Proctolin

Description

Proctolin was the first bioactive peptide to be isolated from insect tissues and structurally characterized. Proctolin shows various activities, including a myotropic action, regulation of JH synthesis, and behavioral influences.

Discovery

Proctolin was first identified in 1975 from the whole body of the American cockroach Periplaneta americana, based upon its ability to stimulate hindgut contractions.

Synthesis

The gene encoding a proctolin precursor protein was first identified in the fruit fly Drosophila melanogaster. The predicted protein encoded by Proct has a single copy of the Arg-Tyr-Leu-Pro-Thr sequence that directly follows the predicted signal peptidase cleavage point flanked by a potential peptide cleaving site, and similar precursor structures are conserved in other insects and in noninsect arthropods. The proctolin gene has been found in a various arthropods except for Hymenoptera, Lepidoptera, and the yellow fever mosquito Aedes aegypt.Proctolin is thought to be synthesized and packaged into dense core vesicles in the cell body of neurons and then transported down the axon to the synaptic terminals.In arthropods, proctolin acts as a cotransmitter as well as a neurohormone.

Biological functions

Proctolin displays potent myotropic activity in the visceral, cardiac, and skeletal muscle from a range of insect species. In addition, proctolin may act as a releasing factor for adipokinetic hormone (AKH) and juvenile hormone (JH) in the locust.However, it does not regulate JH release in the cockroach. Moreover, proctolin plays a modulatory role in a neuronal circuit controlling sexual behavior in the bow-winged grasshopper Chorthippus biguttulus.

Uses

Proctolin is a neuropeptide present in insects and crustaceans.

Enzyme inhibitor

This insect neuromodulator/neurotransmitter/ neurohormone (FW = 648.76 g/mol; CAS : 100930-02-7; Sequence: L-Arg-L-Tyr-L-Leu-L-Pro-L-Thr) exerts its proctolinergic action by changing the way impulses are transmitted across a synapse, often assisting a more common neurotransmitter, such as glutamate. Mode of Action: Proctolin potently stimulates visceral and skeletal muscles contraction of a number of in insects. The Drosophila melanogaster proctolin receptor (CG6986) is an orphan G-protein coupled receptor and is strongly expressed in the head, the larval hindgut, the aorta and on neuronal endings in adult hearts. Unlike classical neurotransmitters, proctolin does not change the postsynaptic conductance. It also modulates reproductive tissue, stimulating contractions of the oviducts in the American cockroach Periplaneta americana, as well as Leucophaea maderae, L. migratoria, and spermathecae in L. migratoria and Rhodnius prolixus. Proctolin also speeds up heart rate in some insects. Target(s); dipeptidyl-peptidase III, or aminoenkephalinase.