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

The mechanism by which individual peptide and steroid hormones and cell-substratum interactions regulate milk protein gene expression has been studied in the COMMA-D mammary epithelial cell line. In the presence of insulin, hydrocortisone, and prolactin, growth of COMMA-D cells on floating collagen gels in comparison with that on a plastic substratum resulted in a 2.5- to 3-fold increase in the relative rate of beta-casein gene transcription but a 37-fold increase in beta-casein mRNA accumulation. In contrast, whey acidic protein gene transcription was constitutive in COMMA-D cells grown on either substratum, but its mRNA was unstable and little intact mature mRNA was detected. Culturing COMMA-D cells on collagen also promoted increased expression of other genes expressed in differentiated mammary epithelial cells, including those encoding alpha- and gamma-casein, transferrin, malic enzyme, and phosphoenolpyruvate carboxykinase but decreased the expression of actin and histone genes. Using COMMA-D cells, we defined further the role of individual hormones in influencing beta-casein gene transcription. With insulin alone, a basal level of beta-casein gene transcription was detected in COMMA-D cells grown on floating collagen gels. Addition of prolactin but not hydrocortisone resulted in a 2.5- to 3.0-fold increase in beta-casein gene transcription, but both hormones were required to elicit the maximal 73-fold induction in mRNA accumulation. This posttranscriptional effect of hormones on casein mRNA accumulation preceded any detectable changes in the relative rate of transcription. Thus, regulation by both hormones and cell substratum of casein gene expression is exerted primarily at the post transcriptional level.
Mol Cell Biol 1988 Aug
PMID:Both cell substratum regulation and hormonal regulation of milk protein gene expression are exerted primarily at the posttranscriptional level. 306 79

Seminiferous peritubular cells have previously been shown to secrete a protein termed P-Mod-S which modulates the functions of Sertoli cells. The present study provides an initial characterization of P-Mod-S and examines the actions of P-Mod-S on Sertoli cells. Gel filtration chromatography demonstrates that P-Mod-S has an apparent molecular weight of 70 000 that could not be dissociated to a lower molecular weight form. A 40- to 90-fold purification of P-Mod-S was obtained with a predicted half maximal effective concentration for Sertoli cells of less than 10(-9) M. Through an analysis of the actions of P-Mod-S on Sertoli cells it is demonstrated that P-Mod-S stimulates the Sertoli cell to a greater extent than any single hormone or vitamin known to influence the cell. P-Mod-S maximally stimulates testicular transferrin and androgen-binding protein production by Sertoli cells, but does not stimulate levels of plasminogen activator activity. P-Mod-S also appears to induce the synthesis of several proteins that are not detected in control non-treated Sertoli cell cultures. One such protein whose synthesis was stimulated by P-Mod-S treatment of Sertoli cells was a component having a molecular mass of 20 kDa. This 20 kDa Sertoli cell-secreted protein was specifically immunoprecipitated with an antibody against an epididymal lactalbumin-like protein. This implies that P-Mod-S can induce Sertoli cells to synthesize and secrete a lactalbumin-like protein. P-Mod-S was found not to contain mitogenic activity. Data presented indicate that testicular peritubular cells synthesize and secrete a 70 kDa non mitogenic paracrine factor termed P-Mod-S which has a dramatic influence on Sertoli cell functions. Results are discussed with respect to modulation of epithelial (Sertoli) cell functions by components produced by mesenchymal (peritubular) cells.
Mol Cell Endocrinol 1986 Jan
PMID:Identification of a non-mitogenic paracrine factor involved in mesenchymal-epithelial cell interactions between testicular peritubular cells and Sertoli cells. 308 88

