Switch‐peptides as folding precursors in self‐assembling peptides and amyloid fibrillogenesis

Abstract

The study of conformational transitions of peptides has obtained considerable attention recently because of their importance as a molecular key event in a variety of degenerative diseases. However, the study of peptide selfassembly into β‐sheets and amyloid β (Aβ) fibrils is strongly hampered by their difficult synthetic access and low solubility. We have recently developed a new concept termed “switch‐peptides” that allows the controlled onset of polypeptide folding and misfolding at physiologic conditions. As a major feature, the folding process is initiated by chemically or enzyme triggered O,N‐acyl migration in flexible and soluble folding precursors containing Ser‐ or Thr‐derived switch (S)‐elements. The elaborated methodologies are exemplified for the in situ conversion of NPY‐ and Cyclosporine A‐derived prodrugs, as well as for the onset and reversal of α and β conformational transitions in Aβ peptides. In combining orthogonally addressable switch‐elements, the consecutive switching on of S‐elements gives new insights into the role of individual peptide segments (“hot spots”) in early processes of polypeptide self‐assembly and fibrillogenesis. Finally, the well‐known secondary structure disrupting effect of pseudoprolines (ΨPro) is explored for its use as a building block (S‐element) in switch‐peptides. To this end, synthetic strategies are described, allowing for the preparation of Ψ Pro‐containing folding precursors, exhibiting flexible random‐coil conformations devoid of fibril forming propensity. The onset of β‐sheet and fibril formation by restoring the native peptide chain in a single step classify Ψ Pro‐units as the most powerful tool for inhibiting peptide self‐assembly, and complement the present methodologies of the switch‐concept for the study of fibrillogenesis. © 2007 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 88: 239–252, 2007. This article was originally published online as an accepted preprint. The ‘Published Online’ date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

Systemic Delivery of Tumor-Targeted Bax-Derived Membrane-Active Peptides for the Treatment of Melanoma Tumors in a Humanized SCID Mouse Model

“…To overcome this limitation, we utilized the residue serine118, which is located in the center of the active sequence, to design a depsipeptic derivative of cgg-Poro2 (Figure 2). The displacement of the peptidic chain from the a amino group to the hydroxyl of a serine side chain was proposed simultaneously by the groups of Kiso 45 and Mutter 46 to handle the synthesis of aggregating sequences. The O-acylated derivative of the peptide may undergo an O-N acyl shift in neutral or basic conditions to yield the desired linear peptide sequence.…”

Chemical Synthesis and Expression of the HIV‐1 Rev Protein

“…An important aspect of our synthesis is the use of the one-pot approach to include the desulfurization step; this reduces the number of purification steps and significantly increases the synthesis yield. Having these synthesis tools in hand, we plan to study the effect of post-translational modifications [54][55][56] on the function and structure of the Rev protein, along with introducing chemical switches [57,58] to control Rev folding and self-assembly, to better understand these processes on the function of Rev protein. [4,53,59] …”

Switch‐Peptides: Design and Characterization of Controllable Super‐Amyloid‐Forming Host–Guest Peptides as Tools for Identifying Anti‐Amyloid Agents

“…Previously, we [5][6][7][8] and others [9][10][11][12] have shown that various steps along the amyloid formation pathway, including peptide/ protein misfolding, self-assembly, and amyloid formation and disassembly, can be triggered in a highly controllable manner through the incorporation of molecular switches into the amyloid-forming polypeptides, based on in situ intramolecular O! N acyl migration.…”

“…N acyl migration. [5][6][7][8][9][10][11][12][13][14][15][16] However, because of the special synthetic and purification skills required to prepare the full-length Ab switch-peptides, such peptides are not suitable for use in highthroughput screening assays. Therefore, the development of reliable model systems that are readily accessible and adaptable to automated HTS is of particular interest to understanding the mechanism of amyloid formation and facilitating the discovery of aggregation inhibitors of Ab and other amyloid-forming proteins.…”

“…Herein, we describe the preparation and characterization of affordable and synthetically accessible switch-peptides [5][6][7][8] as model systems for understanding the molecular and structural basis of amyloid formation and to identify small-molecule inhibitors of Ab aggregation and toxicity. These model systems are based on a host-guest system where the hydrophobic core of Ab, which comprises residues 14-24 (HQKLVFFAEDV), is flanked by two b-sheet-promoting (Leu-Ser) n [18] oligomers as host sequences.…”