Characterization of a novel and specific inhibitor for the pro-apoptotic protease Omi/HtrA2

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Omi/HtrA2 is a mitochondrial serine protease homologous to bacterial HtrA chaperones.
• It translocates to the cytoplasm during apoptosis and induces cell death via caspase-dependent and -independent pathways.
• Its protease activity is crucial for caspase-independent cell death.

Purpose of the Study:

• To identify and characterize a specific inhibitor of Omi/HtrA2's proteolytic activity.
• To evaluate the compound's efficacy in inhibiting Omi/HtrA2-induced cell death.

Main Methods:

• High-throughput screening of a combinatorial library using bacterially expressed Omi-(134-458) protease and fluorescein-casein.
• Characterization of inhibitor specificity against various serine proteases.
• Monitoring cellular uptake using the compound's natural fluorescence.
• Testing in caspase-9 (-/-) null fibroblasts to assess inhibition of Omi/HtrA2-induced cell death.

Main Results:

• A novel compound, ucf-101, was identified as a specific inhibitor of Omi/HtrA2 protease activity.
• ucf-101 demonstrated minimal activity against other serine proteases.
• The compound successfully entered mammalian cells and inhibited Omi/HtrA2-induced cell death in caspase-9 deficient cells.

Conclusions:

• ucf-101 is a potent and specific inhibitor of Omi/HtrA2.
• This inhibitor effectively blocks Omi/HtrA2-mediated cell death, highlighting the protease's role in apoptosis.
• ucf-101 represents a promising therapeutic agent for conditions involving Omi/HtrA2 dysregulation.