Group X Secreted Phospholipase A2 Proenzyme Is Matured by a Furin-like Proprotein Convertase and Releases Arachidonic Acid inside of Human HEK293 Cells

• Published in: The Journal of biological chemistry Vol. 286; no. 42; pp. 36509 - 36521
• Main Authors: Jemel, Ikram, Ii, Hiromi, Oslund, Rob C., Payré, Christine, Dabert-Gay, Anne-Sophie, Douguet, Dominique, Chargui, Khaoula, Scarzello, Sabine, Gelb, Michael H., Lambeau, Gérard
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 21.10.2011; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Motifs; Animals; Arachidonic Acid; Arachidonic Acid - genetics; Arachidonic Acid - metabolism; Convertases; Enzyme Precursors; Enzyme Precursors - genetics; Enzyme Precursors - metabolism; Enzyme Processing; Group X Phospholipases A2; Group X Phospholipases A2 - genetics; Group X Phospholipases A2 - metabolism; HEK293 Cells; Humans; Immunology; Life Sciences; Lipids; Mice; Mutation; Phospholipase A; Proprotein Convertases; Proprotein Convertases - antagonists & inhibitors; Proprotein Convertases - genetics; Proprotein Convertases - metabolism; Protease Inhibitors; Protease Inhibitors - pharmacology; Protein Motifs; Protein Processing; Protein Secretion; Recombinant Protein Expression; Convertases; Protein Secretion; Recombinant Protein Expression; Protein Motifs; Protein Processing; Arachidonic Acid; Phospholipase A; Enzyme Processing
• ISSN: 0021-9258; 1083-351X; 1083-351X
• DOI: 10.1074/jbc.M111.268540

Among mammalian secreted phospholipases A2 (sPLA2s), group X sPLA2 has the most potent hydrolyzing activity toward phosphatidylcholine and is involved in arachidonic acid (AA) release. Group X sPLA2 is produced as a proenzyme and contains a short propeptide of 11 amino acids ending with a dibasic motif, suggesting cleavage by proprotein convertases. Although the removal of this propeptide is clearly required for enzymatic activity, the cellular location and the protease(s) involved in proenzyme conversion are unknown. Here we have analyzed the maturation of group X sPLA2 in HEK293 cells, which have been extensively used to analyze sPLA2-induced AA release. Using recombinant mouse (PromGX) and human (ProhGX) proenzymes; HEK293 cells transfected with cDNAs coding for full-length ProhGX, PromGX, and propeptide mutants; and various permeable and non-permeable sPLA2 inhibitors and protease inhibitors, we demonstrate that group X sPLA2 is mainly converted intracellularly and releases AA before externalization from the cell. Most strikingly, the exogenous proenzyme does not elicit AA release, whereas the transfected proenzyme does elicit AA release in a way insensitive to non-permeable sPLA2 inhibitors. In transfected cells, a permeable proprotein convertase inhibitor, but not a non-permeable one, prevents group X sPLA2 maturation and partially blocks AA release. Mutations at the dibasic motif of the propeptide indicate that the last basic residue is required and sufficient for efficient maturation and AA release. All together, these results argue for the intracellular maturation of group X proenzyme in HEK293 cells by a furin-like proprotein convertase, leading to intracellular release of AA during secretion. Background: Group X secreted phospholipase A2 is an enzyme produced as a proenzyme that plays an important role in arachidonic acid release. Results: Group X phospholipase A2 is matured intracellularly by a furin-like proprotein convertase and releases arachidonic acid during secretion. Conclusion: Group X phospholipase A2 can release arachidonic acid intracellularly. Significance: Group X phospholipase A2 may produce lipid mediators during secretion.