The isolated polycystin-1 COOH-terminal can activate or block polycystin-1 signaling

Basavanna, Uma; Weber, Kimberly M.; Hu, Qinghua; Ziegelstein, Roy C.; Germino, Gregory G.; Sutters, Michael

doi:10.1016/j.bbrc.2007.05.114

Cited by 8 publications

(7 citation statements)

References 22 publications

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“…It has been suggested that effects of the cleaved PC1 tail may be due to a dominant-negative effect on endogenous, full-length PC1 (16). To test this possibility, we used Pkd1-null mouse embryonic fibroblasts (MEFs).…”

Section: Resultsmentioning

confidence: 99%

Polycystin-1 regulates STAT activity by a dual mechanism

Talbot

Shillingford

Vasanth

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

127

173

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Mutations in polycystin-1 (PC1) lead to autosomal-dominant polycystic kidney disease (ADPKD), a leading cause of renal failure for which no treatment is available. PC1 is an integral membrane protein, which has been implicated in the regulation of multiple signaling pathways including the JAK/STAT pathway. Here we show that membrane-anchored PC1 activates STAT3 in a JAK2-dependent manner, leading to tyrosine phosphorylation and transcriptional activity. The C-terminal cytoplasmic tail of PC1 can undergo proteolytic cleavage and nuclear translocation. Tail-cleavage abolishes the ability of PC1 to directly activate STAT3 but the cleaved PC1 tail now coactivates STAT3 in a mechanism requiring STAT phosphorylation by cytokines or growth factors. This leads to an exaggerated cytokine response. Hence, PC1 can regulate STAT activity by a dual mechanism. In ADPKD kidneys PC1 tail fragments are overexpressed, including a unique ∼15-kDa fragment (P15). STAT3 is strongly activated in cyst-lining epithelial cells in human ADPKD, and orthologous and nonorthologous polycystic mouse models. STAT3 is also activated in developing, postnatal kidneys but inactivated in adult kidneys. These results indicate that STAT3 signaling is regulated by PC1 and is a driving factor for renal epithelial proliferation during normal renal development and during cyst growth.A utosomal-dominant polycystic kidney disease (ADPKD) is a common life-threatening genetic disease and leading cause of renal failure (1-4). Epithelial-lined cysts develop due to excessive proliferation leading to renal enlargement and destruction of functional renal tissue. No treatment is available to slow disease progression. PKD1 gene mutations cause the majority of cases but the exact function of its gene product, polycystin-1 (PC1), has remained poorly understood. Confusing the issue is the fact that both loss of PC1 as well as PC1 overexpression lead to renal cyst growth in mouse models. Furthermore, in human ADPKD, each clonal cyst within the same patient is thought to exhibit a unique combination of germline and acquired mutations that results in a cyst-by-cyst mosaic of genotypes and resulting variation of expression levels of PC1 harboring various mutations. PC1 has also been implicated in a puzzling variety of intracellular signaling events including JAK-STAT signaling (5, 6) and it has been difficult to elucidate which of these functions may be most important for renal cyst growth in ADPKD.Disruption of primary cilia in kidney epithelial cells leads to proliferation and cyst growth (7). PC1 has been shown to function in ciliary mechanotransduction, and a potential molecular mechanism emerged from the discovery that PC1 undergoes proteolytic cleavage, releasing the C-terminal cytoplasmic tail (∼30 kDa) from the membrane, followed by nuclear translocation (2, 5). PC1 cleavage is triggered upon the cessation of luminal fluid flow (2). The cleaved PC1 tail interacts with the transcription factors STAT6 and P100, enhances STAT6 activity, and STAT6 translocates between ...

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Section: Resultsmentioning

confidence: 99%

Polycystin-1 regulates STAT activity by a dual mechanism

Talbot

Shillingford

Vasanth

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

127

173

View full text Add to dashboard Cite

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“…Interestingly, a number of studies using the C-terminal tail of PC1 over expressed as a fusion protein have found the inverse; the expression of C-terminal tail leads to increases in intracellular Ca 2+ and SOCE [32], [33]. However, in light of recent findings by Basavanna et al (2007)[34] who showed that the over expression of a PC1 C-terminus fusion protein acted as a dominant negative, these seemingly contrary findings may in fact be supportive of our hypothesis that PC1 expression leads to inhibition of the SOCE.…”

Section: Discussionmentioning

confidence: 97%

Identification of a Polycystin-1 Cleavage Product, P100, That Regulates Store Operated Ca2+ Entry through Interactions with STIM1

Woodward

et al. 2010

PLoS ONE

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Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a genetic disorder resulting in large kidney cysts and eventual kidney failure. Mutations in either the PKD1 or PKD2/TRPP2 genes and their respective protein products, polycystin-1 (PC1) and polycystin-2 (PC2) result in ADPKD. PC2 is known to function as a non-selective cation channel, but PC1's function and the function of PC1 cleavage products are not well understood. Here we identify an endogenous PC1 cleavage product, P100, a 100 kDa fragment found in both wild type and epitope tagged PKD1 knock-in mice. Expression of full length human PC1 (FL PC1) and the resulting P100 and C-Terminal Fragment (CTF) cleavage products in both MDCK and CHO cells significantly reduces the store operated Ca2+ entry (SOCE) resulting from thapsigargin induced store depletion. Exploration into the roles of P100 and CTF in SOCE inhibition reveal that P100, when expressed in Xenopus laevis oocytes, directly inhibits the SOCE currents but CTF does not, nor does P100 when containing the disease causing R4227X mutation. Interestingly, we also found that in PC1 expressing MDCK cells, translocation of the ER Ca2+ sensor protein STIM1 to the cell periphery was significantly altered. In addition, P100 Co-immunoprecipitates with STIM1 but CTF does not. The expression of P100 in CHO cells recapitulates the STIM1 translocation inhibition seen with FL PC1. These data describe a novel polycystin-1 cleavage product, P100, which functions to reduce SOCE via direct inhibition of STIM1 translocation; a function with consequences for ADPKD.

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“…Studying PC1 cleavage has been complicated by the fact that there are at least two different C-terminal fragments that can be released by cleavage (Chauvet et al ., 2004; Low et al ., 2006). Expressing a soluble form of the C-terminal fragment could yield information about the effects of these peptides on intracellular signaling pathways, but this gives no insight into the processes that generate the soluble peptides and may actually produce results that are difficult to interpret in a physiological context (Basavanna et al ., 2007). The endogenous fragments produced by these cleavage events within the full-length protein are often short-lived and found in low abundance.…”

Section: Assay Rationale and Historymentioning

confidence: 99%

Detecting the Surface Localization and Cytoplasmic Cleavage of Membrane-Bound Proteins

Chapin

Rajendran

Capasso

et al. 2009

Methods in Cell Biology

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Polycystin-1 (PC1) is a large, membrane-bound protein that localizes to the cilia and is implicated in the common ciliopathy autosomal-dominant polycystic kidney disease. The physiological function of PC1 is dependent upon its subcellular localization as well as specific cleavages that release soluble fragments of its C-terminal tail. The techniques described here allow visualization and quantification of these aspects of the biology of the PC1 protein. To visualize PC1 at the plasma membrane, a live-cell surface labeling immunofluorescence protocol paired with the labeling of an internal antigen motif allows a robust detection of the surface population of this protein. This technique is modified to generate a surface enzyme-linked immunosorbent assay (ELISA), which quantitatively measures the amount of surface protein as a fraction of the total amount of the protein expressed in that cell population. These assays are powerful tools in the assessment of the small but biologically important pool of PC1 that reaches the cell surface. The C-terminal tail cleavage of PC1 constitutes an interesting modification that allows PC1 to extend its functional role into the nucleus. A reporter assay based on Gal4/VP16 luciferase can be used to quantitate the amount of PC1 C-terminal tail that reaches the nucleus. This assay can be paired with quantitative measurement of the protein expression in the cell, allowing a more complete understanding of the pattern of PC1 cleavage and the nuclear localization of the resultant.

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The isolated polycystin-1 COOH-terminal can activate or block polycystin-1 signaling

Cited by 8 publications

References 22 publications

Polycystin-1 regulates STAT activity by a dual mechanism

Polycystin-1 regulates STAT activity by a dual mechanism

Identification of a Polycystin-1 Cleavage Product, P100, That Regulates Store Operated Ca2+ Entry through Interactions with STIM1

Detecting the Surface Localization and Cytoplasmic Cleavage of Membrane-Bound Proteins

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