Myokinin activity in vitro and in vivo
Structure activity studies on BZTC analogues: peptide agonists of the SchistoFLRFamide receptor
Coast GM Department of Biology, Birkbeck College, London WC 1E 7HX, UK. Myokinins are known from several insects, a crustacean (Penaeus vannamei) and a mollusc (Lymnaea stagnalis). They
comprise 6- 15 residues with a C-terminal sequence FXS WGNH2. Position 2 is variable, Pro or Ala may occupy position 3, and Ala-NH2 or Ser-NH2 can be found at position 5. In insects, myokinins stimulate contractions of isolated hindguts and increase primary urine secretion by Malpighian tubules in vitro. They may also have central functions, and Lymnaea kinin is the endogenous ligand of a G-protein coupled receptor cloned from a snail brain cDNA library. Typically, they are active at nanomolar concentrations and their response is mediated by an increase in intracellular Ca2+. This talk will focus on myokinin actions in the housefly, Musca domestica, including evidence for a role in the control of diuresis in vivo.
4;““k RI, Nachman RJ2 and Orchard I’. Department of Zoology, University of Toronto, Toronto, Ontario, Canada; ‘Veterinary Entomology Research Unit, FAPRL, U.S. Department of Agricultural Research Service, College Station, Texas, U.S. Benzethonium chloride (BZTC) is a non-peptide ligand of an invertebrate peptide receptor. BZTC binds to the receptors for SchistoFLRFamide (PDVDHVFLRFamide) on locust oviduct membranes. In addition, BZTC inhibits myogenic and induced contractions of locust oviduct, thereby mimicking the physiological effects of SchistoFLRFamide. In an effort to elucidate the binding and activation regions of the BZTC molecule, eleven structural analogues of BZTC were created. The locust oviduct contraction assay was then employed to compare the structural analogues for their abilities to inhibit a proctolin-induced contraction relative to BZTC. The affinities of the eleven structural analogues to the SchistoFLRFamide receptor were estimated using a recently oftimised radioligand receptor binding assay employing ’ 51Y’SchistoFLRFamide as the tracer.
Mimetic analogs of myotropic insect neuropeptide families
The Enterins: A novel family of neuropeptides isolated from the enteric and central nervous system ofqprrsia.
m, Teal PEA, Williams HJ, Zadina J and Coast GM Veterinary Entomology Research/FAPRL, U.S. Department of Agriculture, 288 1 F&B Rd., College Station, Texas 77845 USA Myotropic neuropeptides mediate gut contractile processes relevant to digestion as well as other critical processes such as diuresis, reproduction and development. They are subject, however, to degradation by peptidases in insect tissues and are limited by an inability to readily penetrate the cuticular surface. Amphiphilic analogs, containing aromatic and non-aromatic hydrophobic components, of the pyrokinin/PBAN family penetrate the cuticle of Heliothis to produce unnaturally prolonged pheromone production. Comparative topical studies demonstrate that the duration of analog penetration can be accelerated , or halted, depending on analog design. Insect kinin analogs incorporating a tetrazole moiety provide unambiguous identification of the diuretic active conformation as a l-4 cisPro type VI P-turn. Tetrazole analogs with D conformation antagonize the diuretic activity of natural insect kinins. This conformation is different from that of the mammalian opiate peptide Tyr-W-MIF-1, which has a sequence identical to the Cterminal tetrapeptide of several natural insect kinins. Solution conformational studies on restricted-conformation analogs of the mammalian peptide indicate that the active conformation is a 2-5 transPro turn. Peptidase-resistant insect kinin analogs show enhanced inhibition of weight gain in Heliothis larvae.
wa Y’, Fujisawa Y*, Minakata Hz, Nakamaru K’, Wakayama H’, Nakabayashi K’, Morishita F’, Matsushima O’, Ellis TA3, Dembrow NC?, Weiss KR3 and Vilim FS3 ‘Dep. Biol. Sci., Fat. Sci., Hiroshima Univ., HigashiHiroshima, Japan. *Suntory Inst. Bioorganic Res., Osaka, Japan, 3Dep. Physiol. & Biophys., Mt. Sinai Sch. Med., New York, USA. Neuropeptides are one of the most diverse signaling molecules in the animal kingdom, and there are numerous examples showing the existence of multiple structurally related peptides in a single species. Using bioassay or ELISA with HPLC purification, we identified a family of structurally related peptides from gut and CNS extracts ofAplysia. We isolated 11 peptides, most of which ended in HSFVamide. All of them inhibited the contraction of ApZysia gut. Because these novel peptides were isolated from the enteric nervous system of Aplysia, we named them enterins. Degenerate RACE was used to identify a precursor for enterins. The precursor predicted 36 copies of 20 different enterins. The distribution of enterins was examined by northern analysis, immunocytochemistry and insitu hybridization. The enterin mRNA was abundant in pedal, buccal cerebral and abdominal ganglia, but undetectable in pleural ganglion. A similar distribution was obtained by in-situ hybridization and immunocytochemistry. Enterin immunopositive processes and varicosities were also observed in the esophagus and crop. The results indicate that enterins are important neuropeptides with multiple functions in Aplysia, including the inhibitory regulation of gut motility.