Expression of the gene encoding an insulin‐related peptide inLocusta (Insecta, Orthoptera)

Abstract

A peptide with significant sequence similarity to mammalian insulins, Locustu insulin-related peptide (LIRP) has recently been isolated from neurohaemal lobes of Lacustu migrutoriu and the corresponding cDNA has been cloned. We report here the cloning of the LIRP gene and we show that this gene is present as a single copykaploid genome. The organization of this gene is similar to that of mammalian insulin genes. There are at least two LIRP transcripts, LIRP T1 and LIRP T2, differing in their 5' untranslated regions and in the 5' end of the coding region resulting in an additional ATG present in LIRP T2. The two transcripts are differentially expressed in Locustu; whereas LIRP T1 is only expressed in neurosecretory cells of the brain, LIRP T2 is present at low levels in all tissues. Our data indicate that the LIRP gene has at least two promoters, the alternative usage of which could account for a differential regulation of expression of LIRP in the neurosecretory cells and in various peripheral tissues.

A Fat Body-Derived IGF-like Peptide Regulates Postfeeding Growth in Drosophila

“…This suggests the lack of processing enzymes to generate mature insulin in the fat body, which probably explains why fat body-derived ILPs in different species have attained similar structural features as IGFLPs (shortened C-peptide and/or the loss of cleavage sites) despite their independent lineages. Studies in orthopteran species (which are considered closer to earlier insect species), where there is only one identified ILP the expression of which is differentially regulated in the brain IPCs and in the fat body (Kromer-Metzger and Lagueux, 1994; Badisco et al, 2008), support our hypothesis.…”

Purification and characterization of an insulin-related peptide in the desert locust, Schistocerca gregaria: immunolocalization, cDNA cloning, transcript profiling and interaction with neuroparsin

“…In D. melanogaster, the mRNAs for most dilps occur in both nervous and peripheral tissues (Brogiolo et al 2001, Ikeya et al 2002, Rulifson et al 2002, Broughton et al 2005. Moreover, in the migratory locust, L. migratoria, Lom-IRP transcripts were also found in a wide variety of tissues (Kromer-Metzger & Lagueux 1994). The presence of IRP transcripts in various peripheral tissues may be an indication for a possible role of the encoded peptide(s) as a paracrine and/or endocrine signal substance, a situation that may resemble that of IGFs and many other growth factors.…”

“…In contrast to genomederived nucleotide sequence data obtained from lepidopteran, dipteran and hymenopteran species, only one single IRP has so far been identified in each of the orthopteran species, L. migratoria and S. gregaria. For both Lom-IRP and Scg-IRP, two transcript (cDNA) variants have now been identified, but these only differ in their 5 0 untranslated region (Kromer-Metzger & Lagueux 1994). Since the genomes of these species have not (yet) been sequenced, it is still unclear whether other IRP genes remain to be discovered in these locusts.…”

Knock-in of diphteria toxin A chain gene at Ins2 locus: effects on islet development and localization of Ins2 expression in the brain

“…During the last decade, many studies have focused on brain cells, probably because these cells might be the common ancestral site of extrapancreatic insulin gene expression in vertebrates and invertebrates. In invertebrates which lack an endocrine pancreas, insulin-related molecules have been described mainly in the central nervous system (Smit et al, 1988;Kromer-Metzger et al, 1994;Pimentel et al, 1996;Wolkow et al, 2000). In vertebrates, insulin or insulin-like transcripts have been found for instance in rat periventricular hypothalamic cells, in rabbit or rat neuron cell cultures and in an human neuroectodermal tumor (Young, 1986;Schechter et al, 1988;Nakamura et al, 2001).…”