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.
Department of Microbiology and Immunology, University of Maryland, Baltimore, MD 21201, USA.
Vladimir U
VU
Toshchakov
Subhendu
S
Basu
Matthew J
MJ
Fenton
Stefanie N
SN
Vogel
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