The protein composition of atheroma-free human thoracic intima was compared with that containing fatty streaks or fibro-fatty lesions utilizing two-dimensional gel electrophoresis (2-DE) and silver staining. Intimal proteins extracted with 9 M urea were separated by nonequilibrium pH gradient electrophoresis (NEPHGE) followed by polyacrylamide gel electrophoresis (PAGE) in the second dimension. NEPHGE-PAGE of proteins extracted from atheroma-free intima revealed several major proteins: actin, tropomyosin-like proteins, proteins with relative molecular weight (Mr) of 250,000 (P250), two proteins with Mr about 15,000 (P15a, P15b), and many medium proteins such as a myosin heavy chain, two myosin light chains, and proteins P47, P44, P32, P27, P20a, P20b, P19a, P19b. Several additional proteins were observed in intimas with fatty streaks and fibro-fatty lesions. Most of them, such as albumin, transferrin, Apo A-I, alpha 1-antitrypsin, fibrinogen beta-chain, IgG, appear to originate from plasma. Differences in protein composition of intima with fibro-fatty streaks compared with adjacent lesion-free intima varied from case to case and need further study. NEPHGE-PAGE in combination with isoelectric focusing (ISO)-PAGE revealed more intimal proteins in atheroma-free and diseased aortas than either method alone, proteins which might be quantitated, isolated for binding studies, and further evaluated for their potential role in atherogenesis.
Exp Mol Pathol 1986 Dec
PMID:Basic proteins in the human aortic intima: nonequilibrium two-dimensional electrophoretic analysis of tissue extracts. 309 75

The evolutionary relationships of six sharks were investigated by comparing their transferrins using the micro-complement fixation method. The immunological distances observed were used to build a tree that confirms that the squaloid and galeoid species examined belong to two separate groups and that Heterodontus, a genus of hitherto uncertain position, belongs with the galeoids. The divergence time estimated from the transferrin comparisons is roughly 240 +/- 65 million years between Heterodontus and galeoids.
J Mol Evol 1987
PMID:Evolutionary relationships of a "primitive" shark (Heterodontus) assessed by micro-complement fixation of serum transferrin. 311 2

Expression of the meningococcal transferrin receptor, detected by assay with human transferrin conjugated to peroxidase, was regulated by the level of iron in the medium. The transferrin receptor was identified by SDS-PAGE and Western blot analysis, as a 71,000 molecular weight iron-regulated outer membrane protein in Neisseria meningitidis B16B6. Growth studies with iron-deficient cells and competition binding experiments demonstrated that the meningococcal receptor was species-specific for human transferrin. Reciprocal competitive binding experiments and limited proteolysis of intact cells indicated that the transferrin and lactoferrin receptors are distinct.
Mol Microbiol 1988 Mar
PMID:Identification and characterization of the transferrin receptor from Neisseria meningitidis. 313 85

Lymph node (LN) T cells from autoimmune MRL/MpJ-lpr/lpr (lpr) mice and control MRL/MpJ-+/+ (+/+) mice were compared as to their cell surface lectin-binding sites and glycosyltransferase activities. T cells from enlarged LN of lpr mice expressed a higher amount of binding sites for lectins reactive to mucin-type sugar chains than normal +/+ mouse T cells. Correspondingly, glycosyltransferase activities involved in the biosynthesis of mucin-type sugar chains were higher in lpr mouse T cells than in +/+ T cells. The activities of UDP-N-acetylgalactosamine (GalNAc):polypeptide GalNAc transferase and UDP-galactose (Gal):asialo bovine submaxillary mucin (BSM) Gal transferase were found to be elevated. The activity of UDP-Gal:asialo-agalacto transferrin Gal transferase, which is involved in the biosynthesis of complex type sugar chains, was also increased in lpr mice but to a smaller extent than the mucin-type Gal transferase activities. An abnormality in sialyltransferase activity was also found in lpr T cells.
Mol Immunol 1988 May
PMID:Enhancement of the activities of glycosyltransferases involved in the biosynthesis of mucin-type sugar chains in autoimmune MRL lpr/lpr mouse T cells. 313 57

