Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Oligodendrocytes derived in the laboratory from stem cells have been proposed as a treatment for acute and chronic injury to the central nervous system (CNS). Platelet-derived growth factor-receptor alpha (PDGFRÑ)w signaling is known to play an important role for regulation of oligodendrocyte progenitor cell numbers both during development and adulthood. Here, we analyze the effect of PDGFRÑ signaling on CNS stem cells derived from embryonic day 13.5 murine cortex and cultured in monolayer. Fetal and adult CNS stem cells express PDGFRÑ, and PDGF-AA treatment increases viability and proliferation of these cells. In the absence of insulin, this effect of PDGF-AA is very clear. Consistent with this result, PDGF-AA strongly stimulates glycolytic rate. PDGF-AA treatment rapidly induces morphological changes in the cells although the cells maintain expression of a wide range of precursor markers. We show that a brief exposure to PDGF-AA rapidly and efficiently induces oligodendrocytes from CNS stem cells. Our data suggest that phosphoinositide kinase-3 (PI3K)/Akt, mitogen-activated protein/extracellular signal-regulated kinase kinase/extracellular signal-related kinase (MEK/Erk), mammalian target of rapamycin (mTOR) regulate survival, proliferation, glycolytic rate, and oligodendrogliogenesis induced by PDGF-AA. By treating with PDGF-AA, progenitor cells directly from embryonic cortex can be expanded and differentiated into oligodendrocytes with high efficiency. Our results show that PDGF-AA promotes oligodendrocyte progenitor generation from CNS stem cells and supports their survival and proliferation. The derivation of oligodendrocytes demonstrated here may support the safe and effective use of stem cells in the development of new therapies targeting this cell type.

Thesis (Ph. D.)--University of Oklahoma. / Bibliography: leaves 147-164.

Growth factor receptors have significant effects on various normal function of body such as cell proliferation, differentiation and apoptosis. They are also involved in neuronal function and dysfunction, cardiovascular diseases, and malignancies. Recently, multiple G protein-coupled receptors (GPCRs) have been shown to transactivate receptor tyrosine kinases (RTKs). Since both classes of receptors have complicated downstream cascades individually, understanding the signaling differences between GPCR-induced growth factor receptor transactivation and direct ligand activation is an important challenge. To clarifying this phenomenon we investigated the phosphorylation profile and downstream effectors of ligand-activated vs. transactivated PDGF?? receptors. Dopamine receptors (one of the receptors of the GPCRs family) were used to compare the PDGF?? receptor phosphorylation and activity during direct activation and transactivation. Dose-response and time-course data between these two stimuli were evaluated. Furthermore, the phosphorylation site profiles and the intracellular signaling pathways of PDGF?? receptor after direct activation and transactivation were examined. In addition, possible synergic effects between transactivation and direct activation were explored. The results of this project showed that the phosphorylation profile and downstream effectors of ligand activated receptors versus transactivated receptors are different. Our data indicated that transactivation-induced pathways are more involved in survival and proliferation effects compared to ligand activation. This research answered basic questions about transactivation phenomena and proposes that these transactivation pathways could be exploited as a therapeutic approach for neurodegenerative diseases.