Innate immunity pathways regulate the nephropathy gene Apolipoprotein L1.

Area of Science:

• Nephrology
• Immunology
• Genetics

Background:

• Apolipoprotein L1 (APOL1) risk variants are a major genetic factor for kidney disease, particularly in individuals of African ancestry.
• Collapsing focal segmental glomerulosclerosis (FSGS) is a severe form of kidney disease.
• Therapeutic interferons have been observed in patients with APOL1 high-risk genotypes who developed FSGS.

Purpose of the Study:

• To investigate the role of interferons and Toll-like receptor (TLR) agonists in APOL1 expression and kidney disease pathogenesis.
• To elucidate the molecular pathways involved in interferon-induced APOL1 upregulation.
• To compare the cellular toxicity of APOL1 risk variants versus wild-type APOL1.

Main Methods:

• Analysis of patient cohorts with APOL1 high-risk genotypes and FSGS.
• Cell culture experiments stimulating cells with interferons and TLR agonists (e.g., PolyI:C).
• Molecular techniques including gene expression analysis, pharmacological inhibition, small hairpin RNA knockdown, and chromatin immunoprecipitation.

Main Results:

• Interferons and TLR agonists significantly increased APOL1 expression (up to 200-fold) in cell culture.
• PolyI:C activated APOL1 expression via both interferon-dependent and independent pathways, the latter involving IRF3.
• The interferon-independent pathway utilized signaling through TBK1, NF-κB, Jak kinases, and transcription factors IRF1, IRF2, and STAT2.
• APOL1 risk variants were more toxic to cells than wild-type APOL1.

Conclusions:

• Antiviral pathways, including interferon and TLR signaling, can induce APOL1 expression and contribute to kidney disease in individuals with high-risk APOL1 genotypes.
• The identified molecular pathways offer potential therapeutic targets for preventing or treating APOL1-associated kidney disease.