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Growth Factor Stimulation (growth + factor_stimulation)
Selected AbstractsMeasurement of barbed ends, actin polymerization, and motility in live carcinoma cells after growth factor stimulation,CYTOSKELETON, Issue 4 2004Mike Lorenz Abstract Motility is associated with the ability to extend F-actin-rich protrusions and depends on free barbed ends as new actin polymerization sites. To understand the function and regulation of different proteins involved in the process of generating barbed ends, e.g., cofilin and Arp2/3, fixed cell approaches have been used to determine the relative barbed end concentration in cells. The major disadvantages of these approaches are permeabilization and fixation of cells. In this work, we describe a new live-cell time-lapse microscopy assay to determine the increase of barbed ends after cell stimulation that does not use permeabilization and provides a better time resolution. We established a metastatic carcinoma cell line (MTLn3) stably expressing GFP-,-actin at physiological levels. Stimulation of MTLn3 cells with epidermal growth factor (EGF) causes rapid and transient lamellipod protrusion along with an increase in actin polymerization at the leading edge, which can be followed in live cell experiments. By measuring the increase of F-actin at the leading edge vs. time, we were able to determine the relative increase of barbed ends after stimulation with a high temporal resolution. The F-actin as well as the barbed end concentration agrees well with published data for this cell line. Using this newly developed assay, a decrease in lamellipod extension and a large reduction of barbed ends was documented after microinjecting an anti-cofilin function blocking antibody. This assay has a high potential for applications where rapid changes in the dynamic filament population are to be measured. Cell Motil. Cytoskeleton 57:207,217, 2004. © 2004 Wiley-Liss, Inc. [source] Down-regulation of the PI3-kinase/Akt pathway by ERK MAP kinase in growth factor signalingGENES TO CELLS, Issue 9 2008Hideko Hayashi The ERK MAP kinase and PI3-kinase/Akt pathways are major intracellular signaling modules, which are known to regulate diverse cellular processes including cell proliferation, survival and malignant transformation. However, it has not been fully understood how these two pathways interact with each other. Here, we demonstrate that inhibition of the ERK pathway by the MEK inhibitor U0126 or PD98059 significantly potentiates EGF- and FGF-induced Akt phosphorylation at both Thr308 and Ser473. We also show that hyperactivation of the ERK pathway greatly attenuates EGF- and FGF-induced Akt phosphorylation. Furthermore, the enhanced Akt phosphorylation induced by U0126 is inhibited by the PI3-kinase inhibitor LY294002, and is accompanied by the up-regulation of Ras activity. These results suggest that the ERK pathway inhibition enhances Akt phosphorylation through the Ras/PI3-kinase pathway. Thus, our results demonstrate that the ERK pathway negatively modulates the PI3-kinase/Akt pathway in response to growth factor stimulation. [source] Atypical protein kinase C activity is required for extracellular matrix degradation and invasion by Src-transformed cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2009Elena M. Rodriguez Atypical protein kinase C (aPKC) isoforms have been shown to mediate Src-dependent signaling in response to growth factor stimulation. To determine if aPKC activity contributes to the transformed phenotype of cells expressing oncogenic Src, we have examined the activity and function of aPKCs in 3T3 cells expressing viral Src (v-Src). aPKC activity and tyrosine phosphorylation were found to be elevated in some but not all clones of mouse fibroblasts expressing v-Src. aPKC activity was inhibited either by addition of a membrane-permeable pseudosubstrate, by expression of a dominant-negative aPKC, or by RNAi-mediated knockdown of specific aPKC isoforms. aPKC activity contributes to morphological transformation and stress fiber disruption, and is required for migration of Src-transformed cells and for their ability to polarize at the edge of a monolayer. The , isoform of aPKC is specifically required for invasion through extracellular matrix in Boyden chamber assays and for degradation of the extracellular matrix in in situ zymography assays. Tyrosine phosphorylation of aPKC, is required for its ability to promote cell invasion. The defect in invasion upon aPKC inhibition appears to result from a defect in the assembly and/or function of podosomes, invasive adhesions on the ventral surface of the cell that are sites of protease secretion. aPKC was also found to localize to podosomes of v-Src transformed cells, suggesting a direct role for aPKC in podosome assembly and/or function. We conclude that basal or elevated aPKC activity is required for the ability of Src-transformed cells to degrade and invade the extracellular matrix. J. Cell. Physiol. 