Abstract
The term “amyloid” refers to proteinaceous deposits of peptides that might be generated from larger precursor proteins e.g., by proteolysis. Common to these peptides is a stable cross-β dominated secondary structure which allows self-assembly, leading to insoluble oligomers and lastly to fibrils. These highly ordered protein aggregates have been, for a long time, mainly associated with human neurodegenerative diseases such as Alzheimer’s disease (Amyloid-β peptides). However, they also exert physiological functions such as in release of deposited hormones in human beings. In the light of the rediscovery of our microbial commensals as important companions in health and disease, the fact that microbes also possess amyloidogenic peptides is intriguing. Transmission of amyloids by iatrogenic means or by consumption of contaminated meat from diseased animals is a well-known fact. What if also our microbial commensals might drive human amyloidosis or suffer from our aggregated amyloids? Moreover, as the microbial amyloids are evolutionarily older, we might learn from these organisms how to cope with the sword of Damocles forged of endogenous, potentially toxic peptides. This review summarizes knowledge about the interplay between human amyloids involved in neurodegenerative diseases and microbial amyloids.
Highlights
Amyloidogenic peptides or proteins are well known to be the main culprit of various human diseases, but more recently, several of these proteins with physiological function have been identified in humans
Out of the known amyloidogenic proteins found in humans, 37 are correlated to diseases [5] such as systemic primary amyloidosis caused by monoclonal light chains (AL) or hereditary ALs such as those caused by ApoA1 or lysozyme [6,7]
Many more amyloids will in future be identified in microorganisms
Summary
Amyloidogenic peptides or proteins are well known to be the main culprit of various human diseases, but more recently, several of these proteins with physiological function have been identified in humans (reviewed in [1]). Odoribacter and Blautia as well as Alistipes have been shown to be increased in human and mouse model studies (summarized in [19]). These are still only observational studies and lack functional conjunction between microbiota composition and pathogenesis. The fact, that bacteria, fungi, and viruses are capable of producing amyloidogenic proteins or Their effect has been proven in many studies (e.g., [22,23]). Focus was laid on the potentialproteins interplayorof those that bacteria, fungi, and capable of producing amyloidogenic peptides microbial andin this theirreview, producers withlaid the proteins andinterplay peptides underlying human Agar and the biofilm stained with ThT (shown is a merge of bright field and green fluorescent channel)
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