Certain hydrogel forming de novo proteins that utilize different crosslinking methods are studied experimentally on a rheometer. The stress reaxation modulus of CRC, a telechelic, triblock protein, is shown to be that of a stretched exponential function with a value of β ≅ 0.5. The insertion of an integrin binding domain and changes in pH within the range 6.5–8.5 are shown not to significantly affect the resulting rheological behavior. A selective chemical crosslinker is used on CRC hydrogel systems and is shown to change the rheological behavior of the system to that of a combination of a chemically and physically crosslinked system. Chemically crosslinked hydrogels composed of W6, a wheat gluten-based protein, demonstrate a storage modulus weakly dependent on the angular frequency that is much greater than the loss modulus, with a modulus concentration dependence of c^9/4.

The imidazoline I1 receptor (I1-R) is a novel receptor found primarily in the brain and nervous tissue where it modulates neurotransmission. It is named for its high affinity for compounds with an imidazoline structure such as the anti-hypertensive drugs, clonidine and moxonidine. The imidazoline receptor antisera-selected protein (IRAS) is the putative clone of the I1-R. IRAS has a unique structure, which does not resemble any other receptor protein. IRAS is present throughout the body with highest levels in the brain. There is a growing body of research examining the physiological roles of IRAS as an I1-R, in cell survival, migration and protein trafficking. However, there is little research into its neuronal functions. IRAS interacts with other membrane receptors: the mouse homologue of IRAS reorganises the actin cytoskeleton through interaction with the α5β1 fibronectin receptor. IRAS also binds insulin receptor substrate 4 and enhances insulin-induced extracellular signal-regulated kinase1/2 (ERK1/2) activation. Actin reorganisation and ERK1/2 activation are important for the development of neurites during neuronal differentiation. Therefore, the work described in this thesis aimed to investigate the effects of IRAS on neuronal differentiation. Studies reported in this thesis also aimed to investigate whether IRAS affected ERK1/2 signalling of other receptors involved in neuronal differentiation such as the NGF receptor, TrkA, and lysophospholipid receptors. The above aims were carried out in neuronal model PC12 cells transfected with either IRAS or a vector plasmid. Fluorescence microscopy and Western blotting techniques were used to examine the effect of IRAS on cell morphology and ERK1/2 signalling. The work described in this thesis found that IRAS reorganises the actin cytoskeleton and enhances growth cone development in PC12 cells. This study also shows that IRAS differentially enhances or inhibits NGF-induced PC12 cell differentiation depending on the presence or absence of serum in the media. In full-serum conditions, IRAS enhanced neurite outgrowth and this was accompanied by an increase in ERK1/2 activation. In serum-starved cells, IRAS inhibited neurite outgrowth with similar levels of ERK1/2 activation observed in vector- and IRAS-transfected cells. Finally, studies presented in this thesis found that IRAS enhances lysophosphatidic acid-induced ERK1/2 activation and that IRAS interacting with lysophospholipid receptor agonists present in serum is a potential mechanism by which it enhances NGF-induced ERK1/2 activation in full-serum conditions. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1345359 / Thesis (Ph.D.) - University of Adelaide, School of Medical Sciences, 2008

