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CD14 is a co-receptor for TLR4 in the S100A9-induced pro-inflammatory response in monocytes

He, Zhifei LU ; Riva, Matteo LU ; Björk, Per; Swärd, Karl LU ; Mörgelin, Matthias LU ; Leanderson, Tomas LU and Ivars, Fredrik LU (2016) In PLoS One 11(5).
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... (More)

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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publication status
published
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in
PLoS One
volume
11
issue
5
publisher
Public Library of Science
external identifiers
  • Scopus:84971267184
ISSN
1932-6203
DOI
10.1371/journal.pone.0156377
language
English
LU publication?
yes
id
91ba4bba-2290-4926-a607-15ada5a98c0b
date added to LUP
2016-06-14 10:05:39
date last changed
2016-09-20 03:10:07
@misc{91ba4bba-2290-4926-a607-15ada5a98c0b,
  abstract     = {<p>The cytosolic Ca<sup>2+</sup>-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.</p>},
  author       = {He, Zhifei and Riva, Matteo and Björk, Per and Swärd, Karl and Mörgelin, Matthias and Leanderson, Tomas and Ivars, Fredrik},
  issn         = {1932-6203},
  language     = {eng},
  number       = {5},
  publisher    = {ARRAY(0x9159ed0)},
  series       = {PLoS One},
  title        = {CD14 is a co-receptor for TLR4 in the S100A9-induced pro-inflammatory response in monocytes},
  url          = {http://dx.doi.org/10.1371/journal.pone.0156377},
  volume       = {11},
  year         = {2016},
}