Differential involvement of BB loops of toll-IL-1 resistance (TIR) domain-containing adapter proteins in TLR4- versus TLR2-mediated signal transduction.
TLRs sense pathogens and transmit intracellular signals via the use of specific adapter proteins. We designed a set of "blocking peptides" (BPs) comprised of the 14 aa that correspond to the sequences of the BB loops of the four known Toll-IL-1 resistance (TIR) domain-containing adapter proteins (i.e., MyD88, TIR domain-containing adapter inducing IFN-beta (TRIF), TRIF-related adapter molecule (TRAM), and TIR-domain containing adapter protein (TIRAP)) linked to the cell-penetrating segment of the antennapedia homeodomain. LPS (TLR4)-mediated gene expression, as well as MAPK and transcription factor activation associated with both MyD88-dependent and -independent signaling pathways, were disrupted by all four BPs (TRAM approximately MyD88 > TRIF > TIRAP), but not by a control peptide. In contrast, none of the BPs inhibited TLR2-mediated activation of MAPKs. Only the MyD88 BP significantly blocked Pam3Cys-induced IL-1beta mRNA; however, the inhibitory effect was much less than observed for LPS. Our data suggest that the interactions required for a fully functional TLR4 signaling "platform" are disrupted by these BPs, and that the adapter BB loops may serve distinct roles in TLR4 and TLR2 signalosome assembly.
Toshchakov
Vladimir U
VU
Department of Microbiology and Immunology, University of Maryland, Baltimore, MD 21201, USA.
Basu
Subhendu
S
Fenton
Matthew J
MJ
Vogel
Stefanie N
SN
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D000943:Antigens, Differentiation / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D066298:In Vitro Techniques; D050856:Interferon Regulatory Factor-1; D050838:Interferon Regulatory Factor-3; D008070:Lipopolysaccharides / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D053594:Myeloid Differentiation Factor 88; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D011971:Receptors, Immunologic / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017472:Receptors, Interleukin-1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D050794:STAT1 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000943:Antigens, Differentiation; D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; D050838:Interferon Regulatory Factor-3; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D053594:Myeloid Differentiation Factor 88; D010446:Peptide Fragments; D010750:Phosphoproteins; D011971:Receptors, Immunologic; D017472:Receptors, Interleukin-1; D050794:STAT1 Transcription Factor; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D015534:Trans-Activators; D014157:Transcription Factors; C494258:Irf1 protein, mouse; C494233:Irf3 protein, mouse; C507780:Myd88 protein, mouse; C494080:Stat1 protein, mouse; C476286:Ticam1 protein, mouse; C499045:TIRAP protein, mouse; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse