In sílico identification and characterization of putative Dot/Icm secreted virulence effectors in the fish pathogen Piscirickettsia salmonis

• Published in: Microbial pathogenesis 2016-03, Vol.92, p.11-18
• Main Authors: Labra, Álvaro, Arredondo-Zelada, Oscar, Flores-Herrera, Patricio, Marshall, Sergio H., Gómez, Fernando A.
• Format: Article
• Language: English
• Subjects: Animals; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - secretion; Computational Biology - methods; Fish Diseases - microbiology; Fishes - microbiology; Gene Expression; Genome, Bacterial; Models, Molecular; Open Reading Frames; Piscirickettsia - classification; Piscirickettsia - genetics; Piscirickettsia - metabolism; Piscirickettsia - pathogenicity; Protein Conformation; Protein Interaction Domains and Motifs; Protein Transport; Type IV Secretion Systems; Virulence
• ISSN: 0882-4010; 1096-1208
• DOI: 10.1016/j.micpath.2015.12.002

Piscirickettsia salmonis seriously affects the Chilean salmon industry. The bacterium is phylogenetically related to Legionella pneumophila and Coxiella burnetii, sharing a Dot/Icm secretion system with them. Although it is well documented that L. pneumophila and C. burnetii secrete different virulence effectors via this Dot/Icm system in order to attenuate host cell responses, to date there have been no reported virulence effectors secreted by the Dot/Icm system of P. salmonis. Using several annotations of P. salmonis genome, here we report an in silico analyses of 4 putative Dot/Icm effectors. Three of them contain ankyrin repeat domains and the typical conserved 3D structures of this protein family. The fourth one is highly similar to one of the Dot/Icm-dependent effectors of L. pneumophila. Additionally, all the potential P. salmonis effectors contain a classical Dot/Icm secretion signal in their C-terminus, consisting of: an E-Block, a hydrophobic residue in −3 or −4 and an electronegative charge. Finally, qPCR analysis demonstrated that these proteins are overexpressed early in infection, perhaps contributing to the generation of a replicative vacuole, a key step in the neutralizing strategy proposed for the Dot/Icm system. In summary, this report identifies four Dot/Icm-dependent effectors in P. salmonis. [Display omitted] In this work was possible detect four putative Dot/Icm substrates in the genome of the fish pathogen Piscirickettsia salmonis. These proteins have similitudes with Legionella pneumophila and Coxiella burnetii Dot/Icm substrates such as: i) eukaryotic conserved domains and ii) a typical Dot/Icm secretion signal in the C-terminal. Finally, the P. salmonis putative Dot/Icm substrates are overexpressed during infection process in vitro, with similar patters to those reported for the Dot/Icm secretion apparatus. •Where detected 4 putative Dot/Icm substrates in Piscirickettsia salmonis genome.•3 proteins contain eukaryotic conserved domains (Ankyrins).•The proteins share features with Legionella and Coxiella Dot/Icm substrates.•The 4 proteins have the classical Dot/Icm secretion signal in the C-terminal.•The proteins are over-expressed in infection kinetics in vitro, suggesting that could be implicated in P. salmonis intracellular survival and multiplication.