title: 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.
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 Ca(2+) and cAMP production and inappropriate ERK signaling in PC2-defective cholangiocytes. Cystic cholangiocytes were isolated from PC2 conditional-KO (knockout) mice (Pkd2(flox/-) :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-Ca(2+) (measured with Fura-2 and Mag-Fluo4) levels are decreased and store-operated Ca(2+) entry (SOCE) is inhibited, whereas the expression of Ca(2+) -sensor stromal interaction molecule 1 (STIM1) and store-operated Ca(2+) channels (e.g., the Orai1 channel) are unchanged. In Pkd2KO cells, ER-Ca(2+) 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).
  
  
  CONCLUSIONS
  These data suggest that PC2 plays a key role in SOCE activation and inhibits the STIM-dependent activation of AC6 by ER Ca(2+) 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.
authors: Department of Internal Medicine, Liver Center and Digestive Diseases Section, Yale University, New Haven, CT 06520, USA.
authors: Carlo
authors: C
authors: Spirli
authors: Luigi
authors: L
authors: Locatelli
authors: Romina
authors: R
authors: Fiorotto
authors: Carola M
authors: CM
authors: Morell
authors: Luca
authors: L
authors: Fabris
authors: Tullio
authors: T
authors: Pozzan
authors: Mario
authors: M
authors: Strazzabosco
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001652:Bile Ducts / Q000166:cytology* / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels; D020013:Calcium Signaling / Q000502:physiology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006706:Homeostasis; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D023421:Models, Animal; D010766:Phosphorylation; D015398:Signal Transduction / Q000502:physiology; D000071737:Stromal Interaction Molecule 1; D050396:TRPP Cation Channels / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D000262:Adenylyl Cyclases; D002118:Calcium; D015220:Calcium Channels; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D008562:Membrane Glycoproteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000071737:Stromal Interaction Molecule 1; D050396:TRPP Cation Channels; D042461:Vascular Endothelial Growth Factor A; C100757:Stim1 protein, mouse; C121100:adenylyl cyclase 6