Abstract: Bursicon, a kind of neuropeptide hormone, regulates insect cuticle sclerotization and wing expansion. Bursicon is a heterodimer protein which consists of two cystine knot proteins, BURS and PBURS. BURS and PBURS are conserved in structure and evolution, and the amino acid sequences of both contain 11 conserved cystines. Bursicon is synthesized by thorax and abdomen ganglions. Once released into hemolymph, bursicon binds with its receptor, LGR2, and then activates cAMP/PKA pathway, which activates tyrosine hydroxylase (TH) by phosphorylation. The activated TH transforms tyrosine into DOPA, resulting in insect cuticle sclerotization. At the same time, cAMP/PKA promotes apoptosis of wing hypodermal cells and causes wing expansion. BURS or PBURS homodimers also regulate insect immune reactions by activating the transcriptional factor Relish via IMD pathway. In this article, the progress in the molecular characteristics, molecular mechanisms and functions of bursicon was reviewed in order to provide a reference for further elucidating bursicon action in insects.

Key words: Insect, bursicon, heterodimer, sclerotization, wing expansion, immune response