221: 171,182, 2009. © 2009 Wiley-Liss, Inc [source] EGF and NGF injected into the brain of old mice enhance BDNF and ChAT in proliferating subventricular zoneJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2003Paola Tirassa Abstract The response of cells localized in the brain subventricular zone (SVZ) to growth factor stimulation has been largely described for development and adult life, whereas no information on their behavior during aging is available. To address the question of whether the cells in the SVZ of old mice respond to the intracerebroventricular administration of epidermal growth factor (EGF) and nerve growth factor (NGF), we studied the distribution of proliferating cells and the effects on ChAT and brain-derived neurotrophic factor (BDNF) synthesis in forebrain and SVZ. It was found that the conjoint administration of EGF + NGF produced a major increase in ChAT expression in both forebrain and SVZ. The ChAT mRNA levels and the number of ChAT positive cells localized in the ventricular border and in the parenchyma of SVZ area were also increased significantly in the mice receiving EGF + NGF. Enhanced numbers of SVZ cells expressing proliferative markers were also discovered in EGF + NGF treated mice and some of these cells expressed cholinergic markers, as demonstrated by double immunostaining. In addition, EGF and NGF treatments significantly upregulate BDNF protein and mRNA levels in this brain region. The present study demonstrates that cells localized in SVZ of aged mouse brain retain the capacity to respond to EGF and NGF and that after stimulation with these two growth factors, the synthesis of ChAT and BDNF also increases. The implication that cells of the SVZ remain a reservoir of cholinergic and BDNF-positive neurons in aged brain opens a new perspective for understanding the role of growth factors during neurodegenerative disorders associated with aging. © 2003 Wiley-Liss, Inc. [source] The role of p28GANK in rat oval cells activation and proliferationLIVER INTERNATIONAL, Issue 2 2006Yun-Feng Shan Abstract: Background: Human gankyrin gene product (p28GANK) is a novel oncogenic protein ubiquitously overexpressed in hepatocellular carcinoma and also plays a role in cell cycle progression in normal hepatocytes and liver regeneration. However, little is known about the physiological role of p28GANK in the liver oval cell activation and proliferation. We investigated the possible involvement of p28GANK in oval cell-mediated liver regeneration and cell cycle progression. Methods: We examined the different p28GANK expression in 2-acetylaminofuorene/partial heptectomy (2-AAF/PH) rats, as a model of oval cell activation, and PH rats by Western blot and immunohistochemistry. Oval cells isolated from 2-AAF/PH rat model were cultured in our study. p28GANK expression was examined in the oval cells after mitogenic stimulation. Results: In 2-AAF/PH rats, p28GANK was expressed in the activated oval cells and located in the nucleus. p28GANK protein expression was increased in 2-AFF/PH rats after hepatectomy lasting for 96 h when retinoblastoma maintained hyperphosphorylation status at Ser-795. The isolated oval cells express AFP, OV6, CK19, CD34, CD45, c-kit and albumin. After epidermal growth factor stimulation, p28GANK protein was up-regulated in oval cells from 24 to 72 h, which coincided with increased expression of CyclinD1, CDK4 and decreased of Rb protein. Conclusions: p28GANK expression was increased in oval cell-mediated liver regeneration and oval cells after mitogenic stimulation. Thus, p28GANK may play a role in oval cell-mediated liver regeneration and liver oval cell cycle progression. [source] Regenerative approaches in the craniofacial region: manipulating cellular progenitors for oro-facial repairORAL DISEASES, Issue 5 2007PG Buxton This review aims to highlight the potential for regeneration that resides within the bony tissues of the craniofacial region. We examine the five main cues which determine osteogenic differentiation: heritage of the cell, mechanical cues, the influence of the matrix, growth factor stimulation and cell-to-cell contact. We review how successful clinical procedures, such as guided tissue regeneration and distraction osteogenesis exploit this resident ability. We explore the developmental origins of the flat bones of the skull to see how such programmes of differentiation may inform new therapies or regenerative techniques. Finally we compare and contrast existing approaches of hard tissue reconstruction with future approaches inspired by the regenerative medicine philosophy, with particular emphasis on the potential for using chondrocyte-inspired factors and replaceable scaffolds. [source] Rho kinase,dependent activation of SOX9 in chondrocytesARTHRITIS & RHEUMATISM, Issue 1 2010Dominik R. Haudenschild Objective The transcription factor SOX9 directly regulates the expression of the major proteoglycans and collagens comprising the cartilage extracellular matrix. The DNA binding activity and cellular localization of SOX9 is controlled through posttranslational modifications, including