Talin is a multifunctional cytoskeletal protein that plays a critical role in linking the actin cytoskeleton to the integrin family of transmembrane cell adhesion receptors. Two distinct integrin binding sites have been identified in talin, one present in the globular head domain (IBS1) and involved in integrin activation, and a second (IBS2), that has been delineated to a 130 residue fragment of the talin rod domain, but whose functional role is still elusive (Tremuth et al.2004). The objective of the present study was to define the minimal structure of talin IBS2 and to investigate its functional role in the integrin-cytoskeleton connection.<p>In the first part of this study, we used a combination of three different experimental approaches to define the minimal structure of talin IBS2: 1) an in silico bioinformatics approach to analyse sequence conservation of talin IBS2, 2) an in vivo cell biology approach to study the subcellular localization of recombinant talin fragments covering IBS2 in CHOáIIbâ3 cells, and 3) an in vitro biochemical approach consisting in protein overlay, pull down and Surface Plasmon Resonance (SPR) assays, to study the direct interaction between talin IBS2 and the integrin â3 subunit. We delineated IBS2 to a single amphipathic á-helical repeat of 23 residues within the talin rod domain. We further provided evidence that a two amino acid mutation(L2094I2095/AA) was sufficient to inactivate the IBS2 site, due to a disruption of the á helix structure, as demonstrated by infrared spectroscopy. In addition, we identified 2 lysine residues (K2085, K2089) exposed on the solvent face of á helix 50, which are directly involved in the talin IBS2-integrin interaction.<p>In the second part of this study, we investigated the functional role of talin IBS2 in spreading defective talin (-/-) cells and showed that in contrast to full-length wild type talin, an IBS2 LI/AA mutant talin was unable to fully rescue the spread phenotype of these cells. These results provide the first direct evidence that IBS2 in the talin rod is essential to link integrins to the actin cytoskeleton. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Les adhérences focales (AF), structures adhésives reliant la cellule à la matrice extra-cellulaire (MEC), constituent de véritables plateformes de signalisation biochimique et mécanique qui contrôlent l'adhérence, la migration, la différenciation et la survie cellulaire. Les récepteurs transmembranaires intégrines sont au coeur des AF, où elles connectent la MEC au cytosquelette d'actine. Au début des années 2000, la protéine intracellulaire taline, qui se lie aux parties cytoplasmiques bêta des intégrines, était considérée comme le principal activateur des intégrines. Néanmoins, il a depuis été montré que la kindline, autre protéine intracellulaire se liant aux parties bêta cytoplasmiques, jouait également un rôle essentiel dans l'activation des intégrines. Ainsi,plusieurs études ont mis en évidence que la kindline et la taline étaient complémentaires et avaient une action synergique durant l'activation des intégrines. Les bases moléculaires de ces phénomènes restent à déterminer. De plus, la plupart des données sur lerôle de la kindline dans l'adhérence et l'activation des intégrines provient d'expériences menées sur des cellules en suspension et/ou avec l'intégrine plaquettaire αIIbβ3. Ainsi, la régulation de ces processus par la kindline dans les cellules adhérentes est encore peu comprise. Dans cette étude, nous combinons la microscopie PALM et le suivi de protéines individuelles pour révéler le rôle et le comportement de la kindline à l'intérieur et à l'extérieur des AF au cours des événements moléculaires clés se déroulant au niveau de la membrane plasmique, et qui mènent à l'activation des intégrines. Nous avons observé que les intégrines bêta1 etbêta3 portant une mutation ponctuelle inhibant l'interaction avec la kindline montrent un défaut d'immobilisation dans les AF. Nous avons également observé que la kindline-2, qui est enrichie dans les AF, diffusait librement au niveau de la membrane plasmique,à l'intérieur et à l'extérieur des AF. Ceci constitue une distinction majeure par rapport à la taline, qui, au niveau de la membrane plasmique, est essentiellement observée dans les AF où elle est immobile, montrant qu'elle est recrutée dans les AF directement depuis le cytosol sans diffusion latérale membranaire (Rossier et al. 2012). Afin d'identifier les bases moléculaires du recrutement et de la diffusion membranaire de la kindline, nous avons utilisé différents variants mutés de kindline précédemment décrits. Le mutant kindline-2-QW614/615AA (liaison aux intégrines inhibée) montre une diffusion membranaire accrue, ce qui suggère que la kindline peut diffuser au