Cutting edge: cells that carry A null allele for toll-like receptor 2 are capable of responding to endotoxin.
Toll-like receptor (TLR) 2 and TLR4 have been implicated in the responses of cells to LPS (endotoxin). CD14-transfected Chinese hamster ovary (CHO)-K1 fibroblasts (CHO/CD14) are exquisitely sensitive to endotoxin. Sequence analysis of CHO-TLR2, compared with human and mouse TLR2, revealed a single base pair deletion. This frameshift mutation resulted in an alternative stop codon, encoding a protein devoid of transmembrane and intracellular domains. CHO-TLR2 cDNA failed to enable LPS signaling upon transient transfection into human epithelial kidney 293 cells. Site-directed mutagenesis of CHO-TLR2 enabled expression of a presumed full-length hamster TLR2 that conferred LPS responsiveness in human epithelial kidney 293 cells. Genomic TLR2 DNA from primary hamster macrophages also contained the frameshift mutation found in CHO fibroblasts. Nevertheless, hamster peritoneal macrophages were found to respond normally to LPS, as evidenced by the induction of cytokines. These results imply that expression of TLR2 is sufficient but not essential for mammalian responses to endotoxin.
Heine
H
H
Maxwell Finland Laboratory for Infectious Diseases, Boston University School of Medicine, MA 02118, USA.
Kirschning
C J
CJ
Lien
E
E
Monks
B G
BG
Rothe
M
M
Golenbock
D T
DT
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells / Q000276:immunology / Q000378:metabolism*; D003001:Cloning, Molecular; D006224:Cricetinae; D029721:Drosophila Proteins; D005260:Female; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D017737:Macrophages, Peritoneal / Q000276:immunology / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
D029721:Drosophila Proteins; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; 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