Two roles for the Drosophila IKK complex in the activation of Relish and the induction of antimicrobial peptide genes

• Published in: Proceedings of the National Academy of Sciences - PNAS 2009-06, Vol.106 (24), p.9779-9784
• Main Authors: Ertürk-Hasdemir, Deniz, Broemer, Meike, Leulier, François, Lane, William S, Paquette, Nicholas, Hwang, Daye, Kim, Chan-Hee, Stöven, Svenja, Meier, Pascal, Silverman, Neal
• Format: Article
• Language: English
• Subjects: Animals; Anti-Infective Agents; Antibodies; antimicrobial peptides; Antimicrobials; Bacteria; Biological Sciences; caspase; Cell lines; Cellular immunity; disease resistance; DNA; Drosophila; Drosophila immunity; Drosophila melanogaster; Drosophila Proteins - chemistry; Drosophila Proteins - metabolism; Drosophila Proteins - physiology; Epistasis, Genetic; Gene Expression Regulation; Genes; Genetics; I-kappa B Kinase - chemistry; I-kappa B Kinase - physiology; immune response; innate immunity; Insects; NF-kappa B; nuclear factor-kappaB; Peptides; Peptides - genetics; Phosphorylation; Promoter Regions, Genetic; protein kinases; protein phosphorylation; protein precursors; Proteins; proteolysis; RNA; Serine - metabolism; transcription factors; Transcription Factors - metabolism
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.0812022106

The Drosophila NF-κB transcription factor Relish is an essential regulator of antimicrobial peptide gene induction after Gram-negative bacterial infection. Relish is a bipartite NF-κB precursor protein, with an N-terminal Rel homology domain and a C-terminal IκB-like domain, similar to mammalian p100 and p105. Unlike these mammalian homologs, Relish is endoproteolytically cleaved after infection, allowing the N-terminal NF-κB module to translocate to the nucleus. Signal-dependent activation of Relish, including cleavage, requires both the Drosophila IκB kinase (IKK) and death-related ced-3/Nedd2-like protein (DREDD), the Drosophila caspase-8 like protease. In this report, we show that the IKK complex controls Relish by direct phosphorylation on serines 528 and 529. Surprisingly, these phosphorylation sites are not required for Relish cleavage, nuclear translocation, or DNA binding. Instead they are critical for recruitment of RNA polymerase II and antimicrobial peptide gene induction, whereas IKK functions noncatalytically to support Dredd-mediated cleavage of Relish.