Manipulating the type VI secretion system spike to shuttle passenger proteins

Abstract

The type VI secretion system (T6SS) is a contractile injection apparatus that translocates a spike loaded with various effectors directly into eukaryotic or prokaryotic target cells. Pseudomonas aeruginosa can load either one of its three T6SSs with a variety of toxic bullets using different but specific modes. The T6SS spike, which punctures the bacterial cell envelope allowing effector transport, consists of a torch-like VgrG trimer on which sits a PAAR protein sharpening the VgrG tip. VgrG itself sits on the Hcp tube and all elements, packed into a T6SS sheath, are propelled out of the cell and into target cells. On occasion, effectors are covalent extensions of VgrG, PAAR or Hcp proteins, which are then coined "evolved" components as opposed to canonical. Here, we show how various passenger domains could be fused to the C terminus of a canonical VgrG, VgrG1a from P. aeruginosa, and be sent into the bacterial culture supernatant. There is no restriction on the passenger type, although the efficacy may vary greatly, since we used either an unrelated T6SS protein, βlactamase, a covalent extension of an "evolved" VgrG, VgrG2b, or a Hcp-dependent T6SS toxin, Tse2. Our data further highlights an exceptional modularity/flexibility for loading the T6SS nano-weapon. Refining the parameters to optimize delivery of passenger proteins of interest would have attractive medical and industrial applications. This may for example involve engineering the T6SS as a delivery system to shuttle toxins into either bacterial pathogens or tumour cells which would be an original approach in the fight against antimicrobial resistant bacteria or cancer. OPEN ACCESSCitation: Wettstadt S, Filloux A (2020) Manipulating the type VI secretion system spike to shuttle passenger proteins. PLoS ONE 15(2): e0228941. https://doi.org/10.

Immunity proteins of dual nuclease T6SS effectors function as transcriptional repressors

“…these proteins are important for T6SS-mediated delivery of TseT in P. aeruginosa strain PAO1 (Burkinshaw et al, 2018), we anticipate that their co-expression will enable T6SS-mediated secretion of TseTBg proteins. Indeed, we observed that TseTBg effectors of domains of effectors are required for T6SS-mediated delivery (Hachani et al, 2014;Liang et al, 2015;Lien & Lai, 2017;Wettstadt & Filloux, 2020). In the absence of the carrier and chaperone proteins, T6SS-mediated secretion of TseTBg proteins will be compromised.…”

Solving the Puzzle: Connecting a Heterologous Agrobacterium tumefaciens T6SS Effector to a Pseudomonas aeruginosa Spike Complex

“…However, production of such heterotrimer would be challenging as it would consist of three VgrG proteins with an unknown ratio of WT VgrG1a and chimera A. Furthermore, in a previous study we saw that in presence of two VgrG1a species, WT VgrG1a and modified VgrG1a (Wettstadt and Filloux, 2020), WT VgrG1a was secreted in higher amounts than the modified VgrG1a suggesting a preferred formation of WT VgrG1a spikes to be secreted.…”

Adherent-Invasive E. coli: Update on the Lifestyle of a Troublemaker in Crohn’s Disease

“…On another note, T6SS can also be used by commensal bacteria, notably, Bacteroides fragilis used T6SS to antagonize commensal Bacteroidales species and to kill enterotoxigenic B. fragilis strainsin vivo in mice [183,184]. The pathogen Shigella sonnei specifically outcompeted Escherichia coli in vitro andin vivo in mice in a T6SS-dependant manner [185], whereas a recent study demonstrated that it is possible to manipulate the type VI secretion system of Pseudomonas aeruginosa to shuttle chosen proteins, different of canonical effectors [186]. Hence, it would be interesting to discover if some commensal bacteria are able to target AIEC in T6SS-dependent manner in order to develop a highly specific and safe therapeutic option for CD patients.…”