title: A toll-like receptor-4-interacting surfactant protein-A-derived peptide suppresses tumor necrosis factor-α release from mouse JAWS II dendritic cells.
abstract: Surfactant protein-A (SP-A) and Toll-like receptor-4 (TLR4) proteins are recognized as pathogen-recognition receptors. An exaggerated activation of TLR4 induces inflammatory response, whereas SP-A protein down-regulates inflammation. We hypothesized that SP-A-TLR4 interaction may lead to inhibition of inflammation. In this study, we investigated interaction between native baboon lung SP-A and baboon and human TLR4-MD2 proteins by coimmunoprecipitation/immunoblotting and microwell-based methods. The interaction between SP-A and TLR4-MD2 proteins was then analyzed using a bioinformatics approach. In the in silico model of SP-A-TLR4-MD2 complex, we identified potential binding regions and amino acids at the interface of SP-A-TLR4. Using this information, we synthesized a library of human SP-A-derived peptides that contained interacting amino acids. Next, we tested whether the TLR4-interacting SP-A peptides would suppress inflammatory cytokines. The peptides were screened for any changes in the tumor necrosis factor-α (TNF-α) response against lipopolysaccharide (LPS) stimuli in the mouse JAWS II dendritic cell line. Different approaches used in this study suggested binding between SP-A and TLR4-MD2 proteins. In cells pretreated with peptides, three of seven peptides increased TNF-α production against LPS. However, two of these peptides (SPA4: GDFRYSDGTPVNYTNWYRGE and SPA5: YVGLTEGPSPGDFRYSDFTP) decreased the TNF-α production in LPS-challenged JAWS II dendritic cells; SPA4 peptide showed more pronounced inhibitory effect than SPA5 peptide. In conclusion, we identify a human SP-A-derived peptide (SPA4 peptide) that interacts with TLR4-MD2 protein and inhibits the LPS-stimulated release of TNF-α in JAWS II dendritic cells.
authors.affiliation: Department of Pharmaceutical Sciences, University of Oklahoma Health Science Center, Oklahoma City, OK, USA. shanjana-awasthi@ouhsc.edu
authors.forename: Shanjana
authors.initials: S
authors.lastname: Awasthi
authors.forename: Kevin
authors.initials: K
authors.lastname: Brown
authors.forename: Catherine
authors.initials: C
authors.lastname: King
authors.forename: Vibhudutta
authors.initials: V
authors.lastname: Awasthi
authors.forename: Rajkumar
authors.initials: R
authors.lastname: Bondugula
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002461:Cell Line, Transformed; D003713:Dendritic Cells / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D048530:Papio anubis; D010446:Peptide Fragments / Q000378:metabolism* / Q000502:physiology; D011485:Protein Binding / Q000502:physiology; D037662:Pulmonary Surfactant-Associated Protein A / Q000502:physiology*; D051197:Toll-Like Receptor 4 / Q000378:metabolism* / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000378:metabolism*
chemical_list: D010446:Peptide Fragments; D037662:Pulmonary Surfactant-Associated Protein A; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha