Autosomal dominant polycystic kidney disease (
ADPKD) is the most common monogenic
kidney disease and is responsible for 5-10% of cases of
end-stage renal disease worldwide.
ADPKD is characterized by the relentless development and growth of
cysts, which cause progressive kidney enlargement associated with
hypertension,
pain, reduced quality of life and eventual
kidney failure. Mutations in the PKD1 or PKD2 genes, which encode polycystin-1 (PC1) and polycystin-2 (PC2), respectively, cause
ADPKD. However, neither the functions of these
proteins nor the molecular mechanisms of
ADPKD pathogenesis are well understood. Here, we review the literature that examines how reduced levels of functional PC1 or PC2 at the primary cilia and/or the endoplasmic reticulum directly disrupts intracellular
calcium signalling and indirectly disrupts
calcium-regulated cAMP and purinergic signalling. We propose a hypothetical model in which dysregulated metabolism of cAMP and purinergic signalling increases the sensitivity of principal cells in collecting ducts and of tubular epithelial cells in the distal nephron to the constant tonic action of
vasopressin. The resulting magnified response to
vasopressin further enhances the disruption of
calcium signalling that is initiated by mutations in PC1 or PC2, and activates downstream signalling pathways that cause impaired tubulogenesis, increased cell proliferation, increased fluid secretion and interstitial
inflammation.