User:Jrhodes613/bursicon

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Bursicon (from the Greek bursikos, pertaining to tanning) is an insect hormone which mediates tanning in the cuticle of adult flies.

Structure
The molecular structure of the hormone has been characterized rather recently. Bursicon is a 30 kDa neurohormone heterodimeric protein which is encoded by CG13419 gene and made of two cysteine knot subunits, Burs-α and Burs-β. It is nondialyzable and loses its activity in alcohol, acetone, some proteases and trichloroacetate, renaturates after adding ammonium sulfate.

Function
Bursicon plays a very important role in insect wing expansion during the last step of metamorphosis: maturation of the wing. At this time, the newly emerged adult removes dead cells of larval tissues. In Drosophila and Lucilia cuprina fly, the epidermis of wing is detached by extensive cell death apoptosis, at the time of wing spreading.

The cells that undergo death are removed from the wing cuticle and are absorbed into the thoracic cavity through wing veins. Subsequent wing maturation is disrupted if the process of cell death is inhibited or delayed somehow.

Bursicon is released just after eclosion and induces epidermis cell death. At the same time it hastens the tanning reaction, and hardens the newly expanded cuticle of the wing.

Where the peptide is found
Bursicon is found in different insects and considered to be unspecific. It is produced by median neurosecretory cells in the brain, circulates in blood and stored in corpora cardiaca.

The structure of the protein has been investigated well in fruit fly (Drosophila melanogaster), and in some insect species bursicon gene has been sequenced, including the mosquito (Anopheles gambiae), cricket (Gryllus bimaculatus), locust (Locusta migratoria), and mealworm (Tenebrio molitor).

The hormone is also present in the silkworm (Bombyx mori), blow fly (Calliphora erythrocephala), and cockroach (Periplaneta americana).

Effect of absence
Firstly, mutants of Drosophila melanogaster that lack bursicon gene can not spread their wings after eclosion. Secondly, the elongated abdomen shape of a newly eclosed fly remains for a much longer period of time. In addition, the abdomen of a fly is less melanized.

Using hybridization and immunocytochemistry it has been shown that bursicon is colocalized with Crustacean Cardioactive Peptide (CCAP). CCAP is responsible for activation of the ecdysis motor program. Mutant flies that had a defect in CCAP neurons also couldn’t express bursicon.

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New Bursicon page
Bursicon (from the Greek bursikos, pertaining to tanning) is a hormone which mediates darkening and hardening (or "tanning") of the cuticle of adult insects. While first discovered in blowflies and best described in the fruit fly, Drosophila melanogaster, bursicon is well conserved across many arthropod species.

Discovery
In the early 1960s, researchers at the University of Illinois, Urbana discovered that tanning of both the puparium and the cuticle of the adult blowfly were not directly controlled by ecdysone, the major insect molting hormone known at the time. They successfully isolated this mystery tanning hormone, which they called bursicon, a few years later, and found that it was a roughly 30 kDa protein produced by the median neurosecretory cells of the brain. The genes encoding bursicon were not identified until 2004, more than 40 years after the protein was first described.

Structure
The hormone bursicon is composed of two subunits, formerly referred to as Burs-α and Burs-β and now named Bursicon and Partner of bursicon. The two ~15kDa subunits dimerize via their cystine knot structures to form the complete neurohormone bursicon.

The genes encoding both subunits have been identified in D. melanogaster and are on autosomal chromosomes. Bursicon (formerly CG13419) is located on the right arm of the third chromosome (3R) and Partner of Bursicon (CG15284) is on the left arm of the second chromosome (2L).

Location
- synthesized in median neurosecretory cells

- in response to?

- circulates in blood

- stored in corpora cardiaca

Function
-- Tanning, phenotypes of mutants. Also confirmed to play essential role in tanning of the puparium.

-- binds to rickets (G-protein coupled receptor), which releases downstream cascade of cAMP

Phylogeny
While best described in members of the order Diptera, specifically the fruit fly, Drosophila melanogaster, it is well-conserved across many arthropod species. Both holometabolic and heterometabolic insects have functional copies of the bursicon gene