A miozin foszfatáz új szabályozó funkciói nem-izom sejtekben = Novel regulatory functions of myosin phosphatase in non-muscle cells

A protein foszfataz-1 katalitikus alegyseget (PP1c) es a PP1c-t „celra iranyito” regulator alegyseget (MYPT1) tartalmazo miozin foszfataz (MP) szerepet tanulmanyoztuk nem-izom sejtek sejtfolyamataiban. PP1c specifikus inhibitorok alkalmazasaval, valamint a MYPT1-el kolcsonhato uj feherje partnerek azonositasaval kivantuk feltarni a MP uj funkciot. Tanulmanyoztuk a MYPT-csaladba tartozo TIMAP feherje es a PP1c kolcsonhatasat is es kimutattuk a PP1c-TIMAP komplex szabalyozo szerepet a moezin defoszforilaciojaban. Felismertuk, hogy tanninokban es zold teaban előfordulo polifenolok PP1c szelektiv inhibitorok es csokkentik a daganatos sejtek eletkepesseget. A MYPT1-el kolcsonhato feherjekent es/vagy a MP lehetseges szubsztratjaikent azonositottuk a retinoblasztoma feherjet (Rb), a nitrogen-monoxid szintetazt (NOS) es preszinaptikus neuronalis feherjeket (szinapszin, szintaxin, SNAP-25, CaM-kinaz-II, kalcineurin). Kimutattuk, hogy a Rb MP altal tortenő defoszforilacioja a leukemias sejtek kemoszenzitivitasanak, a neuronalis feherjek (szintaxin, szinapszin) Rho-kinaz/MP altal tortenő foszforilacioja/defoszforilacioja pedig a neurotranszmitter felszabadulas fontos szabalyozo folyamatai. Jellemeztuk a MYPT1 es a kalcineurin kolcsonhatasat es kimutattuk, hogy a MYPT1 kalcineurin altal tortenő defoszforilacioja az endotel sejtek „barrier” funkciojat szabalyozza. Osszefoglalva: a MP uj szabalyozo funkcioinak felismerese bőviti e sejtfolyamatok farmakologiai befolyasolasanak lehetősegeit. | We studied the role of myosin phosphatase (MP) composed of protein phosphatase-1 catalytic subunit and PP1c-targeting regulatory subunit (MYPT1) in cellular processes of non-muscle cells. We wished to uncover novel functions of MP by using PP1c specific inhibitors as well as by identification of novel MYPT1-interacting proteins. The interaction of TIMAP, a MYPT-family protein, with PP1c was also studied and it was shown that the PP1c-TIMAP complex controlled the dephosphorylation of moesin. We identified the polyphenols of tannins and green tea as PP1c selective inhibitors which were implicated in decreasing the viability of malignant cells. The retinoblastoma protein (Rb), the nitrogen-monoxide (NO) synthase (NOS) and presynaptic neuronal proteins (synapsin, syntaxin, CaM-kinase-II,) were identified as MYPT1-interacting proteins and/or possible substrates for MP. We proved that the dephosphorylation of Rb by MP influenced chemosensitivity of leukemic cells, while the phosphorylation/dephosphorylation of neuronal proteins (synapsin, syntaxin) by Rho-kinase/MP had important regulatory roles in the neurotransmitter release. We characterized the interaction of MYPT1 with calcineurin and showed that dephosphorylation of MYPT1 by calcineurin mediated the barrier function of endothelial cells. In summary, the novel regulatory functions of MP recognized here extend the possibilities to pharmacologically influence the above cellular processes.