Albumin domain mutants with enhanced Aβ binding capacity identified by phage display analysis for application in various peripheral Aβ elimination approaches of Alzheimer's disease treatment

Abstract

Deposition of amyloid protein, particularly Aβ1‐42, is a major contributor to the onset of Alzheimer's disease (AD). However, almost no deposition of Aβ in the peripheral tissues could be found. Human serum albumin (HSA), the most abundant protein in the blood, has been reported to inhibit amyloid formation through binding Aβ, which is believed to play an important role in the peripheral clearance of Aβ. We identified the Aβ binding site on HSA and developed HSA mutants with high binding capacities for Aβ using a phage display method. HSA fragment 187–385 (Domain II) was found to exhibit the highest binding capacity for Aβ compared with the other two HSA fragments. To elucidate the sequence that forms the binding site for Aβ on Domain II, a random screening of Domain II display phage biopanning was constructed. A number of mutants with higher Aβ binding capacities than the wild type were identified. These mutants exhibited stronger scavenging abilities than the wild type, as revealed via in vitro equilibrium dialysis of Aβ experiments. These findings provide useful basic data for developing a safer alternative therapy than Aβ vaccines and for application in plasma exchange as well as extracorporeal dialysis.

Advances in Amyloid-β Clearance in the Brain and Periphery: Implications for Neurodegenerative Diseases

“…Numerous studies have shown that human serum albumin targets both species [ 259 ] and inhibits amyloid-β fibrillization both in vitro [ 263 ] and in vivo [ 259 , 264 ], supporting the peripheral sink hypothesis. This strategy is based on the idea that amyloid-β in the brain and peripheral are in equilibrium and that reducing amyloid-β in the periphery can lead to a reduction of amyloid-β in the brain through passive diffusion down a concentration gradient [ 265 , 266 ].…”

“…In addition to immunotherapy, non-immune approaches, such as peripheral amyloid-β-binding agents (e.g., gelsolin, GM1, sRAGE, sLRP fragments) [ 215 , 335 ], blood cells, and protein [ 248 , 265 ], have also made significant progress in disease prevention.…”

Virtual Screening of Human Serum Albumin Mutants to Optimize the Search for its Forms that Increase Affinity to Amyloid-Β Peptide

“…Other promising direction for development of new therapeutic and preventive approaches for AD is search for HSA modifications increasing its affinity to Aβ. For example, it was shown, that the set of HSA Domain II mutants is characterized by high affinity to Aβ [27]. At the same time, mutant forms are potentially able of shifting the balance between the CNS and peripheral blood flow more efficiently than the wild type enhancing the Aβ clearance from the brain of AD patients.…”

Effect of L-thyroxine, a Human Serum Albumin Natural Ligand, on the Kinetics of β-amyloid Peptide Fibril Formation

“…Для спорадических форм БА характерны повышение продукции и снижение скорости выведения β-амилоидного пептида (Aβ). В ряде исследований в качестве перспективной мишени для разработки новых подходов к терапии и профилактике БА рассматривается человеческий сывороточный альбумин (ЧСА), играющий роль депо Aβ в периферическом кровотоке [5,11]. Усиление взаимодействия ЧСА с Aβ должно способствовать сдвигу равновесия между периферическим кровотоком и центральной нервной системой в сторону выведения Aβ.…”