin-2, is thought to be a channel protein [7].
• The C-terminal domain is sufficient but not necessary for the PKD2-TRPC1 association [19].
• The third gene, PKDREJ, encodes a putative 2253 amino acid protein and shows about 35% similarity to both polycystin-1 and polycystin-2 [26].
• We show that PKD2 can directly associate with TRPC1 but not TRPC3 in transfected cells and in vitro [19].
• Kinesin-2 mediates physical and functional interactions between polycystin-2 and fibrocystin [27].
• These results have significant implications for our understanding of PC2 function and disease pathogenesis in ADPKD and provide a new strategy for studying PC2 function [28].

Analytical, diagnostic and therapeutic context of PKD2

• Immunofluorescence experiments showed that PC2 and alpha-actinin were partially co-localized in epithelial MDCK and inner medullary collecting duct cells, NIH 3T3 fibroblasts and hST vesicles [18].
• The PKD2 gene was amplified from genomic DNA using 17 primer pairs and the products were analysed by heteroduplex analysis [29].
• Ultrasonography or computerized tomography revealed that PKD1 patients developed cysts only in kidneys, but PKD2 patients developed cysts in kidneys, liver and pancreas [30].
• A panel of rabbit polyclonal antisera was raised against polycystin-2 and shown to recognize a single band consistent with polycystin-2 in multiple tissues and cell lines by immunoprecipitation and Western blotting [31].
• The PKD1 and PKD2 mRNA and protein were detected in all cells by RT-PCR and by immunocytochemistry [32].

References