Bombyxin F1 gene: structure and expression of a new bombyxin family gene that forms a pair with bombyxin B10 gene

Data for evolutive analysis of insulin related peptides in bilaterian species

In bilaterian species, the amino acid sequence conservation between Insulin related peptides is relatively low except for the cysteine residues involved in the disulphide bonds. In the A chain, the conserved cystein residues are included in a signature motif. Investigating the variations in this motif would give insight into the phylogenetic history of the family. The table presented in this paper contains a large set of insulin-related peptides in bilateral phylogenetic groups (deuterostomian, ecdysozoan, lophotrochozoan). NCBI databases in silico wide screening combined with bibliographic researches provided a framework for identifying and categorising the structural characteristics of these insulin related peptides. The dataset includes NCBI IDs of each sequence with hyperlinks to FASTA format. Moreover, the structural type (α, β or γ), the A chain motif, the total number of cysteins, the C peptide cleavage mode and the potential additional domains (D or E) are specified for each sequence. The data are associated with the research article "Molecular evolution and functional characterisation of insulin-related peptides in molluscs: contributions of Crassostrea gigas genomic and transcriptomic-wide screening" [1]. The table presented here can be found at http://dx.doi.org/10.17632/w4gr8zcpk5.4#file-21c0f6a5-a3e3-4a15-86e0-e5a696458866.

Molecular evolution and functional characterisation of insulin related peptides in molluscs: Contributions of Crassostrea gigas genomic and transcriptomic-wide screening

Insulin Related Peptides (IRPs) belong to the insulin superfamily and possess a typical structure with two chains, B and A, linked by disulphide bonds. As the sequence conservation is usually low between members, IRPs are classified according to the number and position of their disulphide bonds. In molluscan species, the first IRPs identified, named Molluscan Insulin-related Peptides (MIPs), exhibit four disulphide bonds. The genomic and transcriptomic data screening in the Pacific oyster Crassostrea gigas (Mollusc, Bivalvia) allowed us to identify six IRP sequences belonging to three structural groups. Cg-MIP1 to 4 have the typical structure of MIPs with four disulphide bonds. Cg-ILP has three disulphide bonds like vertebrate Insulin-Like Peptides (ILPs). The last one, Cg-MILP7 has a significant homology with Drosophila ILP7 (DILP7) associated with two additional cysteines allowing the formation of a fourth disulphide bond. The phylogenetic analysis points out that ILPs may be the most ancestral form. Moreover, it appears that ILP7 orthologs are probably anterior to lophotrochozoa and ecdysozoa segregation. In order to investigate the diversity of physiological functions of the oyster IRPs, we combine in silico expression data, qPCR measurements and in situ hybridization. The Cg-ilp transcript, mainly detected in the digestive gland and in the gonadal area, is potentially involved in the control of digestion and gametogenesis. The expression of Cg-mip4 is mainly associated with the larval development. The Cg-mip transcript shared by the Cg-MIP1, 2 and 3, is mainly expressed in visceral ganglia but its expression was also observed in the gonads of mature males. This pattern suggested the key roles of IRPs in the control of sexual reproduction in molluscan species.

Insulin-like and IGF-like peptides in the silkmoth Bombyx mori: discovery, structure, secretion, and function

A quarter of a century has passed since bombyxin, the first insulin-like peptide identified in insects, was discovered in the silkmoth Bombyx mori. During these years, bombyxin has been studied for its structure, genes, distribution, hemolymph titers, secretion control, as well as physiological functions, thereby stimulating a wide range of studies on insulin-like peptides in other insects. Moreover, recent studies have identified a new class of insulin family peptides, IGF-like peptides, in B. mori and Drosophila melanogaster, broadening the base of the research area of the insulin-related peptides in insects. In this review, we describe the achievements of the studies on insulin-like and IGF-like peptides mainly in B. mori with short histories of their discovery. Our emphasis is that bombyxins, secreted by the brain neurosecretory cells, regulate nutrient-dependent growth and metabolism, whereas the IGF-like peptides, secreted by the fat body and other peripheral tissues, regulate stage-dependent growth of tissues.

