Manipulating the type VI secretion system spike to shuttle passenger proteins.

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• The type VI secretion system (T6SS) is a complex molecular machine used by bacteria like Pseudomonas aeruginosa to inject effector proteins into target cells.
• The T6SS apparatus comprises structural components including VgrG, PAAR, and Hcp, forming a spike for cell envelope penetration.
• Effectors can be canonical proteins or "evolved" components covalently fused to structural T6SS proteins.

Purpose of the Study:

• To investigate the flexibility of the T6SS in Pseudomonas aeruginosa for delivering diverse passenger proteins.
• To explore the potential of fusing various functional domains to the canonical VgrG1a protein.
• To assess the feasibility of engineering the T6SS for targeted delivery applications.

Main Methods:

• Genetic engineering of Pseudomonas aeruginosa to fuse different passenger domains to the C terminus of VgrG1a.
• Analysis of protein secretion into the bacterial culture supernatant using various effector types (e.g., β-lactamase, VgrG2b, Tse2).
• Characterization of the T6SS assembly and effector translocation mechanism.

Main Results:

• Demonstrated successful translocation of diverse passenger proteins, including unrelated T6SS proteins, β-lactamase, and toxins, when fused to VgrG1a.
• Confirmed that the T6SS exhibits significant modularity and flexibility in accommodating different effector types.
• Observed varying degrees of delivery efficacy depending on the nature of the passenger domain.

Conclusions:

• The T6SS of Pseudomonas aeruginosa is a highly adaptable "nano-weapon" capable of delivering a wide range of effector proteins.
• Engineering the T6SS offers promising potential for developing novel therapeutic strategies against bacterial infections and cancer.
• Further optimization of T6SS-mediated delivery systems could have significant medical and industrial applications.