Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Murine macrophage tumor cells infected with Leishmania mexicana mexicana were exposed to the antimycotic drug ketoconazole and to [2-14C]mevalonate, then the amastigotes were isolated, collected, purified, and their free sterols were analyzed by chromatographic and mass spectrometric methods. Control amastigotes contained as products of de novo biosynthesis C28 4-desmethyl sterols (episterol, 5-dehydroepisterol), C29 4-desmethyl sterols (stigmasta-7,24 (28)-dien-3 beta-ol, stigmasta-5,7,24(28)-trien-3 beta-ol), 4-methyl sterols (4 alpha, 14 alpha-dimethylzymosterol, obtusifoliol) and a 4,4-dimethyl sterol (lanosterol). Present also were macrophage sterols (cholesterol, desmosterol) and a putative product of the C-24 alkylation of desmosterol by amastigotes (24-methylenecholesterol). Amastigotes from macrophages exposed to ketoconazole showed notable changes in the proportions, concentrations and specific activities of their free sterols; increased for 4 alpha, 14 alpha-dimethylzymosterol and decreased for the endogenous C28 and C29 4-desmethyl sterols. Such changes were observed at a ketoconazole concentration as low as 0.01 microgram ml-1. By contrast, uninfected macrophages accumulated only small amounts of lanosterol of high specific activity at a ketoconazole concentration of 10 micrograms ml-1. the ketoconazole-induced alterations in amastigote sterols parallel those previously reported in fungi and L. m. mexicana promastigotes, and suggest a biochemical mechanism for the anti-leishmanial activity of the drug in which changes in sterol composition are linked to disturbances of cell membrane structure and function, and hence to cytotoxicity.
Mol Biochem Parasitol 1986 Jul
PMID:Effects of ketoconazole on sterol biosynthesis by Leishmania mexicana mexicana amastigotes in murine macrophage tumor cells. 373 97

Leishmania mexicana mexicana promastigotes grown with cholesterol, supplied in natural products as the free sterol and as cholesteryl esters, were exposed to [2-14C]mevalonate and to the antimycotic drug ketoconazole. Growth was inhibited and cholesterol and 14 alpha-methyl sterols accumulated in free and esterified forms (cholesterol much greater than 4 alpha,14 alpha-dimethylcholesta-8,24-dien-3 beta-ol much greater than 14 alpha-methylcholesta-8,24-dien-3 beta-ol congruent to 14 alpha-methylergosta-8,24(28)-dien-3 beta-ol much greater than 4 alpha,14 alpha-dimethylergosta-8,24(28)-dien-3 beta-ol; identified by capillary gas chromatography/mass spectrometry, and by 1H and 13C nuclear magnetic resonance spectrometry). The 14 alpha-methyl sterols were preferentially labelled with 14C. The cholesterol was unlabelled and substituted for a substantial fraction of the major product of sterol biosynthesis, ergosta-5,7, 24(28)-trien-3 beta-ol (5-dehydroepisterol), but did not replace it and did not offer remarkable protection against either growth inhibition or alteration of sterol biosynthesis. Promastigotes grown with [6-2H]cholesterol or [4-14C]cholesterol did not contain labelled forms of Leishmania sterols, or other sterols. The chromatographic and spectrometric sterol analyses and the isotopic tracer findings suggested that ketoconazole impaired the cytochrome P-450 dependent 14 alpha-demethylation of lanosterol, that cholesterol was neither biosynthesized nor metabolized, and that the physiological functions of 5-dehydroepisterol had sterol structural requirements not entirely met by cholesterol. In all these studies, L. mexicana mexicana demonstrated a sterol biochemistry remarkably similar to that of fungi. This recommends an increase in interest in antimycotic drugs as chemotherapeutic agents for leishmanial infections.
Mol Biochem Parasitol 1985 Jun
PMID:Sterols of ketoconazole-inhibited Leishmania mexicana mexicana promastigotes. 403 89