niveau de la membrane plasmique sans être associée aux intégrines. Par ailleurs, la baisse d'immobilisation au niveau des AF observée avec ce mutant montre qu'une partie de l'immobilisation de la kindline est due aux intégrines, suggérant l'existence d'un complexe intégrine-kindline immobile dans les AF. La délétion du domaine PleckstrinHomology (PH) de la kindline diminue considérablement son recrutement et sa diffusion membranaire. Nous avons évalué le rôle fonctionnel du recrutement et de la diffusion membranaire de la kindline en réexprimant ces mutants dans des cellules déplétéesen kindline-1 et -2 (cellules KO kindline-1 -/-, kindline-2 -/-). Ces expériences montrent que le recrutement et la diffusion membranaire de la kindline sont cruciaux pour l'activation des intégrines durant l'étalement cellulaire et favorisent la formation d’adhérences. Cela suggère que la kindline utilise un chemin différent de celui de la taline pour atteindre et activer les intégrines,ce qui pourrait expliquer au niveau moléculaire comment la kindline complémente la taline durant l'activation des intégrines. / Focal adhesions (FAs) are adhesive structures linking the cell to the extracellular matrix (ECM) and constitute molecular platforms for biochemical and mechanical signals controlling cell adhesion, migration, differentiation and survival. Integrin transmembrane receptors are core components of FAs, connecting the ECM to the actin cytoskeleton. During the early 2000s, the intracellular protein talin, which directly binds to the cytoplasmic tail of β-integrins, was considered as the main integrin activator. Nevertheless, it has been shown that kindlin, another intracellular protein that bind to β-integrin, is also a critical integrin activator. In fact, several studies have shown that kindlin and talin play complementary and synergistic roles during integrin activation. The molecular basis of these phenomena remains to determine. Moreover, most studies focusing on the role of kindlin during integrin activation and cell adhesion have been performed with suspended cells and/or with the platelet integrin αIIbβ3. Here we combined PALM microscopy with single protein tracking to decipher the role and behavior of kindlin during key molecular events occurring outside and inside FAs at the plasma membrane and leading to integrin activation, as we have done previously for talin (Rossier et al., 2012). We found that beta1 and beta3-integrins with a point mutation inhibiting binding to kindlin show reduced immobilization inside FAs. We also found that kindlin-2, which is enriched inside FAs, displayed free diffusion at the plasma membrane outside and inside FAs. This constitutes a major difference with talin, which, at the plasma membrane level, is observed almost exclusively in FAs, where it is immobile, which shows that talin is recruited into FAs directly from the cytosol without lateral diffusion along the plasma membrane (Rossier et al. 2012). To determine the molecular basis of kindlin membrane recruitment and diffusion, we used a kindlin variant known to decrease binding to integrins (kindlin-2- QW614/615AA). This mutant displayed increased membrane diffusion, suggesting that kindlin-2 can freely diffuse at the plasma membrane without interacting with integrins. Moreover, the kindlin-2-QW mutant showed decreased immobilization inside FA, showing that part of kindlin immobilization depends on interaction with integrins. This suggests that kindlin can form an immobile complex with integrins inside focal adhesions. Deletion of the kindlin pleckstrin homology (PH) domain strongly reduced the membrane recruitment and diffusion of kindlin. We assessed the functional role of kindlin membrane recruitment and diffusion by re-expressing different kindlin-2 mutants in kindlin-1/kindlin-2 double KO cells. Those experiments demonstrated that kindlin-2 membrane recruitment and diffusion are crucial for integrin activation during cell spreading and favor adhesion formation. This suggests that kindlin uses a different route from talin to reach integrins and trigger their activation, providing a possible molecular basis for their complementarity during integrin activation.

