Reductively degradable polyester-based block copolymers prepared by facile polycondensation and ATRP: synthesis, degradation, and aqueous micellization

Well-defined reductively degradable amphiphilic block copolymers having disulfide linkages positioned repeatedly on hydrophobic chains, thus exhibiting fast degradation, were prepared by a combination of polycondensation and ATRP. The new method consists of three synthetic steps including, (1) polycondensation of commercially available diols and diacids through carbodiimide coupling or high temperature processes to synthesize degradable polyesters with disulfides labeled on the main chain at regular intervals (ssPES–OH), (2) bromination of ssPES–OH to ssPES–Br, and (3) ATRP for chain extension of ssPES–Br with water-soluble polymethacrylate, yielding ssPES-b-polymethacrylate block copolymers (ssABPs). The reductive cleavage of disulfide linkages in reducing conditions resulted in the degradation of ssPES homopolymers; their degradation rate was significantly enhanced with the increasing amounts of disulfide linkages in ssPES–OH and reducing agents. For ATRP, gel permeation chromatography and 1H-NMR results confirmed the synthesis of well-defined ssABPs and revealed that polymerizations were well controlled. Because of their amphiphilic nature, ssABPs self-assembled in water toward the formation of core/shell micelles consisting of a hydrophobic ssPES core surrounded with polymethacrylate coronas. The effects of the corona's chain length on thermal properties and micellization in water of well-defined ssABPs were examined. Moreover, reductive (or thiol-responsive) degradation of ssABP-based micelles enabled fast release of encapsulated model drugs. Cell culture experiments confirmed nontoxicity and biocompatibility of well-defined ssABPs as effect candidates for targeted delivery applications

Novel Pyrrolopyrimidine-Based α-Helix Mimetics: Cell- Permeable Inhibitors of Protein-Protein Interactions

This document is the Accepted Manuscript version of a Published Work that appeared in final form in the Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://doi.org/10.1021/ja108230s.There is considerable interest in developing nonpeptidic, small molecule α-helix mimetics to disrupt α-helix-mediated protein-protein interactions. Herein, we report the design of a novel pyrrolopyrimidine-based scaffold for such α-helix mimetics with increased conformational rigidity. We also developed a facile solid phase synthetic route, which is amenable to divergent synthesis of a large library. Using a fluorescence polarization-based assay, we identified cell permeable, dual MDMX/MDM2 inhibitors, demonstrating that the designed molecules can act as α-helix mimetics

Potential pharmacological chaperones targeting cancer-associated MCL-1 and Parkinson disease-associated α-synuclein

Pharmacological chaperones are small molecules that bind to proteins and stabilize them against thermal denaturation or proteolytic degradation, as well as assist or prevent certain protein-protein assemblies. These activities are being exploited for the development of treatments for diseases caused by protein instability and/or aberrant protein-protein interactions, such as those found in certain forms of cancers and neurodegenerative diseases. However, designing or discovering pharmacological chaperones for specific targets is challenging because of the relatively featureless protein target surfaces, the lack of suitable chemical libraries, and the shortage of efficient high-throughput screening methods. In this study, we attempted to address all these challenges by synthesizing a diverse library of small molecules that mimic protein α-helical secondary structures commonly found in protein-protein interaction surfaces. This was accompanied by establishing a facile "on-bead" high-throughput screening method that allows for rapid and efficient discovery of potential pharmacological chaperones and for identifying novel chaperones/inhibitors against a cancer-associated protein, myeloid cell leukemia 1 (MCL-1), and a Parkinson disease-associated protein, α-synuclein. Our data suggest that the compounds and methods described here will be useful tools for the development of pharmaceuticals for complex-disease targets that are traditionally deemed "undruggable.

Mechanical unloading activates FoxO3 to trigger Bnip3‐dependent cardiomyocyte atrophy

BACKGROUND: Mechanical assist device therapy has emerged recently as an important and rapidly expanding therapy in advanced heart failure, triggering in some patients a beneficial reverse remodeling response. However, mechanisms underlying this benefit are unclear. METHODS AND RESULTS: In a model of mechanical unloading of the left ventricle, we observed progressive myocyte atrophy, autophagy, and robust activation of the transcription factor FoxO3, an established regulator of catabolic processes in other cell types. Evidence for FoxO3 activation was similarly detected in unloaded failing human myocardium. To determine the role of FoxO3 activation in cardiac muscle in vivo, we engineered transgenic mice harboring a cardiomyocyte‐specific constitutively active FoxO3 mutant (caFoxO3(flox);αMHC‐Mer‐Cre‐Mer). Expression of caFoxO3 triggered dramatic and progressive loss of cardiac mass, robust increases in cardiomyocyte autophagy, declines in mitochondrial biomass and function, and early mortality. Whereas increases in cardiomyocyte apoptosis were not apparent, we detected robust increases in Bnip3 (Bcl2/adenovirus E1B 19‐kDa interacting protein 3), an established downstream target of FoxO3. To test the role of Bnip3, we crossed the caFoxO3(flox);αMHC‐Mer‐Cre‐Mer mice with Bnip3‐null animals. Remarkably, the atrophy and autophagy phenotypes were significantly blunted, yet the early mortality triggered by FoxO3 activation persisted. Rather, declines in cardiac performance were attenuated by proteasome inhibitors. Consistent with involvement of FoxO3‐driven activation of the ubiquitin‐proteasome system, we detected time‐dependent activation of the atrogenes program and sarcomere protein breakdown. CONCLUSIONS: In aggregate, these data point to FoxO3, a protein activated by mechanical unloading, as a master regulator that governs both the autophagy‐lysosomal and ubiquitin‐proteasomal pathways to orchestrate cardiac muscle atrophy

