A Legionella pneumophila T4SS effector protein (Ravl) triggers mitochondrial fragmentation through phosphoinositide...

Area of Science:

• Microbiology
• Cell Biology
• Biochemistry

Background:

• Legionella pneumophila evades host defenses by manipulating macrophage membrane trafficking.
• Mitochondria are crucial for L. pneumophila infection, with effector proteins mediating their recruitment and fragmentation.
• A specific T4SS effector protein responsible for mitochondrial recruitment and fragmentation remained unidentified.

Purpose of the Study:

• To identify and characterize a novel Legionella pneumophila T4SS effector protein involved in mitochondrial manipulation.
• To elucidate the mechanism by which this effector protein affects mitochondrial function and host cell fate.

Main Methods:

• Crystal structure determination of the L. pneumophila T4SS effector protein RavL.
• Subcellular localization studies using mitochondrial targeting sequences.
• Biochemical assays to determine RavL's enzymatic activity on phosphoinositides.
• Apoptosis assays in THP-1 macrophages.

Main Results:

• The crystal structure of RavL, a L. pneumophila T4SS effector, was determined.
• RavL possesses a mitochondrial targeting sequence, localizes to the mitochondrial membrane, and induces mitochondrial fragmentation.
• RavL functions as a phosphatidylinositol polyphosphate 5-phosphatase, hydrolyzing PtdIns(4)P.
• RavL disrupts mitochondrial function and triggers apoptosis in macrophages.

Conclusions:

• RavL is a novel L. pneumophila T4SS effector that actively manipulates host phosphoinositide metabolism.
• RavL's phosphatase activity leads to mitochondrial dysfunction and apoptosis, facilitating bacterial infection.
• This study reveals a new mechanism of bacterial pathogenesis involving targeted disruption of mitochondrial metabolism.