Study links antimicrobial peptides to amyloid disease and neurodegeneration

Background

For decades, antimicrobial peptides (AMPs) and amyloid-forming peptides were studied in largely separate contexts. AMPs were viewed primarily as innate immune effectors helping the host control microbial invasion, whereas amyloid aggregation was more commonly linked to disorders such as Alzheimer's disease (Aβ), Parkinson's disease (α-synuclein), type 2 diabetes (hIAPP), and systemic amyloidosis. Yet a growing body of evidence challenges this clean separation.

Both molecular families share striking structural and functional overlaps: they can adopt β-sheet-rich conformations, self-assemble into fibrillar aggregates, and disrupt lipid membranes through similar mechanisms. This convergence raises a medically profound question - can AMPs directly shape the course of amyloid disease, and might amyloid aggregates in turn compromise host defense against infection? Key Contributions In this comprehensive review published in Research, Prof. Jie Zheng and co-workers at the University of Texas at San Antonio (UTSA) synthesize emerging evidence that AMPs and disease-related amyloids can influence one another through heterotypic cross-seeding interactions. The key scientific contributions include:

① A unified mechanistic framework. The authors systematically identify three molecular mechanisms by which β-sheet-rich AMPs modulate amyloid fibrillization: (a) structural compatibility - shared β-sheet topology enables template-directed cross-seeding; (b) directional seeding asymmetry - cross-seeding is inherently asymmetric, with AMPs promoting fibrillization in one direction but not the other, explaining the diverse and sometimes opposing effects of AMPs on amyloid assembly; and (c) surface-mediated catalysis - membrane-bound AMPs act as two-dimensional nucleation templates, dramatically lowering the kinetic barrier for amyloid fibril formation. Critically, the effects of AMPs extend beyond simple inhibition and include pathway rerouting, heterotypic co-assembly, fibril capping, remodeling of toxic intermediates, and modulation of immune responses.

② A bidirectional pathogen-amyloid feedback loop. The review proposes and substantiates a self-reinforcing disease cycle: microbial infection induces host AMP and amyloid production (amyloid-β itself functions as an endogenous AMP in the brain), while amyloid aggregates amplify neuroinflammation through sustained innate immune activation - creating a chronic, self-perpetuating loop. This cross-seeding-mediated communication axis provides a compelling mechanistic link between infection biology and neurodegeneration, two processes previously considered largely independent.

③ Rational design of dual-function AMP inhibitors. Building on these mechanistic foundations, the authors present recent advances in engineering next-generation AMP-derived inhibitors with enhanced amyloid specificity (targeting Aβ, hIAPP, and α-synuclein), improved proteolytic stability, and translational potential. These dual-function peptides simultaneously suppress amyloid aggregation and retain antimicrobial activity - a multifunctional therapeutic strategy uniquely suited to diseases where infection, inflammation, and aberrant aggregation are intertwined.

④ Open challenges and future roadmap. The authors identify several key unresolved questions: Which sequence or structural features determine whether an AMP selectively recognizes a given amyloid species? Under what conditions does an AMP suppress aggregation, redirect it toward less toxic states, or - in some cases - accelerate heterotypic assembly? How do membranes, metal ions, inflammatory mediators, and the microbiome shape these outcomes in vivo? And how can peptide stability, CNS delivery, and target specificity be improved for clinical use? Broader Impact By placing infection, innate immunity, and protein misfolding within a single mechanistic framework, this review opens new conceptual territory at a neglected disease interface. Conventional anti-amyloid strategies typically focus on a single pathogenic target. AMPs, by contrast, may offer genuine multifunctionality - combining antimicrobial activity, immunomodulation, and anti-amyloid potential within one molecular scaffold. This makes them particularly attractive as templates for next-generation therapeutics in neurodegeneration, metabolic disease, and systemic amyloidosis.

By bringing together findings across neurodegeneration, microbiology, amyloid biophysics, and peptide engineering, this review provides not just a literature summary, but a forward-looking framework for data-driven discovery and the rational design of multifunctional peptides - encouraging researchers to rethink amyloid disease as part of a broader biological interface where host defense, infection, and pathological aggregation converge.