Novel Noncompetitive Type Three Secretion System ATPase Inhibitors Shut Down Shigella Effector Secretion

Area of Science:

• Microbiology
• Structural Biology
• Drug Discovery

Background:

• Shigella causes bacillary dysentery, leading to millions of infections and deaths annually.
• Shigella utilizes a type three secretion system (T3SS) for virulence, relying on the Spa47 ATPase.
• Spa47 is a critical regulator of T3SS and a potential therapeutic target.

Purpose of the Study:

• To discover novel small molecule inhibitors of the Shigella T3SS ATPase, Spa47.
• To characterize the mechanism of inhibition and assess potential for cross-pathogen therapeutics.

Main Methods:

• Computational screening of 7.6 million compounds using the Spa47 crystal structure.
• In vitro biochemical assays to measure ATPase activity inhibition.
• In vivo assays to assess T3SS protein secretion reduction.
• Kinetic analyses to determine inhibition mechanism.

Main Results:

• Identified novel Spa47 inhibitors reducing ATPase activity by up to 87.9% and T3SS secretion by 94.7%.
• Inhibitors exhibit low cytotoxicity and a noncompetitive inhibition mechanism.
• Inhibitors show cross-reactivity with T3SS ATPases from E. coli and Salmonella.

Conclusions:

• The study provides a platform for developing broadly effective cross-pathogen T3SS ATPase inhibitors.
• Targeting Spa47 offers a promising strategy against Shigella and other Gram-negative pathogens.
• Novel inhibitors demonstrate potential for therapeutic development against bacterial infections.