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Περίληψη
Στην παρούσα διατριβή μελετήθηκε η εμπλοκή της PKCε στην ογκογένεση του νευρικού συστήματος μέσω αλληλεπίδρασής της με την ογκοκατασταλτική πρωτεΐνη νευροϊνιδίνη και το MAPK/ERK μονοπάτι μεταγωγής σήματος και ρύθμισης των διαδικασιών του πολλαπλασιασμού και της διαφοροποίησης. Αρχικά, χρησιμοποιώντας φαρμακολογικές προσεγγίσεις, μελετήθηκε το πώς επιδρά η ενεργοποίηση της ενδογενούς PKCε στον κακοήθη όγκο των περιφερικών νευρικών ελύτρων. Αποδείχθηκε ότι η ενεργοποίηση της PKCε προάγει την κυτταρική διαφοροποίηση και την απώλεια του διεισδυτικού φαινοτύπου στα μετασχηματισμένα Schwann κύτταρα. Προκειμένου να μελετηθεί η σημασία αυτής της ενεργοποίησης σε οργανισμικό επίπεδο, κατασκευάστηκαν διπλά σταθερά διαμολυσμένοι καρκινικοί κλώνοι κυττάρων επιθηλιακής και νευρικής προελεύσεως, όπου η έκφραση της PKCε και της κυρίαρχα αρνητικής μορφής της βρίσκεται υπό το ρυθμιζόμενο έλεγχο δοξυκυκλίνης (Σύστημα Tet-Οff). Πριν, όμως μελετηθεί ολόκληρος ο οργανισμός, διαλευκάνθηκε ο μηχανισμός δράση ...
Περίληψη σε άλλη γλώσσαft;mar
In the present study we investigated the involvement of PKCε in nervous system tumorigenesis through its interaction with neurofibromin, a tumor suppressor protein, and MAPK/ERK signaling pathway during proliferation and differentiation processes. Using pharmacological approaches, we first studied the result of endogenous PKCε activation in malignant peripheral nerve sheath tumor, a frequent cancer of the PNS with poor prediction, and showed that PKCε activation induces cellular differentiation and loss of invasiveness in transformed Schwann cells. To study the significance of this activation in an organismal level we constructed double stable cancer clones of epithelial and neuronal origin, where PKCε and dominant negative PKCε are under doxycycline regulation (Tet-Off system). Before proceeding in animal experiments we elucidated the mechanisms of action and intermolecular interactions of PKCε during neuroblastoma cell differentiation. We found that differentiation in SHSY-5Y cells i ...
In the present study we investigated the involvement of PKCε in nervous system tumorigenesis through its interaction with neurofibromin, a tumor suppressor protein, and MAPK/ERK signaling pathway during proliferation and differentiation processes. Using pharmacological approaches, we first studied the result of endogenous PKCε activation in malignant peripheral nerve sheath tumor, a frequent cancer of the PNS with poor prediction, and showed that PKCε activation induces cellular differentiation and loss of invasiveness in transformed Schwann cells. To study the significance of this activation in an organismal level we constructed double stable cancer clones of epithelial and neuronal origin, where PKCε and dominant negative PKCε are under doxycycline regulation (Tet-Off system). Before proceeding in animal experiments we elucidated the mechanisms of action and intermolecular interactions of PKCε during neuroblastoma cell differentiation. We found that differentiation in SHSY-5Y cells is characterized by intense, PKCε-dependent signaling and ERK activation. More importantly, PKC-dependent phosphorylation of neurofibromin was recognized as a focal point in neuroblastoma differentiation. We further studied PKCε interaction with neurofibromin in terminally differentiated chick embryo neurons and showed that neurofibromin abundance in the CNS is controlled by nuclear proteasomal degradation, under PKCε regulation. Namely, PKCε-dependent phosphorylation of neurofibromin at Ser2808 offers protein stability and regulates nucleocytoplasmic shuttling of neurofibromin. We, next, assessed the implication of neurofibromin and the importance of its phosphorylation by PKCε in glioblastoma proliferation. We showed, for the first time, that neurofibromin abundance, subcellular localization and intermolecular interactions are regulated during the cell cycle of SF268 CNS tumor cells. Interestingly, we recorded corresponding changes in PKCε-dependent phosphorylation at the C-tail of neurofibromin. More importantly, we showed that neurofibromin co-localizes with the mitotic apparatus during all mitotic phases of both transformed and normal glial cells. Taken together our results proved that PKCε activation and interaction with neurofibromin regulates differentiation of transformed PNS cells, while in the CNS, PKCε-dependent phosphorylation at Ser2808 offers stability and regulates nucleocytoplasmic shuttling of neurofibromin for functions related to mitosis.
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