1 Previous studies have indicated a role for extracellular ATP in the regul
ation of epidermal homeostasis. Here we have investigated the expression of
P2Y(2) receptors by human keratinocytes, the cells which comprise the epid
ermis.
2 Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed express
ion of mRNA for the G-protein-coupled, P2Y(2) receptor in primary cultured
human keratinocytes.
3 In situ hybridization studies of skin sections revealed that P2Y(2) recep
tor transcripts were expressed in the native tissue. These studies demonstr
ated a striking pattern of localization of P2Y(2) receptor transcripts to t
he basal layer of the epidermis, the site of cell proliferation.
4 Increases in intracellular free Ca2+ concentration ([Ca2+](i)) in keratin
ocytes stimulated with ATP or UTP demonstrated the presence of functional P
2Y receptors.
5 In proliferation studies based on the incorporation of bromodeoxyuridine
(BrdU), ATP, UTP and ATP gamma S were found to stimulate the proliferation
of keratinocytes.
6 Using a real-time firefly luciferase and luciferin assay we have shown th
at under static conditions cultured human keratinocytes release ATP.
7 These findings indicate that P2Y(2) receptors play a major role in epider
mal homeostasis, and may provide novel targets for therapy of proliferative
disorders of the epidermis, including psoriasis.