Synthesis and characterization of 5,7-dihydroxyflavanone derivatives as novel protein tyrosine phosphatase 1B inhibitors

A series of 5,7-dihydroxyflavanone derivatives were synthesized and identified as reversible and competitive protein tyrosine phosphatase (PTP) 1B inhibitors with IC₅₀ values in the micromolar range. Compound 4k had the most potent in vitro inhibition activity against PTP1B (IC₅₀ = 2.37?±?0.37 μM) and the greatest selectivity (3.7-fold) for PTP1B relative to T-cell protein tyrosine phosphatase. Cell-based studies revealed that 4k was membrane-permeable and enhanced insulin receptor tyrosine phosphorylation in CHO/hIR cells.     

His22 of TLXI plays a critical role in the inhibition of glycoside hydrolase family 11 xylanases

Recently, a novel wheat thaumatin-like protein, TLXI, which inhibits microbial glycoside hydrolase family (GH) 11 xylanases has been identified. It is the first xylanase inhibitor that exerts its inhibition in a non-competitive way. In the present study we gained insight into the interaction between TLXI and xylanases via combined molecular modeling and mutagenic approaches. More specifically, site-specific mutation of His22, situated on a loop which distinguishes TLXI from other, non-inhibiting, thaumatin-like proteins, and subsequent expression of the mutant in Pichia pastoris resulted in a protein lacking inhibition capacity. The mutant protein was unable to form a complex with GH11 xylanases. Based on these findings, the interaction of TLXI with GH11 xylanases is discussed.     

Circulating tumor cells: detection,molecular profiling and future prospects

Disseminated malignancy is responsible for the vast majority of cancer-related deaths. During this process, circulating tumor cells (CTC) are generated, spread from the primary tumor, colonize distant organs and lead to overt metastatic disease. CTC are essential for establishing metastasis; however, they are not sufficient as this process is highly inefficient and most will fail to grow in target sites. Several CTC die during migration while others remain dormant for several years and very few grow into macrometastases. CTC have been well documented in the bloodstream of cancer patients; however, the clinical relevance of this detection is still the subject of controversies and their biology is poorly understood. Indeed, available markers fail to distinguish between subgroups of CTC, and several current methods lack sensitivity, specificity or reproducibility in CTC characterization and detection. The advent of more precise technologies is renewing the interest in CTC biology. We will review herein recent findings on CTC biology, on the role of host–tumor interactions in CTC shedding and implantation, available methods of CTC detection and future perspectives for the molecular characterization of the CTC subset(s) responsible for the development of metastasis. Ultimately, understanding CTC biology and host–tumor ‘complementarities’ will help define metastasis-related biomarkers providing formidable and tailored novel therapeutic targets.     

Role for protein–protein interaction databases in human genetics

Proteomics and the study of protein–protein interactions are becoming increasingly important in our effort to understand human diseases on a system-wide level. Thanks to the development and curation of protein-interaction databases, up-to-date information on these interaction networks is accessible and publicly available to the scientific community. As our knowledge of protein–protein interactions increases, it is important to give thought to the different ways that these resources can impact biomedical research. In this article, we highlight the importance of protein–protein interactions in human genetics and genetic epidemiology. Since protein–protein interactions demonstrate one of the strongest functional relationships between genes, combining genomic data with available proteomic data may provide us with a more in-depth understanding of common human diseases. In this review, we will discuss some of the fundamentals of protein interactions, the databases that are publicly available and how information from these databases can be used to facilitate genome-wide genetic studies.     

Systemizing the structures and structuring the system

This Keystone symposium, entitled ‘Biomolecular Interactions and Networks: function and disease’, was held in Quebec City, Canada, 7–12 March 2010. The conference was distinctive in that it bridged two fields that may be perceived as having little in common: structural and systems biology. However, the growth in structural and omics data brings these two fields closer and closer. Indeed, in two sections of this article we cover talks on systematic analyses of protein structures, as well as systems level approaches that incorporate structural information. In two other sections, we report studies that aim at charting and analyzing cellular systems, and finally we discuss talks that pointed to the issue of promiscuity in biological networks.     

Tsetse flies,trypanosomes, humans and animals: what is proteomics revealing about their crosstalks?

