Browsing by Subject "protein-protein interaction"

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  • Bösl, Korbinian; Ianevski, Aleksandr; Than, Thoa T.; Andersen, Petter I.; Kuivanen, Suvi; Teppor, Mona; Zusinaite, Eva; Dumpis, Uga; Vitkauskiene, Astra; Cox, Rebecca J.; Kallio-Kokko, Hannimari; Bergqvist, Anders; Tenson, Tanel; Merits, Andres; Oksenych, Valentyn; Bjørås, Magnar; Anthonsen, Marit W.; Shum, David; Kaarbø, Mari; Vapalahti, Olli; Windisch, Marc P.; Superti-Furga, Giulio; Snijder, Berend; Kainov, Denis; Kandasamy, Richard K. (2019)
    Viruses are one of the major causes of acute and chronic infectious diseases and thus a major contributor to the global burden of disease. Several studies have shown how viruses have evolved to hijack basic cellular pathways and evade innate immune response by modulating key host factors and signaling pathways. A collective view of these multiple studies could advance our understanding of virus-host interactions and provide new therapeutic perspectives for the treatment of viral diseases. Here, we performed an integrative meta-analysis to elucidate the 17 different host-virus interactomes. Network and bioinformatics analyses showed how viruses with small genomes efficiently achieve the maximal effect by targeting multifunctional and highly connected host proteins with a high occurrence of disordered regions. We also identified the core cellular process subnetworks that are targeted by all the viruses. Integration with functional RNA interference (RNAi) datasets showed that a large proportion of the targets are required for viral replication. Furthermore, we performed an interactome-informed drug re-purposing screen and identified novel activities for broad-spectrum antiviral agents against hepatitis C virus and human metapneumovirus. Altogether, these orthogonal datasets could serve as a platform for hypothesis generation and follow-up studies to broaden our understanding of the viral evasion landscape.
  • Titov, Soubir (Helsingfors universitet, 2010)
    Protein-protein interactions (PPIs) regulate many different cellular processes including transcription, translation, cell division, signal transduction, and oncogenic transformation. It is therefore important to develop sensitive and versatile techniques for the detection of these protein-protein interactions in order to fully understand protein functions. The most commonly used and traditional technique, the yeast two-/three hybrid (Y2H/Y3H) method, often results in false positives and false negatives, and other widely used techniques, such as bioluminescence resonance energy transfer (BRET), fluorescence resonance energy transfer (FRET), and bimolecular fluorescence complementation (BiFC) require extensive instrumentation. When compared with other PPI detection methods, the luciferase-based complementation assay specially split luciferase is believed to deliver the most sensitive and highest dynamic range, making it ideal for large-scale analysis. Therefore, for testing PPIs in planta, split Renilla luciferase complementation assay was chosen. In order to conduct this experiment, a series of plasmid constructs were made to enable the transient expression of fusion proteins. A well known protein pair, Arabidopsis nuclear Histone 2A and 2B, was tested initially as a proof of concept, and then three more proteins of the Gerbera MADS-box B class were investigated. For Arabidopsis Histone 2A and 2B, the intensity in all combinations was on average 9.4-fold higher in Relative Luminescence Units (RLUs) than the mock treated protoplasts. Moreover, in the case of Gerbera MADS-box B class proteins, the protein pairs GDEF1-GDEF2, GDEF1-GGLO1, and GDEF2-GGLO1 showed 8.4-19.4, 9.5-15.8, and 8.3-9.1-fold higher signals than the mock treated protoplasts. These results suggest that various complexes formed from different combinations of these three B class MADS-box proteins may increase the complexity of their regulatory functions, thus specifying the molecular basis of whorl morphogenesis and combinatorial interactions of floral organ identity genes in Gerbera. Finally, it was concluded that split Renilla luciferase can be a simple, reliable, fast, and effective method for examining PPIs in planta.
  • Xiang, Jiale (Helsingin yliopisto, 2014)
    Flavonoids are a group of secondary metabolites, which are not only important for plants’ survival, but also have been found to have medicinal properties for human health. Several enzymes are involved in the flavonoid biosynthesis. It is thought that these enzymes work together and may form enzymatic complexes. But the way of these enzymes interact with each other is still not clear. In arabidopsis, the number of gene family members that encode these enzymes is less than in other model plants, which makes it as a suitable model to investigate the interactions of enzymes involved in the flavonoid biosynthetic pathway. In this study, ten full-length flavonoid pathway genes were successfully amplified from cDNA of the arabidopsis flower. They are PAL1, C4H, CHS, CHI, F3H, F3’H, DFR, FLS1, ANS and GT. These genes were cloned into different prey vectors (pPR3-N and pPR3-SUC) and bait vectors (pDHB1 and pBT3-SUC). After that, the constructs were transformed separately into yeast. The protein-protein interactions were analyzed via yeast two-hybrid system.
