| 1. |
- Björkman, Per, et al.
(författare)
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Common Interactions between S100A4 and S100A9 Defined by a Novel Chemical Probe.
- 2013
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- S100A4 and S100A9 proteins have been described as playing roles in the control of tumor growth and metastasis. We show here that a chemical probe, oxyclozanide (OX), selected for inhibiting the interaction between S100A9 and the receptor for advanced glycation end-products (RAGE) interacts with both S100A9 and S100A4. Furthermore, we show that S100A9 and S100A4 interact with RAGE and TLR4; interactions that can be inhibited by OX. Hence, S100A4 and S100A9 display similar functional elements despite their primary sequence diversity. This was further confirmed by showing that S100A4 and S100A9 dimerize both in vitro and in vivo. All of these interactions required levels of Zn(++) that are found in the extracellular space but not intracellularly. Interestingly, S100A4 and S100A9 are expressed by distinct CD11b(+) subpopulations both in healthy animals and in animals with either inflammatory disease or tumor burden. The functions of S100A9 and S100A4 described in this paper, including heterodimerization, may therefore reflect S100A9 and S100A4 that are released into the extra-cellular milieu.
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| 2. |
- He, Zhifei, et al.
(författare)
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CD14 is a co-receptor for TLR4 in the S100A9-induced pro-inflammatory response in monocytes
- 2016
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:5
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Tidskriftsartikel (refereegranskat)abstract
- The cytosolic Ca2+-binding S100A9 and S100A8 proteins form heterodimers that are primarily expressed in human neutrophils and monocytes. We have recently shown that S100A9 binds to TLR4 in vitro and induces TLR4-dependent NF-κB activation and a pro-inflammatory cytokine response in monocytes. In the present report we have further investigated the S100A9-mediated stimulation of TLR4 in monocytes. Using transmission immunoelectron microscopy, we detected focal binding of S100A9 to monocyte membrane subdomains containing the caveolin-1 protein and TLR4. Furthermore, the S100A9 protein was detected in early endosomes of the stimulated cells, indicating that the protein could be internalized by endocytosis. Although stimulation of monocytes with S100A9 was strictly TLR4-dependent, binding of S100A9 to the plasma membrane and endocytosis of S100A9 was still detectable and coincided with CD14 expression in TLR4-deficient cells. We therefore investigated whether CD14 would be involved in the TLR4-dependent stimulation and could show that the S100A9-induced cytokine response was inhibited both in CD14-deficient cells and in cells exposed to CD14 blocking antibodies. Further, S100A9 was not internalized into CD14-deficient cells suggesting a direct role of CD14 in endocytosis of S100A9. Finally, we could detect satiable binding of S100A9 to CD14 in surface plasmon resonance experiments. Taken together, these results indicate that CD14 is a co-receptor of TLR4 in the S100A9-induced cytokine response.
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| 3. |
- He, Zhifei
(författare)
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S100A9 in inflammation
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- S100A9 is a small (13 kD) cytosolic calcium-binding protein. The protein is mainly expressed in neutrophils and monocytes in human but can also be expressed in other cell types under inflammatory conditions. S100A9 is normally co-expressed with S100A8 and forms S100A8/S100A9 heterodimers. Previous publications had suggested that S100A9 could be expressed without S100A8 in certain conditions. Various functions for cytosolic S100A8/S100A9 heterodimers have been described. The heterodimer can promote NADPH oxidase activation, is involved in reactions mediated by the iNOS enzyme and assists in tubulin polymerization. Extracellular S100A9 can bind to TLR4 and RAGE. Upon binding TLR4, S100A9 functions as a DAMP molecule inducing a pro-inflammatory cellular response. This thesis mainly focuses on the pro-inflammatory function of hS100A9.In paper I, the main questions we asked were: in what condition hS100A9 could exist in cells without hS100A8? We found that the half-life of hS100A9 protein was short and degraded fast in cells, but can be stabilized by co-expressing with hS100A8 or by proteasome inhibitor. We also found that inflammatory stimuli could also stabilized hS100A9 protein and promoted the formation of proteolytically-resistant homodimer. This paper suggests that during inflammatory condition, hS100A9 protein might be able to exist as homodimer without hS100A8 and that it therefore may function as DAMP molecule after it has been released out of the cell.In paper II, we showed that a chemical probe oxyclozanide could inhibit S100A9, S100A4 and S100A4/S100A9 binding to TLR4 and RAGE and inhibiting tumor progression in a mouse model. We also showed that hS100A4 and hS100A9 can form heterodimers. Further, we showed that S100A4 and S100A9 are differentially expressed in mouse myeloid cell populations. In paper III, we wanted to identify co-receptor(s) involved in S100A9-mediated stimulation of TLR4. We show that CD14 is an essential co-receptor of this stimulation. Our data also suggest that some other co-receptor(s) might exist that help in S100A9 binding to cell membrane. However CD14 was crucial both for S100A9 signaling and internalization. In summary, in this thesis we discuss the relation between S100A9 and inflammation. We show that during inflammation, the pro-inflammatory cytokine could stabilize the unstable hS100A9 by promoting it forming proteolytically-resistant homodimer. After S100A9 released out of the cell, they could function as DAMP molecule activating TLR4 in a CD14 dependent way. By blocking the interaction between the S100s with their receptors using OX, we propose a compound with clinical potential for treating inflammation and cancer.
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| 4. |
- Riva, Matteo, et al.
(författare)
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Human S100A9 Protein Is Stabilized by Inflammatory Stimuli via the Formation of Proteolytically-Resistant Homodimers.
- 2013
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- S100A8 and S100A9 are Ca(2+)-binding proteins that are associated with acute and chronic inflammation and cancer. They form predominantly heterodimers even if there are data supporting homodimer formation. We investigated the stability of the heterodimer in myeloid and S100A8/S100A9 over-expressing COS cells. In both cases, S100A8 and S100A9 proteins were not completely degraded even 48 hrs after blocking protein synthesis. In contrast, in single transfected cells, S100A8 protein was completely degraded after 24 h, while S100A9 was completely unstable. However, S100A9 protein expression was rescued upon S100A8 co-expression or inhibition of proteasomal activity. Furthermore, S100A9, but not S100A8, could be stabilized by LPS, IL-1β and TNFα treatment. Interestingly, stimulation of S100A9-transfected COS cells with proteasomal inhibitor or IL-1β lead to the formation of protease resistant S100A9 homodimers. In summary, our data indicated that S100A9 protein is extremely unstable but can be rescued upon co-expression with S100A8 protein or inflammatory stimuli, via proteolytically resistant homodimer formation. The formation of S100A9 homodimers by this mechanism may constitute an amplification step during an inflammatory reaction.
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