phosphorylation. The activity of Rho kinase (ROCK) has profound effects on the actin cytoskeleton, and these effects are instrumental in determining the phenotype and differentiation of chondrocytes. However, the mechanisms linking ROCK to altered chondrocyte gene expression remain unknown. The purpose of the present study was to test for a direct interaction between ROCK and SOX9. Methods Human SW1353 chondrosarcoma cells were transfected with constructs coding for RhoA, ROCK, Lim kinase, and SOX9. The interaction between ROCK and SOX9 was tested on purified proteins, and was verified within a cellular context using induced overexpression and activation of the Rho pathway. The effects of SOX9 transcriptional activation were quantified with a luciferase reporter plasmid containing SOX9 binding sites from the COL2A1 enhancer element. Results SOX9 was found to contain a consensus phosphorylation site for ROCK. In vitro, ROCK directly phosphorylated SOX9 at Ser181, and the overexpression of ROCK or the activation of the RhoA pathway in SW1353 chondrosarcoma cells increased SOX9Ser181 phosphorylation. ROCK caused a dose-dependent increase in the transcription of a SOX9-luciferase reporter construct, and increased phosphorylation and nuclear accumulation of SOX9 protein in response to transforming growth factor , treatment and mechanical compression. Conclusion These results demonstrate a new interaction that directly links ROCK to increased cartilage matrix production via activation of SOX9 in response to mechanical and growth factor stimulation. [source] Enhanced differentiation of embryonic stem cells using co-cultivation with hepatocytesBIOTECHNOLOGY & BIOENGINEERING, Issue 6 2008Rebecca N. Moore Abstract We examined the effects of co-cultivated hepatocytes on the hepatospecific differentiation of murine embryonic stem (ES) cells. Utilizing an established mouse ES cell line expressing high or low levels of E-cadherin, that we have previously shown to be responsive to hepatotrophic growth factor stimulation (Dasgupta et al., 2005. Biotechnol Bioeng 92(3):257,266), we compared co-cultures of cadherin-expressing ES (CE-ES) cells with cultured rat hepatocytes, allowing for either paracrine interactions (indirect co-cultures) or both juxtacrine and paracrine interactions (direct co-cultures, random and patterned). Hepatospecific differentiation of ES cells was evaluated in terms of hepatic-like cuboidal morphology, heightened gene expression of late maturation marker, glucose-6-phosphatase in relation to early marker, alpha-fetoprotein (AFP), and the intracellular localization of albumin. Hepatocytes co-cultured with growth factor primed CE-ES cells markedly enhanced ES cell differentiation toward the hepatic lineage, an effect that was reversed through E-cadherin blockage and inhibited in control ES cells with reduced cadherin expression. Comparison of single ES cell cultures versus co-cultures show that direct contact co-cultures of hepatocytes and CE-ES cells maximally promoted ES cell commitment towards hepatodifferentiation, suggesting cooperative effects of cadherin-based juxtacrine and paracrine interactions. In contrast, E-cadherin deficient mouse ES (CD-ES) cells co-cultured with hepatocytes failed to show increased G6P expression, confirming the role of E-cadherin expression. To establish whether albumin expression in CE-ES cells was spatially regulated by co-cultured hepatocytes, we co-cultivated CE-ES cells around micropatterned, pre-differentiated rat hepatocytes. Albumin localization was enhanced "globally" within CE-ES cell colonies and was inhibited through E-cadherin antibody blockage in all but an interfacial band of ES cells. Thus, stem cell based cadherin presentation may be an effective tool to induce hepatotrophic differentiation by leveraging both distal/paracrine and contact/juxtacrine interactions with primary cells of the liver. Biotechnol. Bioeng. © 2008 Wiley Periodicals, Inc. [source] E-cadherin synergistically induces hepatospecific phenotype and maturation of embryonic stem cells in conjunction with hepatotrophic factorsBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2005Anouska Dasgupta Abstract Since effective cell sourcing is a major challenge for the therapeutic management of liver disease and liver failure, embryonic stem (ES) cells are being widely investigated as a promising source of hepatic-like cells with their proliferative and pluripotent capacities. Cell,cell interactions are crucial in embryonic development modulating adhesive and signaling functions; specifically, the cell,cell adhesion ligand, cadherin is instrumental in gastrulation and hepatic morphogenesis. Inspired by the role of cadherins in development, we investigated the role of expression of E-cadherin in cultured murine ES cells on the induction of hepatospecific phenotype and maturation. The cadherin-expressing embryonic stem (CE-ES) cells intrinsically formed pronounced cell aggregates and cuboidal morphology whereas cadherin-deficient cadherin-expressing embryonic