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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study shows that the Fisher rat thyroidal cell line (FRTL-5) can iodinate newly synthesized thyroglobulin. Iodinated thyroglobulin was found intra- and extracellularly. Both the synthesis of thyroglobulin and its subsequent iodination were found to be thyrotropin (TSH) dependent, with optimal activity at 10-100 microU TSH/ml. Thyroglobulin was the only protein in the culture medium, that was iodinated with high specificity and in a TSH-dependent fashion. Albumin, which was abundantly present in the culture medium, was only weakly iodinated. Various proteins, including thyroglobulin, were found to be iodinated intracellularly. Of these iodoproteins only thyroglobulin appeared in the medium suggesting selective secretion of iodinated thyroglobulin. It was shown that the other intracellular iodoproteins were no thyroglobulin breakdown products. Their function is as yet unknown.
Mol Cell Endocrinol 1989 Oct
PMID:Iodination of newly synthesized thyroglobulin by FRTL-5 cells is selective and thyrotropin dependent. 261 32

Isolated perfused rat hearts were used to assess the effect of 30 or 60 mins of hypoxia on the ultrastructure of the capillary endothelium and particularly on the interendothelial junctions. Perfusions were carried out both in the presence and absence of albumin. Albumin had no effect on ultrastructure or membrane spacing in the interendothelial clefts, neither in oxygenated controls nor in hypoxic hearts. After 30 and 60 mins of hypoxia some capillaries showed endothelial swelling while after 60 mins the endothelium of others was attenuated. The wide regions of the intercellular cleft were not affected by hypoxia but the "narrow zone" gap between membranes became significantly smaller. We conclude that factors within the clefts other than the "tightness" of the narrow zones are responsible for changes in permeability in hypoxia and with albumin.
J Mol Cell Cardiol 1989 Dec
PMID:Effect of hypoxia on endothelial morphology and interendothelial junctions in the isolated perfused rat heart. 263 15

Transport of palmitate from the albumin-palmitate complex in the plasma to inside mitochondria where it undergoes beta-oxidation is a multistep process. Albumin's large size prevents permeation via interendothelial clefts. Palmitate dissociation from albumin in solution is too slow to provide an adequate supply of the unbound palmitate. The discovery that the dissociation occurs upon albumin binding to an endothelial surface receptor resolves the conundrum. Palmitate transport across the luminal surface membrane may be either carrier-mediated or passive. Fatty-acid binding protein inside endothelial and cardiac muscle cells facilitates diffusion through cytosol while maintaining the unbound palmitate concentration at a very low level. Within the interstitium, albumin is again the palmitate carrier. Still controversial is whether or not there is a saturable sarcolemmal transporter or simply passive exchange. Inside the myocyte palmitate is again bound to the fatty acid binding protein which buffers the free palmitate concentration, facilitates diffusion, and may facilitate further intracellular reactions.
Mol Cell Biochem
PMID:Modeling of palmitate transport in the heart. 267 67

In adult Xenopus serum, albumin gene expression is regulated by estrogen through the selective destabilization of its mRNA during the vitellogenic response. The present study reports the cDNA sequence of both the 68K and 74K Xenopus albumin mRNAs, their derived amino acid sequence, and the regulation of albumin gene expression during embryogenesis. Albumin mRNA has a 39 nucleotide 5' untranslated region terminating in a consensus translation initiation site. The derived amino acid sequence yields a 24-amino acid hydrophobic leader sequence (terminating in Lys-Arg) that shares significant homology with the leader peptide of rat albumin. Overall there is 37% sequence identity between rat and frog albumin, with exact conservation of all but one Cys residue and the Pro residues responsible for the three domain structure of the mature protein. The 74K albumin (unlike the 68K albumin) is glycosylated; a point mutation converting Lys256 to Asn introduces an N-linked glycosylation site that is similar to one found in the sequence of mammalian alpha-fetoproteins. A larval albumin-like protein was not detectable by silver staining in serum of tadpoles before the beginning of metamorphosis at stage 48. Albumin mRNA is absent from early tadpoles (stages 22-47); however, it is rapidly induced at stage 48 as one of the earliest manifestations of metamorphosis. Exposure of embryos to 10(-8) M T3, which regulates amphibian metamorphosis, resulted in the premature induction of albumin mRNA, such that it is evident by stage 43.
Mol Endocrinol 1989 Mar
PMID:Xenopus laevis serum albumin: sequence of the complementary deoxyribonucleic acids encoding the 68- and 74-kilodalton peptides and the regulation of albumin gene expression by thyroid hormone during development. 274 53

