Protein mimetic amyloid inhibitor potently abrogates cancer-associated mutant p53 aggregation and restores tumor suppressor function.

Missense mutations in p53 are severely deleterious and occur in over 50% of all human cancers. The majority of these mutations are located in the inherently unstable DNA-binding domain (DBD), many of which destabilize the domain further and expose its aggregation-prone hydrophobic core, prompting self-assembly of mutant p53 into inactive cytosolic amyloid-like aggregates. Screening an oligopyridylamide library, previously shown to inhibit amyloid formation associated with Alzheimer's disease and type II diabetes, identified a tripyridylamide, ADH-6, that abrogates self-assembly of the aggregation-nucleating subdomain of mutant p53 DBD. Moreover, ADH-6 targets and dissociates mutant p53 aggregates in human cancer cells, which restores p53's transcriptional activity, leading to cell cycle arrest and apoptosis. Notably, ADH-6 treatment effectively shrinks xenografts harboring mutant p53, while exhibiting no toxicity to healthy tissue, thereby substantially prolonging survival. This study demonstrates the successful application of a bona fide small-molecule amyloid inhibitor as a potent anticancer agent.

Mummichog (Fundulus heteroclitus) are less sensitive to 17α-ethinylestradiol (EE2) than other common model teleosts: A comparative review of reproductive effects.

The environmental estrogen 17α-ethinylestradiol (EE2) will depress or completely inhibit egg production in many common model teleosts at low concentrations (≤0.5 ng/L; Runnalls et al., 2015). This inhibition is not seen in the estuarine killifish, or mummichog (Fundulus heteroclitus), even when exposed to 100 ng/L EE2. This relative insensitivity to EE2 exposure indicates species-specific mechanisms for compensating for exogenous estrogenic exposure. This review compares various reproductive responses elicited by EE2 in mummichog to other common model teleosts, such as zebrafish (Danio rerio) and fathead minnow (Pimephales promelas), identifying key endpoints where mummichog differ from other studied fish. For example, EE2 accumulates primarily in the liver/gall bladder of mummichog, which is different than zebrafish and fathead minnow in which accumulation is predominantly in the carcass. Despite causing species-specific differences in fecundity, EE2 has been shown to consistently induce hepatic vitellogenin in males and cause feminization/sex reversal during gonadal differentiation in larval mummichog, similar to other species. In addition, while gonadal steroidogenesis and plasma steroid levels respond to exogenous EE2, it is generally at higher concentrations than observed in other species. In mummichog, production of 17ß-estradiol (E2) by full grown ovarian follicles remains high; unlike other teleost models where E2 synthesis decreases as 17α,20ß-dihydroxy-4-prenen-3-on levels increase to induce oocyte maturation. New evidence in mummichog indicates some dissimilarity in gonadal steroidogenic gene expression responses compared to gene expression responses in zebrafish and fathead minnow exposed to EE2. The role of ovarian physiology continues to warrant investigation regarding the tolerance of mummichog to exogenous EE2 exposure. Here we present a comprehensive review, highlighting key biological differences in response to EE2 exposure between mummichog and other commonly used model teleosts.

Foldamer-Mediated Structural Rearrangement Attenuates Aß Oligomerization and Cytotoxicity.

The conversion of the native random coil amyloid beta (Aß) into amyloid fibers is thought to be a key event in the progression of Alzheimer's disease (AD). A significant body of evidence suggests that the highly dynamic Aß oligomers are the main causal agent associated with the onset of AD. Among many potential therapeutic approaches, one is the modulation of Aß conformation into off-pathway structures to avoid the formation of the putative neurotoxic Aß oligomers. A library of oligoquinolines was screened to identify antagonists of Aß oligomerization, amyloid formation, and cytotoxicity. A dianionic tetraquinoline, denoted as 5, was one of the most potent antagonists of Aß fibrillation. Biophysical assays including amyloid kinetics, dot blot, ELISA, and TEM show that 5 effectively inhibits both Aß oligomerization and fibrillation. The antagonist activity of 5 toward Aß aggregation diminishes with sequence and positional changes in the surface functionalities. 5 binds to the central discordant α-helical region and induces a unique α-helical conformation in Aß. Interestingly, 5 adjusts its conformation to optimize the antagonist activity against Aß. 5 effectively rescues neuroblastoma cells from Aß-mediated cytotoxicity and antagonizes fibrillation and cytotoxicity pathways of secondary nucleation induced by seeding. 5 is also equally effective in inhibiting preformed oligomer-mediated processes. Collectively, 5 induces strong secondary structure in Aß and inhibits its functions including oligomerization, fibrillation, and cytotoxicity.

Cytotoxicity of prion protein-derived cell-penetrating peptides is modulated by pH but independent of amyloid formation.

Prion diseases are associated with conversion of cellular prion protein (PrPC) into an abnormally folded and infectious scrapie isoform (PrPSc). We previously showed that peptides derived from the unprocessed N-termini of mouse and bovine prion proteins, mPrP1-28 and bPrP1-30, function as cell-penetrating peptides (CPPs), and destabilize model membrane systems, which could explain the infectivity and toxicity of prion diseases. However, subsequent studies revealed that treatment with mPrP1-28 or bPrP1-30 significantly reduce PrPSc levels in prion-infected cells. To explain these seemingly contradictory results, we correlated the aggregation, membrane perturbation and cytotoxicity of the peptides with their cellular uptake and intracellular localization. Although the peptides have a similar primary sequence, mPrP1-28 is amyloidogenic, whereas bPrP1-30 forms smaller oligomeric or non-fibrillar aggregates. Surprisingly, bPrP1-30 induces much higher cytotoxicity than mPrP1-28, indicating that amyloid formation and toxicity are independent. The toxicity is correlated with prolonged residence at the plasma membrane and membrane perturbation. Both ordered aggregation and toxicity of the peptides are inhibited by low pH. Under non-toxic conditions, the peptides are internalized by lipid-raft dependent macropinocytosis and localize to acidic lysosomal compartments. Our results shed light on the antiprion mechanism of the prion protein-derived CPPs and identify a potential site for PrPSc formation.