Research article

Inhibition of the MEK1/ERK pathway reduces arachidonic acid release independently of cPLA₂ phosphorylation and translocation

John H Evans , Daniel J Fergus and Christina C Leslie

Program in Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, Colorado USA 80206

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BMC Biochemistry 2002, 3:30doi:10.1186/1471-2091-3-30

Published:	8 October 2002

Abstract

Background

The 85-kDa cytosolic phospholipase A₂ (cPLA₂) mediates arachidonic acid (AA) release in MDCK cells. Although calcium and mitogen-activated protein kinases regulate cPLA₂, the correlation of cPLA₂ translocation and phosphorylation with MAPK activation and AA release is unclear.

Results

MEK1 inhibition by U0126 inhibited AA release in response to ATP and ionomycin. This directly correlated with inhibition of ERK activation but not with phosphorylation of cPLA₂ on Ser⁵⁰⁵, which was only partially inhibited by ERK inhibition. Inhibition of AA release by U0126 was still observed when stoichiometric phosphorylation of cPLA₂ on Ser⁵⁰⁵ was maintained by activating p38 with anisomycin. Translocation kinetics of wild-type cPLA₂ and cPLA₂ containing S505A or S727A mutations to Golgi were similar in response to ATP and ionomycin and were not affected by U0126.

Conclusions

These results suggest that the ability of cPLA₂ to hydrolyze membrane phospholipid is reduced by inhibition of the MEK1/ERK pathway and that the reduction in activity is independent of cPLA₂ phosphorylation and translocation to membrane. The results also demonstrate that cPLA₂ mutated at the phosphorylation sites Ser⁵⁰⁵ and Ser⁷²⁷ translocated with similar kinetic as wild-type cPLA₂.