We have investigated the influence of steroid hormones on insulin-like growth factor II (IGF-II) expression. Hepatic IGF-II mRNA decreased gradually during postnatal development, reaching adult levels at 3 weeks of age. Treatment of 1-day-old rats for 4 days with 10 micrograms/day of the glucocorticoid dexamethasone (DEX) reduced IGF-II mRNA levels 10-fold in liver and inhibited body weight gain. Estradiol and testosterone did not affect IGF-II expression. A dose-response relationship between IGF-II mRNA levels and the different amounts of DEX injected was seen. IGF-II levels remained low after withdrawal of DEX, indicating an irreversible effect. Albumin expression was increased in newborn rat livers after DEX treatment. Our results suggest that glucocorticoids play an important role in the regulation of IGF-II expression. The mechanism for glucocorticoid-induced reduction of IGF-II mRNA is still unclear; however, our findings indicate that DEX inhibits IGF-II by causing premature differentiation of the liver.
Mol Endocrinol 1989 May
PMID:Developmental and steroid hormonal regulation of insulin-like growth factor II expression. 275 59

The objective of the present study was to characterize further the albumin fraction of rat testicular fluid (rTF), which can enhance luteinizing hormone (LH)-stimulated pregnenolone production by immature Leydig cells in vitro. Testicular fluid, obtained from 300 rat testes was fractionated by sequential ammonium sulfate precipitation, dye-affinity, anion-exchange chromatography, chromatofocussing and an additional heat treatment. The final fraction showed a single band when analyzed on a silver-stained sodium dodecyl sulfate-polyacrylamide gel and isoelectric focussing gel. The protein had a molecular weight of 67 kDa, an isoelectric point of 5.0 and was identified as albumin after Western blotting using an antibody against rat serum albumin. Albumin in this fraction gave a dose-dependent (0.1-2% protein, w/v) increase in LH-induced pregnenolone production, up to 4-fold, and the increase in specific bioactivity when compared to rTF was 1.4-fold. Selective depletion of albumin from testicular fluid was used as another approach to confirm that albumin itself is the main biologically active component in rTF. rTF from mutant analbuminemic rats (albumin content 0.02 mg/ml) did not stimulate LH-induced steroid production in our assay, in contrast to rTF from normal rats (albumin content 40 mg/ml). Albumin fractions obtained from rat, bovine and human sera were also effective in stimulation of steroid production in the presence of LH, in contrast to chicken serum albumin which gave no stimulation. The stimulatory effect of albumin is not caused by bound fatty acids, nor by the presence of modified forms of albumin such as testibumin or the albumin-bilirubin complex. Our results indicate that Leydig cells are more active in steroid production when surrounded by high but physiological concentrations of albumin.
Mol Cell Endocrinol 1989 Jun
PMID:Albumin, a biologically active protein acting on Leydig cells. 275 39

A well-differentiated rat hepatoma cell line, Fu5-5, yields variant clones whose rate of secretion of serum albumin ranges from 40 to less than 0.08 micrograms of albumin/mg of cell protein per 48 h. Clones were classified as high producers (10 to 40 micrograms/mg per 48 h), intermediate producers (1 to 10 micrograms/mg per 48 h), low producers (0.1 to 1.0 micrograms/mg per 48 h), and null variants (less than 0.1 micrograms/mg per 48 h). Albumin synthetic rates are proportional to secretion rates and range from 0.9 to less than 0.002% of total protein synthesis as measured by pulse-labeling. Steady-state albumin mRNA levels were measured by filter hybridization of fragmented, end-labeled mRNA and by Northern blotting. Message levels are proportional to albumin synthetic rates except for a high producer in which albumin mRNA is less elevated than the synthetic rate. The extent of methylation was quantitated at each of 24 CpG-containing sites or site clusters at the albumin locus. These sites span a region that contains the albumin gene as well as 10 kilobases of the 5' flank and 1 kilobase of the 3' flank. An 8-kilobase region is described, with boundaries in the 5' flank and in the middle of the gene, within which all 11 sites examined showed a correlation of undermethylation with the high-producer phenotype. In contrast, 12 of 13 sites outside of this region showed no phenotype correlation. Null variants derived from a high producer underwent de novo methylation of this domain. Six independent hybrid clones derived from the cross of a high producer with a null variant showed extinction of albumin production and hypermethylation of the domain. Apparently these cells retain the capacity for the de novo methylation of these specific sites.
Mol Cell Biol 1985 Jan
PMID:A domain of methylation change at the albumin locus in rat hepatoma cell variants. 298 51

