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

The addition of glycophospholipid (GPL) anchors to certain membrane proteins occurs in the rough endoplasmic reticulum and is essential for transport of the proteins to the plasma membrane. Limited circumstantial evidence suggests that dolichol-phosphoryl-mannose (DPM) is a donor of mannose residues of these anchors. We here report studies of a CHO cell mutant (B421) transfected to express the GPL-anchored protein, placental alkaline phosphatase (AP). Only a few transfectants were found to express GPL-anchored AP on their surface, and these clones synthesized DPM. Moreover, and most strikingly, when surface AP-negative transfectants were treated with tunicamycin to cause accumulation of DPM, these cells expressed lipid-anchored AP. Fusion of a cloned surface AP-negative transfectant of B421 with the Thy-1-class E mutant thymoma, which is also deficient in DPM synthesis, produced hybrids that synthesized DPM and expressed AP and Thy-1. Thus, two mutations can interrupt DPM synthesis, and three sets of observations point to an essential role of DPM for addition of GPL anchors.
Mol Cell Biol 1991 Jan
PMID:Two different mutants blocked in synthesis of dolichol-phosphoryl-mannose do not add glycophospholipid anchors to membrane proteins: quantitative correction of the phenotype of a CHO cell mutant with tunicamycin. 198 34

Glucocorticoids induce dramatic biochemical and morphological changes in lymphocytes through an unknown process that requires RNA and protein synthesis. In order to identify genes involved in this response, we previously isolated 11 cDNA clones from the murine WEHI-7TG thymoma cell line that correspond to mRNAs induced by glucocorticoids. We now report the isolation of two new cDNA clones whose gene expression is regulated by glucocorticoids in WEHI-7TG cells. We further characterize the two new cDNA clones, as well as those described previously, by examining the response of each of the corresponding mRNAs to glucocorticoids in murine thymocytes. With the exception of two, all cDNAs correspond to genes that are induced by glucocorticoids in murine thymocytes within 4 h of treatment. We previously identified two of the cDNAs as the mouse VL30 retrovirus-like element and the mouse homolog of chondroitin sulfate proteoglycan core protein. We have now identified four additional cDNA clones that correspond to the genes for calmodulin, mitochondrial phosphate carrier protein, immunoglobulin (Ig)-related glycoprotein (GP-70), and the 70 kilodalton autoantigen for Lupus and Graves diseases. Two other cDNA clones represent previously undescribed genes: one shares a high similarity to known sequences for the family of G-protein-coupled receptors and the other to a human placental-specific protein, PP11. Another cDNA appears to contain sequences for an unknown gene and the remnants of a mouse transposon. ETn. The remaining clones represent new, unidentified genes induced by glucocorticoids in murine thymocytes and in the WEHI-7TG cell line.
Mol Endocrinol 1991 May
PMID:Genes newly identified as regulated by glucocorticoids in murine thymocytes. 207 23

Monoclonal antibodies specific to the infective-stage promastigotes of Leishmania major are needed for developing rapid diagnostic assays of infected sand flies. An in vitro immunization protocol was applied for the production of monoclonal antibodies using small amounts of L. major. Infective-stage promastigotes were isolated from sand flies (Phlebotomus papatasi) 7-10 days after infection and used as antigen for immunization. Two weeks after a primary immunization, murine splenocytes were removed and immunized in vitro with antigen in murine EL-4 thymoma cell conditioned medium. Three fusions were performed using X63-Ag.653 myeloma cells as fusion partners and two fusions were performed using FOX-NY cells. Antibodies specific to promastigotes were detected using an indirect enzyme-linked immunosorbent assay (ELISA). Initially 56 monoclonal antibodies were selected, and their species and stage specificity were determined using both an ELISA and an indirect fluorescent antibody assay (IFA). Twelve monoclonal antibodies showed species specificity to L. major when tested against four sympatric species of Leishmania. Four other monoclonal antibodies showed species and infective-stage specificity to L. major promastigotes. When tested in immunoblots, all four species- and stage-specific monoclonal antibodies bound to five protein bands that were unique to the infective-stage promastigotes.
Mol Cell Probes 1990 Dec
PMID:Species- and infective stage-specific monoclonal antibodies to Leishmania major produced by an in vitro immunization method. 208 35

