Abstract
AIP56 (apoptosis-inducing protein of 56 kDa) is a major virulence factor of Photobacterium damselae piscicida (Phdp), a Gram-negative pathogen that causes septicemic infections, which are among the most threatening diseases in mariculture. The toxin triggers apoptosis of host macrophages and neutrophils through a process that, in vivo, culminates with secondary necrosis of the apoptotic cells contributing to the necrotic lesions observed in the diseased animals. Here, we show that AIP56 is a NF-κB p65-cleaving zinc-metalloprotease whose catalytic activity is required for the apoptogenic effect. Most of the bacterial effectors known to target NF-κB are type III secreted effectors. In contrast, we demonstrate that AIP56 is an A-B toxin capable of acting at distance, without requiring contact of the bacteria with the target cell. We also show that the N-terminal domain cleaves NF-κB at the Cys(39)-Glu(40) peptide bond and that the C-terminal domain is involved in binding and internalization into the cytosol.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Animals
-
Apoptosis / physiology*
-
Apoptosis Regulatory Proteins / physiology*
-
Bacterial Toxins / metabolism*
-
Bass
-
Fish Diseases / metabolism
-
Host-Pathogen Interactions
-
Leukocytes / metabolism
-
Leukocytes / pathology
-
Metalloproteases / metabolism*
-
Photobacterium / metabolism*
-
Recombinant Proteins
-
Transcription Factor RelA / metabolism*
-
Virulence Factors / metabolism*
Substances
-
Apoptosis Regulatory Proteins
-
Bacterial Toxins
-
Recombinant Proteins
-
Transcription Factor RelA
-
Virulence Factors
-
Metalloproteases
Grants and funding
Daniela S. Silva and Liliana M. G. Pereira were funded by FCT fellowships SFRH/BD/35865/2007 and SFRH/BD/43501/2008, respectively. Ana do Vale was supported by Programa Ciência – funded by POPH - QREN - Tipologia 4.2 - Promoção do Emprego Científico, co-funded by Fundo Social Europeu and National funding from MCTES. This work was supported by FCT projects PTDC/BIA-PRO/101111/2008, PTDC/CVT/099544/2008 PTDC/MAR/101143/2008 and PEst-C/SAU/LA0002/2011 (EU-FEDER funding through COMPETE). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.