Tom Yao-Hsiang Wu

Synthetic small molecules that control stem cell fate

In an attempt to better understand and control the processes that regulate stem cell fate, we have set out to identify small molecules that induce neuronal differentiation in embryonic stem cells (ESCs). A high-throughput phenotypic cell-based screen of kinase-directed combinatorial libraries led to the discovery of TWS119, a 4,6-disubstituted pyrrolopyrimidine that can induce neurogenesis in murine ESCs. The target of TWS119 was shown to be glycogen synthase kinase-3β (GSK-3β) by both affinity-based and biochemical methods. This study provides evidence that GSK-3β is involved in the induction of mammalian neurogenesis in ESCs. This and such other molecules are likely to provide insights into the molecular mechanisms that control stem cell fate, and may ultimately be useful to in vivo stem cell biology and therapy.

Development and Characterization of Nonpeptidic Small Molecule Inhibitors of the XIAP/Caspase-3 Interaction

Elevated expression of inhibitor of apoptosis protein (IAP) family members in various types of cancers is thought to provide a survival advantage to these cells. Thus, antiapoptotic functions of IAPs, and their potential as novel anticancer targets have attracted considerable interest. Among the IAPs, the X chromosome-linked inhibitor of apoptosis protein (XIAP) is regarded as the most potent suppressor of mammalian apoptosis through direct binding and inhibition of caspases. A high-throughput biochemical screen of a combinatorial chemical library led to the discovery of a novel nonpeptidic small molecule that has the ability to disrupt the XIAP/caspase-3 interaction. The activity of this nonpeptidic small molecule inhibitor of the XIAP/caspase-3 interaction has been characterized both in vitro and in cells. Molecules of this type can be used to conditionally inhibit the cellular function of XIAP and may provide insights into the development of therapeutic agents that act by modulating apoptotic pathways.

Optimization of Xenon Biosensors for Detection of Protein Interactions

Hyperpolarized 129Xe NMR spectroscopy can detect the presence of specific low‐concentration biomolecular analytes by means of a xenon biosensor that consists of a water‐soluble, targeted cryptophane‐A cage that encapsulates the xenon. In this work, we use the prototypical biotinylated xenon biosensor to determine the relationship between the molecular composition of the xenon biosensor and the characteristics of protein‐bound resonances. The effects of diastereomer overlap, dipole–dipole coupling, chemical‐shift anisotropy, xenon exchange, and biosensor conformational exchange on the protein‐bound biosensor signal were assessed. It was found that an optimal protein‐bound biosensor signal can be obtained by minimizing the number of biosensor diastereomers and using a flexible linker of appropriate length. Both the line width and sensitivity of chemical shift to protein binding of the xenon biosensor were found to be inversely proportional to linker length.

Small-Molecule Inducer of β Cell Proliferation Identified by High-Throughput Screening

The identification of factors that promote β cell proliferation could ultimately move type 1 diabetes treatment away from insulin injection therapy and toward a cure. We have performed high-throughput, cell-based screens using rodent β cell lines to identify molecules that induce proliferation of β cells. Herein we report the discovery and characterization of WS6, a novel small molecule that promotes β cell proliferation in rodent and human primary islets. In the RIP-DTA mouse model of β cell ablation, WS6 normalized blood glucose and induced concomitant increases in β cell proliferation and β cell number. Affinity pulldown and kinase profiling studies implicate Erb3 binding protein-1 and the IκB kinase pathway in the mechanism of action of WS6.

Strategies for designing synthetic immune agonists

Enhancing the immune system is a validated strategy to combat infectious disease, cancer and allergy. Nevertheless, the development of immune adjuvants has been hampered by safety concerns. Agents that can stimulate the immune system often bear structural similarities with pathogen‐associated molecular patterns found in bacteria or viruses and are recognized by pattern recognition receptors (PRRs). Activation of these PRRs results in the immediate release of inflammatory cytokines, up‐regulation of co‐stimulatory molecules, and recruitment of innate immune cells. The distribution and duration of these early inflammatory events are crucial in the development of antigen‐specific adaptive immunity in the forms of antibody and/or T cells capable of searching for and destroying the infectious pathogens or cancer cells. However, systemic activation of these PRRs is often poorly tolerated. Hence, different strategies have been employed to modify or deliver immune agonists in an attempt to control the early innate receptor activation through temporal or spatial restriction. These approaches include physicochemical manipulation, covalent conjugation, formulation and conditional activation/deactivation. This review will describe recent examples of discovery and optimization of synthetic immune agonists towards clinical application.