Expression of the gene encoding an insulin-related peptide in Locusta (Insecta, Orthoptera). Evidence for alternative promoter usage.

A peptide with significant sequence similarity to mammalian insulins, Locusta insulin-related peptide (LIRP) has recently been isolated from neurohaemal lobes of Locusta migratoria 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 copy/haploid 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 Locusta; 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.