Lipopolysaccharide-activated kinase, an essential component for the induction of the antimicrobial peptide genes in Drosophila melanogaster cells.
Eukaryotic organisms use a similar Rel/NF-kappaB signaling cascade for the induction of innate immune genes. In Drosophila, lipopolysaccharide (LPS) signal-induced activation of the Rel/NF-kappaB family transcription factors is an essential step in the transcriptional activation of inducible antimicrobial peptide genes. However, the mechanism by which the LPS-induced signaling pathway proceeds remains largely unknown. Here we have cloned a novel Drosophila LPS-activated kinase (DLAK) that is structurally related to mammalian IkappaB kinases. DLAK is expressed and transiently activated in LPS-responsive Drosophila cells following LPS stimulation. Furthermore, DLAK can interact with Cactus, a Drosophila IkappaB and phosphorylate recombinant Cactus, in vitro. Overexpression of dominant-negative mutant DLAK (DLAK(K50A)) blocks LPS-induced Cactus degradation. DLAK-bound Cactus can be degraded in a LPS signal-dependent fashion, whereas the DLAK(K50A) mutant-bound Cactus is completely resistant to degradation in the presence of LPS. The DLAK(K50A) mutant also inhibits nuclear kappaB binding activity and kappaB-dependent diptericin reporter gene activity in a dose-dependent manner, but the kappaB-dependent diptericin reporter gene activity can be rescued by overexpression of wild type DLAK. Moreover, mRNA analysis of various kappaB-dependent antimicrobial peptide genes shows that LPS inducibility of these genes is greatly impaired in cells overexpressing DLAK(K50A). These results establish that DLAK is a novel LPS-activated kinase, which is an essential signaling component for the induction of antimicrobial peptide genes following LPS treatment in Drosophila cells.
Kim
Y S
YS
Laboratory of Immunology, Medical Research Center, College of Medicine, Yonsei University, Shinchon-Dong 134, Seoul, South Korea.
Han
S J
SJ
Ryu
J H
JH
Choi
K H
KH
Hong
Y S
YS
Chung
Y H
YH
Perrot
S
S
Raibaud
A
A
Brey
P T
PT
Lee
W J
WJ
D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002460:Cell Line; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000201:enzymology*; D005260:Female; D020573:Genes, rel / Q000235:genetics; D051550:I-kappa B Kinase; D017403:In Situ Hybridization; D008070:Lipopolysaccharides / Q000378:metabolism*; D008297:Male; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000737:chemistry; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013997:Time Factors; D015854:Up-Regulation
D000890:Anti-Infective Agents; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D008070:Lipopolysaccharides; D016328:NF-kappa B; D010750:Phosphoproteins; C077938:cact protein, Drosophila; D017346:Protein Serine-Threonine Kinases; D051550:I-kappa B Kinase; C496563:IKKbeta protein, Drosophila