The present paper examines the steroidogenic responsiveness of immature porcine Leydig cells in primary culture. Both testosterone (T) and dehydroepiandrosterone sulfate (DHAS) secretion were measured under basal conditions and after stimulation with human chorionic gonadotropin (hCG) (25 ng/ml). In medium supplemented with insulin, transferrin, epidermal growth factor (3H) and 0.1% calf serum, cells survived 3-5 days in culture. The production of steroids (under hCG stimulation) is poor on day 0-1 of the culture. On day 2-4 basal T and DHAS levels are 1.9 and 17.0 ng/10(6) cells/24 h. The addition of hCG stimulated T and DHAS production 19- and 6-fold respectively and the average productions were 37 and 109 ng/10(6) cells/24 h. Increasing the serum to 0.5% did not change the viability of the cultures, but increased hCG stimulated T and DHAS production (183 and 188 ng/10(6) cells/24 h). The addition of alpha-tocopherol (vitamin E) to 0.1% calf serum led to a 4-fold increase in stimulated T production (142 ng/10(6) cells/24 h) and maintained full cell viability for more than 5 days. Measurement of 3 beta-ol steroid dehydrogenase activity indicates that the amount of enzyme is 4 times higher at day 2 than at day 0 and 1 (with or without hCG), suggesting a spontaneous maturation of the cells in culture. This might explain the increased T production with time in culture. In cumulative experiments (24 h) the cells do not seem to be desensitized to hCG stimulation following prolonged exposure to 25 ng hCG since the daily steroid production is increasing with time in culture. However, kinetic studies show that steroidogenesis is not linear over a 24 h period. In cumulative experiments the steroid production stops between 12 and 16 h following hCG exposure (5 and 100 ng/ml) and resumes following a medium change. These results suggest that some inhibitory compounds are accumulated in the medium and are controlling the Leydig cell function. Moreover high doses of hCG (100 ng/ml) result in a lower production of steroids and an earlier plateau in the case of DHAS. These results demonstrate that porcine Leydig cells can live and differentiate in hormone- and vitamin-supplemented medium and that auto-feedback mechanisms inhibiting steroid accumulation take place under in vitro conditions.
Mol Cell Endocrinol 1983 Apr
PMID:Androgen production in primary culture of immature porcine Leydig cells. 622 Sep 34

The major sterol of promastigotes of stocks of Leishmania tropica, L. donovani and 3 subspecies of L. mexicana has been identified as ergosta-5,7,24(28)-trien-3 beta-ol; and of an L. major stock as ergosta-7,24(28)-dien-3 beta-ol. 24-Methylcholesta-5,7,22-trien-3 beta-ol and 24-ethylcholesta-5,7,22-trien-3 beta-ol were minor constituents, and traces of ergosta-5,7,22,24(28)-tetraen-3 beta-ol and a C27-diene were also recognized in some species. Lanosterol and 4,4-dimethylcholesta-8,24-dien-3 beta-ol were detected in all species studied, and squalene was identified in a stock of L. tropica. The sterol composition of members of the genus Leishmania and the sterol biosynthetic pathways it implies are characteristic of yeast and other fungi.
Mol Biochem Parasitol 1984 Feb
PMID:Sterols of Leishmania species. Implications for biosynthesis. 670 Jun 38

The effect of estrogen structure on the conformation of the complex formed with estrogen receptor (ER) and the consensus estrogen response element (EREc) has been examined with gel mobility shift assay. Proteins in MCF-7 cell extracts formed three distinct complexes with ERE. Only the slowest moving complex contained ER as indicated by binding with anti-ER antibodies H222 and D547. This ER-ERE complex displayed increased electrophoretic mobility when formed in the presence of estradiol (E2) and bound radiolabeled 16 alpha-iodoestradiol. The antiestrogen ICI 164,384 decreased the mobility of the ER-ERE complex and blocked the effect of E2. The results reported here indicate that the position and location of hydroxyl groups on the estratriene nucleus is an important factor in determining the mobility of ER-EREc (or a variant ERE) in gel shift assays. The ability of E2 analogs to cause conformational changes detectable as altered mobility was not directly related either to their binding affinity for ER or to their ability to activate E2 responsive genes. Although several dihydroxyestrogens (estradiol-16 alpha, 1- and 2-hydroxyestratrien-17 beta-ol) caused an increase in the mobility of the ER-EREc, other ligands (estradiol-17 alpha, 4-hydroxyestratriene-17 beta-ol, 3-hydroxy estratriene, estratrien-17 beta-ol and 5-androsten-3 beta, 17 beta-diol) with a capacity for activating at least some E2 responsive genes in MCF-7 cells had little or no effect. On the basis of these and previously published results, it can be concluded that specific structure features of estrogens are responsible for conformational changes of ER-ERE complexes detectable in gel-shift assays. Furthermore, the identified structural characteristics of the ligand which are required for gel-shift are not the same as those previously reported to be essential for stimulation of transcriptional activity of ER.
J Steroid Biochem Mol Biol 1995 Sep
PMID:Relationship between estrogen structure and conformational changes in estrogen receptor/DNA complexes. 757 1