Alveolar macrophages have the ability to downregulate immune processes in vitro. We have recently suggested the presence of interleukin-1 (IL-1) inhibitors in the supernatants of human bronchoalveolar lavage cells from patients with idiopathic pulmonary fibrosis or sarcoidosis. In the present study, we further analyze the cellular origin and the biologic properties of a 20- to 25-kD IL-1 inhibitor spontaneously produced by cultured human alveolar macrophages (AM). The inhibitor blocks IL-1-induced prostaglandin E2 production by human fibroblasts and the IL-1-related increase of phytohemagglutinin-induced murine thymocyte proliferation. After rigorous IL-1 alpha and IL-1 beta depletion, supernatants of lung macrophages specifically block the binding of IL-1 to its receptor on the murine thymoma cell line EL4-6.1 in a dose-dependent manner. These results indicate that AM from both normal donors and patients produce a specific IL-1 inhibitor that may be of importance in protecting the alveolar environment from the deleterious effects of excessive IL-1 production.
Am J Respir Cell Mol Biol 1990 Oct
PMID:Characterization of a specific 20- to 25-kD interleukin-1 inhibitor from cultured human lung macrophages. 214 78

The macrophage-derived cytokine interleukin-1 (IL-1) can provide a second signal with antigen to elicit production of interleukin-2 (IL-2) by helper T cells. The pathway(s) involved remains controversial, with protein kinase C and cyclic AMP (cAMP) invoked as possible second messengers. In the murine thymoma EL4.E1, IL-1 could synergize with the phosphoinositide pathway, because the cells made higher levels of IL-2 in the presence of IL-1 than could be induced by phorbol ester plus calcium ionophore alone. IL-1 is unlikely to act through a sustained increase in cAMP in these cells because it did not raise cAMP levels detectably and because IL-1 and forskolin had opposite effects on IL-2 gene expression. Inducible expression of a transfected reporter gene linked to a cloned fragment of the murine IL-2 gene promoter was initially increased by IL-1 costimulation, implying that IL-1 can increase the rate of transcription of IL-2. The minimal promoter elements required for iL-1 responsiveness were located within 321 bp of the IL-2 RNA cap site, and further upstream sequences to -2800 did not modify this response. IL-1 costimulation resulted in enhanced activity of both an inducible NF-kappa B-like factor and one of two distinct AP-1-like factors that bind to IL-2 regulatory sequences. Neither was induced, however, by IL-1 alone. Another AP-1-like factor and NFAT-1, while inducible in other cell types, were expressed constitutively in the EL4.E1 cells and were unaffected by IL-1. These results are discussed in terms of the combinatorial logic of IL-2 gene expression.
Mol Cell Biol 1990 Dec
PMID:Interleukin-1 synergy with phosphoinositide pathway agonists for induction of interleukin-2 gene expression: molecular basis of costimulation. 217 6

An expression cDNA library was constructed from the helper T cell hybridoma, A.1.1, which has been shown to produce constitutively proteins involved in the down regulation of the immune response. From this library we identified and characterized a cDNA clone, J6B7, by screening with a polyclonal antibody specific for secreted immune regulatory proteins. The mRNA for J6B7 is expressed specifically in some T cells, but not in the thymoma BW5147 or liver cells. J6B7 is 2937 nucleotides in length and contains one open reading frame encoding for a peptide of predicted Mr of 98,042. The nucleotide and deduced amino acid sequences of J6B7 did not reveal significant homology to any published sequences. Hybridization and translation experiments reveal that the J6B7 can hybrid select mRNA from total RNA isolated from either A.1.1 cells or thymic tissue which can be translated in vitro to a peptide which is bound by a monoclonal antibody (mAb) specific for antigenic determinant(s) shared by immune regulatory proteins. Furthermore, the in vitro translated proteins obtained from A.1.1 cells and thymus showed significant suppression of a mixed lymphocyte reaction (MLR) in a dose dependent manner, reaching maximum suppression of 71% and 89%, respectively. These results suggest that the cDNA, J6B7, codes for an immune regulatory protein.
Mol Immunol 1990 Nov
PMID:Cloning of a cDNA for a T cell produced molecule with a putative immune regulatory role. 224 90

The effect of temperature on the kinetic association and dissociation binding parameters, and equilibrium constants of four monoclonal antibodies to the murine Ly-2.1 and Ly-3.1 antigens has been studied using flow cytometry. All four monoclonal antibodies were conjugated to FITC and their association to, and dissociation from, the surface of murine thymoma cells was observed at 15 sec intervals, at temperatures between 1 and 37 degrees C. The initial association rate constant and the dissociation rate constant for each antibody at each temperature were calculated from graphs of the first-order reactions and it was demonstrated that an increase in temperature caused an increase in both association rate and dissociation rate of the antibodies. Generally the increase in association rate with temperature was less than the increase in dissociation rate. Differences between antibodies to the same antigen (Ly-2.1) suggest that changes in membrane fluidity were not solely responsible for the changes in association rate. However, the equilibrium constants (Keq) did not always show a simple relationship of increasing temperature causing decreasing values for Keq. For one antibody the highest value for Keq was seen at 17 degrees C rather than at 37 degrees C and differences in Keq between individual antibodies were greater at 1 degree C than at 37 degrees C. Kinetic rate constants are usually measured at 4 degrees C or room temperature, therefore for antibodies under consideration for in vivo use, measurements at 37 degrees C are more appropriate.
Mol Immunol 1990 Apr
PMID:The effect of temperature on the binding kinetics and equilibrium constants of monoclonal antibodies to cell surface antigens. 235 11

