Molecular physiology of crustacean and insect neuropeptides

Abstract

One of the principal hallmarks of a living organism is its ability to respond to stimuli. As the unicellular organisms evolved into multicellular metazoans, the external signals perceived had to be transduced to several other cells requiring a neuronal network with its accompanying biochemical neurotransmitters. The progressive increase in complexity of the organisms necessitated the need for an integrated signal transducing system collecting external sensory stimuli and sending them to effector systems such that a dynamic equilibrium or homeostasis, which is essential for survival, could be maintained. During the course of evolution many advanced sense organs were developed to detect various parameters in the environment, and concomitantly different internal effector systems were formed to respond to these signals received from outside to maintain homeostasis. Coordination was achieved with a network of electrical conductors in the form of an arborized nervous system and a variety of hydrophilic biochemicals that acted as neurotransmitters carrying the sensory signals to the internal effector systems. As the animal became increasingly complex, a sophisticated neurotransmission system catering to the spatial and temporal needs during growth, development and reproduction had to be in place. Parts of the nervous tissue in many locations took on a secretory role and released protein signal transducers, the neuropeptides. A panoply of such neuropeptides exist in all organisms functioning as neurohormones, neurotransmitters or neuromodulators. Aspects of neuropeptide structure and function in insects and crustaceans have been reviewed by various authors. [1][2][3][4][5][6][7][8][9][10] The neuropeptides are ligands to their cognate receptors in the ef- Organisms have to constantly respond to environmental conditions to maintain a status of dynamic homeostasis for survival. As single celled organisms evolved into multicellular animals, intercellular and inter-organ communications became indispensable not only to orchestrate homeostasis but also to control the many events punctuating metazoan development. To accomplish this need, a signal transduction system was evolved, consisting of an arborized network of nerves as well as a collection of oligopeptide neurotransmitters (neuropeptides) along with their cognate receptors. We review here the current state of our understanding of the physiology of neuropeptides in the most species-rich group of animals, the crustaceans and insects. The vast majority of neuropeptides signal through cell-surface guanosine-protein coupled receptors (GPCRs). These neuropeptide-receptor systems control a variety of physiological functions, for instance the numerous involuntary movements of internal ducts that are precisely timed for transporting reproductive, digestive and secretory materials. The rigid exoskeleton in Crustaceans and Insects require periodic molts to accomplish growth and metamorphosis and this is harmoniously regulated by a cascade of neuropeptides. Neuropeptides also regul...

Neuropeptide Action in Insects and Crustaceans

“…CHH/MIH-like peptides are not as common in insects. The ion transport peptide is the only CHH-like peptide that has been characterized; it functions by stimulating Cl − transport across the hindgut epithelium (Mercier et al 2007). …”

“…These relatively small polypeptides, many of which are less than 9 kDa, control a wide range of physiological processes (reviewed in Gäde et al 1997; Nässel 2002; Gäde and Marco 2006; Nässel and Homberg 2006; Mercier et al 2007). The action of many arthropod neuropeptides is mediated by binding to G protein–coupled receptors (GPCRs) and involves cyclic nucleotide and Ca 2+ second messenger systems (reviewed in Hauser et al 2006, 2008; Mercier et al 2007; Zitnan et al 2007; De Loof 2008; Huang et al 2008). Here we report recent developments in neuropeptide control of molting, osmoregulation, metabolite utilization, and cardiovascular function that illustrates how these neuropeptides can modify the nervous and endocrine systems toward a new physiological/behavioral state.…”

Mode of Action of aDrosophilaFMRFamide in Inducing Muscle Contraction

“…Neuropeptides usually elicit physiological responses via G-proteincoupled receptors (GPCRs) which, in turn, act through second messenger pathways (Mercier et al, 2007;Meeusen et al, 2003;Vauquelin and von Mentzer, 2007). Many 'RFamide' peptides (i.e.…”

Role of allatostatin‐like factors from the brain of Tenebrio molitor females

“…Allatotropin appears to be involved in controlling the reproductive system, as a cardioactive peptide, as a circulating neurohormone, and also as a co-transmitter and coexisting neuromodulator (Paemen et al, 1991;Veenstra, 1994: Rudwall et al, 2000Koladich et al, 2002). Furthermore, allatotropin-like peptide may be involved in the control of hindgut contractility in some insects (Nässel, 2002;Mercier et al, 2007). A second group regulating JHs level are allatostatins (AST) isolated from numerous insect species, which can be divided into three groups of bioanalogues.…”

“…The first, AST-A peptides, were isolated from the cockroach Diploptera punctata (Woodhead et al, 1989). Currently, the list of peptide isoforms of this family is long and includes members of holo-and hemimetabolous insects (Bellés et al, 1999;Bendena et al, 1999;Nässel, 2002;Stay and Tobe, 2007;Mercier et al, 2007). These peptides inhibit JH biosynthesis in vitro in the corpora allata of cockroaches and related insects, but not in higher insects (i.e., flies) (Simonet et al, 2004).…”