title: Pkd2 haploinsufficiency alters intracellular calcium regulation in vascular smooth muscle cells.
abstract: Autosomal-dominant polycystic kidney disease is a multiorgan disease and its vascular manifestations are common and life-threatening. Despite this, little is known about their pathogenesis. Somatic mutations to the normal PKD allele in cystic epithelia and cyst development associated with the unstable Pkd2(WS25) allele suggest a two-hit model of cystogenesis. However, it is unclear if this model can account for the cardiovascular pathology or if haploinsufficiency alone is disease-associated. In the present study, we found a decreased polycystin-2 (PC2, protein encoded by Pkd2 gene) expression in Pkd2( +/-) vessels, roughly half the wild-type level, and an enhanced level of intracranial vascular abnormalities in Pkd2 (+/-) mice when induced to develop hypertension. Consistent with these observations, freshly dissociated Pkd2 (+/-) vascular smooth muscle cells have significantly altered intracellular Ca(2+) homeostasis. The resting [Ca(2+)](i) is 17.1% lower in Pkd2 (+/-) compared with wild-type cells (P=0.0003) and the total sarcoplasmic reticulum Ca(2+) store (emptied by caffeine plus thapsigargin) is decreased (P<0.0001). The store operated Ca(2+) (SOC) channel activity is also decreased in Pkd2 (+/-) cells (P=0.008). These results indicate that inactivation of just one Pkd2 allele is sufficient to significantly alter intracellular Ca(2+) homeostasis, and that PC2 is necessary to maintain normal SOC activity and the SR Ca(2+) store in VSMCs. Based on these findings, and the fact that [Ca(2+)](i) signaling is essential to the regulation of contraction, production and secretion of extracellular matrix, cellular proliferation and apoptosis, we propose that the abnormal intracellular Ca(2+) regulation associated with Pkd2 haploinsufficiency is directly related to the vascular phenotype.
authors.affiliation: Department of Medicine, Division of Nephrology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. qian.qi@mayo.edu
authors.forename: Qi
authors.initials: Q
authors.lastname: Qian
authors.forename: Larry W
authors.initials: LW
authors.lastname: Hunter
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.forename: Miguel
authors.initials: M
authors.lastname: Marin-Padilla
authors.forename: Y S
authors.initials: YS
authors.lastname: Prakash
authors.forename: Stefan
authors.initials: S
authors.lastname: Somlo
authors.forename: Peter C
authors.initials: PC
authors.lastname: Harris
authors.forename: Vicente E
authors.initials: VE
authors.lastname: Torres
authors.forename: Gary C
authors.initials: GC
authors.lastname: Sieck
mesh_terms: D000483:Alleles; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D017931:DNA Primers; D004195:Disease Models, Animal; D005455:Fluorescent Antibody Technique; D008565:Membrane Proteins / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008817:Mice, Mutant Strains; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D016891:Polycystic Kidney, Autosomal Dominant / Q000235:genetics*; D016133:Polymerase Chain Reaction; D050396:TRPP Cation Channels
chemical_list: D002118:Calcium; D017931:DNA Primers; D008565:Membrane Proteins; D050396:TRPP Cation Channels