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Molecular Signaling Pathways (molecular + signaling_pathway)
Selected AbstractsSmad3-dependent signaling underlies the TGF-,1-mediated enhancement in astrocytic iNOS expressionGLIA, Issue 11 2010Mary E. Hamby Abstract We previously demonstrated that transforming growth factor-,1 (TGF-,1), while having no effect alone, enhances nitric oxide (NO) production in primary, purified mouse astrocytes induced by lipopolysaccharide (LPS) plus interferon-, (IFN-,), by recruiting a latent population of astrocytes to respond, thereby enhancing the total number of cells that express Nos2. In this investigation, we evaluated the molecular signaling pathway by which this occurs. We found that purified murine primary astrocytes express mRNA for TGF,RII as well as the TGF,RI subunit activin-like kinase 5 (ALK5), but not ALK1. Immunofluorescence microscopy confirmed the expression of TGF,RII and ALK5 protein in astrocytes. Consistent with ALK5 signaling, Smad3 accumulated in the nucleus of astrocytes as early as 30 min after TGF-,1 (3 ng/mL) treatment and persisted upto 32 hr after TGF-,1 administration. Addition of ALK5 inhibitors prevented TGF-,1-mediated Smad3 nuclear accumulation and NO production when given prior to the Nos2 induction stimuli, but not after. Finally, astrocyte cultures derived from Smad3 null mutant mice did not exhibit a TGF-,1-mediated increase in iNOS expression. Overall, this data suggests that ALK5 signaling and Smad3 nuclear accumulation is required for optimal enhancement of LPS plus IFN,-induced NO production in astrocytes by TGF-,1. © 2010 Wiley-Liss, Inc. [source] Verapamil Toxicity Dysregulates the Phosphatidylinositol 3-Kinase PathwayACADEMIC EMERGENCY MEDICINE, Issue 4 2008Laura K. Bechtel PhD Abstract Objectives:, Recent animal research and clinical case reports suggest benefit from high-dose insulin therapy (HDIT) for the treatment of calcium channel blocker (CCB) toxicity. One molecular signaling pathway, the phosphatidylinositol 3-kinase (PI3K) pathway, that contributes to CCB toxicity and the efficacy of HDIT, was examined for a role in this phenomenon. Methods:, A differentiated 3T3-L1 adipocyte model system was utilized to characterize metabolic and molecular signaling events dysregulated in response to acute CCB toxicity. Glucose uptake assays were performed in the presence of representatives of three classes of CCB drugs, and the ability of HDIT to reverse observed inhibition was assessed. Western blot analyses were utilized to probe which insulin-dependent signaling pathway was inhibited by CCB toxicity. Results:, Representative compounds from the dihydropyridine and phenylalkylamine classes of CCBs were more effective at inhibiting glucose uptake in differentiated 3T3-L1 adipocytes than a representative from the benzothiazepine class. Phosphorylation at serine 473 of the Akt protein (P-Akt), a protein representing a common pathway for insulin receptors (IR), insulinlike growth factor receptors (IGFR), and hybrid receptors formed by IR and IGFR subunits, was abolished in the presence of toxic doses of the phenylalkylamine CCB verapamil. Phosphorylation at serine 473 of Akt was rescued in the presence high concentrations of insulin. Conclusions:, These data suggest that dysregulation of the insulin-dependent PI3K pathway is partially responsible for insulin resistance and the hyperglycemic state observed in response to acute CCB toxicity. [source] Small-Molecule Inhibitors of the Hedgehog Signaling Pathway as Cancer TherapeuticsCHEMMEDCHEM, Issue 4 2010Stefan Peukert Dr. Abstract Inhibitors of the Hedgehog (Hh) molecular signaling pathway have emerged in recent years as a promising new class of potential therapeutics for cancer treatment. Numerous drug discovery efforts have resulted in the identification of a wide variety of small molecules that target different members of this pathway, including Smoothened (Smo), Sonic hedgehog protein (Shh), and Gli1. Several Smo inhibitors have now entered human clinical trials, and successful proof-of-concept studies have been carried out in patients with defined genetic mutations in the Hh pathway. This review provides a general overview of three main topics in this rapidly expanding area: 1),the various types of biological assays and in,vivo models that have been employed for the identification and optimization of Hh pathway inhibitors; 2),Smo inhibitors reported to date, including recent clinical results where available; and 3),efforts toward the identification and characterization of inhibitors of other members of the Hh pathway. [source] Force propagation and force generation in cells,CYTOSKELETON, Issue 9 2010Oliver Jonas Abstract Determining how forces are produced by and propagated through the cytoskeleton (CSK) of the cell is of great interest as dynamic processes of the CSK are intimately correlated with many molecular signaling pathways. We are presenting a novel approach for integrating measurements on cell elasticity, transcellular force propagation, and cellular force generation to obtain a comprehensive description of dynamic and mechanical properties of the CSK under force loading. This approach uses a combination of scanning force microscopy (SFM) and Total Internal Reflection Fluorescence (TIRF) microscopy. We apply well-defined loading schemes onto the apical cell membrane of fibroblasts using the SFM and simultaneously use TIRF microscopy to image the topography of the basal cell membrane. The locally distinct changes of shape and depth of the cytoskeletal imprints onto the basal membrane are interpreted as results of force propagation through the cytoplasm. This observation provides evidence for the tensegrity model and demonstrates the usefulness of our approach that does not depend on potentially disturbing marker compounds. We confirm that the actin network greatly determines cell stiffness and represents the substrate that mediates force transduction through the cytoplasm of the cell. The latter is an essential feature