Visit our Expo - Redox and Inflammation signaling 2012

VIII. Inflammation specific signaling Poster VIII, 17
Novel Serine Protease-Induced Signaling in Human Peripheral Monocytes
Yves Laumonnier, Tatiana Syrovets, Thomas Simmet
Department of Pharmacology of Natural Products & Clinical Pharmacology, University
of Ulm, D-89081 Ulm, Germany. E-mail: yves.laumonnier@uni-ulm.de
Besides its important role in fibrinolysis, plasmin is a potent proinflammatory serine protease
activating human peripheral monocytes. Plasmin induces lipid mediator release, expression of
proinflammatory genes and chemotaxis. However, the exact nature of its receptor in
monocytes remains elusive. In this context we have now investigated the role of annexin A2
described as a surface protein involved into the binding of the inactive zymogen plasminogen.
In contrast to neutrophils, primary monocytes respond to plasmin and express the annexin A2
heterotetramer consisting of annexin A2 and S100A10 as shown by Western immunoblot,
flow cytometry, immunofluorescence microscopy and co-immunoprecipitation. Using a
biotin-labeled tri-functional plasmin cross-linker, we were able to biotinylate both annexin A2
and S100A10 suggesting that plasmin is indeed binding to the subunits of the annexin A2
heterotetramer. To assess the role of the annexin A2 heterotetramer as a receptor for plasmin
signaling, plasmin-induced chemotaxis was analyzed after treatment with neutralizing
antibodies. Antibodies directed against either annexin A2 or S100A10 impaired the plasmininduced
signaling but not that induced by FMLP. Similarly, antisense oligodeoxynucleotides
(ODN) directed against annexin A2 or S100A10, but not the respective sense controls,
reduced the plasmin-induced chemotaxis, but not that to FMLP. Consistently, monocytes
pretreated with antisense ODN showed a decreased release of the proinflammatory cytokine
tumor necrosis factor (TNF)-alpha confirming that annexin A2 and S100A10 are essential for
the plasmin-induced signaling. At the molecular level plasmin induced cleavage of the
annexin A2 heterotetramer at position 27 as demonstrated by point mutation. Finally, we
found that the plasmin-mediated cleavage triggers dissociation of the annexin A2
heterotetramer.
These data identify the annexin A2 heterotetramer as a signaling receptor for plasmin in
human peripheral monocytes. The dissociation of the heterotetramer after the plasmininduced
cleavage of annexin A2 is apparently the molecular initiator for the plasmin-induced
proinflammatory signaling in human peripheral monocytes.
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