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Gα 12 specifically regulates COX‐2 induction by sphingosine 1‐phosphate
Author(s) -
Ki Sung Hwan,
Choi Min Jung,
Lee Chang Ho,
Kim Sang Geon
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a978-d
Subject(s) - sphingosine 1 phosphate , transfection , phosphorylation , sphingolipid , sphingosine , microbiology and biotechnology , chemistry , sphingosine kinase 1 , knockout mouse , g protein coupled receptor , signal transduction , receptor , biology , biochemistry , gene
Sphingosine 1‐phosphate (S1P), a sphingolipid released from activated platelets, stimulates COX‐2 induction. S1P activates GPCRs coupled to Gα family members. This study investigated whether Gα 12 family regulates COX‐2 induction by S1P and if so, what the molecular basis is for its COX‐2 regulation. Gene knockout or chemical inhibitor experiments revealed that S1P induction of COX‐2 requires Gα 12 , but not Gα 13 , Gα q or Gα i/o . The specific role of Gα 12 in COX‐2 induction by S1P was verified by promoter luciferase assay, Gα 12 transfection and siRNA experiments. Absence of Gα 12 inhibited NF‐κB DNA binding activity. Immunocytochemistry, ChIP and NF‐κB site mutation analyses confirmed the functional role of NF‐κB in COX‐2 gene transcription by S1P. Gα 12 deficiency unaffected S1P‐mediated IκBα phosphorylation, but abrogated its ubiquitinylation and degradation, thereby abolishing p65 nuclear translocation. Chemical inhibition of S1P‐activated JNK abolished IκBα ubiquitinylation by S1P. Consistently, JNK transfection caused S1P to degrade IκBα during Gα 12 deficiency. S1P injection induced COX‐2 in the lungs and livers of mice with an increase in the plasma PGE 2 , which was prevented by Gα 12 gene knockout. Of the Gα proteins coupled to S1P receptors, Gα 12 specifically regulates NF‐κB‐mediated COX‐2 induction by S1P, which is mediated by ubiquitinylation and degradation, but not phosphorylation, of IκBα.