Tissue-specific expression of the diazepam-binding inhibitor in Drosophila melanogaster: cloning, structure, and localization of the gene.

Abstract

The diazepam-binding inhibitor (DBI; also called acyl coenzyme A-binding protein or endozepine) is a 10-kDa polypeptide found in organisms ranging from yeasts to mammals. It has been shown that DBI and its processing products are involved in various specific biological processes such as GABAA/benzodiazepine receptor modulation, acyl coenzyme A metabolism, steroidogenesis, and insulin secretion. We have cloned and sequenced the Drosophila melanogaster gene and cDNA encoding DBI. The Drosophila DBI gene encodes a protein of 86 amino acids that shows 51 to 56% identity with previously known DBI proteins. The gene is composed of one noncoding 5' and two coding exons and is localized on the chromosomal map at position 65E. Several transcription initiation sites were detected by RNase protection and primer extension experiments.Computer analysis of the promoter region revealed features typical of housekeeping genes, such as the lack of TATA and CCAAT elements. However, in its low GC content and lack of a CpG island, the region resembles promoters of tissue-specific genes. Northern (RNA) analysis revealed that the expression of the DBI gene occurred from the larval stage onwards throughout the adult stage. In adult flies, DBI mRNA and immunoreactivity were detected in the cardia, part of the Malpighian tubules, the fat body, and gametes of both sexes. Developmentally regulated expression, disappearing during metamorphosis, was detected in the larval and pupal brains. No expression was detected in the adult nervous system. On the basis of the expression of DBI in some but not all tissues with high energy consumption, we propose that in D. melanogaster, DBI is involved in energy metabolism in a manner that depends on the substrate used for energy production.The diazepam-binding inhibitor (DBI) is a 10-kDa polypeptide that was first purified from rat brain on the basis of its ability to displace diazepam from the -y-aminobutyric acid receptor type A (GABAA)/benzodiazepine receptor (24). More recently DBI has also been purified from several peripheral organs such as pig intestine (14) and from bovine and rat liver (34,44,47). DBI has been shown to be expressed in several rat tissues (3, 9). The highest expression has been observed in the adrenal gland, liver, and somatic tissue of the testes, while the lowest levels have been detected in spleen, lung, and muscle (34,45,68). Nevertheless, DBI expression is restricted to certain cell types. In the rat brain, DBI is localized in selected neuronal populations, ependymal and glial cells (2, 3). DBIlike peptides have also been found in the central nervous systems of trout (Salmo gairdneri) (39) and frogs (Rana ridibunda) (40). In the adrenal gland, DBI is expressed in cortical cells, whereas chromaffin cells of the medulla are immunonegative (9). DBI and its metabolites octadecaneuropeptide (DBI33_50) and triakontatetraneuropeptide (DBI17-50) are involved in the regulation of multiple biological processes. In rats, intracerebroventricular injection of DBI or one of its metabolit...

Genome-wide transcription profile of field- and laboratory-selected dichlorodiphenyltrichloroethane (DDT)-resistant Drosophila

“…2). Diazepam-binding inhibitor (DBI) is a polypeptide found in several organisms that has been shown to be involved in benzodiazepine receptor modulation, acyl CoA metabolism, steroidogenesis, insulin secretion, and drug dependence (36,37). The relative transcript expression of DBI in Rst(2)DDT 91-R and Rst(2)DDT Wisconsin was 108-and 89-fold greater than Canton-S, suggesting a possible association between DDT resistance and cholesterol metabolism (Fig.…”

Cellular distribution, levels, and function of the diazepam-binding inhibitor/acyl-CoA-binding protein in last instar Manduca sexta midgut

“…This protein called the diazepambinding inhibitor (DBI) has since been found in non-vertebrates such as yeast, insects, and plants (Rose et al 1992;Kolmer et al 1994;Genbank T04081). All DBI proteins are 9-10 kDa in molecular weight, 86-104 residues, and share sequence identities of ≥50%.…”

Role of long-chain fatty acyl-CoA esters in the regulation of metabolism and in cell signalling

“…In other tissues ACBP is reported to be be present at high concentrations in specialized cells such as steroid-producing cells of the adrenal cortex and testis, and in epithelial cells specialized in secretion and in water and electrolyte transport, which are all characterized by high energy metabolism. In Drosophila melanogaster, ACBP has been found primarily expressed in tissues that are associated with high energy production or fat metabolism [135]. ACBP has been purified, cloned and sequenced from a large number of different species and tissues, and shows a high degree of similarity among the different species (Figure 2).…”

“…Sources : human-1 [171], human-2 [172], rat [112], mouse [173], bovine [113], pig [174], dog, tortoise, duck, chicken, Arabidopsis thaliana [130], frog [175], Manduca sexta [130], Drosophila melanogaster [135], yeast-1, yeast-2 [140], Brassica napus [176], cotton [177] and endozepine-like peptide (ELP) [134].…”