PcToll2 positively regulates the expression of antimicrobial peptides by promoting PcATF4 translocation into the nucleus. (November 2016)

• Record Type: Journal Article
• Authors: Lan, Jiang-Feng; Zhao, Li-Juan; Wei, Shun; Wang, Yuan; Lin, Li; Li, Xin-Cang
• Is Part Of: Fish & shellfish immunology. Volume 58(2016:Nov.)
• Page Start: 59
• Page End: 66
• Publication Date: 2016-11
• Subjects: Procambarus clarkii -- PcToll2 -- PcATF4 -- Vibrio parahemolyticus -- Expression profiles -- Nuclear translocation; Fishes -- Immunology -- Periodicals; Shellfish -- Immunology -- Periodicals; Poissons -- Immunologie -- Périodiques; Crustacés -- Immunologie -- Périodiques; 571.9617
• DOI: 10.1016/j.fsi.2016.09.007
• Languages: English
• ISSNs: 1050-4648

Abstract

Abstract: Drosophila Toll and mammalian Toll-like receptors (TLRs) are a family of evolutionarily conserved immune receptors that play a crucial role in the first-line defense against intruded pathogens. Activating transcription factor 4 (ATF4), a member of the ATF/CREB transcription factor family, is an important factor that participates in TLR signaling and other physiological processes. However, in crustaceans, whether ATF4 homologs were involved in TLR signaling remains unclear. In the current study, we identified a Toll homolog PcToll2 and a novel ATF4 homolog Pc ATF4 from Procambarus clarkii, and analyzed the likely regulatory activity of Pc ATF4 in Pc Toll2 signaling. The complete cDNA sequence of PcToll2 was 4175 bp long containing an open reading frame of 2820 bp encoding a 939-amino acid protein, and the cDNA sequence of PcATF4 was 2027 bp long with an open reading frame of 1296 bp encoding a 431-amino acid protein. Pc Toll2 and human TLR4 shared the high identity and they were grouped into a cluster. Furthermore, Pc Toll2 had a close relationship with other shrimp TLRs that possessed potential antibacterial activity. PcToll2 was highly expressed in the hemocytes, heart and gills, while PcATF4 mainly distributed in gills. Upon challenge with Vibrio parahemolyticus, PcToll2 and PcATF4 together with the antimicrobial peptides of ALF1 and ALF2 were significantly up-regulated in the hemocytes, and the Pc ATF4 was translocated into the nucleus. After PcToll2 silencing and challenge with Vibrio, the translocation of Pc ATF4 into the nucleus was inhibited and the expression of ALF1 and ALF2 was reduced, but the expression of PcDorsal and PcSTAT was not affected. Furthermore, after PcATF4 knockdown and challenge with or without Vibrio, the expression of ALF1 and ALF2 was also decreased while the expression of Pc Toll2 was upregulated. These results suggested that PcToll2 might regulate the expression of ALF1 and ALF2 by promoting the import of Pc ATF4, instead of the routine transcription factor Pc Dorsal, into the nucleus participating in the immune defense against Gram-negative bacteria. Highlights: PcToll2 and PcATF4 were widely expressed in all detected crayfish tissues. PcToll2 and PcATF4 together with ALF1 and ALF2 were up-regulated by Vibrio challenge. Either PcToll2 or PcATF4 knockdown decreased the expression of ALF1 and ALF2. PcToll2 silencing inhibited the nuclear import of Pc ATF4 caused by Vibrio challenge.