The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.

wikigene or wiki gene protein drug chemical gene disease author authorship tracking collaborative publishing evolutionary knowledge reputation system wiki2.0 global collaboration genes proteins drugs chemicals diseases compound
Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

Calcium restriction allows cAMP activation of the B-Raf/ ERK pathway, switching cells to a cAMP-dependent growth-stimulated phenotype.

cAMP can be either mitogenic or anti-mitogenic, depending on the cell type. We demonstrated previously that cAMP inhibited the proliferation of normal renal epithelial cells and stimulated the proliferation of cells derived from the cysts of polycystic kidney disease (PKD) patients. The protein products of the genes causing PKD, polycystin-1 and polycystin-2, are thought to regulate intracellular calcium levels, suggesting that abnormal polycystin function may affect calcium signaling and thus cause a switch to the cAMP growth-stimulated phenotype. To test this hypothesis, we disrupted intracellular calcium mobilization by treating immortalized mouse M-1 collecting duct cells and primary cultures of human kidney epithelial cells with calcium channel blockers and by lowering extracellular calcium with EGTA. Calcium restriction for 3-5 h converted both cell types from a normal cAMP growth-inhibited phenotype to an abnormal cAMP growth-stimulated phenotype, characteristic of PKD. In M-1 cells, we showed that calcium restriction was associated with an elevation in B-Raf protein levels and cAMP-stimulated, Ras-dependent activation of B-Raf and ERK. Moreover, the activity of Akt, a negative regulator of B-Raf, was decreased by calcium restriction. Inhibition of Akt or phosphatidylinositol 3-kinase also allowed cAMP-dependent activation of B-Raf and ERK in normal calcium. These results suggest that calcium restriction causes an inhibition of the phosphatidylinositol 3-kinase/Akt pathway, which relieves the inhibition of B-Raf to allow the cAMP growth-stimulated phenotypic switch. Finally, M-1 cells stably overexpressing an inducible polycystin-1 C-terminal cytosolic tail construct were shown to exhibit a cAMP growth- stimulated phenotype involving B-Raf and ERK activation, which was reversed by the calcium ionophore A23187. We conclude that disruption of calcium mobilization in cells that are normally growth-inhibited by cAMP can derepress the B-Raf/ ERK pathway, thus converting these cells to a phenotype that is growth-stimulated by cAMP.[1]


  1. Calcium restriction allows cAMP activation of the B-Raf/ERK pathway, switching cells to a cAMP-dependent growth-stimulated phenotype. Yamaguchi, T., Wallace, D.P., Magenheimer, B.S., Hempson, S.J., Grantham, J.J., Calvet, J.P. J. Biol. Chem. (2004) [Pubmed]
WikiGenes - Universities