The insect gut: A new source of ecdysiotropic peptides

Gelman, Dale B.; Thyagaraja, Belgaum S.; Kelly, Thomas J.; Masler, Edward P.; Bell, Robert A.; Bořkovec, Alexej B.

doi:10.1007/bf02041259

Cited by 33 publications

(21 citation statements)

References 25 publications

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“…Further analyses of RNAs from various tissues by reverse transcription of PTTH mRNA and PCR amplification of the resulting cDNAs, however, proved that the gut, and most probably the epidermis and silk gland also, contained PTTH mRNA in small amounts. The detection of PTTH mRNA in the gut at a relatively high concentration is particularly interesting because proteins with the PTTH activity have been obtained from proctodaea of the European corn borer Ostrinia nubilalis and the gypsy moth Lymantria dispur [25,261. Many brain secretory peptides have been located in the gut in both invertebrates and vertebrates [32].…”

Section: Discussionmentioning

confidence: 99%

Structure and expression of the gene for the prothoracicotropic hormone of the silkmoth Bombyx mori

Adachi‐Yamada

Iwami

Kataoka

et al. 1994

European Journal of Biochemistry

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We cloned and characterized two allelic variants of the gene for the Bombyx mori prothoracicotropic hormone (PTTH), a homodimeric 30-kDa brain secretory protein. These PTTH genes contain five exons that encode a precursor protein consisting of 224 amino acid residues whose C-terminal 109 residues represent the PTTH subunit. The Bombyx haploid genome contains a single copy of the PTTH gene. The major site of PTTH expression is the brain but expression at a very low level occurs in the gut. One Bombyx brain at day 0 of the fifth larval instar contained 2.4-2.8 pg PTTH mRNA, and this amount did not change markedly during larval-pupal development.Prothoracicotropic hormone (PTTH), an insect brain secretory protein, stimulates the prothoracic glands to synthesize and release ecdysone necessary for growth, moulting and metamorphosis, thereby playing a central role in the endocrine network controlling insect development [ 11. Many attempts have been made to purify and characterize this important neurohormone from several insect species but its primary structure has only recently been determined for PTTH of the silkmoth Bombyx mori. Thus, direct chemical analyses of purified natural PTTH 121 and of Escherichia coli recombinant PTTH (unpublished results) and analyses of the PTTH cDNA structure [3] unraveled the following molecular features of PTTH. Bombyx PTTH is a 30-kDa glycoprotein whose carbohydrate moiety is not essential for biological activity; it is a dimeric molecule whose subunits are linked by a disulfide bond; the two subunits are identical in structure, or nearly identical, differing only by deletion of short segments at the.N-terminus and probably at the C-terminus too; a 224-amino-acid precursor protein containing a 109-aminoacid PTTH subunit at the C-terminus is first synthesized, then a mature dimeric PTTH consisting of two PTTH subunits connected by a disulfide bond is liberated from the precursor molecule by proteolytic cleavage. Bombyx PTTH has been shown to be produced by two pairs of dorsolateral neurosecretory cells of Bombyx brain by means of immunohistochemistry [4] and in situ hybridization for PTTH mRNA [3].In the present study, we cloned and characterized two allelic variants of the PTTH gene that encode the precursor molecule for the PTTH subunit. The PTTH gene is present as a single copy in the Bombyx haploid genome, indicating that the microheterogeneity in the terminal portions of natu- of Science, Nagoya University, Chikusa-ku, Nagoya, Japan 464-01 ral PTTH, as revealed by chemical analyses [2], may be due either to the posttranslational modification or to denaturation of PTTH during purification and/or storage of material. The mode of expression of the PTTH gene in brain and other tissues of Bombyx is also described. Part of the results of this paper has been briefly incorporated into a review article [ 5 ] . MATERIALS AND METHODS AnimalsTwo races of B. mori, Kinshu and Showa, and three racial hybrids, Kinshu X Showa, Shunrei X Shogetsu and J122 XC11.5, were used. The larvae were reared ...

