Abstract: TH-PO0689
Serine Protease HTRA1: Regulator of Complement Activation at the GBM
Session Information
- Glomerular Diseases: Immunopathogenesis and Targeted Therapeutics
November 06, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology
Authors
- Takayama, Suguru, University of Utah Health, Salt Lake City, Utah, United States
- Demir, Fatih, Aarhus Universitet, Aarhus, Central Denmark Region , Denmark
- Caza, Tiffany, Arkana Laboratories, Little Rock, Arkansas, United States
- Beck, Laurence H., Boston University, Boston, Massachusetts, United States
- Rinschen, Markus M., Aarhus Universitet, Aarhus, Central Denmark Region , Denmark
- Al-Rabadi, Laith, University of Utah Health, Salt Lake City, Utah, United States
Background
Apolipoprotein E (APOE), a known complement regulator, has been recently suggested to have a differentiating role between Dense Deposit Disease (DDD) and C3 glomerulonephritis. Human samples from some DDD patients were enriched in Serine protease HTRA1. A link between HTRA1 and APOE has been reported in ophthalmology literature as both are implicated in age related macular degeneration. Moreover, the formation of an extracellular APOE fragment may have important biologic roles. Herein, we investigated the degradation of APOE by HTRA1.
Methods
We performed in vitro digestion assays, incubating recombinant APOE and HTRA1 over different time intervals and analyzed degradation over time using immunoblotting. To confirm in vitro results, we then performed similar digestions ex vivo using human glomerular extract (HGE). Proteolytic fragments were investigated using N terminomic mass spectrometry approach to identify cleavage sites of APOE.
Results
We confirmed the presence of different truncated forms of APOE in HGE. Recombinant APOE4 showed time-dependent degradation when incubated with active HTRA1 (almost complete signal loss observed after 24 hours) but not mutant inactive mutant HTRA1 (S328A). APOE cleavage sites as represented (heatmap below) were uniquely different between WT and HTRA1 KO mice.
Conclusion
HTRA1 may have an important role in regulating complement pathway by specifically cleaving APOE. Future studies will investigate the biological significance of this cleavage event and potential impact on complement activation.
Funding
- NIDDK Support