thapsigargin and Polycystic-Kidney--Autosomal-Dominant

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in genes encoding the polycystin (PC) 1 and 2 proteins. The goal of this study was to determine the role of calcium in regulating cyst growth. Stromal interaction molecule 1 (STIM1) protein expression was 15-fold higher in PC1-null proximal tubule cells (PN) than in heterozygote (PH) controls and 2-fold higher in an inducible, PC1 knockout, mouse model of ADPKD compared to a non-cystic match control. IP3 receptor protein expression was also higher in the cystic mice. Knocking down STIM1 with siRNA reduced cyst growth and lowered cAMP levels in PN cells. Fura2 measurements of intracellular Ca

Topics: Animals; Calcium; Cyclic AMP; Endoplasmic Reticulum; Mice, Inbred C57BL; Polycystic Kidney, Autosomal Dominant; Stromal Interaction Molecule 1; Thapsigargin; TRPP Cation Channels

Autosomal dominant polycystic kidney disease (ADPKD) is associated with progressive enlargement of multiple renal cysts, often leading to renal failure that cannot be prevented by a current treatment. Two proteins encoded by two genes are associated with ADPKD: PC1 (

Topics: Animals; Calcium; Calcium Chelating Agents; Calcium Signaling; Cell Line; Cyclic AMP; Cysts; Disease Models, Animal; Histone Deacetylase 6; Histone Deacetylase Inhibitors; Histone Deacetylases; Mice; Mice, Knockout; Mice, Transgenic; Polycystic Kidney, Autosomal Dominant; Protein Kinase C; Thapsigargin; TRPP Cation Channels

We previously found that polycystin-1 accelerated the decay of ligand-activated cytoplasmic calcium transients through enhanced reuptake of calcium into the endoplasmic reticulum (ER; Hooper KM, Boletta A, Germino GG, Hu Q, Ziegelstein RC, Sutters M. Am J Physiol Renal Physiol 289: F521-F530, 2005). Calcium flux across the ER membrane is determined by the balance of active uptake and passive leak. In the present study, we show that polycystin-1 inhibited calcium leak across the ER membrane, an effect that would explain the capacity of this protein to accelerate clearance of calcium from the cytoplasm following a calcium release response. Calcium leak was detected by measurement of the accumulation of calcium in the cytoplasm following treatment with thapsigargin. Heterologous polycystin-1, stably expressed in Madin-Darby canine kidney cells, attenuated the thapsigargin-induced calcium peak with no effect on basal calcium stores, mitochondrial calcium uptake, or extrusion of calcium across the plasma membrane. The capacity of polycystin-1 to limit the rate of decay of ER luminal calcium following inhibition of the pump was shown indirectly using the calcium ionophore ionomycin, and directly by loading the ER with a low-affinity calcium indicator. We conclude that disruption of ER luminal calcium homeostasis may contribute to the cyst phenotype in autosomal dominant polycystic kidney disease.

Topics: Animals; Calcium; Cell Membrane; Cells, Cultured; Dogs; Endoplasmic Reticulum; Enzyme Inhibitors; Gene Expression; Homeostasis; Humans; Ionomycin; Ionophores; Kidney; Polycystic Kidney, Autosomal Dominant; Thapsigargin; Transfection; TRPP Cation Channels