Human Plasma Protein Corona of Aβ Amyloid and Its Impact on Islet Amyloid Polypeptide Cross-Seeding

Alzheimer's disease (AD) is the most severe form of neurological disorder, characterized by the presence of extracellular amyloid-β (Aβ) plaques and intracellular tau tangles. For decades, therapeutic strategies against the pathological symptoms of AD have often relied on the delivery of monoclonal antibodies to target specifically Aβ amyloid or oligomers, largely to no avail. Aβ can be traced in the brain as well as in cerebrospinal fluid and the circulation, giving rise to abundant opportunities to interact with their environmental proteins. Using liquid chromatography tandem-mass spectrometry, here we identified for the first time the protein coronae of the two major amyloid forms of Aβ-Aβ1-42 and Aβ1-40-exposed to human blood plasma. Out of the proteins identified in all groups, 58 proteins were unique to the Aβ1-42 samples and 31 proteins unique to the Aβ1-40 samples. Both fibrillar coronae consisted of proteins significant in complement activation, inflammation, and protein metabolic pathways involved in the pathology of AD. Structure-wise, the coronal proteins often possessed multidomains of high flexibility to maximize their association with the amyloid fibrils. The protein corona hindered recognition of Aβ1-42 fibrils by their structurally specific antibodies and accelerated the aggregation but not the β-cell toxicity of human islet amyloid polypeptide, the peptide associated with type 2 diabetes. This study highlights the importance of understanding the structural, functional, and pathological implications of the amyloid protein corona for the development of therapeutics against AD and a range of amyloid diseases.

Graphene quantum dots rescue protein dysregulation of pancreatic β-cells exposed to human islet amyloid polypeptide

The amyloid aggregation of peptides and proteins is a hallmark of neurological disorders and type 2 diabetes. Human islet amyloid polypeptide (IAPP), co-secreted with insulin by pancreatic β-cells, plays dual roles in both glycemic control and the pathology of type 2 diabetes. While IAPP can activate the NLRP3 inflammasome and modulate cellular autophagy, apoptosis and extracellular matrix metabolism, no data is available concerning intracellular protein expression upon exposure to the polypeptide. More surprisingly, how intracellular protein expression is modulated by nanoparticle inhibitors of protein aggregation remains entirely unknown. In this study, we first examined the changing proteomes of βTC6, a pancreatic β-cell line, upon exposure to monomeric, oligomeric and fibrillar IAPP, and detailed cellular protein expression rescued by graphene quantum dots (GQDs), an IAPP inhibitor. We found that 29 proteins were significantly dysregulated by the IAPP species, while majority of these proteins were nucleotide-binding proteins. Collectively, our liquid chromatography tandem-mass spectrometry, fluorescence quenching, helium ion microscopy, cytotoxicity and discreet molecular dynamics simulations data revealed a remarkable capacity of GQDs in regulating aberrant protein expression through H-bonding and hydrophobic interactions, pointing to nanomedicine as a new frontier against human amyloid diseases.