gastrins and leucosulfakinin

The feeding cycle of the adult female cockroach Blattella germanica parallels vitellogenesis. The study of the mechanisms that regulate this cycle led us to look for food-intake inhibitors in brain extracts. The antifeedant activity of brain extracts was tested in vivo by injecting the extract and measuring the carotenoids contained in the gut from carrot ingested after the treatment. By HPLC fractionation and tracking the biological activity with the carrot test, we isolated the sulfakinin EQFDDY(SO3H) GHMRFamide (Pea-SK). A synthetic version of the peptide inhibited food intake when injected at doses of 1 microg (50% inhibition) and 10 microg (60% inhibition). The sulfate group was required for food-intake inhibition. These biological and structural features are similar to those of the gastrin-cholecystokinin (gastrin-CCK) family of vertebrate peptides. However, heterologous feeding assays (human CCK-8 tested on B. germanica, and Pea-SK tested on the goldfish Carassius auratus) were negative. In spite of this, alignment and cluster analysis of these and other structurally similar peptide families suggest that sulfakinins and gastrin-CCKs are homologous, and that mechanisms of feeding regulation involving these regulatory peptides may have been conserved during evolution between insects and vertebrates.

Topics: Amino Acid Sequence; Animals; Appetite; Brain Chemistry; Cholecystokinin; Chromatography, High Pressure Liquid; Cluster Analysis; Cockroaches; Feeding Behavior; Female; Gastrins; Goldfish; Mass Spectrometry; Molecular Sequence Data; Neuropeptides

Perisulfakinin, a peptide with sequence similarity to gastrin and cholecystokinin, was isolated from the corpora cardiaca of the American cockroach. Its sequence was determined to be Glu-Gln-Phe H-Asp-Asp-Tyr(SO3H)-Gly-His-Met-Arg-Phe-amide. The peptide induced hindgut contractions in the same species at concentrations as low as 250 pM. A related non-sulfated peptide was also isolated and sequenced; it was found to be identical with non-sulfated leucosulfakinin II (pGlu-Ser-Asp-Asp-Tyr-Gly-His-Met-Arg-Phe-amide). This peptide did not stimulate hindgut contractions. The structures of the cockroach peptides of the leucosulfakinin family are thus much more conserved than the cockroach hypertrehalosemic hormones.

Topics: Amino Acid Sequence; Animals; Cholecystokinin; Cockroaches; Gastrins; Molecular Sequence Data; Neuropeptides; Sequence Homology, Nucleic Acid

The leucosulfakinins (LSKs), isolated from head extracts of the cockroach Leucophaea maderae, are sulfated neuropeptides with homology to gastrin and cholecystokinin. The undecapeptide LSK and decapeptide LSK-II stimulate contractions of the isolated cockroach hindgut. Several structural aspects of the two gastrin/CCK-like insect leucosulfakinins (LSKs) and their relation to FMRF-amide are discussed. Replacement of the oxidation sensitive Met residue with isosteric norleucine leads to an analog with retention of biological activity. The Arg residue of the LSKs is critical for cockroach hindgut contractile stimulatory activity, as its introduction into gastrin II transforms the inactive peptide into an active analog. As demonstrated by the equipotent [His14,Arg16]gastrin II, the His8 and Asp5 residues of LSK are not critical for activity. The common C-terminal tetrapeptide of the LSKs ([8-11]LSK) is inactive. Taken together with a comparison of the two LSK structures, the data suggest that the LSK active core resides between [8-11]LSK and [4-11]LSK. This is confirmed by considerable activity displayed by the sulfate analog of LSK-II, which contains an extra sulfate group on the Ser2 residue in the N-terminal region. Homology between the LSKs and molluscan cardioacceleratory and rectum contractile neuropeptide FMRF-amide and Met-enkephalin-Arg6-Phe7 is discussed. The insect LSKs may represent a molecular evolutionary link between the vertebrate gastrin/CCK family and this mammalian enkephalin.

Topics: Amino Acid Sequence; Cholecystokinin; Enkephalin, Methionine; FMRFamide; Gastrins; Insect Hormones; Molecular Sequence Data; Neuropeptides; Neurotransmitter Agents; Pyrrolidonecarboxylic Acid; Sequence Homology, Amino Acid

A sulfated, myotropic neuropeptide termed leucosulfakinin (Glu-Gln-Phe-Glu-Asp-Tyr(SO3H)-Gly-His-Met-Arg-Phe-NH2) was isolated from head extracts of the cockroach Leucophaea maderae. The peptide exhibits sequence homology with the hormonally active portion of the vertebrate hormones human gastrin II and cholecystokinin, suggesting that these peptides are evolutionarily related. Six of the 11 amino acid residues (55 percent) are identical to those in gastrin II. In addition, the intestinal myotropic action of leucosulfakinin is analogous to that of gastrin.

Topics: Amino Acid Sequence; Animals; Aplysia; Brachyura; Cholecystokinin; Cockroaches; Gastrins; Humans; Insect Hormones; Muscle Contraction; Nerve Tissue Proteins; Neuropeptides; Sequence Homology, Nucleic Acid