Bursicon

Bursicon is a neurohormone found in insects that promotes post-ecdysial tanning and hardening of the cuticle (sclerotization), as well as wing expansion after eclosion. It functions as a heterodimer composed of two subunits, bursicon alpha and bursicon beta, which in many species are encoded by the pburs and burs gene pair. The two subunits form a covalent or noncovalent complex that is secreted into the insect’s hemolymph.

Bursicon is produced by a small set of neurosecretory cells in the brain and ventral nerve cord and is released into the circulatory system shortly after molting. Upon release, it acts on epidermal tissues and developing wings through a specific receptor pathway. The receptor for bursicon is a G-protein coupled receptor (GPCR) known as rickets (rk); activation of this receptor triggers intracellular signaling that leads to cuticle tanning, cross-linking of cuticular proteins, and the biochemical changes required for hardening.

The primary physiological roles of bursicon include initiating post-ecdysial tanning and facilitating wing expansion, processes essential for the insect to achieve a fully functional exoskeleton and proper flight ability. Disruption of bursicon signaling, through genetic or pharmacological means, often results in soft, poorly sclerotized cuticle and improper wing maturation, while exogenous bursicon can partially rescue these defects in some species.

Bursicon is of interest in comparative endocrinology and developmental biology because its signaling pathway integrates hormonal cues with epidermal remodeling during metamorphosis and maturation in insects.