L’adhérence, l’activation et l’agrégation des plaquettes sanguines sont essentielles à l’hémostase mais peuvent également conduire à la thrombose artérielle sur plaque d’athérosclérose, aujourd’hui première cause de mortalité dans le monde. Les anti-thrombotiques actuels, dirigés contre l’activation et l’agrégation plaquettaires, ont une efficacité reconnue mais ont pour inconvénient d’augmenter le risque de saignement. L’objectif de cette thèse a été d’explorer de nouvelles stratégies réduisant la thrombose tout en préservant l’hémostase. L’utilisation de souris modifiées génétiquement a mis en évidence que l’intégrine alpha6 beta1, impliquée dans l’adhérence des plaquettes aux laminines, joue un rôle critique en thrombose expérimentale mais pas en hémostase. De plus, nous avons montré dans un système de perfusion de sang qu’une protéine préférentiellement exprimée dans les plaques d’athérosclérose, la ténascine-C, permet l’adhérence et l’activation des plaquettes. En revanche, la beta-arrestine-1, une protéine de signalisation, ne contribue que modestement aux fonctions plaquettaires et à la thrombose. En conclusion, ce travail a permis de dégager deux nouvelles pistes anti-thrombotiques potentiellement capables de préserver l’hémostase, basées sur le ciblage de l’intégrine alpha6 beta1 ou de l’interaction plaquette/ténascine-C. / Following vascular injury, blood platelet adhesion, activation and aggregation are essential for hemostasis but can also lead to arterial thrombosis, which is a leading cause of death worldwide. Current antithrombotic drugs impede platelet activation and aggregation, thereby considerably reducing cardiovascular mortality, but their use is linked to an increased bleeding risk. This thesis aimed to explore more selective strategies causing minimal perturbation of hemostasis. The use of genetically-modified mice has revealed an unsuspected important contribution of integrin alpha6 beta1, which mediates platelet adhesion to laminins, to experimental arterial thrombosis but not hemostasis. In addition, we showed that tenascin-C, an extracellular matrix protein overexpressed in atherosclerotic plaques, can support platelet adhesion and activation under flow. In contrast, the signaling protein beta-arrestin-1 does not play a major role in platelet function, hemostasis and thrombosis. In conclusion, this work provides two interesting candidates, namely integrin alpha6 beta1 and tenascin-C, to put into practice the concept of targeting thrombosis while minimally impairing hemostasis.

Made available in DSpace on 2015-07-22T20:49:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-11-24. Added 1 bitstream(s) on 2015-08-11T03:26:29Z : No. of bitstreams: 1 Publico-393.pdf: 1637068 bytes, checksum: 4fe3757007f6a049eac930eb08b63c88 (MD5) / O melanoma é o tipo de câncer de pele menos frequente, mas que tem um grande poder de letalidade devido ao seu potencial de formar metástases. Para as células adquirirem a capacidade de formar metástases, estas precisam ter a característica de sobreviver independente de interações com a matriz extracelular e consequentemente apresentar resistência ao anoikis. Por isso, a importância de se estudar as alterações que ocorrem com células tumorais que adquirem essa capacidade. Em nosso laboratório foi desenvolvido um modelo que nos permite estudar diferentes etapas da gênese do melanoma. Melanócitos murinos melan-a que sobreviveram depois de 1, 2, 3 e 4 ciclos de impedimento de ancoragem por 96 horas apresentaram modificações na morfologia e crescimento independente de PMA, e foram denominadas 1C, 2C, 3C e 4C, respectivamente. Diferentes linhagens de melanoma (4C11-, 4C11+, Tm1, Tm5, etc) foram estabelecidas após submeter os esferóides sobreviventes da 4C à diluição limitante. Dados prévios de nosso laboratório mostraram aumento da expressão de Timp1 ao longo da transformação maligna de melanócitos e aumento da resistência ao anoikis. Melanócitos melan-a superexpressando o gene Timp1 adquirem fenótipo de resistência ao anoikis. No entanto, o mecanismo pelo qual Timp1 medeia essa sinalização de sobrevivência não é conhecido. Dados da literatura mostram interação entre CD63, Timp1 e &#61538;1-integrinas em células epiteliais de mama humana e que essa interação regula processos fisiológicos como apoptose. Além disso, a glicosilação aberrante em moléculas de adesão celular, como integrinas, pode conferir às células capacidade de sobreviver em condições independentes de ancoragem. O objetivo do presente estudo foi analisar a possível interação entre