Five Crustacean Hyperglycemic Family Hormones of Penaeus monodon: Complementary DNA Sequence and Identification in Single Sinus Glands by Electrospray Ionization-Fourier Transform Mass Spectrometry

Five novel neuropeptides, designated Pm-sgp-I to -V, of the crustacean hyperglycemic hormone (CHH) family have been identified from the giant tiger prawn Penaeus monodon by isolation of the preprohormone genes from an eyestalk complementary DNA library. On the basis of sequence similarity, the encoded peptides have been classified as CHH-like type I hormones, which include all known CHHs and the molt-inhibiting hormone (MIH) of the lobster Homarus americanus. Consistent with CHH type I preprohormones, the Pm-sgp precursors include a signal peptide, a CHH precursor-related peptide (CPRP), and the CHH-like hormone. Analysis by electrospray ionization-Fourier transform mass spectrometry enabled the neuropeptide complement of individual sinus glands to be resolved. It also confirmed the presence of the five Pm-sgp neuropeptides within the sinus gland of an individual animal, in that the masses observed were consistent with those predicted from the gene sequence of the Pm-sgps after posttranslational modification. These modifications included cleavage of the signal peptide and precursor protein, carboxy-terminal amidation, and formation of three disulfide bridges. Analysis of crude extracts of single sinus glands from different animals revealed variation in neuropeptide content and will provide a tool for determining whether the content varies as a function of the physiological state of the animal. Received March 26, 1999; accepted September 10, 1999.     

Immunocytochemical Study of the Distribution of hcs2 Gene Products in Command Neurons of the Helix lucorum Snail

The distribution of the putative protein products of gene hcs2 in giant command neurons of the parietal ganglia of the terrestrial snail Helix lucorum has been studied using light- and electron-microscopic immunocytochemistry. The product of the hcs2 gene is a hybrid protein belonging to the EF-hand family of Ca²⁺-binding proteins and is a precursor of several neuropeptides. Polyclonal antibodies to neuropeptides CNP3 and CNP4 and the C-terminal Ca²⁺-binding domain of the precursor protein have been used to determine their intracellular localization. The targets for all three types of antibodies have been found in cytoplasmic secretory granules. The label (colloidal gold) density in the secretory granules is two times higher in the case of neuropeptides CNP3 and CNP4 than in the case of the Ca²⁺-binding domain. Thus, a specific association between the putative products of the hcs2 gene and the cell secretory apparatus has been demonstrated. This agrees with the earlier hypothesis that hcs2 products may serve as neurotransmitters or neuromodulators.     

Genome-wide identification of neuropeptides and their receptor genes in Bemisia tabaci and their transcript accumulation change in response to temperature stresses

Insect neuropeptides play an important role in regulating physiological functions such as growth,development,behavior and reproduction.We identified temperaturesensitive neuropeptides and receptor genes of the cotton whitefly,Bemisia tabaci.We identified 38 neuropeptide precursor genes and 35 neuropeptide receptors and constructed a phylogenetic tree using additional data from other insects.As temperature adaptability enables B.tabaci to colonize a diversity of habitats,we performed quantitative polymerase chain reaction with two temperature stresses(low=4℃ and high=40℃)to screen for temperature-sensitive neuropeptides.We found many neuropeptides and receptors that may be involved in the temperature adaptability of B.tabaci.This study is the first to identify B.tabaci neuropeptides and their receptors,and it will help to reveal the roles of neuropeptides in temperature adaptation of B.tabaci.     

LFRFamides: a novel family of parasitation-induced -RFamide neuropeptides that inhibit the activity of neuroendocrine cells in Lymnaea stagnalis

We report the characterization of a cDNA encoding a novel -RFamide neuropeptide precursor that is up-regulated during parasitation in the snail Lymnaea stagnalis. Processing of this precursor yields five structurally related neuropeptides, all but one ending with the C-terminal sequence -LFRFamide, as was confirmed by direct mass spectrometry of brain tissue. The LFRFamide gene is expressed in a small cluster of neurons in each buccal ganglion, three small clusters in each cerebral ganglion, and one cluster in each lateral lobe of the cerebral ganglia. Application of two of the LFRFamide peptides to neuroendocrine cells that control either growth and metabolism or reproduction induced similar hyperpolarizing K+-currents, and inhibited electrical activity. We conclude that up-regulation of inhibitory LFRFamide neuropeptides during parasitation probably reflects an evolutionary adaptation that allows endoparasites to suppress host metabolism and reproduction in order to fully exploit host energy recourses.     

Nervous control of reproduction in Octopus vulgaris: a new model

The classic study of Wells and Wells on the control of reproduction in Octopus demonstrated that the activity of the subpedunculate lobe of the brain and environmental illumination both inhibit the release of an unknown gonadotropin from the optic gland. This inhibitory control may be exerted by the neuropeptide Phe-Met-Arg-Phe-NH₂ (FMRFamide). It was later demonstrated that the olfactory lobe is also likely to be involved in the control of optic gland activity. The presence of gonadotropin-releasing hormone in the olfactory lobe suggested that it might exert an excitatory action on optic gland activity. Other neuropeptides have now been localised in the olfactory lobe: neuropeptide Y, galanin, corticotropin-releasing factor, Ala-Pro-Gly-Trp-NH₂ (APGWamide), as well as steroidogenic enzymes and an oestrogen receptor orthologue. This supports the hypothesis that this lobe may also play a part in the control of reproduction in Octopus. The olfactory lobe receives distant chemical stimuli and also appears to be an integrative centre containing a variety of neuropeptides involved in controlling the onset of sexual maturation of Octopus, via the optic gland hormone. This review attempts to summarise current knowledge about the role of the olfactory lobe and optic gland in the control of sexual maturation in Octopus, in the light of new findings and in the context of molluscan comparative physiology.