# Studies on the Structure of Basement Membranes

> **NIH NIH R01** · VANDERBILT UNIVERSITY MEDICAL CENTER · 2020 · $746,708

## Abstract

Hundreds of variants in the COL4A3, COL4A4 and COL4A5 genes cause a broad range of glomerulopathies
affecting the function of the glomerular basement membrane (GBM). These genes encode the assembly of
collagen IV α345 scaffolds, the major constituent of the GBM, the autoantigen in Goodpasture’s (GP)
autoimmune disease, and the protein mutated in Alport syndrome and other genetic glomerulopathies. GP
disease has and continues to serve as the vanguard for unlocking mysteries of the molecular structure of the
α345 scaffold and pathogenic mechanisms underlying both acquired and genetic glomerulopathies. Our
overarching hypothesis is: Collagen IV α345 scaffold tethers macromolecules forming supramolecular
complexes and perturbation of scaffold causes glomerulopathies. Four specific aims address key
unanswered questions that are defined based on our previous and recent discoveries. Aim 1: α345NC1
Hexamer. To determine the atomic structure of the α345NC1 hexamer and mechanism of GP epitopes
formation. The structure of the 345NC1 hexamer, GP autoantigen, is unknown. We hypothesize that upon
perturbation of quaternary structure of the non-immunogenic 345NC1 hexamer, EA and EB regions
undergo conformational changes forming pathogenic GP neoepitopes. Aim 2: α3 Zurich Mutation. To
determine the impact of α3 Zurich mutation on GP epitopes formation. We found a mutation in α3NC1
domain associated with the first case of familial GP disease, providing genetic evidence for a triggering
mechanism. We hypothesize that the mutation causes structural perturbation of the EA and EB regions of
α3NC1, which can contribute to GP epitopes presentation. Aim 3. Chloride ring. To determine role of
chloride in assembly of the collagen IV α345 scaffold and formation of GP epitopes. Whereas structure,
assembly and functions of the α121 scaffold has been successfully studied for over 40 years, our knowledge
about the α345 scaffold remains obscure. We demonstrated that chloride concentration is a critical factor in GP
antibody binding. We hypothesize that assembly of the 345NC1 hexamer, its stability and GP-reactivity is
dependent on chloride ions. Aim 4: α121 Supramolecular complexes. To characterize the supramolecular
complexes of α121 collagen IV within a basement membrane. We discovered a garland architecture of the
α121 scaffold coated with proteoglycans. This suprastructure is a potential core feature of basement membrane.
We hypothesize that collagen IV α121 scaffold tethers macromolecules forming distinct supramolecular
complexes which enable basement membrane assembly. The achievement of the aims will yield new insights
to the etiology of GP disease and the structure and assembly of collagen IV scaffolds, leading to a framework
for development of novel therapeutic strategies for GBM diseases.

## Key facts

- **NIH application ID:** 9970128
- **Project number:** 2R01DK018381-49
- **Recipient organization:** VANDERBILT UNIVERSITY MEDICAL CENTER
- **Principal Investigator:** Sergey Petrovich Budko
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $746,708
- **Award type:** 2
- **Project period:** 1986-09-01 → 2024-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9970128

## Citation

> US National Institutes of Health, RePORTER application 9970128, Studies on the Structure of Basement Membranes (2R01DK018381-49). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9970128. Licensed CC0.

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