Allatostatins are
neuropeptide in
and
crustacea. They have a twofold function: they both inhibit the generation of
juvenile hormone and reduce their food intake. They are therefore putative targets for
insecticide research.
Types
There are three distinct Allatostatin types: A, B, and C. Allatostatin C's have 3 subtypes as a result of gene multiplication: C, CC, and CCC.
Each Allatostatin type has a unique evolutionary history resulting in distinct conservation and functions across the animal kingdom.
Although originally identified in different insects, all three type are found in
Drosophila (needs source).
Allatostatin A
Allatostatin A (AstA) peptides are found in all arthropods and contain a C-terminus Y/FXFGLamide.
In
Drosophila, there are 4 AstA peptides (AstA-1, AstA-2, AstA-3, AstA-4) and 2 AstA receptors (AstA-R1 and AstA-R2).
The AstA receptor is a GIRK1 channel and is homologous to the mammalian
galanin receptor
Control of food intake
Allatostatin is found in the cells in a small neuronal cluster, the frontal ganglion. It is also present in the axons which leave the frontal ganglion and run across the surface of the gut. Application of low concentrations of Allatostatin inhibit the spontaneous contractions of the gut. All three forms of Allatostatin appear to inhibit gut motility in all the insects which have been tested.
Interaction with juvenile hormone
Juvenile hormone is synthesised in the
corpora allata. In every insect tested, at least one of the three types of Allatostatin inhibits the biosynthesis of juvenile hormone. This is achieved by
paracrine release of Allatostatin from neurons in the brain which terminate in the corpora allata. The signal is transduced by
GPCR receptors, but the intracellular pathway is not yet known. Other
amine and
neuropeptide neurotransmitters may also inhibit juvenile hormone biosynthesis.
