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Les flavonoïdes sont étudiés depuis des années pour leurs propriétés préventives et leur potentiel comme agents thérapeutiques. Plusieurs mécanismes pourraient intervenir dans leur activité anti-cancéreuse dont une inhibition de l'adhérence et de l'étalement cellulaire et une inhibition des propriétés invasives des cellules cancéreuses. Les dérivés de 3-aryl-2-quinolones sont structurellement proches des flavonoïdes et ont été caractérisés comme étant des composés anti-migratoires (Joseph et Al., J.Med.Chem, 2002). Comme la migration cellulaire est hautement dépendante des structures adhésives assemblées par la cellule, nous avons étudié l'activité de ces composés sur les adhérences focales et fibrillaires. Ces larges complexes protéiques impliquent notamment les intégrines et leurs partenaires cytoplasmiques les liant au cytosquelette. Les intégrines permettent à la cellule de percevoir son microenvironnement et de s'y adapter. Les structures d'adhérence contenant les intégrines sont en retour capables de contrôler cet environnement (dégradation matricielle, fibrillogenèse…). Nos travaux montrent que les dérivés de 3-aryl-2-quinolone sont capables d'inhiber l'étalement cellulaire et de provoquer le désassemblage de structures adhésives préalablement établies de façon dose-dépendante et indépendamment de la composition de la matrice extracellulaire. L'activité des composés est finement liée à leur structure et de légères modifications de la composition chimique de leur chaîne latérale peuvent inhiber leur activité. Nous avons pu établir une relation structure-activité pour cette famille de composés et avons étudié les mécanismes moléculaires menant au désassemblage des structures d'adhérences quand les cellules sont traitées par ces molécules. Des études par RMN ont montré une interaction directe entre le chef de file de cette famille de composés et le domaine cytoplasmique des intégrines à chaîne béta 3 et nous avons pu montrer que cette interaction inhibait la liaison sur l'intégrine de l'un de ces activateurs, la kindline. L'agrégation plaquettaire est dépendante de l'activation des intégrines et constitue un excellent système d'étude physiologique pour les inhibiteurs de ces récepteurs. Le chef de file des dérivés de 3-aryl-2-quinolone est capable d'inhiber l'agrégation plaquettaire et la formation du thrombus, ce qui en fait un bon candidat médicament comme anti-thrombotique. / Flavonoïds have been studied for years for their potential chemopreventive and chemotherapeutic action. Several mechanisms might account for their anticancer activity, among which inhibition of cell adhesion and spreading, or inhibition of tumor cell invasion. 3-aryl-2-quinolone derivatives are chemical structures close to flavonoïds and were first designed as anti-migratory agents (Joseph et Al., J.Med.Chem, 2002). As cell migration is highly dependent on the cell adhesion machinery, we decided to investigate the action of these molecules on focal and fibrillar adhesions. These large protein complexes include heterodimeric transmembrane proteins, the integrins, and their cytoplasmic interactors able to link to the cytoskeleton. Integrins allow microenvironment sensing and cellular response to it. Adhesive structures containing integrins are also able to control cell microenvironment (matrix degradation, fibrillogenesis…). Our studies show that 3-aryl-2-quinolone derivatives are able not only to prevent cell spreading but also to disrupt already well-established focal adhesions in a reversible and ECM composition independent manner. The activity of the molecule is closely linked with its structure, as very slight modification of the lateral chain of the compound can totally impair its activity. Our work is focused on establishing a Structure-Activity Relationship of 3-aryl-2-quinolone derivatives and on investigating the molecular mechanisms underlying this activity. Osteoblasts treatment by 3-aryl-2-quinolone derivatives triggers a rapid disassembly of focal and fibrillar adhesions. NMR experiments show a direct interaction between the lead compound of the family and 3 integrin cytoplasmic tail and pull-down assay show that it is able to reduce the interaction between 3 integrin and kindlin, one of its coactivator. As platelet activation is an archetype of 3 integrin activation, we tested the activity of 3-aryl-2-quinolone on this physiological process. Under treatment, platelets failed to become activated and are unable to trigger thrombus formation, providing an interest to the 3-aryl-2-quinolone derivatives as potential anti-thrombotic agents.

Fundamental to cell adhesion and migration, integrins are large heterodimeric membrane proteins that link the extracellular matrix to the actin cytoskeleton. Uniquely, these adhesion receptors mediate inside-out signal transduction, whereby extracellular adhesion is activated from within the cell by talin, a large cytoskeletal protein that binds to the cytoplasmic tail of the β integrin subunit via its PTB-like F3 domain. Features of the interface between talin1 and small β3 fragments only have been described previously. Through NMR studies of full-length integrin β tails, we have found that β tails differ widely in their interactions with different talin isoforms. The muscle-specific β1D/talin2 complex exhibited particularly high affinity, leading to the X-ray crystal structure of the β1D tail/talin2 F2-F3 complex. Further NMR and biological experiments demonstrated that integrin activation is induced by a concerted series of interactions between the talin F3 domain and the β tail and between the talin F2 domain and the cell membrane. Additional studies revealed the structural determinants of tight talin2/β1D binding and the basis of more general differences between β1 and β3 talin binding. NMR studies were also performed on tyrosine-phosphorylated integrin tails binding to the PTB domains of talin1 and Dok1, an inhibitor of integrin activation; these revealed that phosphorylation can inhibit integrin activation by increasing the affinity of the β tail for talin competitors. Key residues governing this switch were identified, and proteins were engineered with reversed affinities, offering potentially useful biological tools. Taken together, these results reveal the remarkable complexity of structural features that enable talin and its competitors to mediate this important form of transmembrane signalling.

No description available.