Isogenic strain construction and gene mapping in Candida albicans.

Archaeoglobus fulgidus is the first sulphur-metabolizing organism to have its genome sequence determined. Its genome of 2,178,400 base pairs contains 2,436 open reading frames (ORFs). The information processing systems and the biosynthetic pathways for essential components (nucleotides, amino acids and cofactors) have extensive correlation with their counterparts in the archaeon Methanococcus jannaschii. The genomes of these two Archaea indicate dramatic differences in the way these organisms sense their environment, perform regulatory and transport functions, and gain energy. In contrast to M. jannaschii, A. fulgidus has fewer restriction-modification systems, and none of its genes appears to contain inteins. A quarter (651 ORFs) of the A. fulgidus genome encodes functionally uncharacterized yet conserved proteins, two-thirds of which are shared with M. jannaschii (428 ORFs). Another quarter of the genome encodes new proteins indicating substantial archaeal gene diversity.

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The complete genome sequence of the hyperthermophilic, sulphate-reducing archaeon Archaeoglobus fulgidus

https://www.cell.com/trends/pharmacological-sciences/pdf/S0165-6147(06)00153-2.pdf

Translocator protein (18kDa): new nomenclature for the peripheral-type benzodiazepine receptor based on its structure and molecular function.

Neurosteroids: endogenous bimodal modulators of the GABAA receptor. Mechanism of action and physiological significance.

The mechanism regulating the production of steroids in response to trophic hormone stimulation has been the subject of investigation for over three decades. When considering the effects of trophic hormones on the steroidogenic process it is necessary to first distinguish between acute effects and chronic effects. Acute effects are those which result in the very rapid (within minutes) synthesis and secretion of steroids in response to hormone stimulation and involve the rapid translocation of intracellular cholesterol to the site of its cleavage, as will be discussed later. Chronic effects are those which occur on the order of hours to tens of hours and involve increased gene transcription and translation of the proteins involved in the biosynthesis of steroids. This chapter will focus on studies designed to elucidate the mechanisms involved in the acute regulation of steroid production in response to hormone stimulation. Overviews of the effects of chronic stimulation on steroidogenic enzymes have appeared in several excellent review articles (Simpson and Waterman 1983; Miller 1988; Hanukoglu 1992).

Regulation of the acute production of steroids in steroidogenic cells.

Peripheral-type benzodiazepine receptors mediate translocation of cholesterol from outer to inner mitochondrial membranes in adrenocortical cells.

The peripheral-type benzodiazepine receptor is functionally linked to Leydig cell steroidogenesis.

Recent observations on the steroid synthetic capability within the brain open the possibility that benzodiazepines may influence steroid synthesis in nervous tissue through interactions with peripheral-type benzodiazepine recognition sites, which are highly expressed in steroidogenic cells and associated with the outer mitochondrial membrane. To examine this possibility nine molecules that exhibit a greater than 10,000-fold difference in their affinities for peripheral-type benzodiazepine binding sites were tested for their effects on a well-established steroidogenic model system, the Y-1 mouse adrenal tumor cell line. 4'-Chlorodiazepam, PK 11195, and PK 14067 stimulated steroid production by 2-fold in Y-1 cells, whereas diazepam, flunitrazepam, zolpidem, and PK 14068 displayed a lower (1.2- to 1.5-fold) maximal stimulation. In contrast, clonazepam and flumazenil did not stimulate steroid synthesis. The potencies of these compounds to inhibit 3H-labeled PK 11195 binding to peripheral-type benzodiazepine recognition sites correlated (r = 0.985) with their potencies to stimulate steroid production. Similar findings were observed in bovine and rat adrenocortical cell preparations. These results suggest that ligands of the peripheral-type benzodiazepine recognition site acting on this mitochondrial receptor can enhance steroid production. This action may contribute specificity to the pharmacological profile of drugs preferentially acting on the benzodiazepine recognition site associated with the outer membrane of certain mitochondrial populations.

Mitochondrial benzodiazepine receptors regulate steroid biosynthesis.

Immunoblot analysis, using antibodies against distinct N-methyl-d-aspartic acid (NMDA) receptor subunits, illustrated that the NR2A and NR2B subunit proteins have developmental profiles in cultured cortical neurons similar to those seen in vivo. NR1 and NR2B subunits display high levels of expression within the first week. In contrast, the NR2A subunit is barely detectable at 7 days in vitro (DIV) and then gradually increased to mature levels at DIV21. Immunocytochemical analysis indicated that NMDA receptor subunits cluster in the dendrites and soma of cortical neurons. Clusters of NR1 and NR2B subunits were observed as early as DIV3, while NR2A clusters were rarely observed before DIV10. At DIV18, NR2B clusters partially co-localize with those of NR2A subunits, but NR2B clusters always co-localize with those of NR1 subunits. Synapse formation, as indicated by the presence of presynaptic synaptophysin staining, was observed as early as 48–72 h after plating. However, in several neurons at ages less than DIV5 where synapses were scarce, NR2B and NR1 clusters were abundant. Furthermore, while NR2B subunit clusters were seen both at synaptic and extrasynaptic sites, NR2A clusters occurred almost exclusively in front of synaptophysin-labelled boutons. This result was supported by electrophysiological recording of NMDA-mediated synaptic activity [NMDA-excitatory postsynaptic currents (EPSCs)] in developing neurons. At DIV6, but not at DIV12, CP101, 606, a NR1/NR2B receptor antagonist, antagonized spontaneously occurring NMDA-EPSCs. Our data indicate that excitatory synapse formation occurs when NMDA receptors comprise NR1 and NR2B subunits, and that NR2A subunits cluster preferentially at synaptic sites.

Developmental changes in localization of NMDA receptor subunits in primary cultures of cortical neurons

A recognition site for benzodiazepines structurally different from that linked to various γ-aminobutyric acid A (GABAA) receptor subtypes is located on the outer mitochondrial membranes of steroidogenic cells. This protein has been signified to be important in the regulation of steroid biosynthesis. Because of its location it is designated herein as the mitochondrial benzodiazepine receptor (MBR). A putative endogenous ligand for MBR is the peptide diazepam binding inhibitor (DBI), previously shown to displace drugs from MBR and to be expressed and stored in steroidogenic cells rich in MBR. The two model systems used to study steroidogenic regulation by DBI were the Y-l adrenocortical and MA-10 Leydig cell lines previously shown to be applicable in studies of mitochondrial steroidogenesis. Both cell lines contain DBI as well as DBI processing products, including the DBI fragments that on reverse phase HPLC coelute with the naturally occurring triakontatetraneuropeptide [TTN; DBI-(17–50)] and octadecaneuro...

Diazepam binding inhibitor and its processing products stimulate mitochondrial steroid biosynthesis via an interaction with mitochondrial benzodiazepine receptors.

Karl E. Krueger

Papers

Peripheral-type benzodiazepine receptors mediate translocation of cholesterol from outer to inner mitochondrial membranes in adrenocortical cells.

The peripheral-type benzodiazepine receptor is functionally linked to Leydig cell steroidogenesis.

Mitochondrial benzodiazepine receptors regulate steroid biosynthesis.

Developmental changes in localization of NMDA receptor subunits in primary cultures of cortical neurons

Diazepam binding inhibitor and its processing products stimulate mitochondrial steroid biosynthesis via an interaction with mitochondrial benzodiazepine receptors.