Cryo-EM structure and polymorphic maturation of a viral transduction enhancing amyloid fibril

Abstract

Amyloid fibrils have emerged as innovative tools to enhance the transduction efficiency of retroviral vectors in gene therapy strategies. In this study, we used cryo-electron microscopy to analyze the structure of a biotechnologically engineered peptide fibril that enhances retroviral infectivity. Our findings show that the peptide undergoes a time-dependent morphological maturation into polymorphic amyloid fibril structures. The fibrils consist of mated cross-β sheets that interact by the hydrophobic residues of the amphipathic fibril-forming peptide. The now available structural data help to explain the mechanism of retroviral infectivity enhancement, provide insights into the molecular plasticity of amyloid structures and illuminate the thermodynamic basis of their morphological maturation.

Multiscale Simulations of Self-Assembling Peptides: Surface and Core Hydrophobicity Determine Fibril Stability and Amyloid Aggregation

“…Here, the resulting aggregated fibril structure is different compared to VHDCVNITIK, where the fibrils align in a way that maximizes their contact while maintaining lysine-rich surfaces on each side. Remarkably, this aggregated fibril morphology resembles the morphologies that were extracted in Cryo-EM for a similar phenylalanine containing PNF (CKFKFQF), where individual fibrils stacked together over time to form thicker morphologies with multiple hydrophobic and polar contact modes …”

“…Remarkably, this aggregated fibril morphology resembles the morphologies that were extracted in Cryo-EM for a similar phenylalanine containing PNF (CKFKFQF), where individual fibrils stacked together over time to form thicker morphologies with multiple hydrophobic and polar contact modes. 32 Recent experiments 59 have shown evidence of disulfide bridge formation between the N-terminal cysteine residues in self-assembled fibrils. Because the disulfide bridge is a chemical bond that forms between the sulfur atoms of two cysteine residues, we are not able to observe it in our coarse-grained simulations.…”

“…In fact, it has been hypothesized that pathological and functional amyloids differ from each other in their assembly kinetics that depend on the intermolecular interactions at the given conditions. − Several decades of extensive research recognized that peptide–peptide interactions for initial amyloid formation are mainly driven by hydrophobic and electrostatic interactions. − However, comparably less is known about the fibril–fibril interactions that determine the microscopic amyloid aggregation process. Although there is no conclusive evidence yet, it is thought that certain fibril surface properties, such as hydrophobic interactions, − ion salt bridges, and polar interactions , contribute to the aggregation of fibrils into larger structures. ,− For example, fibrils with a hydrophobic surface expel water from the interface and prefer to interact with other hydrophobic fibrils. , However, fibrils with polar surface groups can form hydrogen bonds between polar amino acids displayed at the surface, which also promotes aggregation. , In the latter case, the environmental conditions, e.g., buffer salts, can suppress hydrophilic interactions in water, which then reduces fibril–fibril interactions …”

“… 24 − 27 However, comparably less is known about the fibril–fibril interactions that determine the microscopic amyloid aggregation process. Although there is no conclusive evidence yet, it is thought that certain fibril surface properties, such as hydrophobic interactions, 28 − 30 ion salt bridges, 25 and polar interactions 31 , 32 contribute to the aggregation of fibrils into larger structures. 31 , 33 − 35 For example, fibrils with a hydrophobic surface expel water from the interface and prefer to interact with other hydrophobic fibrils.…”

α-Synuclein fibrils enhance HIV-1 infection of human T cells, macrophages and microglia

“…1a). While EF-C forms brils instantaneously in solution 33,37 , Aβ40 and α-synuclein were agitated for several days, as described in the methods section. Fibrillar but not freshy dissolved Aβ40 and α-synuclein e ciently bound Thio avin T amyloid dye (Fig.…”