Involvement of toll-like receptor (TLR) 2 and TLR4 in cell activation by mannuronic acid polymers.
The alginate capsule produced by the human pathogen Pseudomonas aeruginosa is composed mainly of mannuronic acid polymers (poly-M) that have immunostimulating properties. Poly-M shares with lipopolysaccharide the ability to stimulate cytokine production from human monocytes in a CD14-dependent manner. In the present study we examined the role of Toll-like receptor (TLR) 2 and TLR4 in responses to poly-M. Blocking antibodies to TLR2 and TLR4 partly inhibited tumor necrosis factor production induced by poly-M in human monocytes, and further inhibition was obtained by combining the antibodies. By transiently transfecting HEK293 cells, we found that membrane CD14 together with either TLR2 or TLR4/MD-2 could mediate activation by poly-M. Transfection of HEK293 cells with TLR2 and fluorescently labeled TLR4 followed by co-patching of TLR2 with an antibody revealed no association of these molecules on the plasma membrane. However, macrophages from the Tlr4 mutant C3H/HeJ mice and TLR4 knockout mice were completely non-responsive to poly-M, whereas the tumor necrosis factor release from TLR2 knockout macrophages was half of that seen with wild type cells. Taken together the results suggest that both TLR2 and TLR4 are involved in cell activation by poly-M and that TLR4 may be required in primary murine macrophages.
Flo
Trude H
TH
Institute of Cancer Research and Molecular Biology and the Institute of Biotechnology, Norwegian University of Science and Technology, 7489 Trondheim, Norway.
Ryan
Liv
L
Latz
Eicke
E
Takeuchi
Osamu
O
Monks
Brian G
BG
Lien
Egil
E
Halaas
Øyvind
Ø
Akira
Shizuo
S
Skjåk-Braek
Gudmund
G
Golenbock
Douglas T
DT
Espevik
Terje
T
D000818:Animals; D001704:Biopolymers / Q000502:physiology*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D029721:Drosophila Proteins; D006603:Hexuronic Acids / Q000378:metabolism*; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D008809:Mice, Inbred C3H; D020033:Protein Isoforms / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000502:physiology*; D015398:Signal Transduction; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
D001704:Biopolymers; D029721:Drosophila Proteins; D006603:Hexuronic Acids; D015850:Interleukin-6; D008562:Membrane Glycoproteins; D020033:Protein Isoforms; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; C008324:mannuronic acid