of tensegrity. Most importantly, our new finding that, both intact actin and microtubule networks are required for enabling the cell to produce work, can only be understood within the framework of the tensegrity model. We also provide, for the first time, a direct measurement of the cell's mechanical power output under compression at two femtowatts. © 2010 Wiley-Liss, Inc. [source] Cellular Adaptation to Chronic Ethanol Results in Altered Compartmentalization and Function of the Scaffolding Protein RACK1ALCOHOLISM, Issue 10 2003Alicia J. Vagts Background: Previously, we found that acute ethanol induces the translocation of the scaffolding protein RACK1 to the nucleus. Recently, we found that nuclear RACK1 mediates acute ethanol induction of immediate early gene c-fos expression. Alterations in gene expression are thought to lead to long-term changes that ultimately contribute to the development of alcohol addiction and toxicity. Therefore, we sought to determine the effects of chronic exposure of cells to ethanol on the cellular compartmentalization of RACK1 and on c-fos messenger RNA (mRNA) and protein expression. Methods: Rat C6 glioma cells were used as the cell culture model. Immunohistochemistry was implemented to visualize the localization of RACK1 and to monitor the protein level of c-fos. Reverse-transcription polymerase chain reaction was used to measure c- fos mRNA levels. The Tat-protein transduction method was used to transduce recombinant Tat-RACK1 into cells as previously described. Results: Chronic exposure of cells to 200 mM ethanol for 24 and 48 hr resulted in the gradual re-distribution of RACK1 out of the nucleus. It is interesting to note that acute ethanol re-challenge immediately after chronic treatment did not result in RACK1 translocation to the nucleus, and nuclear compartmentalization of RACK1 in response to acute ethanol was detected only after 24 hr of withdrawal. Similar patterns were obtained for c-fos expression. Chronic exposure to ethanol did not result in an increase in mRNA or protein levels of c-fos. Furthermore, acute ethanol exposure did not increase c-fos protein levels in cells that were first treated chronically with ethanol. However, transduction of exogenous RACK1 expressed as a Tat-fusion protein was able to rescue c- fos mRNA expression after chronic ethanol exposure. Conclusions: Our data suggest that RACK1 nuclear compartmentalization and ethanol-induced c-fos expression are transient and are desensitized to ethanol during prolonged exposure to high concentrations. The desensitization is temporary, and RACK1 can respond to acute ethanol treatment after a 24-hr withdrawal period. Our data further suggest that the altered compartmentalization of RACK1 leads to differences in c-fos expression upon acute or chronic exposure to ethanol. In summary, RACK1 is an important molecular mediator of the acute and chronic actions of ethanol on the expression of c-fos. These findings could have implications for the molecular signaling pathways leading to pathologic states associated with alcoholism, including toxicity. [source] Development of the vertebrate central nervous system: formation of the neural tubePRENATAL DIAGNOSIS, Issue 4 2009Nicholas D. E. Greene Abstract The developmental process of neurulation involves a series of coordinated morphological events, which result in conversion of the flat neural plate into the neural tube, the primordium of the entire central nervous system (CNS). Failure of neurulation results in neural tube defects (NTDs), severe abnormalities of the CNS, which are among the commonest of congenital malformations in humans. In order to gain insight into the embryological basis of NTDs, such as spina bifida and anencephaly, it is necessary to understand the morphogenetic processes and molecular mechanisms underlying neural tube closure. The mouse is the most extensively studied mammalian experimental model for studies of neurulation, while considerable insight into underlying developmental mechanisms has also arisen from studies in other model systems, particularly birds and amphibians. We describe the process of neural tube formation, discuss the cellular mechanisms involved and highlight recent findings that provide links between molecular signaling pathways and morphogenetic tissue movements. Copyright © 2009 John Wiley & Sons, Ltd. [source] Proliferation- and migration-enhancing effects of ginseng and ginsenoside Rg1 through IGF-I- and FGF-2-signaling pathways on RSC96 Schwann cellsCELL BIOCHEMISTRY AND FUNCTION, Issue 4 2009Ming-Chin Lu Abstract The aim of the present study is to evaluate the proliferation- and migration-enhancing effects of ginseng and its component, ginsenoside (Rg1) on RSC96 Schwann cells. We investigated the molecular signaling pathways, which include: (1) survival signaling, IGFs-IGFIR-Akt-Bcl2 and proliferative signaling, cell cycle factors and mitogen-activated protein kinase (MAPK) pathways, (2) migrating and anti-scar signaling, FGF-2-uPA-MMPs. We treated RSC96 cells with different concentrations (100, 200, 300, 400, 500,µg,ml,1) of ginseng and its constituent, Rg1 (5, 10, 15, 20, 25,µg,ml,1). We observed a proliferative effect in a dose-dependent manner by PCNA western blotting assay, MTT assay, and wound healing test. Furthermore, we also found in the results of western blotting assay, ginseng and Rg1 enhance protein expression of IGF-I pathway regulators, cell cycle controlling proteins, and MAPK signaling pathways to promote the cell proliferation. In addition, ginseng and Rg1 also stimulated the FGF-2-uPA-MMP 9 migrating pathway to enhance the migration of RSC96 Schwann cells. Using MAPK chemical inhibitors, U0126, SB203580, and SP600125, the proliferative effects of ginseng and Rg1 on RSC96 cells were identified to be MAPK signaling-dependent. On the basis of the results, applying appropriate doses of ginseng and Rg1 with biomedical materials would be a potential approach for enhancing neuron regeneration. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||