Natural Product Inhibitors of Hsp90: Potential Leads for Drug Discovery

This thesis represents a discussion of the advancements made in the area of Hsp90 therapeutics, and the development of a novel Hsp90 inhibitory scaffold of natural product origin. Through utilization of a recently reported firefly luciferase assay, our group was able to conduct a high-throughput screen that resulted in the identification of several Hsp90 inhibitors that contained a 1,4-naphthoquinone scaffold. From this, a library of naphthoquinones was synthesized. To further probe structure-activity relationships, a comparative molecular field analysis was performed, and a second generation of 1,4-naphthoquinones was developed. Although the results were promising, concerns arose regarding the nature of the scaffold itself. It is well documented that quinone-based scaffolds exert cytotoxicity through Michael reaction chemistry or redox activity. To circumvent this concern, the core scaffold was changed from a 1,4-naphthoquinone core to a structurally similar flavone. This was completed through utilization of molecular modeling and Western Blot analyses

Synthesis and Preliminary Evaluation Steroidal AntiestrogenGeldanamycin Conjugates

Three novel steroidal antiestrogen-geldanamycin conjugates were prepared using a convergent strategy. The antiestrogenic component utilized the 11β-(4-functionalized-oxyphenyl) estradiol scaffold, while the geldanamycin component was derived by replacement of the 17-methoxy group with an appropriately functionalized amine. Ligation was achieved in high yield using azide alkyne cyclization reactions. Evaluation of the products against two breast cancer cell lines indicated that the conjugates retained significant antiproliferative activity

Structure-Activity Relationships in Toll-like Receptor-2 agonistic Diacylthioglycerol Lipopeptides

The N-termini of bacterial lipoproteins are acylated with a (S)-(2,3-bisacyloxypropyl)cysteinyl residue. Lipopeptides derived from lipoproteins activate innate immune responses by engaging Toll-like receptor 2 (TLR2), and are highly immunostimulatory and yet without apparent toxicity in animal models. The lipopeptides may therefore be useful as potential immunotherapeutic agents. Previous structure-activity relationships in such lipopeptides have largely been obtained using murine cells and it is now clear that significant species-specific differences exist between human and murine TLR responses. We have examined in detail the role of the highly conserved Cys residue as well as the geometry and stereochemistry of the Cys-Ser dipeptide unit. (R)-diacylthioglycerol analogues are maximally active in reporter gene assays using human TLR2. The Cys-Ser dipeptide unit represents the minimal part-structure, but its stereochemistry was found not to be a critical determinant of activity. The thioether bridge between the diacyl and dipeptide units is crucial, and replacement by an oxoether bridge results in a dramatic decrease in activity

Identification of Redox and Glucose-Dependent Txnip Protein Interactions

Thioredoxin-interacting protein (Txnip) acts as a negative regulator of thioredoxin function and is a critical modulator of several diseases including, but not limited to, diabetes, ischemia-reperfusion cardiac injury, and carcinogenesis. Therefore, Txnip has become an attractive therapeutic target to alleviate disease pathologies. Although Txnip has been implicated with numerous cellular processes such as proliferation, fatty acid and glucose metabolism, inflammation, and apoptosis, the molecular mechanisms underlying these processes are largely unknown. The objective of these studies was to identify Txnip interacting proteins using the proximity-based labeling method, BioID, to understand differential regulation of pleiotropic Txnip cellular functions. The BioID transgene fused to Txnip expressed in HEK293 identified 31 interacting proteins. Many protein interactions were redox-dependent and were disrupted through mutation of a previously described reactive cysteine (C247S). Furthermore, we demonstrate that this model can be used to identify dynamic Txnip interactions due to known physiological regulators such as hyperglycemia. These data identify novel Txnip protein interactions and demonstrate dynamic interactions dependent on redox and glucose perturbations, providing clarification to the pleiotropic cellular functions of Txnip

Nonlinear spectral image fusion

In this paper we demonstrate that the framework of nonlinear spectral decompositions based on total variation (TV) regularization is very well suited for image fusion as well as more general image manipulation tasks. The well-localized and edge-preserving spectral TV decomposition allows to select frequencies of a certain image to transfer particular features, such as wrinkles in a face, from one image to another. We illustrate the effectiveness of the proposed approach in several numerical experiments, including a comparison to the competing techniques of Poisson image editing, linear osmosis, wavelet fusion and Laplacian pyramid fusion. We conclude that the proposed spectral TV image decomposition framework is a valuable tool for semi- and fully-automatic image editing and fusion

A review of applying second-generation wavelets for noise removal from remote sensing data.