Glucocorticoids and cyclic AMP exert dramatic effects on the proliferation and viability of murine T lymphocytes through unknown mechanisms. To identify gene products which might be involved in glucocorticoid-induced responses in lymphoid cells, we constructed a lambda cDNA library prepared from murine thymoma WEHI-7TG cells treated for 5 h with glucocorticoids and forskolin. The library was screened with a subtracted cDNA probe enriched for sequences induced by the two drugs, and cDNA clones representing 11 different inducible genes were isolated. The pattern of expression in BALB/c mouse tissues was examined for each cDNA clone. We have identified two clones that hybridized to mRNAs detected exclusively in the thymus. Other clones were identified that demonstrated tissue-specific gene expression in heart, brain, brain and thymus, or lymphoid tissue (spleen and thymus). The kinetics of induction by dexamethasone and forskolin were examined for each gene. The majority of the cDNA clones hybridized to mRNAs that were regulated by glucocorticoids and forskolin, two were regulated only by glucocorticoids, and three hybridized to mRNAs that required both drugs for induction. Inhibition of protein synthesis by cycloheximide resulted in the induction of all mRNAs that were inducible by glucocorticoids. Preliminary sequence analysis of four of the 11 cDNAs suggests that two cDNAs represent previously undescribed genes while two others correspond to the mouse VL30 retrovirus-like element and the mouse homolog of chondroitin sulfate proteoglycan core protein.
Mol Cell Biol 1989 Aug
PMID:Isolation and characterization of glucocorticoid- and cyclic AMP-induced genes in T lymphocytes. 255 95

Functional receptors for insulin-like growth factors (IGF) I and II have been identified in rat thymocytes and mouse thymoma cell lines R1.1 and S49.1. IGF-I receptor alpha-subunit (MW 130,000) bind IGF-I and IGF-II with equal affinity (Kd approximately 4-7 nM), and insulin with approximately 100 times lower affinity. Tyrosine kinase activity and autophosphorylation of the IGF-I receptor beta-subunit (MW 95,000) are stimulated by IGF-I and IGF-II with equal potency (ED50 approximately 0.5 nM). IGF-II receptors (MW 250,000) bind IGF-II with Kd approximately 0.3 nM and IGF-I with 30 times lower affinity, but not insulin. IGF-I and IGF-II do not cross-react with the insulin receptor to which insulin binds with an apparent Kd approximately 1 nM, and stimulates its tyrosine kinase activity with ED50 approximately 3 nM. In thymocytes, alpha-aminoisobutyric acid transport is stimulated 2-fold by IGF-I and IGF-II with identical potency (ED50 approximately 2 nM), and by insulin with ED50 approximately 10 nM. Activation of thymocytes by concanavalin A increased the number of IGF-II receptors 2-fold, whereas IGF-I receptor binding and IGF-stimulated amino acid transport were unaltered. We conclude that the effect of IGF-I and IGF-II in thymocytes is mediated via binding to the IGF-I receptor and stimulation of its tyrosine kinase. The presence of functional IGF receptors on thymocytes and thymoma cells suggests that IGF-I and IGF-II play a role in the regulation of thymic functions.
Mol Cell Endocrinol 1989 Dec
PMID:Functional receptors for insulin-like growth factors I and II in rat thymocytes and mouse thymoma cells. 255 37

The mechanism of action of the cytokine, interleukin-1 (IL-1), has been investigated. Mouse thymoma (EL4 6.1) cells were preincubated with [3H]-glycerol and then incubated with recombinant IL-1 beta for varying periods. Interleukin-1 caused a rapid increase in diacylglycerol production (approx. 2 fold at 30 secs). This reproducible enhancement of diacylglycerol accumulation was abolished by pretreatment of the cells with pertussis toxin. Interestingly, a similar IL-1 induced increase in diacylglycerol was observed when the cells were preincubated with [3H]-myristic acid. These results appear to suggest a novel mode of action of interleukin-1 which involves a G-protein mediated breakdown of a membrane lipid resulting in the production of diacylglycerol. It is suggested that one possible candidate for this parent lipid may be a phosphatidylinositol glycan.
J Mol Endocrinol 1989 May
PMID:Interleukin-1 induces a pertussis toxin-sensitive increase in diacylglycerol accumulation in mouse thymoma cells. 278 52


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