stem (CD-ES) cells remained more spread out and corded in morphology. Through controlled stimulation with single or combined forms of hepatotrophic growth factors; hepatocyte growth factor (HGF), dexamethasone (DEX) and oncostatin M (OSM), we investigated the progressive maturation of CE-ES cells, in relation to the control, CD-ES cells. Upon growth factor treatment, the CE-ES cells adopted a more compacted morphology, which exhibited a significant hepatocyte-like cuboidal appearance in the presence of DEX-OSM-HGF. In contrast, the CD-ES cells exhibited a mixed morphology and appeared to be more elongated in the presence of DEX-OSM-HGF. Reverse-transcriptase polymerase chain reaction was used to delineate the most differentiating condition in terms of early (alpha-fetoprotein (AFP)), mid (albumin), and late-hepatic (glucose-6-phosphatase) markers in relation to growth factor presentation for both CE-ES and CD-ES cells. We report that following the most differentiating condition of DEX-OSM-HGF stimulation, CE-ES cells expressed increased levels of albumin and glucose-6-phosphatase, whereas the CD-ES cells showed low levels of AFP and marginal levels of albumin and glucose-6-phosphatase. These trends suggest that the membrane expression of E-cadherin in ES cells can elicit a marked response to growth factor stimulation and lead to the induction of later stages of hepatocytic maturation. Thus, cadherin-engineered ES cells could be used to harness the cross-talk between the hepatotrophic and cadherin-based signaling pathways for controlled acceleration of ES hepatodifferentiation. © 2005 Wiley Periodicals, Inc. [source] Infection with Toxoplasma gondii results in dysregulation of the host cell cycleCELLULAR MICROBIOLOGY, Issue 5 2008Robert E. Molestina Summary Mammalian cells infected with Toxoplasma gondii are characterized by a profound reprogramming of gene expression. We examined whether such transcriptional responses were linked to changes in the cell cycle of the host. Human foreskin fibroblasts (HFFs) in the G0/G1 phase of the cell cycle were infected with T. gondii and FACS analysis of DNA content was performed. Cell cycle profiles revealed a promotion into the S phase followed by an arrest towards the G2/M boundary with infection. This response was markedly different from that of growth factor stimulation which caused cell cycle entry and completion. Transcriptional profiles of T. gondii -infected HFF showed sustained increases in transcripts associated with a G1/S transition and DNA synthesis coupled to an abrogation of cell cycle regulators critical in G2/M transition relative to growth factor stimulation. These divergent responses correlated with a distinct temporal modulation of the critical cell cycle regulator kinase ERK by infection. While the kinetics of ERK phosphorylation by EGF showed rapid and sustained activation, infected cells displayed an oscillatory pattern of activation. Our results suggest that T. gondii infection induces and maintains a ,proliferation response' in the infected cell which may fulfill critical growth requirements of the parasite during intracellular residence. [source] RNAi-mediated MEK1 knock-down prevents ERK1/2 activation and abolishes human hepatocarcinoma growth in vitro and in vivoINTERNATIONAL JOURNAL OF CANCER, Issue 6 2010Luc Gailhouste Abstract The mitogen-activated protein kinases MEK/ERK pathway regulates fundamental processes in malignant cells and represents an attractive target in the development of new cancer treatments especially for human hepatocarcinoma highly resistant to chemotherapy. Although gene extinction experiments have suggested distinct roles for these proteins, the MEK/ERK cascade remains widely considered as exhibiting an overlap of functions. To investigate the functionality of each kinase in tumorigenesis, we have generated stably knock-down clones for MEK1/2 and ERK1/2 isoforms in the human hepatocellular carcinoma line HuH7. Our results have shown that RNAi strategy allows a specific disruption of the targeted kinases and argued for the critical function of MEK1 in liver tumor growth. Transient and stable extinction experiments demonstrated that MEK1 isoform acts as a major element in the signal transduction by phosphorylating ERK1 and ERK2 after growth factors stimulation, whereas oncogenic level of ERK1/2 phosphorylation appears to be MEK1 and MEK2 dependent in basal condition. In addition, silencing of MEK1 or ERK2 abolished cell proliferation and DNA replication in vitro as well as tumor growth in vivo after injection in rodent. In contrast, targeting MEK2 or ERK1 had no effect on hepatocarcinoma progression. These results strongly corroborate the relevance of targeting the MEK cascade as attested by pharmacologic drugs and support the potential application of RNAi in future development of more effective cancer therapies. Our study emphasizes the importance of the MEK/ERK pathway in human hepatocarcinoma cell growth and argues for a crucial role of MEK1 and ERK2 in this regulation. [source] | |||||||||||||