14-3-3 Activated Bacterial Exotoxins AexT and ExoT Share Actin and the SH2 Domains of CRK Proteins as Targets for ADP-Ribosylation

• Published in: Pathogens (Basel) Vol. 11; no. 12; p. 1497
• Main Authors: Ebenwaldner, Carmen, Hornyak, Peter, García-Saura, Antonio Ginés, Torretta, Archimede, Anoosheh, Saber, Hofer, Anders, Schüler, Herwig
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.12.2022; MDPI
• Subjects: 14-3-3 activated bacterial exotoxins; 14-3-3 protein; Actin; Adenosine diphosphate; ADP-ribosylation; Aeromonas salmonicid; Aeromonas salmonicid; Agmatine; Analysis; Bacterial toxins; Binding sites; Biochemistry and Molecular Biology; Biokemi och molekylärbiologi; Biologi; Biological Sciences; Care and treatment; Catalysis; Complications and side effects; Cytoskeleton; Exoenzyme S; Exotoxins; Gram-negative bacterial infections; Homology; Hydrophobic surfaces; Kinases; Medicin och hälsovetenskap; Morphology; Muscle proteins; Natural Sciences; Naturvetenskap; Nosocomial infections; Pathogens; Phylogenetics; protein refolding; Proteins; Pseudomonas aeruginosa; Pseudomonas aeruginosa; Ribosylation; Toxins; Transcription factors; type III secretion system; Virulence; Sweden; Aeromonas salmonicid; protein refolding; actin; Pseudomonas aeruginosa; type III secretion system; 14-3-3 activated bacterial exotoxins; ADP-ribosylation
• ISSN: 2076-0817; 2076-0817
• DOI: 10.3390/pathogens11121497

Bacterial exotoxins with ADP-ribosyltransferase activity can be divided into distinct clades based on their domain organization. Exotoxins from several clades are known to modify actin at Arg177; but of the 14-3-3 dependent exotoxins only exoenzyme T (AexT) has been reported to ADP-ribosylate actin. Given the extensive similarity among the 14-3-3 dependent exotoxins, we initiated a structural and biochemical comparison of these proteins. Structural modeling of AexT indicated a target binding site that shared homology with Exoenzyme T (ExoT) but not with Exoenzyme S (ExoS). Biochemical analyses confirmed that the catalytic activities of both exotoxins were stimulated by agmatine, indicating that they ADP-ribosylate arginine residues in their targets. Side-by-side comparison of target protein modification showed that AexT had activity toward the SH2 domain of the Crk-like protein (CRKL), a known target for ExoT. We found that both AexT and ExoT ADP-ribosylated actin and in both cases, the modification compromised actin polymerization. Our results indicate that AexT and ExoT are functional homologs that affect cytoskeletal integrity via actin and signaling pathways to the cytoskeleton.