Physiological polyamines: simple primordial stress molecules

Abstract

Physiological polyamines are ubiquitous polycations with pleiotropic biochemical activities, including regulation of gene expression, cell proliferation and modulation of cell signalling. Reports that the polyamines with cytoprotective activities were induced by diverse stresses raised the hypothesis that physiological polyamines may play a role in inducing stress response. In a wide range of organisms, physiological polyamines were not only induced by diverse stresses, such as reactive oxygen species (ROS), heat, ultraviolet (UV) and psychiatric stress but were able to confer beneficial effects for survival. Recent biochemical and genetic evidences show that polyamines can function as an ROS scavenger, acid tolerance factor and chemical chaperone, and positive regulators for expression of stress response genes which may explain their protective functions against diverse stresses. Taken together, these data suggest that physiological polyamines can function as primordial stress molecules in bacteria, plants and mammals, and may play an essential role in regulation of pathogen-host interactions.

1

Metabolic pathways of physiological polyamines in prokaryotes and eukaryotes. Eukaryote- and prokaryote-specific pathways are represented in red colour and blue one, respectively. ODC, ornitine decarboxylase; LDC, lysine decarboxylase; GDC, glutamine decarboxylase; ADC, arginine decarboxylase; AZI, antizyme inhibitor; AdoMET, S-adenosylmethionine; DcAdoMET, decarboxylated AdoMET; Spmd, spermidine; Spm, spermine; Cad, cadaverine; GABA, γ-aminobutyric acid; PAO, polyamine oxidase; SSAT, spermidine/spermine N1-acetyltransferase; NcSpmd, N1-acetylspermidine; NcSpm, N1-acetylspermine, eIF5A, eukaryotic initiation factor 5A; PAAXs, polyamine antiporters; PAAL, Lys:Cad antiporter; PAAG, Glu:GABA antiporter; DAX, diamine transporter.

2

Schematic model for the stress response mediated by physiological polyamines. In response to diverse stresses, levels of physiological polyamines levels are up regulated by positive feedback regulation, which activates stress-related regulons represses general gene expression. AntiT, antitoxin; PP, polyphosphate; PPX, exopolyphosphatase; PPK, polyphosphate kinase; HSF, heat shock transcription factor; PAAXs, polyamine antiporters; XDCs, amino acid decarboxylases.