TRPC6 G757D Loss-of-Function Mutation Associates with FSGS

Area of Science:

• Nephrology
• Molecular Biology
• Genetics

Background:

• Focal Segmental Glomerulosclerosis (FSGS) is a chronic kidney disease (CKD) characterized by heavy proteinuria and progression to End-Stage Renal Disease (ESRD).
• Hereditary FSGS is often associated with mutations in the TRPC6 gene, encoding a nonselective cation channel.
• While most known TRPC6 mutations lead to a gain-of-function phenotype causing podocyte cell death, the precise molecular mechanisms remain incompletely understood.

Purpose of the Study:

• To investigate the molecular mechanisms underlying FSGS caused by TRPC6 gene mutations.
• To characterize the functional impact of specific FSGS-related TRPC6 mutations, particularly those predicted to affect channel complex integrity.

Main Methods:

• Utilized three-dimensional in silico modeling to analyze the structure of tetrameric TRPC6 and predict the effects of mutations.
• Performed functional characterization of TRPC6 mutants, including coexpression studies to mimic patient heterozygosity.
• Analyzed 19 distinct human FSGS-associated TRPC6 mutations.

Main Results:

• In silico modeling predicted that the G757D mutation disrupts the TRPC6-TRPC6 interface, suggesting a loss-of-function mechanism.
• Functional analysis confirmed that five of the 19 studied TRPC6 mutations (N125S, L395A, G757D, L780P, R895L) exhibit a loss-of-function phenotype.
• Coexpression of wild-type TRPC6 with TRPC6 G757D demonstrated a dominant-negative effect, indicating impaired channel function in heterozygous states.

Conclusions:

• Loss of TRPC6 channel function represents an additional pathogenic mechanism in hereditary FSGS.
• The study provides molecular insights into how specific TRPC6 mutations, like G757D, lead to a loss-of-function phenotype and contribute to FSGS development.