Disease relevance of DBI

• A fraction highly enriched for recombinant ACBP was obtained by extracting induced E. coli cells with 1 M-acetic acid [1].
• The photocrosslinked acyl-CoA-ACBP complex was separated from unlabelled ACBP on reverse-phase h.p.l.c. and the purified complex was digested with trypsin, Staphylococcus aureus V8 proteinase or endoproteinase Asp-N [2].

High impact information on DBI

• The folding kinetics of bovine acyl-CoA binding protein was studied by (15)N relaxation dispersion measurements under equilibrium conditions [3].
• The formation of a native-like structure containing eight conserved hydrophobic residues is rate limiting in two-state protein folding of ACBP [4].
• Frog DBI contains two paired basic amino acids (Lys-Lys) at positions 14-15 and 62-63 and a single cysteine within the biologically active region of the molecule [5].
• The distribution of both DBI mRNA and DBI-like immunoreactivity indicates that DBI is selectively expressed in glial cells [5].
• Endozepine competes with benzodiazepines for saturable binding sites in synaptosomes and in mitochondria of specific peripheral tissues [6].

Biological context of DBI

• Complete amino acid sequences of bovine and human endozepines. Homology with rat diazepam binding inhibitor [7].
• A comparison between the sequences of bovine and human endozepines with the partial sequences of the functionally related diazepam binding inhibitor from rat brain reveals significant sequence homology [7].
• Residual dipolar couplings in the denatured state of bovine acyl-coenzyme A binding protein (ACBP) oriented in strained polyacrylamide gels have been shown to be a sensitive, sequence-specific probe for residual secondary structure [8].
• cDNAs containing the entire coding sequence of endozepine, a putative ligand of the benzodiazepine receptor, were isolated from bovine and human cDNA libraries [9].
• The endozepine proteins are highly conserved, as illustrated by the finding that the nucleotide sequences of the coding regions are 93% conserved between the bovine and human forms [9].

Anatomical context of DBI

• Our microscopic results point to the role of ACBP as an intermembrane transporter of acyl-CoA and demonstrate the ability of AFM to reveal the remodelling of membranes by surfactants and proteins [10].
• The regional distribution of DBI in the human brain is similar to that observed in rat brain: high concentrations in cortical and limbic areas, cerebellum, and brainstem, and low concentrations in the basal ganglia [11].
• Measurements of CA activity in intact red blood cells were conducted to confirm DBI remains extracellular [12].
• Moreover, the biosynthesis of DBI is up-regulated in the cerebellum and cerebral cortex of rats made tolerant to diazepam, suggesting that changes in the biosynthesis of DBI might be one of the mechanisms eliciting tolerance to benzodiazepine [13].
• Data presented here suggest that (i) Ep/DBI levels are not regulated by trophic hormones in these steroidogenic cell lines, and (ii) that the peptide has a relatively long half-life (greater than 3 h), a finding incompatible with suggestions of it having a rapid turnover [14].

Associations of DBI with chemical compounds

• Both endozepine and DBI have been shown to elicit behavioral effects, suggesting that they function as pharmacologically-active ligands of the GABA (gamma-aminobutyric acid) receptor complex [15].
• Human endozepine, an 86 amino acid polypeptide, was originally isolated from human brain tissue as a putative ligand of the benzodiazepine receptor [15].
• Inhibition of total CA activity with acetazolamide and inhibition of extracellular-facing membrane-associated CA with DBI caused an identical intracellular pH decrease in intact NPE cells [12].
• Diazepam binding inhibitor (DBI) is a peptide, initially identified for its ability of displacing the binding of diazepam [13].
• We have used two cell lines (Y-1 mouse adrenal cell tumour and MA-10 mouse Leydig cell tumour), both of which exhibit hormone stimulated steroid production, to investigate the role of Ep/DBI in acute hormone stimulated steroidogenesis [14].

Other interactions of DBI

• Addition of endozepine in nanomolar concentrations to a system for side-chain cleavage reconstituted from highly purified P-450scc and electron carriers (adrenodoxin reductase and adrenodoxin) stimulates the conversion of cholesterol to pregnenolone (side-chain cleavage) [16].

Analytical, diagnostic and therapeutic context of DBI

• The majority of the purified ACBP was focused at pH 5.9 in isoelectric focusing and could be shown to be N-acetylated ACBP without any further modifications [17].
• Northern blot analysis showed that DBI mRNA is expressed at a high level in the brain but is virtually absent in peripheral tissues [5].
• The distribution of DBI mRNA and DBI-like immunoreactivity in the frog brain was studied by in situ hybridization and immunocytochemistry [5].
• Using a specific radioimmunoassay for human DBI, we investigated the distribution of this peptide in different brain areas [11].
• We characterized with high-pressure liquid chromatography the DBI immunoreactivity in brain tissue obtained by biopsy and autopsy; we detected one molecular species of DBI in both instances [11].

References