LY-294002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one] affects calcium signaling in airway smooth muscle cells independently of phosphoinositide 3-kinase inhibition.
Phosphoinositide 3-kinase (PI3K) may potentially influence intracellular [Ca(2+)](i) concentration by several mechanisms. We have investigated the effects of phosphoinositide 3-kinase (PI3K) inhibitors wortmannin and LY-294002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one] on Ca(2+) signaling in rat airway smooth muscle (ASM) cells using fura-2 and imaging methodology. Wortmannin (1 microM) and LY-294002 (1 and 10 microM) had opposite effects: wortmannin caused a small increase, whereas LY-294002 caused a significant decrease of peak Ca(2+) responses to serotonin (5-HT). LY-294002 (10 microM) diminished 5-HT-induced ASM cell contraction, measured as a change in cell surface area, and inositol phosphate formation, measured by anion exchange chromatography. Thin layer chromatography revealed that the levels of phospholipase C (PLC) substrate phosphatidylinositol 4,5-bisphosphate were not affected. SDS polyacrylamide gel electrophoresis and Western blotting have shown that both wortmannin and LY-294002 inhibited platelet-derived growth factor-induced PI3K activation. However, PI3K activation could not be detected after 5-HT stimulation. The specific casein kinase-2 (CK2) inhibitor 5,6-dichloro-1-beta-d-ribofuranosyl-benzimidazole (10-40 microM) reduced 5-HT-triggered responses to a similar extent as LY-294002. We conclude that LY-294002 modulates Ca(2+) signaling in rat ASM independently of its action on PI3K by acting on, or upstream of, PLC, possibly by inhibiting CK2.
Tolloczko
Barbara
B
Meakins-Christie Laboratories, McGill University, 3626 St-Urbain Street, Montreal, Quebec, Canada H2 2P2.
Turkewitsch
Petra
P
Al-Chalabi
Mustafa
M
Martin
James G
JG
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001980:Bronchi / Q000166:cytology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D002867:Chromones / Q000494:pharmacology*; D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology; D004347:Drug Interactions; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008297:Male; D009025:Morpholines / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051381:Rats; D011916:Rats, Inbred F344; D012701:Serotonin / Q000494:pharmacology; D000077191:Wortmannin
D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D012701:Serotonin; D004004:Dichlororibofuranosylbenzimidazole; D002118:Calcium; D000077191:Wortmannin