Agmatine Suppresses Proliferation by Frameshift Induction of Antizyme and Attenuation of Cellular Polyamine Levels

Abstract

Polyamines are required for entry and progression of the cell cycle. As such, augmentation of polyamine levels is essential for cellular transformation. Polyamines are autoregulated through induction of antizyme, which represses both the rate-limiting polyamine biosynthetic enzyme ornithine decarboxylase and cellular polyamine transport. In the present study we demonstrate that agmatine, a metabolite of arginine via arginine decarboxylase (an arginine pathway distinct from that of the classical polyamines), also serves the dual regulatory functions of suppressing polyamine biosynthesis and cellular polyamine uptake through induction of antizyme. The capacity of agmatine to induce antizyme is demonstrated by: (a) an agmatine-dependent translational frameshift of antizyme mRNA to produce a fulllength protein and (b) suppression of agmatine-dependent inhibitory activity by either anti-antizyme IgG or antizyme inhibitor. Furthermore, agmatine administration depletes intracellular polyamine levels to suppress cellular proliferation in a transformed cell line. This suppression is reversible with polyamine supplementation. We propose a novel regulatory pathway in which agmatine acts as an antiproliferative molecule and potential tumor suppressor by restricting the cellular polyamine supply required to support growth.Polyamines (putrescine, spermidine, and spermine) are required for DNA replication, proliferation, and cell homeostasis (1-3). Ornithine decarboxylase (ODC) 1 is the first rate-limiting enzyme of polyamine biosynthesis and one of the most highly regulated eukaryotic enzymes. Cellular polyamine transporters are stimulated by many of the same factors that induce ODC activity, and similarly, enhanced cellular polyamine uptake occurs both in normal but rapidly proliferating cells (4) and in tumor cell lines (5-8). Cells in vivo can acquire polyamines released into the circulation by other cells, dietary sources, and gut flora. Polyamines have been demonstrated to play an important role in the transformation process. Conversely, polyamine depletion results in growth arrest (9, 10).Intracellular polyamine concentrations are autoregulated by the induction of the protein antizyme (11). Antizyme is the only known endogenous protein that binds to ODC, inhibiting activity and accelerating its degradation (12). In addition to inhibiting polyamine biosynthesis, antizyme has recently been shown to concurrently suppress polyamine transporter(s) (13,14). Pharmacological inhibition of ODC activity, however, has been shown to result in compensatory cellular polyamine uptake (6). Beneficial therapeutic intervention must therefore address both polyamine transport as well as biosynthesis (for review see Ref. 15).The metabolism of arginine to agmatine by ADC has only recently been demonstrated in mammals (16). As agmatine and polyamines are structurally analogous polycationic molecules derived from distinct arginine-dependent pathways (6), we speculated that the ADC metabolite agmatine may play a role in regulating intracellul...

Arginine metabolism: nitric oxide and beyond

“…Agmatine binds to α # -adrenergic and imidazoline receptors [271], suggesting a role in cell signalling. Agmatine can also inhibit ODC activity by inducing synthesis of antizyme, thus suppressing cell proliferation by reducing cellular polyamine concentrations [278]. Finally, agmatine is a weak competitive inhibitor of the NOS isoenzymes [279], suggesting that it may be an endogenous regulator of NO synthesis if local agmatine concentrations are sufficiently high.…”

Antizyme1 mediates AURKAIP1-dependent degradation of Aurora-A

“…It has been shown that treatment of cells with the rare polyamine, agmatine, suppresses proliferation by frame-shift induction of Az and attenuation of cellular polyamine levels (Satriano et al, 1998). Moreover, HTC (rat liver hepatoma derived from Morris hepatoma) cells treated with agmatine showed a progressive accumulation of cells in G 2 /M phase of the cell cycle with no evident signs of apoptosis or necrosis (Gardini et al, 2003).…”

Agmatine Suppresses Mesangial Cell Proliferation by Modulating Polyamine Metabolism

“…Increased polyamine uptake also accompanies growth as polyamine transport is stimulated by many of the same factors that induce ODC. Polyamines are autoregulated through induction of the inhibitory protein, namely (ODC-) antizyme, which inhibits both ODC for polyamine synthesis and cellular polyamine transport (Satriano et al 1998). In previous studies we have shown that agmatine administration induces antizyme expression, depletes intracellular polyamine levels, and suppresses cellular proliferation in a transformed murine proximal tubule cell line (Satriano et al 1998).…”

“…Polyamines are autoregulated through induction of the inhibitory protein, namely (ODC-) antizyme, which inhibits both ODC for polyamine synthesis and cellular polyamine transport (Satriano et al 1998). In previous studies we have shown that agmatine administration induces antizyme expression, depletes intracellular polyamine levels, and suppresses cellular proliferation in a transformed murine proximal tubule cell line (Satriano et al 1998). Furthermore, agmatine utilizes, and is dependent upon, the polyamine transporter for cellular uptake (Satriano et al 2001b).…”

“…Agmatine has the capacity to regulate nitric oxide (NO) synthase activity (Galea et al 1996;Abe et al 2000;Satriano et al 2001a) and has been ascribed roles in association with neurotransmitter receptors (Li et al 1994), modulation of opioid analgesia (Kolesnikov et al 1996), and as an ADP-ribose acceptor (Murayama et al 1993). It is structurally analogous to polyamines (putrescine, spermidine and spermine) and can regulate intracellular polyamine content (Satriano et al 1998).…”