Algumas das estratégias utilizadas para entender a biologia de células tronco embrionária (CTE) são baseadas na identificação de cascatas de sinalização que induzem a diferenciação e auto-renovação das CTE através da interferência seletiva de processos específicos. A família das proteínas quinase C (PKC) é conhecida por participar dos processos de auto-renovação e diferenciação celular em CTE, entretanto, o papel específico das diferentes isoenzimas das PKCs ainda precisa ser elucidado. Desta forma investigamos. o papel das PKCs atípicas (aPKCs) em CTE indiferenciadas utilizando um inibidor específico para estas serina/ treonina quinases, o peptídeo pseudossubstrato das aPKCs, e fosfoproteômica. A maioria das proteinas identificadas cuja fosforilação reduziu após o tratamento com o inibidor das aPKC, são proteínas envolvidas com o metabolismo principalmente com a via glicolítica. Além disso, a inibição das aPKCs levou a redução do consumo de glicose, secreção de lactato, acompanhada da redução da atividade da lactato desidrogenase, e aumento da fosforilação oxidativa, sendo analisada através do consumo de oxigênio após o tratamento com oligomicina e FCCP. Verificamos também que as aPKCs são capazes de fosforilar diretamente a piruvato quinase. A glicólise aeróbica parece ser fundamental para a manutenção da indiferenciação das CTE, e demonstramos que as aPKCs participam deste processo auxiliando na auto-renovação das CTE indiferenciadas. Também observamos que as aPKCs assim como a PKCβI modulam a fosforilação da α-tubulina, porém ao passo que as aPKCs interagem com a α-tubulina durante a interfase, a PKCβI interage com a mesma apenas durate a mitose. Estes resultados motivaram a segunda parte da tese, na qual o papel da fosforilação da α-tubulina pela PKCβI foi investigado. O resíduo de treonina 253, conservado em diversas espécies de vertebrados e localizado na interface de polimerização entre a α- e a β-tubulina foi identificado, como um novo sítio de fosforilação da α-tubulina pela PKCβI. Este sítio não está em um consenso linear para a PKC, entretanto é um consenso formado estruturalmente, onde aminoácidos básicos distantes na sequência linear se tornam justapostos na estrutura terciária da proteína. Estudos de simulação por dinâmica molecular demonstraram que a interação entre a α e β-tubulina aumenta após esta fosforilação, uma vez que T253 fosforilada passa a interagir com K105, um residuo conservado na β-tubulina. A fosforilação in vitro de α-tubulina aumenta a taxa de polimerização da tubulina e a inibição da PKCβI em células reduziu a taxa de repolimerização do microtubulo após o tratamento com nocodazol. Além disso, a importância da fosforilação deste sítio foi demonstrada pelo fato de que um mutante fosfomimético GFP-α-tubulina, T253E ser mais incorporado no fuso mitótico ao passo que T253A foi menos incorporado do que a proteína selvagem. Nossos dados suportam a hipótese que os consensos estruturais formados podem ser importantes sítios de reconhecimento pelas quinases e que a fosforilação de T253 da α-tubulina afeta a estabilidade do polímero. Em conclusão, utilizando métodos de fosfoproteômica e interferência seletiva de vias de sinalização, combinados a validações experimentais dos alvos identificados podemos propor a importância funcional das aPKCs e PKCβI em CTE indiferenciadas. / Some of the strategies used to understand stem cell biology are based on the identification of signalling cascades that lead to differentiation and self-renewal of embryonic stem cells (ESC) by selective interference of specific signalling processes. The protein kinase C (PKC) family is known to participate in ESC self-renewal and differentiation, however, the specific role of the different PKC isoenzymes in these cells remains to be determined. Therefore, we investigated the role of atypical PKCs (aPKC) in undifferntiated ESC using a