Control of ecdysteroidogenesis in prothoracic glands of insects: a review

The very first step in the study of the endocrine control of insect molting was taken in 1922. Stefan Kopec characterized a factor in the brain of the gypsy moth, Lymantria dispar which appeared to be essential for metamorphosis. This factor was later identified as the neuropeptide prothoracicotropic hormone (PTTH), the first discovery of a series of factors involved in the regulation of ecdysteroid biosynthesis in insects. It is now accepted that PTTH is the most important regulator of prothoracic gland (PG) ecdysteroidogenesis. The periodic increases in ecdysteroid titer necessary for insect development can basically be explained by the episodic activation of the PGs by PTTH. However, since the characterization of the prothoracicostatic hormone (PTSH), it has become clear that in addition to 'tropic factors', also 'static factors', which are responsible for the 'fine-tuning' of the hemolymph ecdysteroid titer, are at play. Many of these regulatory factors are peptides originating from the brain, but also other, extracerebral factors both of peptidic and non-peptidic nature are able to affect PG ecdysteroidogenesis, such as the 'classic' insect hormones, juvenile hormone (JH) and the molting hormone (20E) itself. The complex secretory pattern of ecdysteroids as observed in vivo is the result of the delicate balance and interplay between these ecdysiotropic and ecdysiostatic factors.

Signaling and function of insulin-like peptides in insects

Insulin-like peptides (ILPs) exist in insects and are encoded by multigene families that are expressed in the brain and other tissues. Upon secretion, these peptides likely serve as hormones, neurotransmitters, and growth factors, but to date, few direct functions have been demonstrated. In Drosophila melanogaster, molecular genetic studies have revealed elements of a conserved insulin signaling pathway, and as in other animal models, it appears to play a key role in metabolism, growth, reproduction, and aging. This review offers (a) an integrated summary of the efforts to characterize the distribution of ILPs in insects and to define this pathway and its functions in Drosophila and (b) a few considerations for future studies of ILP endocrinology in insects.

Insulin-like system and growth regulation in the Pacific oyster Crassostrea gigas: hrIGF-1 effect on protein synthesis of mantle edge cells and expression of an homologous insulin receptor-related receptor

The involvement of molecules belonging to the insulin/IGF family in regulation of growth has been investigated in the Pacific oyster Crassostrea gigas. In vitro biological effects of human recombinant IGF-1 (hrIGF-1) on mantle edge cells, involved in oyster shell and soft body growth, were studied over an annual cycle. In mantle edge cells hrIGF-1 stimulates protein synthesis of 56+/-5.1% over basal for 10(-10) M in September with in addition a clear dose-effect corresponding to the highest shell growth period, and 57.5+/-3.45% over basal for 10(-11) M in March and 51+/-5.4% over basal for 10(-10) M in April corresponding to the period of mantle growth. These insulin-like effects were associated with the expression of a recently identified C. gigas insulin receptor-related receptor (CIR) in mantle edge cells as demonstrated by RT-PCR. Moreover, in situ hybridisation (ISH) confirmed this expression at the level of the inner and outer epithelia involved in mantle growth and shell formation.

Insulin-related peptides and their conserved signal transduction pathway

The 'insulin superfamily' is an ancient category of small, structurally related proteins, such as insulin, insulin-like growth factors (IGF) and relaxin. Insulin-like signaling molecules have also been described in different invertebrates, including nematodes, mollusks, and insects. They initiate an evolutionary conserved signal transduction mechanism by binding to a heterotetrameric, membrane-spanning receptor tyrosine kinase. Recent physiological and genetic studies have revealed that, in different metazoans, the insulin signaling pathway plays a pivotal role in the regulation of a variety of interrelated, fundamental processes, such as metabolism, growth, reproduction and aging.

Bombyxin exhibits an insulin-like response to modification in the N-terminal region of the A chain

Bombyxin is an insect neurohormone with an insulin-like structure. The N-terminal A chain helix, a region which is considered part of the active site in insulin, is almost identical between the two hormones. Bombyxin analogues with modifications at the N-terminus of the A-chain were synthesized and investigated for their ability to bind to bombyxin-specific receptors. While N-acetylation reduced the affinity to the bombyxin receptor to 18% the removal of glycine (A1) inactivated the hormone completely. Replacement of glycine (A1) by L-amino acids caused a significant loss in activity (11%) while its replacement by D-amino acid resulted in active bombyxin analogues (55%). Comparative CD spectroscopy indicated a change in structure for desGly(A1)bombyxin. Although the insect hormone does not have an insulin-like function it exhibits mammalian insulin-like structural sensitivity for A chain modifications.