Human serum albumin was glycosidated by prolonged protein incubation in phosphate buffer, pH 6.8-7.0, with excess glucose at 37 degrees C. epsilon-amino groups of lysine residues of the albumin molecule were alkylated by pyridoxal-5-phosphate in the presence of NaBH4. The solutions of glycosidated and alkylated serum albumin were incubated at different temperature values in the range of 20 to 80 degrees C in phosphate buffer, pH 7.0, over 30 min. The nondenatured monomer and the resulting aggregated were isolated by TSK-HW-55-gel column chromatography and polyacrylamide gel electrophoresis. The stability of modified proteins elevated in parallel to the increase in the number of the ligand molecules covalently bound to albumin amino groups. The 1-3% aqueous solutions of glycosidated serum albumin containing 3-4 glucose residues and those of alkylated albumin containing 6-7 residues of pyridoxal-5-phosphate were stable on heating up to 80 degrees C and did not form aggregates. Under these conditions the initial serum albumin completely aggregated. Preincubation of the aggregated albumin with glucose at 37 degrees C resulted in protein "renaturation" to the monomeric form with a small number of dimers and trimers.
Mol Biol (Mosk)
PMID:[The role of epsilon-amino groups of lysine of human serum albumin in heat-induced protein denaturation. Increased stability of glycosylated and alkylated albumin in aggregation during heating]. 313 10

We have previously shown that estrogen administration to male Xenopus laevis results in the posttranscriptional suppression of serum albumin mRNA concurrent with the transcriptional activation of the genes for the yolk protein precursor vitellogenin. To determine whether the posttranscriptional regulation of albumin gene expression is mediated through a mechanism involving the high affinity estrogen receptor protein or through a receptor-independent mechanism involving a middle affinity cytoplasmic estrogen-binding protein we examined the effects of the competitive estrogen receptor antagonist 4-hydroxytamoxifen. Administration of 4-hydroxytamoxifen 24 h before estradiol completely blocked both the suppression of albumin mRNA and the transcriptional activation of the vitellogenin genes. Albumin gene transcription remained constitutive under all treatment regimens. Competitive binding experiments demonstrated that 4-hydroxytamoxifen has an affinity for the estrogen receptor similar to that of estradiol. However, 4-hydroxytamoxifen displays little or no interaction with the middle affinity cytoplasmic estrogen-binding protein. These data indicate that the estrogen receptor occupies a key role in the posttranscriptional regulation of albumin mRNA.
Mol Endocrinol 1987 Feb
PMID:Posttranscriptional regulation of albumin gene expression in Xenopus liver: evidence for an estrogen receptor-dependent mechanism. 345 73

The purpose of this study was to investigate the suppression of albumin mRNA by estrogen in Xenopus liver. A single dose of estradiol rapidly suppressed albumin mRNA to 30% of the control level. Albumin mRNA remained at this new steady-state level for 9 days, after which it returned to the control level. Transcription 'run-on' experiments in isolated liver nuclei demonstrated a transient decrease of 60-90% in albumin transcription after 2-6 h and approached constitutive transcription by 12 h. Albumin gene transcription then remained constant for the following 12 days. Prolonged and enhanced suppression of albumin mRNA was observed in animals treated repeatedly with estrogen for 12 days. In these animals, albumin gene transcription was decreased 80-90% from the constitutive control level. These data indicate that albumin mRNA is suppressed by both transcriptional and post-transcriptional mechanisms.
Mol Cell Endocrinol 1986 Mar
PMID:Transcriptional and post-transcriptional inhibition of albumin gene expression by estrogen in Xenopus liver. 395 52


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