specific inhibitor for these serine/ threonine kinases, pseudo-substrate peptide of aPKCs, and phosphoproteomics. The majority of proteins whose phosphorylation decreased upon aPKC inhibition, are proteins involved in metabolism in particular with the glycolytic pathway. Besides that, inhibiton of aPKCs led to a decrease in glucose uptake and lactate secretion, followed by a decrease in lactate dehydrogenase activity, and an increase in mitochondrial activity as measured by oxygen consumption after treatment with olygomycin and a chemical uncoupler. We also verified that aPKCs are able to directly phosphorylated pyruvate kinase. Aerobic glicolysis seems to be fundamental for the maintainance of undifferentiated ESC, and we demonstrated that aPKCs participte in these processes helping to maintain self-renewal of undifferentiated ESC. We also observed that aPKCs as PKCβI modulate the phosphorylation of α-tubulin, however, while aPKCs interact with α-tubulin during interfase PKCβI interacts with α-tubulin only during mitosis. These results lead to the second part of this thesis. We investigated the role of α-tubulina phosphorylation by PKCβI. Indentifying threonine 253, a conserved residue in several vertebrate species, of localized at the polymerization interface between α- and β-tubulin, as a phosphorylation site of α-tubulin by PKCβI. This site is not in a linear consensus for PKC, however, it is in a structuraly formed consensus, where basic aminoacids distant in the linear sequence are juxtaposed in the three dimentional protein structure. Simulation studies by molecular dynamics show that the interaction between α and β-tubulin increases upon this phosphorylation, once, phosphorylated T253 interacts with com K105, a conserved residue in β-tubulin. The in vitro phosphorylation of α-tubulin increased tubulin polymerization rate and inhibiton of PKCβI in cells reduced repolimeration rate of microtubles upon treatment with nocodazole. Besides that, the importance of this phosphorylation site were demonstrated by the fact that a phosphomimetic mutant GFP-α-tubulina, T253E is more incorporated in mitotic fuses while T253A is less than wild type. Our data support the hypothesis that structural consensus may be important sites recognized and that T253 phosphorylation of α-tubulin afects the polymer stability. In conclusion, using phosphoproteomics methods and selective interference of signal transduction pathways combined with experimental validation studies of the identified targets we can propose roles for aPKCs and PKCβI in undifferentiated ESC.

The invasion of cancer cells is an important aspect of cancer progression. Single tumor cells exhibit at least two types of invasion in 3D environment, mesenchymal and amoeboid invasion. Tumor cells can switch between these two modes of movement depending on cellular status and surrounding environment. Amoeboid-mesenchymal transition (AMT) is less explored then mesenchymal-amoeboid transition (MAT). We performed a proteomic analysis of amoeboid-mesenchymal transition of human melanoma cell line A375M2. We have induced amoeboid-mesenchymal transition by treatment with a ROCK inhibitor Y27632 in 3D matrigel matrices and in 2D environment. Induction of the amoeboid-mesenchymal transition has changed a level of expression of 92 proteins and a level of phosphorylation of 15 proteins. Expression of only 17 proteins and phosphorylation of 8 proteins was identically changed in both of these environments. We found that PKCα regulates amoeboid migration and that treatment of cells with a PKCα inhibitor Gö6976 induces amoeboid-mesenchymal transition. Analysis of the proteomics data have further shown that induction of AMT by the ROCK inhibitor Y27632 leads to activation of antiapoptotic signals and activation of signaling pathways involved in regulation of actin cytoskeleton especially regulation of focal...