CD63, Timp1 e &#61538;1-integrinas ao longo da transformação maligna de melanócitos, a presença de N-glicosilação aberrante em β1-integrinas e o impacto da N-glicosilação aberrante na resistência ao anoikis. Observou-se interação entre CD63 e Timp1 e CD63 e &#61538;1-integrinas nas linhagens 4C, 4C11- e 4C11+, estabelecidas após ciclos de impedimento de ancoragem, já a interação entre Timp1 e &#61538;1-integrinas foi observada somente nas linhagens de melanoma 4C11- e 4C11+. A expressão de &#61538;1-integrinas na superfície celular está aumentada na linhagem de melanoma agressivo 4C11+, assim como a expressão de Mgat-V e N-glicosilação aberrante. Além disso, o perfil eletroforético da &#61538;1-integrina sugere que a mesma apresenta aumento de N-glicosilação aberrante na linhagem de melanoma metastático 4C11+. O tratamento de células de melanoma 4C11+ com o inibidor de N-glicosilação swainsonine resulta em menor capacidade destas células em resistir ao anoikis. Este parece ser o primeiro estudo descrevendo a interação entre Timp1, CD63 e &#61538;1-integrinas em células tumorais. Assim, o presente trabalho favorece o entendimento de como Timp1 regula resistência ao anoikis ao longo da transformação maligna de melanócitos. / Although malignant melanoma is the less frequently diagnosed skin cancer, it shows a poor prognosis due its chemoresistance and metastasis development. One of the adquired abilities of transformed cells is anoikis resistance and this property is closely related to metastasis formation. In our laboratory, we developed a model that allows us to study different steps of melanocyte malignant transformation. Melan-a melanocytes surviving after 1, 2, 3 and 4 deadhesion cycles showed modified morphology and independent PMA growth and have been named, 1C, 2C, 3C and 4C cells, respectively. Different melanoma cell lines were established after submitting 4C spheroids to limiting dilution. Previous results of our group showed increased expression of Timp1 along melanoma genesis and its correlation with anoikis resistance. However, the mechanism involved in this signaling is unknown. Published data demonstrated interaction between CD63, Timp1 and &#61538;1-integrins in human breast epithelial cells and its role in apoptosis. Furthermore, aberrant glycosylation in cell adhesion molecules such as integrins provides to cells the ability to survive under anchorage-independent conditions. The aim of this work was analyze the possible interaction among CD63, Timp1 and &#61538;1-integrins along melanocyte malignant transformation, possible aberrant N-glycosylation patterns of β1-integrins and their impact in anoikis resistance. Aberrant N-glycosylation patterns were observed in tumorigenic cells. We observed interaction between CD63 and Timp1 and between CD63 and &#61538;1-integrins in the melan-a-derived cells 4C, 4C11, and 4C11 +, and interaction between Timp1 and &#61538;1-integrins only in melanoma cell lines 4C11 - and 4C11 +. The presence of Timp1 in supernatant from 4C11+ conferred to melan-a cells anoikis resistance. The expression of &#61538;1-integrins in our study model is increased in aggressive melanoma lineage, 4C11+, as well as the expression of Mgat-V and aberrant N-glycosylation on cell surface. Moreover, the electrophoretic profile of &#61538; 1-integrin suggests that melanoma metastatic 4C11+. Lineage present increased aberrant N-glycosylation in this molecule. Treatment of melanoma cells 4C11 + with the N-glycosylation inhibitor, swainsonine, resulted in reduced capacity of these cells to resist to anoikis. This seems to be the first study describing the interaction between Timp1, CD63 and &#61538;1-integrin in tumor cells and may contribute to a better understanding of how Timp1 regulates resistance to anoikis during the melanocyte malignant transformation. / TEDE / BV UNIFESP: Teses e dissertações

