Overview
Curli are functional amyloid fibers produced by escherichia coli, salmonella, and other Enterobacteriaceae as the primary protein component of their extracellular biofilm matrix. The curli subunit CsgA polymerizes into cross-beta-sheet amyloid fibrils that are structurally homologous to human disease-associated amyloids (Aβ, α-synuclein, tau). This structural homology enables cross-seeding — bacterial curli can nucleate the aggregation of host amyloid proteins, providing a direct microbial-to-neurodegeneration pathway.
Cross-Seeding Mechanism
- CsgA fibers produced in the gut by E. coli/Shigella cross-seed amyloid-beta (Aβ) aggregation in Alzheimer's disease and α-synuclein aggregation in Parkinson's disease [1] [2].
- Curli fibers activate TLR2/TLR1 on macrophages and microglia, triggering neuroinflammation.
- The gut → brain translocation route: curli or curli-seeded amyloid aggregates may propagate via the vagus nerve (gut brain axis) or systemic circulation after barrier failure.
Metal Connection
- Iron and zinc are required for curli fiber assembly — CsgA polymerization is metal-dependent.
- Inflammation-driven iron availability in the dysbiotic gut selects for E. coli/Shigella expansion AND provides the metal cofactors for curli production — a convergent pathological mechanism.
- This connects microbial metallomics directly to neurodegeneration: metal exposure → Enterobacteriaceae bloom → curli production → amyloid cross-seeding → Aβ/α-synuclein aggregation.
Cross-References
- escherichia — primary curli producer
- amyloid beta — cross-seeding target in Alzheimer's
- alpha synuclein — cross-seeding target in Parkinson's
- microbial metallomics — metals→microbes→neurodegeneration pathway
- biofilm — curli as biofilm structural component
- neuroinflammation — curli-TLR2 activation of microglia
- iron — required for curli fiber assembly