| Summary: | 碩士 === 國立政治大學 === 生命科學研究所 === 98 === The neurotrophins play an important role in cell differentiation and survival of the nervous system. Among them, the neuroprotective effects of brain-derived neurotrophic factor (BDNF) is showed to be mediated by extracellular signal-regulated kinase (ERK) and phosphatidylinositol-3 kinase (PI3K) signaling pathway in the recent studies. However, other cellular signaling pathways might be involved in these effects of BDNF. Protein kinase CK2 (casein kinase 2) is a ubiquitous and highly conserved serine/threonine protein kinase and is indicated as a vital cellular role. In recent years, evidences have been mounted in support of the importance of CK2 in the suppression of apoptosis. Serum response factor (SRF) is a transcription factor binding to a consensus DNA sequence SRE (known as a CArG box) which was found in the promoters of some immediately early genes (such as c-fos, Egr) and anti-apoptotic Mcl-1 gene. The activations of SRF-regulated genes were associated with cell proliferation, cell survival and perception of synaptic activity. However, the regulatory mechanism of SRE-mediated genes is not well studied. The SRE-mediated transcription activity through CK2 signaling by BDNF treatment was studied in the PC12 cells in the present study. Results revealed that BDNF significantly increased the SRE promoter activity by luciferase report assay. The SRE-mediated transcription activity was increased by overexpression of CK2α, and the inhibition of endogenous CK2α by small interfering RNA was also shown to reduce this transcription activity. Furthermore, CK2α siRNA treatment antagonized the up-regulation effects of BDNF on SRE-mediated transcription activity. The co-transfection of CK2 and mutant SRF S99A plasmids significantly diminished up-regulatory effects of CK2 on SRE promoter activity. To test this CK2 induction in SRE-mediated transcription plays a role in neuroprotecion, we determined whether over-expression CK2 protects PC12 cells against rotenone-induced apoptosis. The results revealed that the over-expression of CK2α protected cells against rotenone-induced apoptosis and rescued the SRE-mediated transcription activity. Further, these effects of CK2α were blocked by co-transfection of mutant SRF S99A. These above results demonstrate that the up-regulation of BDNF on SRE-mediated genes is through CK2 signaling pathway.
|
|---|