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Section: Discussionmentioning

confidence: 99%

Structure and expression of the gene for the prothoracicotropic hormone of the silkmoth Bombyx mori

Adachi‐Yamada

Iwami

Kataoka

et al. 1994

European Journal of Biochemistry

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“…These observations agree with similar observations in the wax moth, Galleria mellonella, using bombyxin antibodies (223), except that 4 medial and 4 lateral immunopositive MNCs were found along with one pair of cells in the thoracic ganglia. Ecdysteroidogenic activity was recently demonstrated in the gut proctodeum of the European corn borer, Ostrinia nubilalis and L. dispar (224) and appears to be of low molecular weight (225). It is now believed, however, that bombyxin cannot be regarded as a physiological PTTH because of its in vitro activity at exceedingly high doses (226).…”

Section: Ecdysteroidogeninsmentioning

confidence: 99%

Insect Neuropeptides

Kelly

Masler

Menn

1993

Natural and Engineered Pest Management Agents

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The physiological processes regulated by insect neuropeptides are extensive and include growth, development, molting, reproduction, diapause, behavior, color change, ion and water balance, and muscle contraction. Nearly 80 novel insect neuropeptides have been sequenced to date, 10 or so gene sequences have been determined, numerous analogs have been synthesized, and neuropeptide genes have been expressed in vector systems. Investigations into sites of synthesis and release, and tissue specificity and action, continue to reveal complexity in the (classically simple) insect neuroendocrine system. The rapidly increasing knowledge in this area suggests that useful prototypes for the design of selective pest control agents will emerge in the forseeable future.The field of insect neuroendocrinology has expanded rapidly, fostering numerous reviews within the past five years (1-21), including one book entirely devoted to insect neurohormones (22) and one to insect neuropeptides (23). These publications discuss the discovery, physiology, history and chemistry of insect neuropeptides and present potential applications to pest control. These applications may include: blocking neuropeptide synthesis through expression of antisense RNA or inhibition of specific processing enzymes; inactivation of circulating neuropeptides by binding with specific antibodies, antipeptides or by degradation with specific peptidases; disruption of target binding or signal transduction by peptidomimetics; and disruptive expression of natural or modified neuropeptides through baculoviruses or other expression vectors. As suspected in 1988 (4), the number of purified and sequenced insect neuropeptides has continued to increase, and many of the corresponding nucleotide sequences have followed in rapid succession. Nearly eighty novel amino acid sequences for insect neuropeptides have been identified, and novel nucleotide sequences approach ten. This review updates the recent progress in identification of insect neuropeptide structures and their genes and other areas relevant to the development of pest control agents, This chapter not subject to U.S.

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“…To convert 3DE to ecdysone in the incubation medium, after an initial 2 h incubation period the prothoracic glands were removed from the medium, a cocktail of 20 µl ketoreductase preparation was added to 10 µl of the incubation medium and was incubated for 1 h at 30°C (Gelman et al, 1991). The medium of the control half gland (10 µl) was incubated with 20µl Medium 199 containing 0.2 mM NADPH but without hemolymph for 1 h. Ecdysteroid RIA data from this preparation showed the amount of ecdysone secreted by the gland.…”

Section: Determination Of 3-dehydroecdysone and Radioimmunoassaymentioning

confidence: 99%

3-dehydroecdysone secretion by the molting gland of the cockroach,Periplaneta americana (L.)

Richter

Böhm

Leubert

1999

Arch. Insect Biochem. Physiol.

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Prothoracic glands of Periplaneta americana were tested under in vitro conditions for their ability to release 3‐dehydroecdysone (3DE) besides ecdysone. 3DE was identified by RIA after conversion to ecdysone by a ketoreductase‐containing hemolymph preparation as well as in HPLC fractions of incubation medium by an antiserum with affinity to 3DE and ecdysone. The ratio of 3DE to ecdysone secreted into the culture medium was found to vary between 2:1 and 7:1, depending on the period in the last nymphal instar. Enzyme activity of 3β‐ketoreductase showed fluctuations that coincided with the hemolymph ecdysteroid titre. Homogenates of prothoracic glands do not contain ecdysone but contain 3DE. Nevertheless the glands release 3DE as well as ecdysone under in vitro conditions. Different sites where conversion of 3DE to ecdysone takes place are discussed. Arch. Insect Biochem. Physiol. 41:107–116, 1999. © 1999 Wiley‐Liss, Inc.

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The insect gut: A new source of ecdysiotropic peptides

Cited by 33 publications

References 25 publications

Structure and expression of the gene for the prothoracicotropic hormone of the silkmoth Bombyx mori

Structure and expression of the gene for the prothoracicotropic hormone of the silkmoth Bombyx mori

Insect Neuropeptides

3-dehydroecdysone secretion by the molting gland of the cockroach,Periplaneta americana (L.)

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