Extracellular
nucleotides such as
adenosine triphosphate (
ATP) play a role in biliary epithelial cell function. Since
nucleotide receptors are potential targets for various diseases related to epithelial cell dysfunction and
cancer, the purpose of this study was to investigate the expression and to functionally characterize the
nucleotide receptor subtypes in biliary epithelial
cancer cells (Mz-Cha-1). Extracellular
ATP dose-dependently resulted in an intracellular Ca(2+) increase (mean effective concentration (EC(50)) 40 μM).
Uridine triphosphate (
UTP) produced a similar Ca(2+) response and cross-desensitation was observed. The rank order of tested agonists was
ATP=
UTP>>
adenosine>
ADP=
AMP>α,β-methylene-
ATP. This confirms the functional expression of
purinoceptor P2Y2 and P2Y4 in biliary epithelial
cancer cell membranes. mRNAs for P2Y1, P2Y2, P2Y4 and P2Y6
purinergic receptor subtypes were found, whereas western blot analysis suggested only the expression of
P2Y2 receptors. Confocal imaging and nuclear staining was used to compartmentalize
ATP-induced cytosolic and nuclear Ca(2+)-transients, indicating a role for secretory
ATP in regulating nuclear function, by increasing nuclear Ca(2+) concentrations. These data define the expression profile of P2Y receptors on human biliary epithelial
cancer cells and indicate
P2Y2 receptors as being potential targets in new treatment strategies for biliary
cancer.