Expression and responsiveness of P2Y₂ receptors in human endometrial cancer cell lines

In single endometrial carcinoma HEC-1A and Ishikawa cells, ATP induced a rapid and extracellular Ca²⁺-independent rise in cytosolic Ca²⁺ concentration ([Ca²⁺](i)) in a dose-dependent manner, with an ED₅₀ of about 10 μM. The spike phase was followed by a sustained plateau phase that was dependent on Ca²⁺ influx through voltage-insensitive Ca²⁺ channels, whose gating was controlled by a capacitative Ca²⁺ entry mechanism. ADP was less potent in raising the cystolic Ca²⁺ concentration, and AMP and adenosine were ineffective. The order of agonist potency for this receptor was ATP = UTP > ATP-γ-S>>ADP. Several other agonists, including β,γ-methylene-ATP, 2-MeS-ATP, and BzATP were ineffective. This ligand-selective profile indicates the expression of the P2Y₂R subtype in endometrial cells. Accordingly, reverse transcription-PCR using P2Y₂ primers amplified the expected transcript from both cell lines. The coupling of these receptors to phospholipase C was confirmed by the ability of ATP to increase inositol 1,4,5-trisphosphate and diacylglycerol productions. These receptors are also coupled to the phospholipase D-1 pathway, leading to accumulation of phosphatidic acid. Activation of P2Y₂ receptors by a slowly degradable ATP analog, ATP-γ-S, was associated with a significant suppression of cell proliferation without affecting the cellular apoptosis. These results indicate that P2Y₂ receptors may participate in control of the cell cycle of endometrial carcinoma cells.