Evolution of Hormonal Mechanisms
Résumé
Hormones are key chemical messengers that regulate major physiological and developmental processes. They are extremely diverse and encompass peptdes or small proteins encoded by genes as well as small molecules that are the products of complex metabolic pathways. Their receptors are also diverse from membrane receptors actng via second messengers to nuclear hormone receptors that are ligand-actvated transcripton factors regulatng directly target gene expression. If the mode of acton of hormones is beter and beter known, the queston of their origin and evoluton is stll nimbed in mystery. It is however possible now to draw some common principles underlying their evoluton. At the heart of this queston is the hormone / receptor couple that controls the hormonal response and whose evoluton will be diferent depending on the nature of the ligand. Whatever this nature, the couple did evolve and recent results suggest that even small molecules such as steroids or thyroid hormones can change during evoluton. Another important layer of evolutonary changes are all the mechanisms that exquisitely control hormone levels in peripheral organs. Lastly we can start to ask the queston of the origins of some hormonal systems that are much more ancient than antcipated.
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