Transforming growth factor-alpha stimulates prostaglandin generation through cytosolic phospholipase A(2) under the control of p11 in rat gastric epithelial cells.
The regulatory effects of transforming growth factor (TGF)-alpha on phospholipase A(2) (PLA(2)) isozymes contributing to prostaglandin generation in rat gastric epithelial RGM1 cells were examined. Stimulation with TGF-alpha for 24 h time-dependently induced prostaglandin E(2) generation with an increase in cyclo-oxygenase-2 protein. The TGF-alpha-induced prostaglandin E(2) generation was suppressed by NS-398, a cyclo-oxygenase-2 inhibitor. TGF-alpha stimulated the activity and the protein synthesis of cytosolic PLA(2) (cPLA(2)). A time-dependent increase in cPLA(2) protein occurred in parallel with PGE(2) generation, which was inhibited by methyl arachidonyl fluorophosphonate (MAFP), a cPLA(2) inhibitor. However, no change in activity of secretory PLA(2) or Ca(+2)-independent PLA(2) was observed in the TGF-alpha-stimulated cells. Stimulation with the Ca(2+) ionophore A23187 for 10 min induced MAFP-sensitive arachidonic acid liberation. Interestingly, preincubation with TGF-alpha for 24 h diminished A23187-stimulated arachidonic acid liberation despite the increase in cPLA(2) protein. Under the conditions, TGF-alpha was found to increase p11, an endogenous cPLA(2) suppressor, also known as annexin II light chain. The TGF-alpha-induced increase in p11 was suppressed by tyrphostin AG1478, an inhibitor of tyrosine kinase of epidermal growth factor receptor, which was also found to restore the inhibition by TGF-alpha of A23187-stimulated arachidonic acid liberation. However, TGF-alpha did not alter protein levels of annexin II heavy chain. These results suggest that TGF-alpha stimulates prostaglandin generation through an increase in cPLA(2), the hydrolytic action of which may be under the control of p11.
Akiba
S
S
Department of Pathological Biochemistry, Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan. akiba@mb.kyoto-phu.ac.jp
Hatazawa
R
R
Ono
K
K
Hayama
M
M
Matsui
H
H
Sato
T
T
D000818:Animals; D017306:Annexin A2; D016718:Arachidonic Acid / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003600:Cytosol / Q000201:enzymology*; D005753:Gastric Mucosa / Q000166:cytology / Q000378:metabolism*; D010455:Peptides / Q000502:physiology*; D010741:Phospholipases A / Q000502:physiology*; D011453:Prostaglandins / Q000096:biosynthesis*; D051381:Rats; D009418:S100 Proteins; D016211:Transforming Growth Factor alpha / Q000494:pharmacology*; D000099248:S100 Calcium Binding Protein A10
D017306:Annexin A2; D016718:Arachidonic Acid; D000001:Calcimycin; D002118:Calcium; D010455:Peptides; D010741:Phospholipases A; D011453:Prostaglandins; D009418:S100 Proteins; D016211:Transforming Growth Factor alpha; D000099248:S100 Calcium Binding Protein A10