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EMBO reports 6, 11, 1082–1087 (2005)
doi:10.1038/sj.embor.7400537
AOP Published online: 23 September 2005
The RING-finger scaffold protein Plenty of SH3s targets TAK1 to control immunity signalling in Drosophila
Manabu Tsuda1, Caillin Langmann2, Nicholas Harden2 & Toshiro Aigaki1
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1 Department of Biological Sciences, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji-shi, Tokyo 192-0397, Japan
2 Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
To whom correspondence should be addressed
Toshiro Aigaki Tel: +81 426 77 2575; Fax: +81 426 77 2559; E-mail: aigaki-toshiro@c.metro-u.ac.jp
Received 18 February 2005; Accepted 18 August 2005; Published online 23 September 2005.
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Abstract
Imd-mediated innate immunity is activated in response to infection by Gram-negative bacteria and leads to the activation of Jun amino-terminal kinase (JNK) and Relish, a nuclear factor- B transcription factor responsible for the expression of antimicrobial peptides. Plenty of SH3s (POSH) has been shown to function as a scaffold protein for JNK activation, leading to apoptosis in mammals. Here, we report that POSH controls Imd-mediated immunity signalling in Drosophila. In POSH-deficient flies, JNK activation and Relish induction were delayed and sustained, which indicated that POSH is required for properly timed activation and termination of the cascade. The RING finger of POSH, possessing ubiquitin-ligase activity, was essential for termination of JNK activation. We show that POSH binds to and degrades TAK1, a crucial activator of both the JNK and the Relish signalling pathways. These results establish a novel role for POSH in the Drosophila immune system.
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