Human and animal African trypanosomoses, or sleeping sickness and Nagana, are neglected vector-borne parasitic diseases caused by protozoa belonging to the Trypanosoma genus. Advances in proteomics offer new tools to better understand host–vector–parasite crosstalks occurring during the complex parasitic developmental cycle, and to determine the outcome of both transmission and infection. In this review, we summarize proteomics studies performed on African trypanosomes and on the interactions with their vector and mammalian hosts. We discuss the contributions and pitfalls of using diverse proteomics tools, and argue about the interest of pathogenoproteomics, both to generate advances in basic research on the best knowledge and understanding of host–vector–pathogen interactions, and to lead to the concrete development of new tools to improve diagnosis and treatment management of trypanosomoses in the near future.     

Emerging liquid chromatography–mass spectrometry technologies improving dried blood spot analysis

Dried blood spots (DBS), a micro blood sampling technique, has recently gained interest in drug discovery and development due to its inherent advantages over the conventional whole blood, plasma or serum sample collection. Since the regulatory authorities have agreed to the use of blood as an acceptable biological matrix for drug exposure measurements, its applications have been extended not only to therapeutic drug monitoring but also to toxicokinetic and pharmacokinetic studies. The pharmaceutical industry is keen to promote DBS as a prominent tool in bioanalytical applications due to the financial, ethical and organizational issues involved in clinical trials. This could be accomplished due to the latest advances in modern analytical technology, particularly liquid chromatography–mass spectrometry. The present review discusses some of the emerging liquid chromatography–mass spectrometry technologies in improving DBS analysis for its innovative applications in the development of new drugs.     

Proteomes of pathogenic Escherichia coli/Shigella group surveyed in their host environments

Proteomic studies on Shigella dysenteriae, Shigella flexneri, enterohemorrhagic Escherichia coli and uropathogenic E. coli (UPEC) are reviewed. UPEC causes infections in the urogenital tract, whereas the other species colonize and, to varying degrees, invade the intestinal tract. Type III secretion systems used to breach the mucosal barrier by the intestinal pathogens revealed distinct expression patterns in different host environments. Dynamic adaptations to changes in nutrient availability and oxygen were observed, including increased reliance on anaerobic respiration and mixed acid fermentation in vivo. Utilization of carbon and nitrogen resources by the bacteria varied considerably depending on the host model investigated. Shigellae and UPEC adapted to metal ion sequestration in the mammalian host by enhancing expression of various receptors and transporters for iron and zinc. This appears to reflect the preferred intracellular life stage of Shigella spp. and responses of UPEC to high levels of lipocalin and lactotransferrin in the urinary tract.     

Clinical and Biochemical Manifestations and Molecular Characterization of the Mutation HPRT Jerusalem

A novel point mutation (I137T) was identified in the hypoxanthine‐guanine phosphoribosyltransferase (HPRT) encoding gene, in a patient with partial deficiency of the enzyme. The mutation, ATT to ACT (substitution of isoleucine to threonine), occurred at codon 137, which is within the region encoding the binding site for 5‐phosphoribosyl‐1‐pyrophosphate (PRPP). The mutation caused decreased affinity for PRPP, manifested clinically as a Lesch–Nyhan variant (excessive purine production and delayed acquisition of language skills). The partial HPRT deficiency could be detected only by measuring HPRT activity in intact fibroblasts (uptake of hypoxanthine into nucleotides).     

Nucleoside Modification and Concerted Mutagenesis of the Human A3 Adenosine Receptor to Probe Interactions Between the 2-Position of Adenosine Analogs and Gln167 in the Second Extracellular Loop

Residues of the second extracellular loop are believed to be important for ligand recognition in adenosine receptors. Molecular modeling studies have suggested that one such residue, Gln ¹⁶⁷ of the human A ³ receptor, is in proximity to the C2 moiety of some adenosine analogs when bound. Here this putative interaction was systematically explored using a neoceptor strategy, i.e., by site-directed mutagenesis and examination of the affinities of nucleosides modified to have complementary functionality. Gln ¹⁶⁷ was mutated to Ala, Glu, and Arg, while the 2-position of several adenosine analogs was substituted with amine or carboxylic acid groups. All compounds tested lost affinity to the mutant receptors in comparison to the wild type. However, comparing affinities among the mutant receptors, several compounds bearing charge at the 2-position demonstrated preferential affinity for the mutant receptor bearing a residue of complementary charge. 13, with a positively-charged C2 moiety, displayed an 8.5-fold increase in affinity at the Q167E mutant receptor versus the Q167R mutant receptor. Preferential affinity for specific mutant receptors was also observed for 8 and 12. The data suggests that a direct contact is made between the C2 substituent of some charged ligands and the mutant receptor bearing the opposite charge at position 167.