The functions that have been attributed to polyamines are many, varied and, in some cases, controversial but it is indisputable that polyamines are a requirement for cells to either grow or function in an optimal manner. Since the polyamine levels are increased in cancer cells and tissues as well as in all rapidly proliferating cells, polyamine research has traditionally placed a lot of emphasis on a role of polyamines in normal and malignant cell growth. However, attempts to use inhibitors of biosynthetic enzymes as chemotherapeutic agents have been mostly disappointing. This is apparently attributable to the polyamine transport system and dietary polyamines, but the contribution of abnormally regulated polyamine metabolism is equally obvious. The finding that polyamines are involved in the regulation of specific receptors such as the NMDA receptors and ion channels such as inwardly rectifying K+ channels has renewed interest in polyamine mediated regulation of cellular functions. It has also increased interest in polyamine metabolism in the central nervous system where NMDA receptors and inwardly rectifying K+ channels are both expressed abundantly.
In this study we wanted to elucidate the role of the first and crucial enzyme of polyamine biosynthesis, i.e. ornithine decarboxylase, and its protein inhibitor, antizyme, in the polyamine metabolism of CNS. In particular we were interested in whether the guanosine 5’-phosphate activatable ODC activity could be found in CNS. In another part of this study, we investigated the pathological consequences of lifelong deregulated ODC expression.
Aims of the present study are summarised as follows:
To investigate whether GTP-activatable ODC can be found in the CNS, where the basal activity of ODC has been suggested by others to be resistant to DFMO, which is a characteristic feature of the GTP-activatable ODC activity in tumours and if found, to characterize properties of the GTP-activatable brain ODC and compare them to the properties of tumour enzyme.
To localize and compare ODC and antizyme expression in adult rat brain using in situ hybridization and immunocytochemistry.
To study employing site-directed mutagenesis of aspartate-233, the role of one of the most highly conserved regions in eukaryotic ODCs and at the same time test whether the GTP-activation of ODC could be affected by this mutation.
To generate a transgenic mouse line expressing ODC cDNA under the control of an MMTV-LTR promotor and use it to study the pathological and physiological effects of deregulated ODC expression during the life of transgenic animals.