Targeted Degradation of Transcription Coactivator SRC-1 through the N-Degron Pathway

Aberrantly elevated steroid receptor coactivator-1 (SRC-1) expression and activity are strongly correlated with cancer progression and metastasis. Here we report, for the first time, the development of a proteolysis targeting chimera (PROTAC) that is composed of a selective SRC-1 binder linked to a specific ligand for UBR box, a unique class of E3 ligases recognizing N-degrons. We showed that the bifunctional molecule efficiently and selectively induced the degradation of SRC-1 in cells through the N-degron pathway. Importantly, given the ubiquitous expression of the UBR protein in most cells, PROTACs targeting the UBR box could degrade a protein of interest regardless of cell types. We also showed that the SRC-1 degrader significantly suppressed cancer cell invasion and migration in vitro and in vivo. Together, these results demonstrate that the SRC-1 degrader can be an invaluable chemical tool in the studies of SRC-1 functions. Moreover, our findings suggest PROTACs based on the N-degron pathway as a widely useful strategy to degrade disease-relevant proteins.N

A revised 1.6 Å structure of the GTPase domain of the Parkinson’s disease-associated protein LRRK2 provides insights into mechanisms

Leucine-rich repeat kinase 2 (LRRK2) is a large 286 kDa multi-domain protein whose mutation is a common cause of Parkinson’s disease (PD). One of the common sites of familial PD-associated mutations occurs at residue Arg-1441 in the GTPase domain of LRRK2. Previously, we reported that the PD-associated mutation R1441H impairs the catalytic activity of the GTPase domain thereby traps it in a persistently "on" state. More recently, we reported that the GTPase domain of LRRK2 exists in a dynamic dimer-monomer equilibrium where GTP binding shifts it to the monomeric conformation while GDP binding shifts it back to the dimeric state. We also reported that all of the PD-associated mutations at Arg-1441, including R1441H, R1441C, and R1441G, impair the nucleotide-dependent dimer-monomer conformational dynamics of the GTPase domain. However, the mechanism of this nucleotide-dependent conformational dynamics and how it is impaired by the mutations at residue Arg-1441 remained unclear. Here, we report a 1.6 Å crystal structure of the GTPase domain of LRRK2. Our structure has revealed a dynamic switch region that can be differentially regulated by GTP and GDP binding. This nucleotide-dependent regulation is impaired when residue Arg-1441 is substituted with the PD-associated mutations due to the loss of its exquisite interactions consisting of two hydrogen bonds and a π-stacking interaction at the dimer interface

Effects of Bacillus subtilis and Leuconostoc mesenteroides on the Quality Characteristics of Potato Garaetteok

To investigate the texture and cooking properties of garaetteok elaborated with potato flour, experimental products were elaborated replacing partially the rice flour, traditionally used, with nonfermented (NF) or fermented potato flour with Bacillus subtilis (BS) or Leuconostoc mesenteroides (LM) in percentages of 15% (NF15, BS15, and LM15) and 20% (NF20, BS20, and LM20). The control product (CON) was made using only rice flours. The pH of garaetteok was significantly lower in the BS and LM groups compared to CON and NF. Titratable acidity was the highest in BS20 and LM15. LM groups showed similar textural profiles to CON. The addition of potato flour to garaetteok increased the turbidity of soup (tteokguk), but the fermentation significantly lowered its turbidity. During storage for 24 h, garaetteok with fermented potato flour showed the inhibition of starch retrogradation. All scores of LM15 and LM20 were better than other potato garaetteoks and similar to those of CON with the exception of color acceptance. Consequently, garaetteok-added potato flour fermented with L. mesenteroides was the most preferable in terms of texture, cooking, and sensory characteristics

Differences between Vegetarians and Omnivores in Food Choice Motivation and Dietarian Identity

Vegetarianism is on the rise worldwide and its importance is being emphasized in various ways, such as in its sustainability, environmental, food system, and ethical aspects. The purpose of the study is to identify motivations behind food choices and dietarian identity, to investigate the perceptions about plant-based foods, and to identify differences between vegetarians and omnivores. We conducted an online survey of 245 vegetarians and 246 omnivores. There was a significant difference between vegetarians and omnivores. In food choice motivations, vegetarians scored higher in the factors of ‘ethical concern’, ‘health’, and ‘convenience and price’, while omnivores responded higher in ‘sensory appeal’ and ‘weight control’ factors. In the dietarian identity, vegetarians scored higher in the ‘complex motivation’ and ‘strictness’ factors, while on the other hand omnivores scored higher in ‘out-group regard’ and ‘public regard’ factors. Although the reasons can be different, we confirmed that both vegetarians and omnivores are positive toward plant-based foods. Our results suggest that different strategies will be needed to promote plant-based food consumption to vegetarians and to omnivores