Durch Analyse der Subtraktion-cDNA Bibliothek einer humanen Lungentumor Zelllinie haben wir ein neues Mitglied der S100 Genfamilie identifiziert und charakterisiert, welches S100A14 benannt wurde. Die vollständige cDNA hat eine Länge von 1067 bp und kodiert für ein Protein von 104 Aminosäuren, welches die S100-spezifische Kalzium-bindende Domäne enthält. Das Gen wird in normalen humanen Epithelien ubiquitär exprimiert, zeigt jedoch Expressionsverluste in vielen Tumorzelllinien. Im Gegensatz zu Tumorzelllinien ist S100A14 auf mRNA- und Proteinebene in vielen humanen Primärtumoren stärker exprimiert, unter anderem in Lungen- und Brustkarzinomen. Um den Mechanismus der erhöhten S100A14 Expression in Lungen- und Brustkarzinomen zu verstehen, haben wir die Effekte des EGF (epidermal growth factor) und des TGF-alpha (transforming growth factor-alpha) untersucht. Beide Faktoren sind Liganden des ERBB Rezeptors und induzieren in der immortalisierten bronchialen Epithelzelllinie S100A14 Expression. Unter Verwendung spezifischer Inhibitoren konnte gezeigt werden, dass für die EGF-vermittelte transkriptionelle Induktion der ERK1/2 Signalweg (extracellular signal-regulated kinase) verantwortlich ist und eine de novo Proteinsynthese erfordert. Diese Ergebnisse unterstützend konnte immunhistologisch eine signifikante Korrelation zwischen der Überexpression von ERBB2 und S100A14 in primären Brustkarzinomen nachgewiesen werden. Phorbolester-12-Myristat-13-Acetat (PMA) verstärkte gleichfalls die S100A14 mRNA Expression in 9442 Zellen, was eine Regulation durch die Protein Kinase C (PKC) vermuten lässt. Die PMA-induzierte Expression von S100A14 wird ebenso wie die TGF-alpha/EGF-Induktion durch die Aktivierung des ERK1/2 Signalweges vermittelt. In Anbetracht der großen Bedeutung der ERK1/2 und PKC Signalwege in der Tumorentstehung und Tumorprogression ist zu vermuten, dass S100A14 über die aberrante Regulation dieser Signalwege an die maligne Transformation gekoppelt ist. / By analysing a human lung tumour cell line subtraction cDNA library, we have identified and characterized a novel member of the human S100 gene family that we designated S100A14. The full-length cDNA is 1067 bp and encodes a putative protein of 104 amino acids. The predicted protein contains the S100-specific EF-hand calcium-binding domain. The gene is ubiquitously expressed in normal human tissues of epithelial origin. S100A14 transcript was found to be down-regulated in many immortalized and tumour cell lines from diverse tissues. In contrast to the tumour cell lines, S100A14 shows up-regulation at the mRNA and protein level in many human primary tumours, including lung and breast carcinomas. To elucidate mechanisms whereby S100A14 expression is enhanced in lung and breast tumours, we studied the effects of epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) on its expression. Both are ligands of ERBB receptor and induced S100A14 expression in the immortalized bronchial epithelial cells. By use of specific inhibitors, we found that EGF-mediated transcriptional induction of S100A14 involves extracellular signal-regulated kinase (ERK1/2) signalling and requires de novo protein synthesis. In support of these findings, we demonstrated by immunohistochemistry a significant correlation between ERBB2 and S100A14 protein overexpression in primary breast carcinomas. Our studies showed that the phorbol ester 12-myristate 13-acetate (PMA) increases S100A14 mRNA expression in immortalized bronchial epithelial cells suggesting regulation by protein kinase C (PKC). Similar to TGF-alpha/EGF induction, the PMA-induced S100A14 expression was also mediated by activation of the ERK1/2 signalling cascade. Considering the importance of the ERK1/2 and PKC signalling pathways in tumour development and progression we suggest that it is the aberrant regulation of these signalling cascades that couples S100A14 to malignant transformation.

