title: Calcium restores a normal proliferation phenotype in human polycystic kidney disease epithelial cells.
abstract: Polycystic kidney disease (PKD) is a lethal disorder characterized by progressive expansion of renal cysts. Genetic mutations associated with PKD are thought to disrupt intracellular Ca2+ regulation, leading to abnormal proliferation of tubule epithelial cells. cAMP stimulates the B-Raf/MEK/extracellular signal-regulated kinase (B-Raf/MEK/ERK) pathway and accelerates the proliferation of cells that are cultured from PKD cysts. By contrast, cAMP inhibits the proliferation of cells from normal human kidneys (NHK) and M-1 mouse collecting duct cells. Previously, it was found that a sustained reduction of intracellular Ca2+ levels in NHK and M-1 cells that were treated with Ca2+ entry blockers allowed cAMP activation of the B-Raf/MEK/ERK pathway, switching the cells to a cAMP-growth stimulated phenotype. In this study, primary cultures of cyst epithelial cells from autosomal dominant (ADPKD) and recessive (ARPKD) PKD kidneys were used to determine whether controlled addition of Ca2+ could reverse the aberrant mitogenic response to cAMP. Steady-state intracellular Ca2+ levels were found to be 20 nM lower in cyst-derived ADPKD cells (57 +/- 2 nM) compared with NHK cells (77 +/- 2 nM). Treatment of ADPKD cells or ARPKD cells with either Bay K8644, a Ca2+ channel activator, or A23187, a Ca2+ ionophore, caused sustained increases in intracellular Ca2+ levels and completely reversed the mitogenic response to cAMP. Elevation of intracellular Ca2+ levels in ADPKD cells increased Akt activity and blocked cAMP-dependent B-Raf and ERK activation. Thus, increases in [Ca2+]i are able to restore the normal anti-mitogenic response to cAMP in cells that are derived from two genetically distinct forms of PKD.
authors.affiliation: Kidney Institute, Department of Medicine, University of Kansas Medical Center, 3901 Rainbow Boulevard, MSN 3018, Kansas City, KS 66160, USA.
authors.forename: Tamio
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Hempson
authors.forename: Gail A
authors.initials: GA
authors.lastname: Reif
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Hedge
authors.forename: Darren P
authors.initials: DP
authors.lastname: Wallace
mesh_terms: D002118:Calcium / Q000378:metabolism*; D049109:Cell Proliferation; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000502:physiology; D010641:Phenotype; D007690:Polycystic Kidney Diseases / Q000378:metabolism / Q000473:pathology*; D016891:Polycystic Kidney, Autosomal Dominant / Q000378:metabolism; D017044:Polycystic Kidney, Autosomal Recessive / Q000378:metabolism; D048493:Proto-Oncogene Proteins B-raf / Q000502:physiology; D015398:Signal Transduction
chemical_list: D000242:Cyclic AMP; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D020930:MAP Kinase Kinase Kinases; D002118:Calcium