L. Homolya et al., Nucleotide-regulated calcium signaling in lung fibroblasts and epithelial cells from normal and P2Y(2) receptor (-/-) mice, J BIOL CHEM, 274(37), 1999, pp. 26454-26460
To test for the role of the P2Y(2) receptor (P2Y(2)-R) in the regulation of
nueleotide-promoted Ca2+ signaling in the lung, we generated P2Y(2)-R-defi
cient (P2Y(2)-R(-/-)) mice and measured intracellular Ca-i(2+) responses (D
elta Ca-i(2+)) to nucleotides in cultured lung fibroblasts and nasal and tr
acheal epithelial cells from wild type and P2Y(2)-R(-/-) mice. In the wild
type fibroblasts, the rank order of potencies for nucleotide-induced Delta
Ca-i(2+) was as follows: UTP greater than or equal to ATP much greater than
ADP > UDP. The responses induced by these agonists were completely absent
in the P2Y(2)-R(-/-) fibroblasts. Inositol phosphate responses paralleled t
hose of Delta Ca-i(2+) in both groups. ATP and UTP also induced Ca-i(2+) re
sponses in wild type airway epithelial cells. In the P2Y(2)-R(-/-) airway e
pithelial cells, UTP was ineffective, A small fraction (25%) of the ATP res
ponse persisted. Adenosine(-) and alpha,beta-methylene ATP were ineffective
, and ATP responses were not affected by adenosine deaminase or by removal
of extracellular Ca-i(2+) indicating that neither P1 nor P2X receptors medi
ated this residual ATP response. In contrast, 2-methylthio-ADP promoted a s
ubstantial Ca-i(2+) response in P2Y(2)-R(-/-) cells, which was inhibited by
the P2Y(1) receptor antagonist adenosine 3'-5'-diphosphate. These studies
demonstrate that P2Y(2)-R is the dominant purinoceptor in airway epithelial
cells, which also express a P2Y(1) receptor, and that the P2Y(2)-R is the
sole purinergic receptor subtype mediating nucleotide-induced inositol lipi
d hydrolysis and Ca2+ mobilization in mouse lung fibroblasts.