Les expériences suivantes testent l’hypothèse que la sérine/thréonine kinase p38α/β MAPK inhibe la rentrée dans le cycle cellulaire des cardiomyocytes ventriculaires de rats nouveau-nés (CVRNs), et induit l’expression d’un panel de cytokines/chimiokines inflammatoires. Le traitement des CVRNs par le phorbol 12,13-butyrate (PDBu), activateur de la protéine kinase C (PKC), aboutit au recrutement de l’isoforme conventionnelle (PKC-α) et des isoformes nouvelles (PKC-δ et PKC-ε) de PKC en l’absence de la rentrée dans le cycle cellulaire. Cette absence d’entrée dans le cycle cellulaire à la suite du traitement par PDBu est associée à une augmentation d’expression des ARNm des gènes qui bloquent la rentrée dans le cycle cellulaire. Les gènes comprennent Runx1(Runt-related transcription factor 1) et CDKN2a (cyclin-dependent kinase inhibitor 2A) également connu sous le nom de p16, inhibiteur du cycle cellulaire. En présence de l’inhibiteur de p38α/β MAPK, SB203580, le traitement PDBu induit une entrée dans le cycle cellulaire de deux populations distinctes de cardiomyocytes caractérisées par l’absence ou l’expression de novo de la protéine filamenteuse Nestine. En parallèle, le co-traitement PDBu/SB203580 atténue l’augmentation du niveau d’expression de l’ARNm de Runx1 et CDKN2a. L’inhibition pharmacologique du recrutement de PKC-α par GF109203X, inhibe sélectivement la rentrée dans le cycle cellulaire des CVRNs qui présentent une expression de novo de Nestine. En parallèle, le traitement par PDBu augmente le niveau d’ARNm d’un panel de cytokines inflammatoires et la co-administration de SB203580 inhibe cette réponse. Ces données révèlent que le cœur des rats nouveau-nés contient deux sous-populations distinctes de cardiomyocytes ventriculaires qui rentrent dans le cycle cellulaire à la suite d’un co-traitement PDBu / SB203580, et que la réponse proliférative est associée à une diminution des cytokines inflammatoires. Collectivement, ces résultats mettent en relief une nouvelle prémisse selon laquelle le recrutement de p38α/β MAPK médié par PKC-α joue un rôle central dans l’inhibition de l’entrée dans le cycle cellulaire et induit une réponse inflammatoire robuste par les CRVNs. / The following experiments test the hypothesis that the serine/threonine kinase p38α/β MAPK inhibits the cell cycle re-entry of neonatal rat ventricular cardiomyocytes (NNVMs) and induces the expression of a panel of inflammatory cytokines/chemokines. Treatment of NNVMs with phorbol 12,13-butyrate (PDBu), an activator of protein kinase C (PKC), results in the recruitment of the conventional isoform (PKC-α) and novel isoforms (PKC-δ and PKC-ε) of PKC in the absence of cell cycle re-entry. This lack of cell cycle re-entry following PDBu treatment is associated with an increase in the expression of mRNA of genes that inhibit cell cycle re-entry. These genes include Runx1 (Runt-related transcription factor 1) and CDKN2a (cyclin-dependent kinase inhibitor 2A), also known as p16, a cell cycle inhibitor. In the presence of the p38α/β MAPK inhibitor, SB203580, PDBu treatment induces cell cycle re-entry in two distinct populations of cardiomyocytes characterized by the absence or de novo expression of the filamentous protein Nestin. In parallel, co-treatment with PDBu/SB203580 attenuates the increase in Runx1 and CDKN2a mRNA levels. Pharmacological inhibition of PKC-α recruitment by GF109203X selectively inhibits cell cycle re-entry of NNVMs exhibiting de novo Nestin expression. Additionally, PDBu treatment increases the mRNA levels of a panel of inflammatory cytokines, and co-administration of SB203580 inhibits this response. These data reveal that the heart of neonatal rats contain two distinct subpopulations of ventricular cardiomyocytes that re-enter the cell cycle following PDBu/SB203580 co-treatment, and that the proliferative response is associated with a decrease in inflammatory cytokines. Collectively, these results highlight a novel premise whereby p38α/β MAPK recruitment mediated by PKC-α plays a central role in inhibiting cell cycle re-entry and induces a robust inflammatory response by NNVMs.