  • Auno, Samuli (Helsingfors universitet, 2019)
    Heart failure is a disease of major social and economic impact. The disease is most commonly onset by extensive cardiomyocyte death following a myocardial infarction. Five-year mortality of heart failure is higher than some cancers. Loss of cardiac muscle tissue leads to pathological thickening and fibrosis of the left ventricular wall, which eventually further diminish cardiac function. Cardiomyocytes hardly proliferate, which also exacerbates the problem. Several cell signalling pathways are indicated in pathological reprogramming of the heart and the exact significance of these pathways remains to be demonstrated. Treatment strategies based on renewing cardiac muscle, such as direct injection of stem cells into the myocardium, have failed to reach clinically significant effects on heart failure patients. Direct inhibition of pathological cardiac reprogramming by using small molecule modulators remains as an auspicious strategy to treat heart failure. GATA4, or GATA binding protein 4, is a transcription factor expressed mainly in heart, lung, intestine, gonad and liver tissues, which regulates tissue renewal and cell proliferation by controlling protein transcription. GATA4 binds to GATA sequences in DNA with two zinc finger moieties and enables transcription of target genes. Interactions of GATA4 and several other transcription factors are in central role of guiding heart development, hypertrophy and fibrosis. One of these transcription factors is NKX2-5, which synergistically interacts with GATA4. Inhibition of this interaction in rat myocardial infarction model has been shown to protect against development of heart failure. A screening campaign against the transcriptional synergy of GATA4 and NKX2-5 found potent small molecule inhibitors of this interaction, but these compounds are characterised with stem cell toxicity. The aim of the study was to design and synthesise novel derivatives of GATA4-NKX2-5 synergy inhibitor hit molecule with reduced stem cell toxicity. Modifications on the phenyl ring of the hit molecule were designed, which either increase electron density of the ring or possibly alter the torsional angle between the phenyl and isoxazole ring moieties. Activity of the compounds was studied on a luciferase reporter gene system in COS-1 cells and toxicity was analysed on IMR90 human induced pluripotent stem cell line. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) bromide and lactate dehydrogenase (LDH) assays were selected to measure toxicity on stem cells. Stem cell toxicity of several previously synthesised compounds was assayed in parallel with the novel derivatives. Ten novel derivatives were designed, synthesised and assayed. Four of the new compounds, a mono-ortho-methyl, a di-ortho-methyl, a di-meta-methoxy and cyclohexyl derivatives were found to be equipotent inhibitors of reporter gene activity compared to the hit compound. Additionally, the mono-ortho-methyl, di-ortho-methyl and di-meta-methoxy derivatives were less toxic to stem cells than the hit molecule in the MTT assay. Several other derivatives were found to be less toxic, but also non-active in the luciferase assay. None of the studied compounds exhibited notable necrotic toxicity on stem cells, as examined by the LDH assay. According to this study it may be concluded that substituents of the hit molecule phenyl ring may be altered to decrease stem cell toxicity of the compound. Some of the alterations, most notably substituents in the para-position of the phenyl ring and substitution of the phenyl ring with smaller saturated hydrocarbon rings, diminish the activity of the hit compound. Remarkable toleration of ortho-substitution reinforces the hypothesis of phenyl-isoxazole torsional angle significance for toxicity. On the other hand, addition of two methoxy groups to both meta positions most likely lacks any substantial effect on the torsional angle, which implies another mechanism of toxicity avoidance. Activity and improved safety of the novel inhibitors should be confirmed in animal models before any decisive conclusions on the effects of structural modifications on the hit molecule can be made. In addition, other mechanisms of toxicity should be studied with relevant cell-based assays.
  • Dillemuth, Pyry (Helsingin yliopisto, 2021)
    Prolyl oligopeptidase (PREP) is a serine protease that is widely found throughout the human body and especially in the brain. The primary function of PREP is thought to be the hydrolysis of the carboxyl side bond of proline residues in oligopeptides. PREP is also shown to increase the dimerization and aggregation of α-synuclein and downregulate the protein phosphatase 2A mediated autophagy in the cell via direct protein-protein interactions (PPI). The accumulation of α-synuclein aggregates in cell is known to cause α-synucleinopathies such as Parkinson’s disease. This makes the PPIs of PREP an attractive target for drug research. The mechanisms of the PPIs of PREP are still poorly understood. Recent studies have shown that these PPIs can be modulated with ligands lacking high inhibitory activity for the proteolytic activity. These studies show that the IC50-value of the ligand does not correlate with ligands ability to affect the PPIs of PREP. Ligands that could selectively modulate the PPIs of PREP without inhibiting the proteolytic activity of PREP could give valuable information on the mechanisms of the PPIs and on how to modulate them. It is hypothesized that the ligands could bind to PREP at a site that does not interfere with its proteolytic activity, and ligand binding is assumed to restrict the dynamic structure of PREP and thereby also modulating the PPIs of PREP. The aim of this study was to synthetize novel peptidic PREP ligands and study their effects on the proteolytic activity of PREP and the PPIs of PREP. The aim was to find and identify ligands and structures that would modulate the PPIs of PREP and observe how the IC50-values of the ligands would correlate. L-Alanyl-pyrrolidine was selected as the scaffold for the compound series and the five-membered heteroaromatics, imidazole, triazole and tetrazole, were added to the 2-position of the pyrrolidine ring. In this position there is an electrophilic group in many PREP inhibitors, although these heteroaromatics are not electrophiles. The scaffold was also expanded by adding phenyalkyl groups with different linker lengths were added to the N-terminal side of the alanine. The ligands were synthesized using four synthesis routes which were based on synthesis methods found in literature. The IC50-values and the effects on α-synuclein dimerization and autophagic flux were determined for five synthetized compounds. The tested compounds were all weak PREP inhibitors and showed no strong activity in the α-synuclein dimerization and autophagy assays. Despite the weak activities in the assays, the importance of the linker length in the phenyalkyl group was shown. Changing the linker by one methylene group had noticeable effect on the overall activity. The results also demonstrate a lack of correlation between the IC50-values and the effects on α-synuclein dimerization and autophagic flux, which further confirms the lack of correlation between the proteolytic function and the PPIs of PREP which was observed also in previous studies.