[Show abstract][Hide abstract] ABSTRACT: Insufficient pancreatic β-cell mass or function results in diabetes mellitus. While significant progress has been made in regulating insulin secretion from β-cells in diabetic patients, no pharmacological agents have been described that increase β-cell replication in humans. Here we report aminopyrazine compounds that stimulate robust β-cell proliferation in adult primary islets, most likely as a result of combined inhibition of DYRK1A and GSK3B. Aminopyrazine-treated human islets retain functionality in vitro and after transplantation into diabetic mice. Oral dosing of these compounds in diabetic mice induces β-cell proliferation, increases β-cell mass and insulin content, and improves glycaemic control. Biochemical, genetic and cell biology data point to Dyrk1a as the key molecular target. This study supports the feasibility of treating diabetes with an oral therapy to restore β-cell mass, and highlights a tractable pathway for future drug discovery efforts.
[Show abstract][Hide abstract] ABSTRACT: Bovine antibody BLV1H12 possesses a unique “stalk–knob” architecture in its ultralong heavy chain CDR3, allowing substitutions of the “knob” domain with protein agonists to generate functional antibody chimeras. We have generated a humanized glucagon-like peptide-1 (GLP-1) receptor agonist antibody by first introducing a coiled-coil “stalk” into CDR3H of the antibody herceptin. Exendin-4 (Ex-4), a GLP-1 receptor agonist, was then fused to the engineered stalk with flexible linkers, and a Factor Xa cleavage site was inserted immediately in front of Ex-4 to allow release of the N-terminus of the fused peptide. The resulting clipped herceptin–Ex-4 fusion protein is more potent in vitro in activating GLP-1 receptors than the Ex-4 peptide. The clipped herceptin–Ex-4 has an extended plasma half-life of approximately four days and sustained control of blood glucose levels for more than a week in mice. This work provides a novel approach to the development of human or humanized agonist antibodies as therapeutics.
[Show abstract][Hide abstract] ABSTRACT: We report the engineering of zinc-finger-like motifs containing the unnatural amino acid (2,2'-bipyridin-5-yl)alanine (Bpy-Ala). A phage-display library was constructed in which five residues in the N-terminal finger of zif268 were randomized to include both canonical amino acids and Bpy-Ala. Panning of this library against a nine-base-pair DNA binding site identified several Bpy-Ala-containing functional Zif268 mutants. These mutants bind the Zif268 recognition site with affinities comparable to that of the wild-type protein. Further characterization indicated that the mutant fingers bind low-spin Fe(II) rather than Zn(II) . This work demonstrates that an expanded genetic code can lead to new metal ion binding motifs that can serve as structural, catalytic, or regulatory elements in proteins.
[Show abstract][Hide abstract] ABSTRACT: Retinal pigment epithelial (RPE) cells form a monolayer adjacent to the retina and play a critical role in the visual light cycle. Degeneration of this layer results in vision loss, causing retinal disorders such as age-related macular degeneration. Cell transplant therapies exist to restore vision loss; however, risks associated with and an inadequate supply of donor cells have limited their therapeutic success. The identification of factors that proliferate RPE cells ex vivo could provide a renewable source of cells for the treatment of such disorders. We show that a small molecule (WS3) can reversibly proliferate primary RPE cells isolated from fetal and adult human donors. Following withdrawal of WS3, RPE cells differentiate into a functional monolayer, as exhibited by their expression of mature RPE genes and phagocytosis of photoreceptor outer segments. Furthermore, chemically expanded RPE cells preserve vision when transplanted into dystrophic Royal College of Surgeons (RCS) rats, a well-established model of retinal degeneration.
ACS Chemical Biology 04/2013; 8(7). DOI:10.1021/cb4001712 · 5.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The identification of factors that promote β cell proliferation could ultimately move type 1 diabetes treatment away from insulin injection therapy and towards 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 (EBP)-1 and the IκB kinase (IKK) pathway in the mechanism of action of WS6.
Journal of the American Chemical Society 01/2013; 135(5). DOI:10.1021/ja309304m · 12.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Here we report the design and evaluation of a bifunctional, small molecule switch that induces a targeted immune response against tumors in vivo. A high affinity ligand for prostate specific membrane antigen (PSMA) was conjugated to a hapten that binds dinitrophenyl (DNP)-specific antibodies. When introduced into hu-PBL-NOD/SCID mice previously immunized with a KLH-DNP immunogen, this conjugate induced a targeted antibody-dependent cellular cytotoxicity (ADCC) response to PSMA-expressing tumor cells in a mouse xenograft model. The ability to create a small molecule inducible antibody response against self-antigens using endogenous non-autoreactive antibodies may provide advantages over the autologous immune response generated by conventional vaccines in certain therapeutic settings.
ACS Chemical Biology 09/2011; 6(11):1223-31. DOI:10.1021/cb200222s · 5.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Epstein-Barr virus-induced gene 2 (EBI2, also known as GPR183) is a G-protein-coupled receptor that is required for humoral immune responses; polymorphisms in the receptor have been associated with inflammatory autoimmune diseases. The natural ligand for EBI2 has been unknown. Here we describe the identification of 7α,25-dihydroxycholesterol (also called 7α,25-OHC or 5-cholesten-3β,7α,25-triol) as a potent and selective agonist of EBI2. Functional activation of human EBI2 by 7α,25-OHC and closely related oxysterols was verified by monitoring second messenger readouts and saturable, high-affinity radioligand binding. Furthermore, we find that 7α,25-OHC and closely related oxysterols act as chemoattractants for immune cells expressing EBI2 by directing cell migration in vitro and in vivo. A critical enzyme required for the generation of 7α,25-OHC is cholesterol 25-hydroxylase (CH25H). Similar to EBI2 receptor knockout mice, mice deficient in CH25H fail to position activated B cells within the spleen to the outer follicle and mount a reduced plasma cell response after an immune challenge. This demonstrates that CH25H generates EBI2 biological activity in vivo and indicates that the EBI2-oxysterol signalling pathway has an important role in the adaptive immune response.
[Show abstract][Hide abstract] ABSTRACT: New tools are needed to study the intracellular pathogen Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), to facilitate new drug discovery and vaccine development. We have developed methodology to genetically incorporate unnatural amino acids into proteins in Mycobacterium smegmatis, BCG and Mtb, grown both extracellularly in culture and inside host cells. Orthogonal mutant tRNATyr/tyrosyl-tRNA synthetase pairs derived from Methanococcus jannaschii and evolved in Escherichia coli incorporate a variety of unnatural amino acids (including photocrosslinking, chemically reactive, heavy atom containing, and immunogenic amino acids) into proteins in response to the amber nonsense codon. By taking advantage of the fidelity and suppression efficiency of the MjtRNA/pIpaRS pair in mycobacteria, we are also able to use p-iodophenylalanine to induce the expression of proteins in mycobacteria both extracellularly in culture and inside of mammalian host cells. This provides a new approach to regulate the expression of reporter genes or mycobacteria endogenous genes of interest. The establishment of the unnatural amino acid expression system in Mtb, an intracellular pathogen, should facilitate studies of TB biology and vaccine development.
PLoS ONE 02/2010; 5(2):e9354. DOI:10.1371/journal.pone.0009354 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: (Figure Presented) Olefin-containing amino acids have been genetically introduced into proteins in Saccharomyces cerevisiae by orthogonal tRNA/aminoacyl-tRNA synthetase pairs. These nonnatural amino acids can be used for selective protein modification through olefin metathesis reactions.