Doctor of Philosophy / Department of Biochemistry / Dolores J. Takemoto / The avascular lens tissue depends on the gap junction channels to facilitate intercellular communication for supplying cells deep within the lens with nutrients and removing waste products of cellular metabolism. In the absence of the protein synthesis machinery in the inner lens fiber cells, the proper regulation of gap junction channels becomes extremely important as disturbance of the lens homeostasis can lead to cataract development. Phosphorylation of gap junction subunit connexin proteins has been shown to play an important channel-modulating role in a variety of tissue. Protein kinase C-[Gamma] (PKC[Gamma]) has been implicated in the phosphorylation of connexins in the lens. Here the role of PKC[Gamma] in the regulation of gap junction coupling in the mouse lens has been investigated. We have compared the properties of coupling in lenses from wild type (WT) and PKC[Gamma] knockout (KO) mice. Western blotting, confocal immunofluorescence microscopy, immunoprecipitation, RT-PCR and quantitative real time PCR were used to study gap junction protein and message expression; gap junction coupling conductance and pH gating were measured in intact lenses using impedance studies. PKC[Gamma]was found to regulate the amount and distribution of Cx43 in the lens. Gap junction coupling conductance in the differentiating fibers (DF) of PKC[Gamma] KO lenses was 34% larger than that of WT. In the mature fiber (MF), the effect was much larger with the KO lenses having an 82% increase in coupling over WT. Absence of PKC[Gamma] in the KO mice also caused abnormal persistence of nuclei in the typical nucleus-free region in the DF. These results suggest a major role for PKC[Gamma] in the regulation of gap junction expression and coupling in the normal lens mediated by phosphorylation of the lens connexins. This becomes very vital in the diabetic lenses which contain a depleted amount of PKC[Gamma] and people suffering from spinocerebellar ataxia type-14 (SCA14) who have a mutated inactive form of PKC[Gamma]. Prolonged exposure of lenses to oxidative stress in these patients can lead to cataract formation. In cultured human lens epithelial cells (HLECs), 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulated the depletion of Cx43 protein level via PKC-mediated phosphorylation of Cx43. At the same time Cx46 protein and message levels were upregulated in response to TPA treatment. So, the PKC activator regulates Cx43 and Cx46 in opposing ways. The possible mitochondria localization of Cx46 reported here could help in finding the non-junctional roles for Cx46.

Le récepteur ionotropique P2X[indice inférieur 7] (P2X[indice inférieur 7]R) est impliqué dans divers rôles physiologiques tels la prolifération, l'apoptose, la réponse inflammatoire et le trafic membranaire dans plusieurs types cellulaires. Cependant, peu est connu quant aux rôles physiologiques du P2X[indice inférieur 7]R dans les cellules épithéliales intestinales (CEIs). Dans la littérature scientifique, le P2X[indice inférieur 7]R est connu pour activer la protéine kinase Dl (PKD1/PKC[mu]) qui est impliquée dans le transport des protéines membranaires. Comme l'un des rôles physiologiques majeurs des CEIs est le transport et l'absorption du glucose, le transporteur à glucose de type 2 (Glut2) a été ciblé afin d'étudier son transport membranaire suite à l'activation du P2X[indice inférieur 7]R. Glut2 est un élément clé dans le métabolisme du glucose par les CEIs. Une hypothèse stipulant que le P2X[indice inférieur 7]R serait impliqué dans le trafic membranaire de Glut2 par une voie dépendante de la PKD1/PKC[mu] a été émise. Les objectifs majeurs de l'étude étaient de déterminer le profil d'expression du P2X[indice inférieur 7]R selon le stade de différenciation des CEIs, d'élucider les mécanismes moléculaires régulant l'expression du P2X[indice inférieur 7]R, d'étudier la signalisation intracellulaire affectant l'expression membranaire de Glut2 induite par l'activation du P2X[indice inférieur 7]R. D'abord, le profil d'expression du P2X[indice inférieur 7]R en fonction de