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S Dower

Publications and source records attributed to S Dower.

11 recordsLinked to original sources
PubMed1999

Studies with a growth hormone antagonist and dual-fluorescent confocal microscopy demonstrate that the full-length human growth hormone receptor, but not the truncated isoform, is very rapidly internalized independent of Jak2-Stat5 signaling.

UNLABELLED: We have investigated trafficking of two negative regulators of growth hormone receptor (GHR) signaling: a human, truncated receptor, GHR1-279, and a GH antagonist, B2036. Fluorescent-labeled growth hormone (GH) was rapidly internalized by the full-length GHR, with >80% of the hormone internalized within 5 min of exposure to GH. In contrast, <5% of labeled GH was internalized by cells expressing truncated GHR1-279. Using another truncated receptor, GHR1-317 fused to enhanced green fluorescent protein (EGFP), we have exploited fluorescence energy transfer to monitor the trafficking of ligand-receptor complexes. The data confirmed that internalization of this truncated receptor is very inefficient. It was possible to visualize the truncated GHR1-317-EGFP packaged in the endoplasmic reticulum, its rapid movement in membrane bound vesicles to the Golgi apparatus, and subsequent transport to the cell membrane. The GH antagonist, B2036, blocked Jak2-Stat5-mediated GHR signaling but was internalized with a similar time course to native GH. THE RESULTS: 1) demonstrate the rapid internalization of GH when studied under physiological conditions; 2) confirm the hypothesis that internalization of cytoplasmic domain truncated human GHRs is very inefficient, which explains their dominant negative action; and 3) show that the antagonist action of B2036 is independent of receptor internalization.

Golgi Apparatus↗
PubMed1998

Four contiguous amino acid substitutions, identified in patients with Laron syndrome, differently affect the binding affinity and intracellular trafficking of the growth hormone receptor.

We have analyzed the GH receptor (GHR) gene in four individuals with Laron syndrome, and a missense mutation was identified for each patient in the extracellular domain of the GHR (D152H, I153T, Q154P, and V155G). The D152H mutation was previously reported. We have reproduced the three novel mutations in the GHR complementary DNA and analyzed their consequences in human 293 transfected cells. In cells expressing the I153T and V155G mutants, binding of [125I]human GH at the cell surface was very low, whereas binding to total membrane fractions was much less affected, suggesting impaired cell surface expression. Binding assays with cells expressing the Q154P mutant revealed severe defects both at the cell surface and in total particulate membrane fractions. Immunofluorescence experiments confirmed that cell surface expression of the three mutants was altered, and colocalization studies suggested that most of the mutant receptors are retained in the endoplasmic reticulum. Endoglycosidase H resistance tests also indicated that the majority of I153T and V155G GHRs are trapped in the endoplasmic reticulum. Thus, mutations on contiguous amino acids of the GHR result in various defects. The I153T, Q154P, and V155G mutations mainly affect intracellular trafficking and binding affinity of the receptor, whereas the D152H mutation affects receptor expression, dimerization, and signaling.

Adult↗
PubMed1995

Interleukins.

Explore the source record for details and available documents.

Humans↗
PubMed1990

IL-1 beta modulation of spontaneous autoimmune diabetes and thyroiditis in the BB rat.

Long term effects of in vivo treatment with human rIL-1 beta on diabetogenesis and thyroid disease were determined in the Biobreeding rat. Administration of high dose (10 micrograms/kg) IL-1 beta accelerated the onset of insulin-dependent diabetes mellitus compared to saline-injected controls. High dose treatment resulted in goiter development, pronounced LT, reduced serum T4 levels, and overall growth reduction. In contrast, low dose IL-1 beta (0.5 microgram/kg) administration significantly reduced the frequency of insulin-dependent diabetes mellitus (48%) compared to placebo (86%) and high dose IL-1 beta (93%) treatment groups. Rats protected by low dose IL-1 beta had unaffected growth rates and minimal to no pancreatic and thyroid pathology. Our results demonstrate that exogenous administration of IL-1 beta modulates Biobreeding rat idiopathic autoimmune diabetes and thyroid disease in a dose-dependent manner.

Animals↗
PubMed1989

Regulation of interleukin 1 and its receptor in human keratinocytes.

Keratinocytes in culture synthesize and respond to interleukin 1 (IL-1). We have measured surface IL-1 receptor (IL-1R) on keratinocytes in culture using radiolabeled IL-1 binding assays. Surface IL-1R levels are less than 2000 receptors per cell in postconfluent cultures but increase 9- to 20-fold 24 hr after treatment with phorbol 12-myristate 13-acetate (PMA) at 10 ng/ml or after raising the extracellular Ca2+ concentration to 2 mM. This induction of surface IL-1R can be blocked by the addition of retinoic acid and parallels induction of squamous differentiation markers. These results imply that IL-1R levels may be related to the degree of differentiation of these cells. In parallel studies IL-1 protein levels were determined by bioassay and by Western blotting (immunoblots). All detectable IL-1 protein and essentially all IL-1 activity was cell-associated. Although constitutive levels of IL-1 biological activity and protein are significant in these cultures, IL-1 levels increase when either PMA or retinoic acid alone are added to cultures. IL-1 does not increase when PMA and retinoic acid are added simultaneously to cultures; nor is it induced when extracellular Ca2+ concentrations are raised to 2 mM. Thus, cell-associated IL-1 levels do not necessarily parallel surface IL-1R levels in these cultures. Taken together, these results demonstrate that IL-1 and surface IL-1R levels are differentially and complexly regulated in keratinocyte cultures. Possible implications of these results in terms of normal and abnormal regulation of proliferation and differentiation are discussed.

