Browsing by Subject "ERK"

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  • Leopold, Anna V.; Chernov, Konstantin G.; Shemetov, Anton A.; Verkhusha, Vladislav V. (2019)
    Optical control over the activity of receptor tyrosine kinases (RTKs) provides an efficient way to reversibly and non-invasively map their functions. We combined catalytic domains of Trk (tropomyosin receptor kinase) family of RTKs, naturally activated by neurotrophins, with photosensory core module of DrBphP bacterial phytochrome to develop opto-kinases, termed Dr-TrkA and Dr-TrkB, reversibly switchable on and off with near-infrared and far-red light. We validated Dr-Trk ability to reversibly light-control several RTK pathways, calcium level, and demonstrated that their activation triggers canonical Trk signaling. Dr-TrkA induced apoptosis in neuroblastoma and glioblastoma, but not in other cell types. Absence of spectral crosstalk between Dr-Trks and blue-light-activatable LOV-domain-based translocation system enabled intracellular targeting of Dr-TrkA independently of its activation, additionally modulating Trk signaling. Dr-Trks have several superior characteristics that make them the opto-kinases of choice for regulation of RTK signaling: high activation range, fast and reversible photoswitching, and multiplexing with visible-light-controllable optogenetic tools.
  • Rinne, Maiju K.; Leino, Teppo O.; Turku, Ainoleena; Turunen, Pauli M.; Steynen, Yana; Xhaard, Henri; Wallen, Erik A. A.; Kukkonen, Jyrki P. (2018)
    One promising series of small-molecule orexin receptor agonists has been described, but the molecular pharmacological properties, i.e. ability and potency to activate the different orexin receptor-regulated signal pathways have not been reported for any of these ligands. We have thus here assessed these properties for the most potent ligand of the series, 4'-methoxy-N,N-dimethyl-3'4N-(3-{[2-(3-methylbenzamido)ethyl]amino}phenyl sulfamoy1]-(1,1'-biphenyl)-3-carboxamide (Nag 26). Chinese hamster ovary-K1 cells expressing human orexin receptor subtypes OX1 and OX2 were used. Ca2+ elevation and cell viability and death were assessed by fluorescent methods, the extracellular signal-regulated kinase pathway by a luminescent Elk-1 reporter assay, and phospholipase C and adenylyl cyclase activities by radioactive methods. The data suggest that for the G(q)-dependent responses, Ca2+, phospholipase C and Elk-1, Nag 26 is a full agonist for both receptors, though of much lower potency. However, saturation was not always reached for OX1, partially due to Nag 26s low solubility and partially because the response decreased at high concentrations. The latter occurs in the same range as some reduction of cell viability, which is independent of orexin receptors. Based on the EC50, Nag 26 was OX2 selective by 20-200 fold in different assays, with some indication of biased agonism (as compared to orexin-A). Nag 26 is a potent orexin receptor agonist with a largely similar pharmacological profile as orexin-A. However, its weaker potency (low-mid micromolar) and low water solubility as well as the non-specific effect in the mid-micromolar range may limit its usefulness under physiological conditions.
  • Kochanczyk, Marek; Kocieniewski, Pawel; Kozlowska, Emilia; Jaruszewicz-Blonska, Joanna; Sparta, Breanne; Pargett, Michael; Albeck, John G.; Hlavacek, William S.; Lipniacki, Tomasz (2017)
    We formulated a computational model for a MAPK signaling cascade downstream of the EGF receptor to investigate how interlinked positive and negative feedback loops process EGF signals into ERK pulses of constant amplitude but dose-dependent duration and frequency. A positive feedback loop involving RAS and SOS, which leads to bistability and allows for switch-like responses to inputs, is nested within a negative feedback loop that encompasses RAS and RAF, MEK, and ERK that inhibits SOS via phosphorylation. This negative feedback, operating on a longer time scale, changes switch-like behavior into oscillations having a period of 1 hour or longer. Two auxiliary negative feedback loops, from ERK to MEK and RAF, placed downstream of the positive feedback, shape the temporal ERK activity profile but are dispensable for oscillations. Thus, the positive feedback introduces a hierarchy among negative feedback loops, such that the effect of a negative feedback depends on its position with respect to the positive feedback loop. Furthermore, a combination of the fast positive feedback involving slow-diffusing membrane components with slower negative feedbacks involving faster diffusing cytoplasmic components leads to local excitation/global inhibition dynamics, which allows the MAPK cascade to transmit paracrine EGF signals into spatially non-uniform ERK activity pulses.
