Human 15-lipoxygenase: induction by interleukin-4 and insights into positional specificity

J Lipid Mediat. Mar-Apr 1993;6(1-3):75-88.

Abstract

Arachidonate 15-lipoxygenase (15-lipoxygenase) is a lipid-peroxidizing enzyme associated with specific inflammatory cells seen in asthma and atherosclerosis. In atherosclerosis, 15-lipoxygenase is induced in the macrophages of human and rabbit lesions and has been implicated in foam cell formation. In human lung, 15-lipoxygenase is preferentially expressed in airway epithelial cells and eosinophils. Our studies have focused both on the regulation of expression and on the structure-function relationships of the enzyme. To determine factors that could regulate expression, peripheral blood monocytes were purified and cultured with combinations of 18 factors. Only interleukin-4 (60 pM) induced 15-lipoxygenase mRNA, protein and enzymatic activity. Interferon-gamma (100 pM) inhibited the interleukin-4 dependent induction of 15-lipoxygenase. Results with cultured human airway cells were similar. These data suggest that expression of 15-lipoxygenase is regulated by interleukin-4, and that 15-lipoxygenase is a potential downstream effector molecule for this potent cytokine. In parallel studies, we have investigated determinants of positional specificity using site-directed mutagenesis and bacterial expression of human 15-lipoxygenase. Hypotheses for mutagenesis were derived from an analysis of conserved differences among multiple lipoxygenase sequences. Switching four amino acids in 15-lipoxygenase to their counterparts in 12-lipoxygenase resulted in a variant enzyme that produced equal 12- and 15-lipoxygenation. Further analysis has identified two amino acids that completely control the positional specificity of 15-lipoxygenase. These data have led to a preliminary model of the enzyme's active site region.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Arachidonate 12-Lipoxygenase / chemistry
  • Arachidonate 12-Lipoxygenase / genetics
  • Arachidonate 15-Lipoxygenase / biosynthesis*
  • Arachidonate 15-Lipoxygenase / chemistry
  • Arachidonate 15-Lipoxygenase / genetics
  • Binding Sites / genetics
  • Cattle
  • Conserved Sequence
  • Enzyme Induction / drug effects
  • Humans
  • Interleukin-4 / pharmacology*
  • Molecular Sequence Data
  • Monocytes / enzymology
  • Rabbits
  • Rats
  • Sequence Homology, Amino Acid
  • Structure-Activity Relationship
  • Trachea / enzymology

Substances

  • Interleukin-4
  • Arachidonate 12-Lipoxygenase
  • Arachidonate 15-Lipoxygenase