la différenciation des CEIs a été déterminé par immunofluorescence indirecte sur des sections de jéjunum de souris normales et par immunobuvardage de type western sur des lysats de cellules Caco-2/15 prolifératives et différenciées. Ensuite, la signalisation induite par l'activation du P2X[indice inférieur 7]R a été étudiée en stimulant des cellules IEC-6 avec de l'ATP ou du BzATP, deux agonistes du P2X[indice inférieur 7]R, et en prétraitant les cellules avec de l'oATP, un antagoniste du P2X[indice inférieur 7]R. Différents inhibiteurs pharmacologiques tels le UO126 (MEK1/2) et la rottlerine (PKC[delta]) ont été utilisés pour déterminer l'ordre des protéines dans les voies de signalisation. Également, différents chélateurs de calcium, comme le BAPTA-AM et l'EGTA, ont été utilisés pour étudier la dépendance des voies trouvées au calcium. L'expression de Glut2 à la membrane plasmique suite à la stimulation du P2X[indice inférieur 7]R a été étudiée par immunofluorescence indirecte et par biotinylation des protéines membranaires de surface. Finalement, la régulation transcriptionnelle du P2X[indice inférieur 7]R dans les cellules HEK 293T et Caco-2/15 a été étudiée par des essais luciférase qui permettent de visualiser l'interaction entre le promoteur du P2X[indice inférieur 7]R et des facteurs de transcription cibles comme Cdx-2, GATA-4, HNF-4[alpha], C/EBP[alpha] et C/EBP[bêta]. Les résultats obtenus démontrent que l'expression du P2X[indice inférieur 7]R augmente en fonction de l'état de différenciation des cellules Caco-2/15, ce qui coïncide avec sa localisation dans les deux tiers supérieurs de la villosité de jéjunum de souris normales. Aussi, l'activation du P2X[indice inférieur 7]R amène une augmentation de la phosphorylation des protéines PKD1/PKC[mu], PKC[delta], ERK1/2, MEK1/2, SAPK/JNK, p90RSK et CREB. Également, la PKC[delta] est en amont des protéines MEK1/2 et ERK1/2 qui elles-mêmes sont en amont de la PKD1/PKC[mu]. Cette voie PKC[delta]/MEK/ERK/PKD est également indépendante du calcium extracellulaire et intracellulaire. Aussi, il y a internalisation et diminution de l'expression membranaire de Glut2 suite à l'activation du P2X[indice inférieur 7]R par le BzATP. Finalement, le P2X[indice inférieur 7]R est régulé au niveau transcriptionnel par les facteurs de transcription HNF-4[alpha], C/EBP[alpha] et C/EBP[bêta] mais pas par Cdx-2 et GATA-4. En résumé, les résultats démontrent que le P2X[indice inférieur 7]R est impliqué dans l'internalisation et la diminution de l'expression membranaire de Glut2 par un mécanisme qui semble dépendant de la voie PKC[delta]/MEK/ERK/PKD calcium-indépendante.

No description available.

Although the processes used for temporarily storing and manipulating neural information have been extensively studied at the synaptic level far less attention has been given to the underlying cellular and molecular mechanisms that contribute to change in the intrinsic excitability of neurons. More importantly, how do these mechanisms of plasticity integrate with ongoing mechanisms of regulation of neural intrinsic excitability and, in turn, homeostasis of entire neural circuits? In this dissertation I describe the underlying mechanisms that contribute to persistent neural activity and, more globally, sensorimotor adaptation using weakly electric fish as my model system. Weakly electric fish have evolved a behavior adaptation known as the jamming avoidance response (JAR), and it is this adaptation that allows the organism to elevate its own electrical discharge in response to intraspecific interactions and subsequent distortions of the animal’s electric field. The elevation operates over a wide range and in vivo can last tens of hours upon cessation of a jamming stimulus. I demonstrate that the underlying mechanisms of the adaptation are mediated by calcium-dependent signaling in the pacemaker nucleus and that calcium-mediated phosphorylation plays an important role in the regulation of the long-term frequency elevation (LTFE). I demonstrate using an in vitro brain slice preparation from the weakly electric fish, Apteronotus leptorhynchus that the engram of memory