  • Annala, Iina (Helsingin yliopisto, 2021)
    Subanesthetic-dose ketamine, an N-methyl-D-aspartate receptor (NMDAR) blocker, exerts rapid antidepressant effects that sustain long after its elimination from the body. The precise mechanism remains unknown, but regulation of TrkB (tropomyosin receptor kinase B), ERK (extracellular-regulated kinase 1 and 2), GSK3β (glycogen synthase kinase 3β) and mTOR (mammalian target of rapamycin) signaling within the prefrontal cortex (PFC) have been deemed important for its antidepressant-like effects in rodents. In addition, activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) is thought to be an important step in its mechanism. Nitrous oxide (N2O), another NMDAR antagonist and a putative rapid-acting antidepressant, regulates the same molecular pathways as ketamine in the rodent PFC. The fast pharmacokinetics of N2O have been exploited to show that markers of neuronal excitation, including phosphorylation of ERK, are upregulated in the PFC during its acute pharmacological effects (NMDAR blockade), while regulation of TrkB, GSK3β and P70S6K emerges only upon N2O withdrawal. In the first part of this study, we investigated the N2O-induced biochemical changes associated with neuronal excitation and BDNF-TrkB signaling in the PFC and further, the requirement for AMPAR activation in inducing them. We focused on the effects seen after the acute pharmacological effects of N2O. N2O (65% for 20 min) was administered to adult male C57BL/6 mice with or without pretreatment with AMPAR antagonist (NBQX, 10 mg/kg) and PFC samples were collected 15 minutes after stopping N2O delivery. Within this time N2O is expected to be completely eliminated. The brain samples were analyzed using western blot, enzyme-linked immunosorbent assay and quantitative reverse transcription PCR. We observed that N2O increased levels of phosphorylated TrkB, GSK3β and P70S6K, and these effects were not attenuated by NBQX pretreatment. At the same time, we observed a decrease in the levels of phosphorylated ERK, which was attenuated in mice that received NBQX prior to N2O. Tissue levels of BDNF protein or messenger RNA (exon IV) were not different between control and experimental groups. These results indicate that the mechanism of N2O is associated with TrkB and ERK signaling that are regulated independently of each other. It appears that AMPAR activation is not required for TrkB signaling, although it might play a role in ERK signaling. Further, N2O-induced TrkB phosphorylation in the PFC is not associated with changes in total levels of BDNF. In the second part of the study, we aimed to search for new ketamine-like NMDAR blockers with antidepressant potential. Ketamine was used as a query compound for in silico substructure search to find commercial ketamine analogs. The retrieved ketamine analogs were filtered by their computed ADMET properties and then further screened virtually by docking them to the pore region of NMDAR complex (protein data bank code: 4TLM), around the predicted binding site of ketamine. Finally, we sought to study if selected ketamine analogs could elicit ketamine-like effects on TrkB and ERK signaling in mouse primary cortical neurons. However, we did not proceed to test the analogs since ketamine (positive control) did not show any effects on TrkB or ERK phosphorylation in our culture. Overall, this study advances the understanding of the mechanism of N2O, possibly giving new insight of the antidepressant mechanisms of NMDAR-blocking agents more generally. Additionally, we found promising ketamine analogs that await experimental testing.
  • Niku, Mikael; Pajari, Anne-Maria; Sarantaus, Laura; Päivärinta, Essi; Storvik, Markus; Heiman-Lindh, Anu; Suokas, Santeri; Nyström, Minna; Mutanen, Marja (2017)
    Western-type diet (WD) is a risk factor for colorectal cancer, but the underlying mechanisms are poorly understood. We investigated the interaction of WD and heterozygous mutation in the Apc gene on adenoma formation and metabolic and immunological changes in the histologically normal intestinal mucosa of Apc(Min/+) (Min/ +) mice. The diet used was high in saturated fat and low in calcium, vitamin D, fiber and folate. The number of adenomas was twofold higher in the WD mice compared to controls, but adenoma size, proliferation or apoptosis did not differ. The ratio of the MM to wild-type allele was higher in the WD mice, indicating accelerated loss of Apc heterozygosity (LOH). Densities of intraepithelial CD3 epsilon(+) T lymphocytes and of mucosal FoxP3(+) regulatory T cells were higher in the WD mice, implying inflammatory changes. Western blot analyses from the mucosa of the WD mice showed suppressed activation of the ERK and AKT pathways and a tendency for reduced activation of the mTOR pathway as measured in phosphoS6/S6 levels. The expression of pyruvate dehydrogenase kinase 4 was up-regulated in both mRNA and protein levels. Gene expression analyses showed changes in oxidation/reduction, fatty acid and monosaccharide metabolic pathways, tissue organization, cell fate and regulation of apoptosis. Together, our results suggest that the high-risk Western diet primes the intestine to tumorigenesis through synergistic effects in energy metabolism, inflammation and oxidative stress, which culminate in the acceleration of LOH of the Apc gene. (C) 2016 Elsevier Inc. All rights reserved.