The processing of remotely sensed data includes compression, noise reduction, classification, feature extraction, change detection and any improvement associated with the problems at hand. In the literature, wavelet methods have been widely used for analysing remote sensing images and signals. The second-generation of wavelets, which is designed based on a method called the lifting scheme, is almost a new version of wavelets, and its application in the remote sensing field is fresh. Although first-generation wavelets have been proven to offer effective techniques for processing remotely sensed data, second-generation wavelets are more efficient in some respects, as will be discussed later. The aim of this review paper is to examine all existing studies in the literature related to applying second-generation wavelets for denoising remote sensing data. However, to make a better understanding of the application of wavelet-based denoising methods for remote sensing data, some studies that apply first-generation wavelets are also presented. In the part of hyperspectral data, there is a focus on noise removal from vegetation spectrum

Modulation of Heat Shock Transcription Factor 1 as a Therapeutic Target for Small Molecule Intervention in Neurodegenerative Disease

A yeast-based small molecule screen identifies a novel activator of human HSF1 and protein chaperone expression and which appears to alleviate the toxicity of protein misfolding diseases

Probing Molecular Mechanisms of the Hsp90 Chaperone: Biophysical Modeling Identifies Key Regulators of Functional Dynamics

Deciphering functional mechanisms of the Hsp90 chaperone machinery is an important objective in cancer biology aiming to facilitate discovery of targeted anti-cancer therapies. Despite significant advances in understanding structure and function of molecular chaperones, organizing molecular principles that control the relationship between conformational diversity and functional mechanisms of the Hsp90 activity lack a sufficient quantitative characterization. We combined molecular dynamics simulations, principal component analysis, the energy landscape model and structure-functional analysis of Hsp90 regulatory interactions to systematically investigate functional dynamics of the molecular chaperone. This approach has identified a network of conserved regions common to the Hsp90 chaperones that could play a universal role in coordinating functional dynamics, principal collective motions and allosteric signaling of Hsp90. We have found that these functional motifs may be utilized by the molecular chaperone machinery to act collectively as central regulators of Hsp90 dynamics and activity, including the inter-domain communications, control of ATP hydrolysis, and protein client binding. These findings have provided support to a long-standing assertion that allosteric regulation and catalysis may have emerged via common evolutionary routes. The interaction networks regulating functional motions of Hsp90 may be determined by the inherent structural architecture of the molecular chaperone. At the same time, the thermodynamics-based “conformational selection” of functional states is likely to be activated based on the nature of the binding partner. This mechanistic model of Hsp90 dynamics and function is consistent with the notion that allosteric networks orchestrating cooperative protein motions can be formed by evolutionary conserved and sparsely connected residue clusters. Hence, allosteric signaling through a small network of distantly connected residue clusters may be a rather general functional requirement encoded across molecular chaperones. The obtained insights may be useful in guiding discovery of allosteric Hsp90 inhibitors targeting protein interfaces with co-chaperones and protein binding clients

Aducanumab: the high costs of false hope

As our collective biomedical knowledge increases, we find ourselves increasingly reliant on the expert consensus of medical specialists in judging the thousands of new medical advancements made each year. We trust that our medical and pharmaceutical regulators will enlist those experts most qualified to judge the efficacy of increasingly complex medical therapies and render appropriate judgement in turn. We similarly trust that the interests and motivations of the medical community and regulators are aligned – in that both should want to protect patients from potentially harmful therapies. The recent United States Food and Drug Administration (FDA) approval of aducanumab (trade name: Aduhelm) serves as a reminder that these assumptions should not go unchallenged. Hailed initially as a breakthrough treatment for Alzheimer’s disease, subsequent randomised controlled trials of aducanumab disappointed all parties involved when they failed to clearly demonstrate clinical efficacy. Despite this, Biogen (aducanumab’s developer) was ultimately still able to bring the drug to market in the United States. Thanks to an increasingly complex and layered drug approval process, there are now avenues by which pharmaceuticals may be brought to market while clinical efficacy is either still in question or altogether lacking. Crucially, it is not clear whether the regulators we trust are making sincere efforts to safeguard patients against their misuse. </p

Parallel Implementation of Wavelet-based Image Denoising on Programmable PC-grade Graphics Hardware

The Discrete Wavelet Transform (DWT) has been extensively used for image compression and denoising in the areas of image processing and computer vision. However, the intensive computation of DWT due to its multilevel data decomposition and reconstruction brings a bottleneck that drastically reduces its performance and implementations for real-time applications when processing large size digital images and/or high-definition videos. Although various software accelerated solutions, such as the lifting scheme, have been proposed and achieved a higher performance in general, the pure software accelerated DWT still struggle to cope with the demands from real-time and interactive applications. With the growing capacity and popularity of graphics hardware, personal computers (PCs) nowadays are often equipped with programmable Graphics Processing Units (GPUs) for graphics acceleration. The GPU offers a cost effective parallel data processing mechanism for operations on large amount of data from applications beyond graphics, known as General-purpose Computing on GPU (GPGPU). This paper presented a GPGPU framework and parallel computing solutions for wavelet based image denoising by using off-the-shelf consumer-level programmable GPUs. This framework can be easily incorporated with different forms of DWT by customising the parameter of the wavelet kernel. Experiment results show that the framework gains applicability in data parallelism and satisfaction performance in accelerating computations for wavelet-based denoising