We have investigated the effects of chronic treatment with the neurosteroid 5 alpha-pregnan-3 alpha-ol-20-one (5 alpha 3 alpha) on the gamma-aminobutyric acid (GABA)A receptor complex in cultured mammalian cortical neurons. Chronic 5 alpha 3 alpha treatment (up to 2 microM, 5 days) did not produce any changes in the morphological appearance or the cell protein content of cortical neurons. The basal binding of [3H]flunitrazepam, [3H]Ro15-1788, and [3H]Ro15-4513 was not altered after the chronic treatment. Chronic 5 alpha 3 alpha treatment did not alter the Kd or Bmax values of [3H]flunitrazepam binding to intact cortical neurons. However, chronic 5 alpha 3 alpha treatment produced uncoupling between GABA, barbiturate, and neurosteroid sites and the benzodiazepine site. The EC50 values of these ligands were not significantly altered; however, their Emax values were decreased after chronic 5 alpha 3 alpha treatment. The 5 alpha 3 alpha-induced uncoupling was time and concentration dependent. The binding of [3H]GABA and t-[35S]butylbicyclophosphorothionate was also decreased after chronic 5 alpha 3 alpha treatment. Chronic 5 alpha 3 alpha treatment decreased the Bmax of the low affinity GABAA receptor sites, without affecting the high affinity sites, and decreased the Bmax of t-butylbicyclophosphorothionate binding sites. The EC50 value for GABA-induced 36Cl- influx was not altered, whereas the Emax value was decreased after chronic 5 alpha 3 alpha treatment. Furthermore, the 5 alpha 3 alpha-induced uncoupling was reversed by concomitant exposure of the cortical neurons to 5 alpha-pregnan-3 beta-ol-20-one or R5135, suggesting an involvement of the neurosteroid and GABA recognition sites in the observed uncoupling. Taken together, these results suggest that chronic 5 alpha 3 alpha treatment produces heterologous uncoupling at the GABAA receptor complex.
Mol Pharmacol 1995 Mar
PMID:Chronic neurosteroid treatment produces functional heterologous uncoupling at the gamma-aminobutyric acid type A/benzodiazepine receptor complex in mammalian cortical neurons. 770 Feb 57

The effect of structure of the estrogen ligand on the accumulation of tPA mRNA and the activity of extracellular fibrinolytic enzyme has been examined in cultures of MCF-7 cells. Estradiol(E2)-stimulated fibrinolytic activity was preceded by an increase in actinomycin D sensitive tPA mRNA synthesis which peaked at 18 h. Ten A- and D-ring structural analogs of E2 affected tPA mRNA accumulation and extracellular fibrinolytic activity. Only in the case of two A-ring isomers (2- and 4-hydroxyestratrien-17 beta-ol) was the decreased effect of the ligand's structural change on tPA mRNA accumulation and fibrinolysis not explained by a comparable decline in affinity of the ligand for estrogen receptor. Both of these analogs functioned as antiestrogens. The stimulatory capacity of androstanediols on the tPA gene required that the 3-hydroxyl group be positioned in the beta-configuration. Absence of the 17 beta-hydroxy group was beneficial to the maximum accumulation of tPA mRNA. As has been reported for other estrogen responsive genes (progesterone receptor, cathepsin D and pS2), regulation by estrogens is not related directly to the affinity of the ligand for ER, but this activity may be determined by the location of the electronegative isopotential above the A-ring of estrogenic ligands.
J Steroid Biochem Mol Biol 1995 May
PMID:Induction of tissue plasminogen activator mRNA and activity by structurally altered estrogens. 774 7

