Common and specific downstream signaling targets controlled by Tlr2 and Tlr5 innate immune signaling in zebrafish

BACKGROUND: Although the responses to many pathogen associated molecular patterns (PAMPs) in cell cultures and extracted organs are well characterized, there is little known of transcriptome responses to PAMPs in whole organisms. To characterize this in detail, we have performed RNAseq analysis of responses of zebrafish embryos to injection of PAMPs in the caudal vein at one hour after exposure. We have compared two ligands that in mammals have been shown to specifically activate the TLR2 and TLR5 receptors: Pam3CSK4 and flagellin, respectively. RESULTS: We identified a group of 80 common genes that respond with high stringency selection to stimulations with both PAMPs, which included several well-known immune marker genes such as il1b and tnfa. Surprisingly, we also identified sets of 48 and 42 genes that specifically respond to either Pam3CSK4 or flagellin, respectively, after a comparative filtering approach. Remarkably, in the Pam3CSK4 specific set, there was a set of transcription factors with more than 2 fold-change, as confirmed by qPCR analyses, including cebpb, fosb, nr4a1 and egr3. We also showed that the regulation of the Pam3CSK4 and flagellin specifically responding sets is inhibited by knockdown of tlr2 or tlr5, respectively. CONCLUSIONS: Our studies show that Pam3CSK4 and flagellin can stimulate the Tlr2 and Tlr5 signaling pathways leading to common and specific responses in the zebrafish embryo system. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12864-015-1740-9) contains supplementary material, which is available to authorized users

Surfactant protein A binds TGF-β1 with high affinity and stimulates the TGF-β pathway

We were able to demonstrate reversible, specific and high-affinity binding of radioactively-labelled TGF-?1 ((125)I-TGF-?1) to immobilized surfactant protein A (SP-A), with an apparent dissociation constant of 53 picomolar at ?21. Addition of a 200-fold molar excess of the latency associated peptide (LAP) prevented and dissociated the binding of (125)I-TGF-?1 to SP-A, whereas latent TGF-?1 had no effect. Using a bioassay for TGF-?1 activity--a luciferase reporter assay--we were able to show that SP-A in the presence of TGF-?1 stimulated the TGF-?1 pathway, whereas SP-A alone had no effect. Studies with structural analogues of the distinct SP-A tail domain and head domain indicated that stimulatory activity of SP-A resided in the head domain. No activation of latent TGF-?1 by SP-A was observed. In addition, we observed that SP-A inhibited TGF-?1 inactivation by LAP. These results indicate that SP-A may have a regulatory role in the TGF-?1-mediated processes in the lung