Several observations have suggested that cAMP is central to the pathogenesis of PKD, by activating the Ras/MAPK pathway resulting in the cell proliferation required for cyst formation and cyst growth, and by activating CFTR to stimulate fluid secretion to fill cysts. The importance of cAMP was recently further confirmed by the successful treatment of PKD in four animal models, using a vasopressin V2 receptor antagonist which presumably lowered renal cAMP. However, while these experiments support the view that cAMP is important, it is not known how a defect in the polycystins causes misregulation of cAMP-mediated mechanisms associated with increased cell proliferation and cyst enlargement. The polycystins are thought to regulate intracellular Ca2+ levels in response to ligand-mediated or mechanosensory stimuli. Recently, we showed that polycystin-1 alone is capable of elevating intracellular Ca2+ through a heterotrimeric G protein-coupled mechanism. We have also shown, using three cell culture model systems, that PKD-like cell proliferation is dependent on cAMP-mediated activation of the Ras/MAPK pathway and to changes in Ca2+-dependent gene expression. All three systems displayed the same phenotypic switch from cAMP-inhibited to cAMP-stimulated cell proliferation. Yet, despite these observations, it is still not clear whether and how the polycystins may be involved. As such, we plan to determine if the PKD-like cAMP-stimulated phenotype is a characteristic of Pkd1 deficient cells. We will use the Pkd1(m1Bei) mouse, which has a single amino acid missense mutation and a full-blown PKD phenotype, and we plan to generate two new mouse models, Pkd1(DeltaL) and Pkd1(Gpro), which will carry, respectively, a single amino acid (aa) deletion mutation in the heterotrimeric G protein binding region of polycystin-1 mimicking a known human mutation, or a 52 aa frameshift mutation in the heterotrimeric G protein binding region of polycystin-1. We also plan to utilize metanephric kidney cultures from these mice to determine whether the PKD-like phenotypic switch occurs in embryonic kidney cells at a time when cysts begin to grow in Pkd1-deficient mouse models and in human ADPKD. Finally, we plan to test polycystin-1 mediated signaling activity under conditions of fluid flow mediated ciliary bending to determine if polycystin-1 can generate a Ca2+ signal sufficient to alter Ca2+- dependent gene expression.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Specialized Center (P50)
Project #
5P50DK057301-08
Application #
7311593
Study Section
Special Emphasis Panel (ZDK1)
Project Start
Project End
Budget Start
2006-09-01
Budget End
2007-08-31
Support Year
8
Fiscal Year
2006
Total Cost
$202,125
Indirect Cost
Name
University of Kansas
Department
Type
DUNS #
016060860
City
Kansas City
State
KS
Country
United States
Zip Code
66160
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Paul, Binu M; Vanden Heuvel, Gregory B (2014) Kidney: polycystic kidney disease. Wiley Interdiscip Rev Dev Biol 3:465-87
Zhou, Xia; Fan, Lucy X; Li, Keguo et al. (2014) SIRT2 regulates ciliogenesis and contributes to abnormal centrosome amplification caused by loss of polycystin-1. Hum Mol Genet 23:1644-55
Swenson-Fields, Katherine I; Vivian, Carolyn J; Salah, Sally M et al. (2013) Macrophages promote polycystic kidney disease progression. Kidney Int 83:855-64
Fan, Lucy X; Li, Xinjian; Magenheimer, Brenda et al. (2012) Inhibition of histone deacetylases targets the transcription regulator Id2 to attenuate cystic epithelial cell proliferation. Kidney Int 81:76-85
Parnell, Stephen C; Puri, Sanjeev; Wallace, Darren P et al. (2012) Protein phosphatase-1ýý interacts with and dephosphorylates polycystin-1. PLoS One 7:e36798
Qiu, Ni; Xiao, Zhousheng; Cao, Li et al. (2012) Conditional mesenchymal disruption of pkd1 results in osteopenia and polycystic kidney disease. PLoS One 7:e46038
Karihaloo, Anil; Koraishy, Farrukh; Huen, Sarah C et al. (2011) Macrophages promote cyst growth in polycystic kidney disease. J Am Soc Nephrol 22:1809-14
Nims, Nancy M; Vassmer, Dianne; Maser, Robin L (2011) Effect of PKD1 gene missense mutations on polycystin-1 membrane topogenesis. Biochemistry 50:349-55
Reif, Gail A; Yamaguchi, Tamio; Nivens, Emily et al. (2011) Tolvaptan inhibits ERK-dependent cell proliferation, Clýýý secretion, and in vitro cyst growth of human ADPKD cells stimulated by vasopressin. Am J Physiol Renal Physiol 301:F1005-13

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