Influence of ornithine decarboxylase antizymes and antizyme inhibitors on agmatine uptake by mammalian cells

Abstract

Agmatine (4-aminobutylguanidine), a dicationic molecule at physiological pH, exerts relevant modulatory actions at many different molecular target sites in mammalian cells, having been suggested that the administration of this compound may have therapeutic interest. Several plasma membrane transporters have been implicated in agmatine uptake by mammalian cells. Here we report that in kidney-derived COS-7 cell line, at physiological agmatine levels, the general polyamine transporter participates in the plasma membrane translocation of agmatine, with an apparent Km of 44 ± 7 µM and Vmax of 17.3 ± 3.3 nmol h(-1) mg(-1) protein, but that at elevated concentrations, agmatine can be also taken up by other transport systems. In the first case, the physiological polyamines (putrescine, spermidine and spermine), several diguanidines and bis(2-aminoimidazolines) and the polyamine transport inhibitor AMXT-1501 markedly decreased agmatine uptake. In cells transfected with any of the three ornithine decarboxylase antizymes (AZ1, AZ2 and AZ3), agmatine uptake was dramatically reduced. On the contrary, transfection with antizyme inhibitors (AZIN1 and AZIN2) markedly increased the transport of agmatine. Furthermore, whereas putrescine uptake was significantly decreased in cells transfected with ornithine decarboxylase (ODC), the accumulation of agmatine was stimulated, suggesting a trans-activating effect of intracellular putrescine on agmatine uptake. All these results indicate that ODC and its regulatory proteins (antizymes and antizyme inhibitors) may influence agmatine homeostasis in mammalian tissues.

Ribosomal frameshifting and transcriptional slippage: From genetic steganography and cryptography to adventitious use

“…Agmatine has long been known to affect antizyme frameshifting (305) and antizyme influences uptake of the nitric oxide synthase inhibitor, agmatine, that has neurological significance (306). The influence of antizymes, both by direct binding and indirectly, on other pathways and the potential role of factors other than polyamines on antizyme frameshifting, is the subject of several reports and of active investigation (291,307,308).…”

Polyamine Metabolism and Oxidative Protein Folding in the ER as ROS-Producing Systems Neglected in Virology

“…Indeed, agmatine is present in mammalian tissues [ 24 , 25 , 26 , 27 ], and has even been claimed to exhibit neurotransmitter activity [ 28 ]. Since then, several papers reported the existence of ADC in mammals, and this enzymatic activity was assigned to antizyme inhibitor 2 (AZIn2) [ 29 , 30 ], a regulatory protein whose place in polyamine metabolism is discussed below. However, other groups did not find evidence for a conversion of arginine into agmatine in the presence of the recombinant AZIn2 or extracts of mammalian tissues (i.e., liver) (for example, [ 31 ]).…”

An exercise in brain genoarchitectonics: Analysis of AZIN2‐Lacz expressing neuronal populations in the mouse hindbrain

“…These are paralogs of ODC that lack enzymatic activity and, due to their structural resemblance to ODC, inhibit AZ1‐3 by binding to them, thus lowering the access of antizymes to ODC and polyamine uptake‐related binding sites. This action enhances ODC‐mediated synthesis of polyamines and polyamine uptake, increasing cytoplasmic polyamine levels (López‐Contreras et al, ; López‐Contreras et al, ; López‐Contreras et al, ; Ramos‐Molina et al, ). It appears that polyamines indirectly promote cell growth.…”

“…The role of AZIN2 in the adult brain, where it is characterized by a discontinuous distribution (expressed selectively in a variety of cell populations, but not in all neurons), is far from understood. Present knowledge suggests that it may increase the intracellular concentration of agmatine (an aminoguanidine derived from L‐arginine) and small polyamines in general (López‐Contreras et al, ; Ramos‐Molina et al, ).…”

“…This work was supported by the Spanish Ministry of Economy and Competitiveness, BFU2014-57516P (with European Community FEDER support); Seneca Foundation (Autonomous Community of Murcia), 19904/GERM/ 15 (to L.P.); Spanish Ministry of Science and Innovation, SAF2008-03638; Spanish Ministry of Economy and Competitiveness (with European Community FEDER support), SAF2011-29051; Seneca Foundation (Autonomous Community of Murcia), 19875/GERM/15 (to R.P.). polyamine uptake, increasing cytoplasmic polyamine levels (L opez-Contreras et al, 2008;L opez-Contreras et al, 2009;L opez-Contreras et al, 2010;Ramos-Molina et al, 2015). It appears that polyamines indirectly promote cell growth.…”