Human ortholog of a plant salicylic acid receptor found in SK-N-SH cell line.

Our previous studies have described the purification and characterization of a novel plant NAD(P)-reductase like protein (RL) from the thermogenic appendix of the Sauromatum guttatum inflorescence. RL is mainly located in cytoplasm of thermogenic plants and it can act like a bistable switch. It adopts a compact conformation during heat-production and a more expanded conformation when heat is not generated. Addition of salicylic acid, a natural thermogenic inducer, at picomolar concentration to a solution of purified RL induced a discontinuous volume phase transition in which the volume of RL in the oligomeric form expanded and shrunk repeatedly every 4-5 min. In the present study using ESI-MS analysis we have demonstrated the existence of RL in the human SK-N-SH cell line and in mouse brain tissue. The molecular mass of human RL is in the same range as of its plant counterpart, 34,140 ± 34 Da. The charge state distribution of the human RL is identical to its plant counterpart from the Sauromatum appendix during heat-production. Human RL was present in the compact state when it was purified from the SK-N-SH cell line When these cells were treated with salicylic acid (10 μM) a shift to a much more compact conformation was observed. It seems that the potential of RL to respond to salicylic acid was conserved. These results may reveal the existence of a thermoregulation system that is evolutionarily conserved and is operating by conformational changes. This discovery may also represent an opportunity for a better understanding of some of the diverse functions of salicylic acid and aspirin in plants and humans.