Academic literature on the topic 'PPIs stabilisers'

AbstractDrug discovery has classically targeted the active sites of enzymes or ligand-binding sites of receptors and ion channels. In an attempt to improve selectivity of drug candidates, modulation of protein–protein interfaces (PPIs) of multiprotein complexes that mediate conformation or colocation of components of cell-regulatory pathways has become a focus of interest. However, PPIs in multiprotein systems continue to pose significant challenges, as they are generally large, flat and poor in distinguishing features, making the design of small molecule antagonists a difficult task. Nevertheless, encouragement has come from the recognition that a few amino acids – so-called hotspots – may contribute the majority of interaction-free energy. The challenges posed by protein–protein interactions have led to a wellspring of creative approaches, including proteomimetics, stapled α-helical peptides and a plethora of antibody inspired molecular designs. Here, we review a more generic approach: fragment-based drug discovery. Fragments allow novel areas of chemical space to be explored more efficiently, but the initial hits have low affinity. This means that they will not normally disrupt PPIs, unless they are tethered, an approach that has been pioneered by Wells and co-workers. An alternative fragment-based approach is to stabilise the uncomplexed components of the multiprotein system in solution and employ conventional fragment-based screening. Here, we describe the current knowledge of the structures and properties of protein–protein interactions and the small molecules that can modulate them. We then describe the use of sensitive biophysical methods – nuclear magnetic resonance, X-ray crystallography, surface plasmon resonance, differential scanning fluorimetry or isothermal calorimetry – to screen and validate fragment binding. Fragment hits can subsequently be evolved into larger molecules with higher affinity and potency. These may provide new leads for drug candidates that target protein–protein interactions and have therapeutic value.

Cherry leaf roll virus (CLRV), Myrobalan latent ringspot virus (MLRSV) and Strawberry latent ringspot virus (SLRSV) were transferred by budding to woody trees, hybrid Ishtara, peach cv. GF 305 and cv. Lesiberian. Three buffers with antioxidants and stabilisers: 0.01M phosphate with 1% caffeine; 0.007M phosphate-0.01M veronal with 0.01M cysteine hydrochloride and 0.007 EDTA; 0.015M phosphate with 1% nicotine and 0.066M phosphate buffer without additives were compared for their efficiency in mechanical transmission from woody sources to herbaceous hosts (Chenopodium quinoa and C. amaranticolor). 0.007M phosphate-0.01M veronal buffer with 0.01M cysteine hydrochloride, and 0.007 EDTA and 0.015M phosphate buffer with 1% nicotine were found to be the best buffers for the three nepoviruses. Both biological transmission to herbaceous assay hosts and detection by ELISA in the investigated tree are necessary to reliably detect the three nepoviruses. Biological detection is reliable from April to June, and in September and October. ELISA detection is also more difficult in July and August. The suitability of C. quinoa and C. amaranticolor to maintain CLRV, MLRSV and SLRSV was compared. C. amaranticolor plants were found to be more suitable for CLRV and SLRSV, infected plants grow over 6 months after mechanical inoculation by the nepoviruses. C. quinoa plants proved to be most suitable for maintenance of MLRSV, while C. amaranticolor is a symptomless host of MLRSV. Reinoculation with the nepoviruses is recommended in intervals of 4 to 6 months.

The relation of polyamine catabolism in the response of Pisum sativum to salinity stress was investigated. Pea seedlings were grown in increasing concentrations of Na⁺ or K⁺ or at different concentration ratios of these ions. We studied the effect of Ca²⁺ supplementation on plants exposed to salinity stress. The parameters measured in the roots and shoots of pea seedlings included biomass production, levels of Na⁺, K⁺, Ca²⁺ and polyamines and activity of enzymes of polyamine catabolism: diamine oxidase, aminoaldehyde dehydrogenase and peroxidases. Salinity induced increased polyamine levels and higher activity of enzymes participating in polyamine degradation. Supplementation of Ca²⁺ had a positive effect on biomass production and in most cases it stabilised both the polyamine level and the activity of the studied enzymes. Our results confirm the role of aminoaldehyde dehydrogenase and polyamine catabolism in defence mechanisms of pea plants under salinity stress.

Abstract In vitro resistance to Glucocorticoids (GC) is an important adverse risk factor in the treatment of ALL. To induce apoptosis in ALL cells, GC have to bind to the GC receptor (hGR), which is tightly regulated by various (co)chaperone molecules. HSP70, ST13 and HSP40 facilitate hGR binding to HSP90 and HOP in an energy dependent fashion. This complex is stabilised by immunophillins FKBP 51, FKBP59, CYP40 and P23 and is necessary for the hGR to be able to bind GC. The ATPase BAG1 can function as negative regulator of HSP70, and may downregulate hGR activity. After the GC-hGR complex is formed, it is transported to the nucleus to regulate GC responsive genes. In this study, we tested the hypothesis that RNA expression levels of these (co) chaperone molecules are important determinants for in vitro prednisolone sensitivity in childhood ALL. Methods: 20 children with leukemic cells in vitro sensitive to prednisolone (LC50<0.1μg/ml) were matched (according to age, immunophenotype and white blood cell count at diagnosis) each with an in vitro resistant patient (LC50 > 150 μg/ml). RNA expression levels of the different (co)chaperone molecules were measured by a quantitative real-time RT-PCR (Taqman) assay and standardised to endogenous GAPDH and RNAseP mRNA levels. In vitro resistance to prednisolone was measured by the MTT assay. Results. The highest median expression levels, indicated as percentage of GAPDH levels were found for HSP90 (29%) and p23 (10%), whereas FKBP51 and ST13 were expressed at 2% and 1.6% respectively. HSP70 (0.1%), HSP40 (0.44%), HOP (0.2%), FKBP59 (0.4%), PPID (0.3%) and BAG-1 (0.4%) were expressed at relatively low levels. Using matched pair analysis, no significant differences were found for the expression levels of the various (co)chaperone molecules between in vitro sensitive and resistant patients. The ratio of different (co)chaperone molecules with opposing effect (HIP versus BAG-1, FKBP-51 versus FKBP-52, HSP-90 versus P23, and HSP-90 versus the functional GR-alpha receptor, positive and negative effect respectively) was not related to GC resistance as well. Conclusion: Glucocorticoid resistance in childhood ALL can not be attributed to basal expression levels of the diverse (co)chaperone molecules involved in GC binding and transport of the GC-GR complex to the nucleus of the GR.