Altered store operated calcium entry increases cyclic 3′,5′-adenosine monophosphate production and extracellular signal-regulated kinases 1 and 2 phosphorylation in polycystin-2-defective cholangiocytes

Authors

  • Carlo Spirli,

    1. Department of Internal Medicine, Liver Center and Digestive Diseases Section, Yale University, New Haven, CT
    2. CeLiveR, Ospedali Riuniti di Bergamo, Bergamo, Italy
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  • Luigi Locatelli,

    1. Department of Internal Medicine, Liver Center and Digestive Diseases Section, Yale University, New Haven, CT
    2. CeLiveR, Ospedali Riuniti di Bergamo, Bergamo, Italy
    3. Department of Clinical Medicine and Prevention University of Milan-Bicocca, Monza, Italy
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  • Romina Fiorotto,

    1. Department of Internal Medicine, Liver Center and Digestive Diseases Section, Yale University, New Haven, CT
    2. CeLiveR, Ospedali Riuniti di Bergamo, Bergamo, Italy
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  • Carola M. Morell,

    1. Department of Internal Medicine, Liver Center and Digestive Diseases Section, Yale University, New Haven, CT
    2. Department of Clinical Medicine and Prevention University of Milan-Bicocca, Monza, Italy
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  • Luca Fabris,

    1. CeLiveR, Ospedali Riuniti di Bergamo, Bergamo, Italy
    2. Department of Gastroenterological Sciences, University of Padova, Padova, Italy
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  • Tullio Pozzan,

    1. Consiglio Nazionale delle Ricerche, Neuroscience Institute, Department of Biomedical Sciences, University of Padova and Venetian Institute of Molecular Medicine, Padova, Italy
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  • Mario Strazzabosco

    Corresponding author
    1. Department of Internal Medicine, Liver Center and Digestive Diseases Section, Yale University, New Haven, CT
    2. CeLiveR, Ospedali Riuniti di Bergamo, Bergamo, Italy
    3. Department of Clinical Medicine and Prevention University of Milan-Bicocca, Monza, Italy
    • Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, 333 Cedar Street, LMP 1080, New Haven, CT 06520
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    • fax: +1-203-785-7273


  • Potential conflict of interest: Nothing to report.

  • This work was supported by the National Institutes of Health (NIH) (DK079005; to M.S.) and by the Yale University Liver Center (NIH DK34989; to M.S. and C.S.). The support of Fondazione S. Martino (Bergamo, Italy) is gratefully acknowledged. T.P.'s work has been supported by an Italian Institute of Technology grant.

Abstract

Mutations in polycystins (PC1 or PC2/TRPP2) cause progressive polycystic liver disease (PLD). In PC2-defective mice, cyclic 3′,5′-adenosine monophosphate/ protein kinase A (cAMP/PKA)-dependent activation of extracellular signal-regulated kinase/ mammalian target of rapamycin (ERK-mTOR) signaling stimulates cyst growth. We investigated the mechanisms connecting PC2 dysfunction to altered Ca2+ and cAMP production and inappropriate ERK signaling in PC2-defective cholangiocytes. Cystic cholangiocytes were isolated from PC2 conditional-KO (knockout) mice (Pkd2flox/−:pCxCreER™; hence, called Pkd2KO) and compared to cholangiocytes from wild-type mice (WT). Our results showed that, compared to WT cells, in PC2-defective cholangiocytes (Pkd2KO), cytoplasmic and ER-Ca2+ (measured with Fura-2 and Mag-Fluo4) levels are decreased and store-operated Ca2+ entry (SOCE) is inhibited, whereas the expression of Ca2+-sensor stromal interaction molecule 1 (STIM1) and store-operated Ca2+ channels (e.g., the Orai1 channel) are unchanged. In Pkd2KO cells, ER-Ca2+ depletion increases cAMP and PKA-dependent ERK1/2 activation and both are inhibited by STIM1 inhibitors or by silencing of adenylyl cyclase type 6 (AC6). Conclusion: These data suggest that PC2 plays a key role in SOCE activation and inhibits the STIM-dependent activation of AC6 by ER Ca2+ depletion. In PC2-defective cells, the interaction of STIM-1 with Orai channels is uncoupled, whereas coupling to AC6 is maximized. The resulting overproduction of cAMP, in turn, potently activates the PKA/ERK pathway. PLD, because of PC2 deficiency, represents the first example of human disease linked to the inappropriate activation of store-operated cAMP production. (HEPATOLOGY 2012)

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