Freeland, Karen;
(2001)
CRE mediated regulation of the CGRP and BCL-2 genes in PC12 cells.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The calcitonin/calcitonin gene-related peptide (CT/CGRP) gene is expressed in sympathetic and sensory neurons in response to the neurotrophin nerve growth factor (NGF) and the second messenger cAMP. It is believed that the effects of these stimuli are mediated by the transcription factor CREB, which is activated by phosphorylation at serine 133, an event that can be induced by many different intracellular signalling mechanisms. CREB binds constitutively to a cAMP response element (CRE) within the CT/CGRP gene promoter. This CRE site is necessary and sufficient for promoter activation by cAMP and is necessary but not sufficient for activation by NGF. This study shows that this difference is paralleled by a difference in the signalling pathways required for each stimulus to activate the CT/CGRP promoter. Whilst the effects of cAMP are mediated by protein kinase A signalling, NGF- mediated promoter stimulation requires the activation of Ras/Raf/mitogen-activated protein kinase kinases 1 and 2 (MEK-l/MEK-2) and the p42/p44 mitogen-activated protein (MAP) kinases. Other signalling pathways activated by NGF, such as protein kinase C and p38 MAP kinase, are not involved in the NGF response. CREB has also been implicated in mediating hypoxia-induced tyrosine hydroxylase (TH) promoter activation. The Bcl-2 promoter, which contains a CRE site, is responsive to NGF and hypoxia in certain neuronal cells. This study has shown that the Bcl-2 CRE is responsive to hypoxia in PC12 cells, although the Bcl-2 promoter is not. Indeed, TH, Bcl-2 and CT/CGRP CRE sites respond differentially to NGF, cAMP and hypoxia, and the responses exhibited by the three CRE sites when linked to a heterologous promoter can differ from those they exhibit in the context of their respective promoters. Some of these differences can be attributed to the sequences of the individual CRE sites, whilst others can be attributed to the proteins which bind to them.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | CRE mediated regulation of the CGRP and BCL-2 genes in PC12 cells |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| Keywords: | Biological sciences; cAMP response element |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10100487 |
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