Avaliamos a capacidade de indução de migração, invasão e secreção de protease pelo peptídeo derivado da laminina, C16 (KAFDITYVRLKF, cadeia g1) em linhagem celular (CAC2) de carcinoma adenóide cístico humano. Laminina g1 foi imunolocalizada no carcinoma adenóide in vivo e in vitro. Ensaio de ferida, em câmara bipartite e em vídeo microscopia (time-lapse) mostraram que C16 estimula migração em células CAC2. C16 também estimulou invasão em ensaio com câmaras bipartites cobertas com Matrigel. Invasão depende de atividade de protease. Zimografia mostrou que C16 aumentou secreção de MMPs 2 e 9. Diferentes vias de sinalização podem estar relacionadas com os efeitos de C16. Immunoblot revelou que C16 aumentou a fosforilação de AKT e ERK. Para o estudo de possíveis receptores do peptídeo, preparações de membrana foram passadas em colunas de afinidade com C16 acoplado. Banda de 40kDa foi eluída e analisada por espectrometria de massa (LC-MS/MS) que identificou a cadeia a1 do colágeno. O fragmento de colágeno eluído poderia ser parte de um complexo protéico envolvendo C16. Integrinas são receptores de colágeno e candidatas a fazerem parte desse complexo. Células CAC2 expressaram as integrinas av, a5, b3 and b1. Silenciamento dessas integrinas promoveu redução da migração e secreção de protease induzidas por C16. Sugerimos que C16 estimularia migração, invasão e secreção de protease em células de carcinoma adenóide cístico através de integrinas a5b1 e avb3. O sinal gerado por C16 seria transduzido pelas vias AKT e ERK1/2. / We studied induction of migration, invasion and protease activity by laminin-derived peptide C16 (KAFDITYVRLKF, g1 chain) in a cell line (CAC2) from adenoid cystic carcinoma. Laminin g1 was immunolocalized in adenoid cystic carcinoma in vivo and in vitro. C16 increased migratory activity of CAC2 cells, as shown by monolayer wound assay, Transwell migration assay and time-lapse video microscopy. This peptide also stimulated cell invasion in Transwell chambers coated with Matrigel. Invasion depends on protease activity. Zymograms showed that C16 increased secretion of MMPs 2 and 9. Different signaling pathways could be related to C16 regulation in CAC2 cells. Immunoblot showed that C16 increased phosphorylation of both AKT and ERK compared to controls. To study putative receptors of this peptide we used affinity chromatography. Membrane preparations were run through C16-affinity columns. A 40kDa band was eluted and analyzed by mass spectrometry (LC-MS/MS) identifying a collagen a1 chain. The collagen fragment eluted could be part of a protein complex involving C16. This protein complex may include integrins, which are collagen receptors. CAC2 cells exhibited av, a5, b3 and b1 integrins. siRNA knockdown of these integrins inhibited both C16-induced migration and protease activity. We propose that C16 increases migration, invasion and protease activity of a human salivary gland adenoid cystic carcinoma cell line through a5b1 and avb3 integrins. The signal generated by C16 is transduced by AKT and ERK1/2 signaling pathways.

Abstract Matrix metalloproteinases, MMPs, are a family of enzymes capable of modulating connective tissue components. The expression of several MMPs is increased in oral squamous cell carcinomas (OSCCs). They are assumed to have an important role in the development and progression of OSCCs. However, the exact role and mechanism of the regulation of MMPs in malignant transformation are still largely unknown. In this study, tumour-associated trypsin-2 (TAT-2) was detected in OSCC tissue sections, and its role in MMP-2 and -9 regulation in carcinoma cells was evaluated. The TAT-2 gene was transfected into two different OSCC cell lines and one immortalized oral epithelial cell line. In TAT-2-transfected cells, MMP-9 activation increased OSCC cell invasion in chicken chorionallantoic membrane assay. Increased intravasation was prevented by tumour-associated trypsin inhibitor or specific gelatinase-inhibiting CTT-peptide. TAT-2 also converted MMP-1, -8, -13 and -3 into smaller molecular weight forms in vitro. However, TAT-2-transfected OSCC cells showed no conversion. TAT-2 was demonstrated to degrade powerfully type I collagen into small fragments in vitro. The cell surface receptor αvβ6 integrin is strongly up-regulated in OSCCs. By using β6-transfected OSCC cells, it was demonstrated that αvβ6 integrin down-regulates MMP-13 expression. However, this integrin did not regulate other collagenases or TIMP-1. β6-transfected cells invaded more efficiently through the basement membrane matrix, but their migration through type I collagen remained unchanged. MMP-8 expression was detected for the first time in head and neck squamous cell carcinoma (HNSCC) cell lines and corresponding cultured dermal and tumour fibroblasts. The localization of MMP-8 in HNSCC was determined by immunohistochemical stainings and in situ hybridization. MMP-8 production levels in carcinoma cells were faint and sporadic in HNSCCs sections. Ninety-two primary mobile tongue SCCs were subjected to MMP-8 immunohistochemical staining, and the staining results were compared to survival rates. MMP-8 was associated with improved disease-free survival in females but not in males.

