Simple syntheses of the polyamine alkaloid tenuilobine and analogues using selectively N-tritylated polyamines and dicarboxylic acids as bridging elements

Effect of polyamines and synthetic polyamine-analogues on the expression of antizyme (AtoC) and its regulatory genes

Background

In bacteria, the biosynthesis of polyamines is modulated at the level of transcription as well as post-translationally. Antizyme (Az) has long been identified as a non-competitive protein inhibitor of polyamine biosynthesis in E. coli. Az was also revealed to be the product of the atoC gene. AtoC is the response regulator of the AtoS-AtoC two-component system and it functions as the positive transcriptional regulator of the atoDAEB operon genes, encoding enzymes involved in short chain fatty acid metabolism. The antizyme is referred to as AtoC/Az, to indicate its dual function as both a transcriptional and post-translational regulator.

Results

The roles of polyamines on the transcription of atoS and atoC genes as well as that of atoDAEB(ato) operon were studied. Polyamine-mediated induction was tested both in atoSC positive and negative E. coli backgrounds by using β-galactosidase reporter constructs carrying the appropriate promoters patoDAEB, patoS, patoC. In addition, a selection of synthetic polyamine analogues have been synthesized and tested for their effectiveness in inducing the expression of atoC/Az, the product of which plays a pivotal role in the feedback inhibition of putrescine biosynthesis and the transcriptional regulation of the ato operon. The effects of these compounds were also determined on the ato operon expression. The polyamine analogues were also tested for their effect on the activity of ornithine decarboxylase (ODC), the key enzyme of polyamine biosynthesis and on the growth of polyamine-deficient E. coli.

Conclusion

Polyamines, which have been reported to induce the protein levels of AtoC/Az in E. coli, act at the transcriptional level, since they cause activation of the atoC transcription. In addition, a series of polyamine analogues were studied on the transcription of atoC gene and ODC activity.

Efficient syntheses of 5-aminoalkyl-1h-tetrazoles and of polyamines incorporating tetrazole rings

Linear N(omega)-tritylated omega-amino thiobenzylamides and N(alpha),N(omega)-ditritylated polyamino mono- or bisthioamides were efficiently converted to the corresponding tetrazole derivatives upon treatment with azidotrimethylsilane under Mitsunobu reaction conditions. [reaction: see text]

AMPA receptor ligands: Synthetic and pharmacological studies of polyamines and polyamine toxins

Alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors (AMPAR), subtype of the ionotropic glutamate receptors (IGRs), mediate fast synaptic transmission in the central nervous system (CNS), and are involved in many neurological disorders, as well as being a key player in the formation of memory. Hence, ligands affecting AMPARs are highly important for the study of the structure and function of this receptor, and in this regard polyamine-based ligands, particularly polyamine toxins, are unique as they selectively block Ca2+ -permeable AMPARs. Indeed, endogenous intracellular polyamines are known to modulate the function of these receptors in vivo. In this study, recent developments in the medicinal chemistry of polyamine-based ligands are given, particularly focusing on the use of solid-phase synthesis (SPS) as a tool for the facile generation of libraries of polyamine toxin analogues. Moreover, the recent development of highly potent and very selective AMPAR ligands is described. Additionally, we provide a detailed account on the mechanism and site of action of AMPAR blockade by polyamine-based ligands, including examples of how these ligands are used as tools to study AMPAR, and a comparison with their action on other ionotropic receptors.