Cytochrome P-450(14DM) catalyzing lanosterol 14 alpha-demethylation was purified from rat liver and was characterized by its catalytic properties and mode of expression. The purified protein, with an apparent molecular mass of 51 kDa, showed 24,25-dihydrolanosterol 14 alpha-demethylation activity (3.05 nmol/min/mg protein) in a reconstituted system with an apparent Km value of 40 microM. The reconstituted enzyme converted 32-hydroxy-24,25-dihydrolanosterol and 32-oxo-24,25-dihydrolanosterol (the oxygenated intermediates of 24,25-dihydrolanosterol) to 4,4-dimethylcholesta-8,14-dien-3 beta-ol (the 32-nor compound). Immunoblot analysis of liver microsomes from male and female rats showed that the enzyme protein was expressed at an early stage of development and attained its maximum at 4 weeks after birth, retaining the same level thereafter. No difference was evident between males and females in the level of cytochrome P-450(14DM) in the liver up to 7 weeks after birth.
Res Commun Mol Pathol Pharmacol 1994 Sep
PMID:Characterization of catalytic properties and expression of cytochrome P-450(14DM), lanosterol 14 alpha-demethylase, in rats. 782 3

The metabolism of varying quantities of pregnenolone has been studied in nuclei-free homogenates from Macaca fascicularis testes by using capillary gas chromatography, after derivatization of metabolites as O-methyl oximes/trimethylsilyl ethers. Evidence was obtained indicating that both pathways for testosterone biosynthesis were operating. 5-Androstene-3 beta, 17 beta-diol was formed in especially high quantities. Two 16-androstenes, namely 5,16-androstadien-3 beta-ol and 5 alpha-androst-16-en-3 beta-ol, were also quantitatively important as metabolites. Co-incubation of stored homogenates with relaxin resulted in 80-100% reduction of the formation of all metabolites quantified except for 5 alpha-androst-16-en-3-one, which was stimulated. Freezing the homogenates at -10 degrees C for 3 weeks resulted in marked 4- to 6-fold reduction in the yields of testosterone and of the 5-ene and 4-ene metabolites from pregnenolone.
Biochem Mol Biol Int 1994 Oct
PMID:Pregnenolone metabolism in testicular homogenates of macaques (Macaca fascicularis): some effects of relaxin and freezing. 786 91

An expanded role for vitamin D (1 alpha,25-(OH)2D3) in mammalian systems has been suggested by recent evidence that its receptor (vitamin D receptor [VDR]) is present not only in classical target organs, but in a variety of normal tissues and organs, tumor tissues, and cancer cell lines. Vitamin D is involved not only in the regulation of calcium homeostasis and bone metabolism, but in the regulation of cell proliferation, differentiation, and immune responses. The role vitamin D may play in normal lung growth, development, and maintenance is unknown. Likewise, its part in lung tumorigenesis is unclear. The present study examined VDR binding activity and VDR expression in normal mouse lung and ethylnitrosourea-induced lung adenomas. Binding of 1 alpha,25-(OH)2D3 was specific and saturable over the concentration range of 0.01 to 0.50 nM, with an affinity (Kd) of 0.93 x 10(-10) M and a total binding capacity (Bmax) of 22 fmol/mg of protein. Scatchard analysis yielded a convex curve, which suggests positive receptor cooperativity. The calculated Hill coefficient equals 1.69, at a receptor concentration of 0.4 nM, consistent with dimerization of the receptor. Western blot analysis showed the presence of 60 kD VDR protein in tumor homogenates, while Northern blot analysis detected the 4.4 kb VDR mRNA in tumor tissue preparations. Immunohistochemistry and in situ hybridization revealed that both adenomatous Clara cells and normal bronchiolar epithelial Clara cells expressed VDR, with the receptor protein present in their nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)
Am J Respir Cell Mol Biol 1994 Oct
PMID:Vitamin D3 receptor expression in N-ethylnitrosourea-induced mouse pulmonary adenomas. 791 16


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>