Insect Myosuppressins and Sulfakinins Stimulate Release of the Digestive Enzyme α‐Amylase in Two Invertebrates: The Scallop Pecten maximus and Insect Rhynchophorus ferrugineus

Abstract

The myosuppressins represent a subfamily of the insect FMRFamide-related peptides that share the common C-terminal heptapeptide sequence Asp-His-Val-Phe-Leu-Arg-Phe-NH,,' and have been identified in diverse insect species including the cockroach Leucophaea maderae, locusts Schistocerca gregaria and Locusta migratoria, the fleshfly Neobelleria bullata, and the fruitfly Drosophila melanogaster. Members of this family affect insect muscles, being potent inhibitors of cardiac and visceral muscle in addition to having effects on skeletal muscle and salivary glands. A related peptide, named ManducaFLRFamide, was isolated from the hawkmoth Manduca sexta and demonstrates myostimulatory activity on dorsal longitudinal flight muscles.'The related sulfakinin insect peptide family shares the C-terminal octapeptide sequence Xaa-Asp-Tyr(S03H)-G1y-His-Met-Arg-Phe-NH2 (Xaa = Glu or Asp) that terminates in HMRFamide, rather than the FLRFamide of the myosuppressins. The sulfakinins also share sequence similarities with the vertebrate gastrin/ cholecystokinin (CCK) hormone family with a C-terminal gastrin octapeptide sequence of Glu-Ala-Tyr(S0,H)-G1y-Trp-Met-Arg-Phe-NH2. Unlike the myosuppressins, the sulfakinins stimulate contractions of the isolated cockroach hindgut, the original bioassay used to isolate t h e~n .~,~ In this study, we report that members of the myosuppressin and sulfakinin Corresponding author. 335 336 ANNALS NEW YORK ACADEMY OF SCIENCES 35 -7

Identification and cardiotropic actions of sulfakinin peptides in the American lobster Homarus americanus

“…It is the belief of many that these structural similarities are the result of a common ancestry for the two groups of peptides (Nachman et al, 1986a;Nachman et al, 1986b;Nichols et al, 1988;Veenstra, 1989;Schoofs et al, 1990;Maestro et al, 2001;Torfs et al, 2001;Nachman et al, 2005). In addition to the observed sequence homologies, the hypothesis of a common ancestor for the CCK/gastrins and the sulfakinins is supported by the findings that both share a number of conserved functions: both groups are myoactive on the gut, induce the release of the enzyme amylase from the digestive system, and serve as satiety factors (Nachman et al, 1997;Wei et al, 2000;Maestro et al, 2001;Harashini et al, 2002;Downer et al, 2007). Moreover, studies of the effects of vertebrate CCK and of a partially purified CCK-like peptide in the spiny lobster showed that CCK itself can activate the neuronal pattern generators that control movements of the foregut in this species (Turrigiano and Selverston, 1989;Turrigiano and Selverston, 1990;Turrigiano et al, 1994).…”

“…While not demonstrated directly, the distributions of sulfakinin-like immunoreactivity in many insects, particularly the dipterans, suggests a neuromodulatory role for this peptide family in the CNS (Duve et al, 1994;Davis et al, 1996;Nichols and Lim, 1996;East et al, 1997). Additionally, sulfakinins have been shown to stimulate the release of ␣-amylase from the midgut of both the weevil Rhynchophorus ferrugineus and the moth Opisina arenosella (Nachman et al, 1997;Harshini et al, 2002), and have been shown to be potent inhibitors of food intake in the locust Schistocerca gregaria, the cockroach Blatella germanica and the blowfly Phormia regina (Wei et al, 2000;Maestro et al, 2001;Downer et al, 2007).…”

An unusual myosuppressin from the blood-feeding bugRhodnius prolixus

“…Moreover, in B. germanica, mRNA expression levels of myosuppressin slightly decrease during maximum food intake . Myosuppressins also stimulate the release of the digestive enzyme -amylase in the red palm weevil (beetle), Rynchphorus ferrugineus (Nachman et al, 1997). Therefore, it appears that myosuppressin may play a role in digestion, acting as a neurotransmitter directly delivered to the hindgut and midgut tissue or locally released from endocrine-like cells.…”

The anterior stomach of larval mosquitoes (Aedes aegypti):effects of neuropeptides on transepithelial ion transport and muscular motility

“…For gastrointestinal functions like muscular motility (Schoofs et al, 1993), salivary gland fluid secretion (Duve et al, 1992), midgut secretion of digestive enzymes (Fusé et al, 1999;Nachman et al, 1997), fluid secretion by Malpighian tubules (Beyenbach, 2003;Coast et al, 2002) and reabsorption by the hindgut (Coast et al, 2002), regulation by peptides is well documented. In contrast, to our knowledge only a single study was performed that is related to the regulation of midgut ion transport by neuropeptides (Lee et al, 1998).…”