Adenylyl cyclase 5 links changes in calcium homeostasis to cAMP-dependent cyst growth in polycystic liver disease.
Genetic defects in polycystin-1 or -2 (PC1 or PC2) cause polycystic liver disease associated with autosomal dominant polycystic kidney disease (PLD-ADPKD). Progressive cyst growth is sustained by a cAMP-dependent Ras/ERK/HIFα pathway, leading to increased vascular endothelial growth factor A (VEGF-A) signaling. In PC2-defective cholangiocytes, cAMP production in response to [Ca2+]ERdepletion is increased, while store-operated Ca2+entry (SOCE), intracellular and endoplasmic reticulum [Ca2+]ERlevels are reduced. We investigated whether the adenylyl cyclases, AC5 and AC6, which can be inhibited by Ca2+, are activated by the ER chaperone STIM1. This would result in cAMP/PKA-dependent Ras/ERK/HIFα pathway activation in PC2-defective cells, in response to [Ca2+]ERdepletion.



PC2/AC6 double conditional knockout (KO) mice were generated (Pkd2/AC6 KO) and compared to Pkd2 KO mice. The AC5 inhibitor SQ22,536 or AC5 siRNA were used in isolated cholangiocytes while the inhibitor was used in biliary organoid and animals; liver tissues were harvested for histochemical analysis.



When comparing Pkd2/AC6 KO to Pkd2 KO mice, no decrease in liver cyst size was found, and cellular cAMP after [Ca2+]ERdepletion only decreased by 12%. Conversely, in PC2-defective cells, inhibition of AC5 significantly reduced cAMP production, pERK1/2 expression and VEGF-A secretion. AC5 inhibitors significantly reduced growth of biliary organoids derived from Pkd2 KO and Pkd2/AC6 KO mice. In vivo treatment with SQ22,536 significantly reduced liver cystic area and cell proliferation in PC2-defective mice. After [Ca2+]ERdepletion in PC2-defective cells, STIM1 interacts with AC5 but not with Orai1, the Ca2+channel that mediates SOCE.



[Ca2+]ERdepletion in PC2-defective cells activates AC5 and results in stimulation of cAMP/ERK1-2 signaling, VEGF production and cyst growth. This mechanism may represent a novel therapeutic target.



Polycystic liver diseases are characterized by progressive cyst growth until their complications mandate surgery or liver transplantation. In this manuscript, we demonstrate that inhibiting cell proliferation, which is induced by increased levels of cAMP, may represent a novel therapeutic target to slow the progression of the disease.
Section of Digestive Diseases, Yale University, New Haven, CT, USA.
Carlo
C
Spirli
Section of Digestive Diseases, Yale University, New Haven, CT, USA; Section of Digestive Diseases, International Center for Digestive Health, Department of Medicine and Surgery, University of Milan-Bicocca, Milan, Italy.
Valeria
V
Mariotti
Section of Digestive Diseases, Yale University, New Haven, CT, USA.
Ambra
A
Villani
Department of Molecular Medicine, University of Padua, Italy.
Luca
L
Fabris
Section of Digestive Diseases, Yale University, New Haven, CT, USA.
Romina
R
Fiorotto
Section of Digestive Diseases, Yale University, New Haven, CT, USA; Section of Digestive Diseases, International Center for Digestive Health, Department of Medicine and Surgery, University of Milan-Bicocca, Milan, Italy. Electronic address: mario.strazzabosco@yale.edu.
Mario
M
Strazzabosco
D000067956:Adenylyl Cyclase Inhibitors / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D049109:Cell Proliferation; D000242:Cyclic AMP / Q000378:metabolism*; D003560:Cysts / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D004195:Disease Models, Animal; D006706:Homeostasis; D006801:Humans; D008107:Liver Diseases / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D020935:MAP Kinase Signaling System; D051379:Mice; D018345:Mice, Knockout; D016891:Polycystic Kidney, Autosomal Dominant / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D034622:RNA Interference; D015398:Signal Transduction; D000071737:Stromal Interaction Molecule 1 / Q000378:metabolism; D050396:TRPP Cation Channels / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases; D002118:Calcium; D000242:Cyclic AMP; D000071737:Stromal Interaction Molecule 1; D050396:TRPP Cation Channels; D042461:Vascular Endothelial Growth Factor A; C100757:Stim1 protein, mouse; C467480:vascular endothelial growth factor A, mouse; C121100:adenylyl cyclase 6; C419510:adenylyl cyclase type V
Adenylyl cyclases; Calcium; Cysts; Mice, knockout; Organoids; Polycystic kidney, autosomal dominant; Polycystic liver diseases; RNA, small interfering; VEGF; cAMP