formation depends on the cooperativity of calcium-dependent protein kinases and protein phosphatases. In addition, I show that the memory formation (in the form of LTFE) does not depend on the continued flux of calcium, but rather the phosphorylation events downstream of NMDA receptor activation. Moreover, I describe the differences in the expression of protein phosphatases and protein kinases as they relate to species-specific differences in sensorimotor adaptation. It is important to note that this is the first time that the cooperativity between different isoforms of protein kinase C (PKC) have been shown to play a role in graded long-term change in neuronal activity and, in turn, providing the neural basis of species-specific behavior. The neural adaptation of the electromotor system in weakly electric fish provides an excellent model system to study the underlying cellular and molecular events of vertebrate memory formation. / text

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Une augmentation de la génération des dérivés réactifs de l’oxygène (DRO), tels que le peroxyde d’hydrogène (H2O2), joue un rôle clé dans la pathophysiologie des maladies cardiovasculaires (MCV). La croissance et la prolifération excessives des cellules musculaires lisses vasculaires (CMLV) ont été suggérées comme étant les mécanismes à la base de la dysfonction vasculaire. Une implication potentielle du facteur de transcription Early growth response protein-1 (Egr-1) dans le développement des dommages vasculaires a été proposée. Des études ont démontré que le H2O2 augmente l’expression de l’Egr-1 dans les CMLV. Cependant, les voies de signalisation intracellulaire menant à l’expression de l’Egr-1 en réponse au H2O2 restent à établir. L’objectif de cette étude vise à examiner les différentes voies de signalisation impliquées dans l’expression de l’Egr-1 induite par le H2O2 dans les CMLV. Le H2O2 augmente l’expression de l’Egr-1 en fonction du temps et de la dose dans les CMLV A10. Le blocage pharmacologique des tyrosines kinases insulin-like growth factor-1 receptor (IGF-1R) et c-Src, par AG1024 et PP2 respectivement, atténue l’expression de l’Egr-1 induite par le H2O2, alors que l’AG1478, un inhibiteur de l’epidermal growth factor receptor (EGFR), et le PP3, l’analogue inactif du PP2, n’ont aucun effet sur l’expression de l’Egr-1. Le blocage pharmacologique de l’extracellular signal-regulated kinase 1/2 (ERK1/2), par UO126, et de la protéine kinase C (PKC), par rottlerin et rö-31-8220, diminue l’expression de l’Egr-1 induite par le H2O2. En résumé, nos résultats suggèrent que le H2O2 déclenche l’expression de l’Egr-1 via l’IGF-1R, la kinase c-Src, l’ERK1/2 et la PKC dans les CMLV. / Increased generation of reactive oxygen species (ROS), such as hydrogen peroxide (H2O2), plays a key role in the pathophysiology of cardiovascular diseases (CVD). Excessive growth and proliferation of vascular smooth muscle cells (VSMCs) has been suggested as an important contributor of vascular dysfunction. A potential involvement of early growth response protein-1 (Egr-1), a zinc-finger transcription factor, in the development of vascular injury has been proposed. Recent studies have shown that H2O2 increases Egr-1 expression in VSMCs. However, signaling events leading to H2O2-induced Egr-1 expression are not fully understood. Therefore, this study aims to examine the signaling pathways implicated in H2O2-induced Egr-1 expression in VSMC. H2O2 increased Egr-1 expression in a time and dose-dependent fashion in A10 VSMC. Pharmacological blockade of tyrosine kinases insulin-like growth factor-1 receptor (IGF-1R) and c-Src, by AG1024 and PP2 respectively, attenuated H2O2-induced Egr-1 expression, while AG1478, an epidermal growth factor receptor (EGFR) inhibitor, and PP3, the inactive analogue of PP2, have no effect on Egr-1 expression. Pharmacological blockade of extracellular signal-regulated kinase 1/2 (ERK1/2), by UO126, and proteine kinase C (PKC), by rottlerin and rö-31-8220, decreased H2O2-induced Egr-1 expression. In summary, our results suggest that H2O2 triggers Egr-1 expression through IGF-1R, c-Src, ERK1/2 and PKC in VSMC.