Polyamine homeostasis

Abstract

The polyamines putrescine, spermidine and spermine are highly regulated polycations present in virtually all cells of higher eukaryotes. They are essential for proper cell growth and differentiation by participating in various physiological processes including DNA, RNA and protein synthesis, apoptosis and interactions with ion-channels. The complexity of polyamine metabolism and the multitude of compensatory mechanisms that are invoked to maintain polyamine homeostasis argue that these molecules are critical for cell survival.

The primary aim of this study was to gain a better understanding of the mode of action of polyamines and the regulatory mechanisms in which they are involved. Transgenic mice overexpressing the polyamine biosynthetic enzymes S-AdoMetDC and ODC were found to maintain their polyamine pools by acetylation of spermidine and spermine and an increased export of these acetylated compounds. The expression of various genes was studied as a response to polyamine deprivation in cell- and kidney organ culture. Among these genes acetyl-CoA synthetase and ornithine decarboxylase were demonstrated to be developmentally regulated. Changes in gene expression patterns, with most of the transcripts upregulated in the polyamine-depleted samples, indicated selective stabilization of mRNAs. Polyamines were shown to play an important role in kidney organogenesis as their depletion results in a reduction of ureteric branching and retardation of tubule formation. The selective changes of various genes in the ureteric bud and mesenchyme indicate that polyamines might have a role in the regulation of epithelial-mesenchymal interactions during mouse kidney development.