Cellular substrates and pro-apoptotic function of the human HtrA4 protease

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• The HtrA4 protein is a serine protease and chaperone involved in oncogenesis, placentation, and preeclampsia.
• Limited knowledge exists regarding HtrA4's biochemical properties and molecular functions.

Purpose of the Study:

• To biochemically characterize the human HtrA4 protein.
• To identify the cellular function and binding partners of HtrA4.

Main Methods:

• Recombinant HtrA4 expression and purification.
• Protease activity assays and thermal stability measurements.
• Proteomic analysis (pull-down assays with mass spectrometry) and biochemical validation (immunoprecipitation, ELISA, fluorescence microscopy) of protein interactions.
• In vitro degradation assays.

Main Results:

• Recombinant HtrA4 is a trimeric protein with moderate thermal stability and lower protease activity than other human HtrA proteases.
• HtrA4 forms complexes with XIAP, caspases 7 and 9, β-tubulin, actin, TCP1α, and S100A6.
• HtrA4 degrades XIAP, caspases, β-tubulin, and actin, but not TCP1α or S100A6.

Conclusions:

• HtrA4 influences cellular processes, including apoptosis, through interactions and degradation of key proteins.
• The identified HtrA4 partners provide a foundation for further research into its biological roles.