We describe here the properties of a variant cell line, termed AF192, selected by exposing mouse LMTK- cells to a cytotoxic form of transferrin prepared by conjugating transferrin to diphtheria toxin. AF192 cells were mildly resistant to the transferrin-diphtheria toxin conjugate and were cross-resistant to the protein toxins modeccin, abrin, ricin, and Pseudomonas aeruginosa exotoxin A. AF192 cells had an aberrant transferrin cycle characterized by an approximately 50% reduction in the rate of iron uptake from diferric transferrin, an approximately 25% reduction in the number of surface transferrin receptors, and a time course for transferrin recycling that resolved into two apparent first-order rate processes. The aberrant transferrin cycle was not the result of a failure of endocytosed transferrin to discharge iron; rather, part, but not all, of the transferrin taken up by AF192 cells was diverted to an intracellular site from which it was recycled very slowly.
Somat Cell Mol Genet 1988 Sep
PMID:Two pathways of transferrin recycling evident in a variant of mouse LMTK- cells. 317 65

It has been reported recently that major kinetic differences exist in the rate of iron uptake and of transferrin synthesis between intact seminiferous tubules and cultured Sertoli cells. To investigate possible causes of these differences, intact isolated rat seminiferous tubules were isolated and pre-incubated overnight. Then the rates of iron uptake and of transferrin synthesis were compared with those of freshly isolated tubules. We found that overnight pre-incubation increased the rate of both processes. Iron depletion was not the cause of these changes, since pre-incubation under iron excess gave comparable results. Possible explanations of these phenomena are discussed.
Mol Cell Endocrinol 1988 Jun
PMID:The influence of pre-incubation on the rate of iron uptake and of transferrin synthesis by intact isolated rat seminiferous tubules. 340 61

Lactotransferrin (LTF), a member of the transferrin family of genes, is the major iron-binding protein in milk and body secretions. The amino acid sequence of LTF consists of two homologous domains homologous to proteins in the transferrin family. Recent isolation of cDNA encoding mouse LTF has expedited the mapping of both mouse and human LTF genes. Southern blot analysis of DNA from mouse-Chinese hamster and human-mouse somatic cell hybrids maps the LTF gene to mouse chromosome 9 and to human chromosome 3, respectively. Furthermore, analysis of cell hybrids containing defined segments of human chromosome 3 demonstrates that the gene is located in the 3q21-qter region. These results suggest that LTF and associated genes of the transferrin family have existed together on the same chromosomal region for 300-500 million years.
Somat Cell Mol Genet 1987 Nov
PMID:Assignment of the lactotransferrin gene to human chromosome 3 and to mouse chromosome 9. 347 18

We examined the effect of various culture conditions on the polarized secretion of androgen binding protein (ABP) and transferrin (Trf) by Sertoli cells (Sc) in vitro. Sc from 18-day-old rats were cultured as confluent monolayers on permeable membranes in two-compartment chambers for up to 11 days. Coating of the membranes with extracellular matrix (ECM) components: collagen IV + laminin (CL) or reconstituted basement membrane (RBM) enhanced ABP and Trf secretion (200% and 150%, respectively), with RBM being more effective than CL in stimulating ABP but not Trf secretion. Neither CL nor RBM significantly influenced the relative amounts of ABP and Trf secreted into the outer (OC) and inner (IC) compartments of the culture chamber (OC/IC ratio). All of these effects were not significantly influenced by the presence of testosterone and serum. Co-culture of Sc with peritubular myoid cells (Pc) significantly increased the secretion of both ABP and Trf, although the magnitude of stimulation and the time-response patterns were different for each protein. Co-culture with Pc also dramatically increased the OC/IC ratios for ABP and Trf. Testosterone (10(-6) M) enhanced the Pc effects. In cultures of Sc alone, presence of 2% fetal bovine serum increased the OC/IC ratios, whereas testosterone had no effect. Based on these results, we suggest a possible role of Pc in the regulation of Sc polarized secretions.
Mol Cell Endocrinol 1987 Jul
PMID:Vectorial secretion of transferrin and androgen binding protein in Sertoli cell cultures: effect of extracellular matrix, peritubular myoid cells and medium composition. 362 19


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