Les intégrines sont des protéines transmembranaires, formées d’une sous-unité α et d’une sous-unité β, qui sont impliquées dans de nombreuses caractéristiques du cancer. Mes travaux de thèses ont montré que l’axe intégrine α5β1/AKT est impliqué dans la résistance à l’apoptose des cellules de glioblastome et dans leur migration. L’inhibition fonctionnelle de l’intégrine α5β1 associée à la réactivation de p53 sensibilise les cellules de glioblastome à l’apoptose. Mes résultats ont mis en évidence que les protéines anti-apoptotiques PEA-15 et Survivine sont deux intervenants majeurs dans cette résistance à l’apoptose. La migration dépendante de l’intégrine α5β1 implique la β-caténine. Les résultats obtenus par ce travail de thèse, donnent, par conséquent, des arguments supplémentaires en faveur de l’implication de l’intégrine α5β1 dans l’agressivité des glioblastomes. Ces résultats permettent également de proposer de nouvelles cibles thérapeutiques ainsi que des biomarqueurs pertinents pour stratifier les patients potentiellement répondeurs à une stratégie anti-intégrine. / Integrins are αβ membrane localised protein heterodimers involved in numerous hallmarks of cancer. My PhD thesis showed that the integrin α5β1/AKT axis is implicated in glioblastoma cells resistance to apoptosis and migration. The inhibition of α5β1 integrin oncogenic pathway sensitizes glioma cells to p53-reactivation dependent apoptotic cues. My results showed that PEA-15 and Survivin are two anti-apoptotic proteins involved in the resistance to apoptosis. α5β1 integrin dependent migration involves the β-catenin pathway. My results confirm that α5β1 integrin has to be considered as an important player in glioblastoma aggressiveness and resistance to therapy. The results of my thesis also suggest new therapeutic targets and pertinent biomarkers for glioblastoma patient stratification.

L’effet photothermique permet de détecter efficacement des nanoparticules d’or avec un microscope en champ lointain grâce à leur forte absorption de la lumière. L’absence de problème photophysique fait des nanoparticules d’or une alternative au marquage de biomolécules par des sondes fluorescentes. La méthode PhACS (Photothermal Absorption Correlation Spectroscopy) utilise les fluctuations de signal photothermique dues au passage de nanoparticules dans le volume de détection pour étudier leur diffusion. Cette méthode permet également la mesure précise de diamètres hydrodynamiques de nanoparticules fonctionnalisées. La méthode SNaPT (Single Nano-Particle Tracking) réalise le suivi bidimensionnel de nanoparticules individuelles grâce à une localisation effectuée par triangulation. Nous avons appliqué cette méthode pour étudier la diffusion des intégrines alphaV-beta3 marquées par des nanoparticules d’or de 5 nm dans les adhérences focales, points d’ancrage entre le cytosquelette de la cellule et la matrice extracellulaire. Nous observons que ces intégrines ont tendance à former des agrégats qui alternent entre un mouvement diffusif et un mouvement confiné. Ce résultat appelle maintenant à un nouveau modèle où nous aurions une redistribution continue des intégrines au sein des adhérences focales. / Gold nanoparticles may be detected with optical far-field microscopy by use of the photothermal effect due to their strong light absorbance. With no photophysic issues, gold nanoparticles are an alternative to fluorescent probes for use in biological systems. The PhACS method (Photothermal Absorption Correlation Spectroscopy) is used to study diffusion by measuring the autocorrelation of photothermal signal fluctuations due to nanoparticles passing through the detection volume. This method is sensitive enough to mesure the precise hydrodynamic diameter of functionalised nanoparticles. The SnaPT method (Single Nano-Particle Tracking) can track 2-dimensional motion of individual nanoparticles by pinpointing the localization with a triangulation method. The SNaPT method was used to study motion of alphaV-beta3 integrins that were bound to a 5 nm gold nanoparticle inside focal adhesion, where the cell cytoskeleton is linked to the extracullular matrix. The integrin was found to organize into clusters oscillating between the bound and diffuse states. These observations require new working models where integrins would be constantly redistributed.