Blotting, Western↗
PubMed1988

Interleukin 1 binds to specific receptors on human keratinocytes and induces granulocyte macrophage colony-stimulating factor mRNA and protein. A potential autocrine role for interleukin 1 in epidermis.

Cultured human keratinocytes have been shown to produce IL-1 alpha and beta mRNA and protein. IL-1 biological activity has been identified in normal human epidermis; in vitro, most biologically active IL-1 resides in a cell-associated compartment. The potential for autocrine effects of IL-1 on human keratinocytes was assessed by measurement of keratinocyte IL-1 receptors. Both high- and low-affinity cell surface receptors that bound recombinant (r) IL-1 alpha and beta with comparable affinities could be identified on cultured human keratinocytes, using 125I-labeled rIL-1. Chemical crosslinking experiments identified a cell surface molecule of roughly 72,500 Mr that bound 125I-labeled IL-1, similar to the molecular weight of previously described IL-1 receptors on fibroblasts, B cells, and T cells. To assess the biological consequences of keratinocyte IL-1 binding, granulocyte-macrophage colony-stimulating factor (GM-CSF) gene expression was measured. The addition of exogenous rIL-1 alpha led to a dose-dependent increase in the accumulation of GM-CSF mRNA, as measured by a sensitive and specific S1 nuclease assay. This increase in mRNA was reflected in a marked increase in GM-CSF biological activity as measured by proliferation of blast cells from chronic myelogenous leukemia patients. The biological activity was completely inhibitable by an antibody to human rGM-CSF. GM-CSF activates mature neutrophils and macrophages and appears to enhance the efficiency of Langerhans cell antigen presentation to T cells. Release of IL-1 from injured or activated keratinocytes may lead to enhanced epidermal GM-CSF gene expression via an autocrine mechanism, thus enhancing local host defense.

Cells, Cultured↗
PubMed1986

Expression of interleukin 2, interferon-gamma, and the IL 2 receptor by human peripheral blood lymphocytes.

Human peripheral blood T lymphocytes were treated with recombinant interleukin 2, mitogens, and dexamethasone. The resulting accumulation of mRNA for interleukin 2 (IL 2), the interleukin 2 receptor (IL 2R), and interferon-gamma (IFN-gamma) was measured. IL 2 was found to regulate the levels of each of these mRNA. The expression of mRNA for IL 2, IL 2R, and IFN-gamma correlated very well with the levels of protein observed. In populations of peripheral blood T lymphocytes, the production of IL 2 and IFN-gamma were not necessarily coordinately expressed. The sequential expression of these mRNA was investigated in order to determine whether they might be independent of the action of IL 2. IFN-gamma and IL 2 mRNA showed biphasic accumulations. IL 2 mRNA accumulated very rapidly, within 60 min after mitogen stimulation and before any detectable IL 2R mRNA accumulation. Similarly, IFN-gamma mRNA accumulated rapidly, simultaneously with IL 2 mRNA. This early peak of IFN-gamma mRNA, therefore, is likely to be independent of IL 2 action. Both IL 2 and IFN-gamma mRNA then showed later peak times of accumulation. IL 2 mRNA levels peaked at 5 hr after mitogen stimulation, whereas IFN-gamma mRNA levels peaked at 20 hr. IL 2R mRNA continued to accumulate for the full 40 hr of these kinetic experiments. The later accumulations of IFN-gamma and IL 2R mRNA and the resulting expression of the corresponding proteins may therefore be dependent on the earlier production of IL 2 and its subsequent interaction with the IL 2R on the surface of such activated T cells.

Dexamethasone↗
PubMed1977

Structure of an antibody combining site by magnetic resonance.

The structure of the combining site of the DNP binding IgA mouse myeloma protein MOPC 315 has been determined by a combination of high resolution nuclear magnetic resonance, electron spin resonance, model building and chemical modifications. This approach yields that general dimensions of the site, its polarity and asymmetry features, the assignment of the DNP-contact residues and their three-dimensional coordinates.

Animals↗
PubMedDate not supplied

Cloning, sequence and expression of human interleukin-2 receptor.

T lymphocytes, essential for the generation of a normal immune response, require the presence of the lymphokine interleukin-2 (IL-2) in order to proliferate. Cells that respond to IL-2 possess a surface receptor glycoprotein specific for this lymphokine. We have recently purified and chemically characterized the IL-2 receptor from both phytohaemagglutinin-activated human T cells and the human T-cell lymphoma HUT-102 (ref. 5). From the NH2-terminal protein sequence obtained in that study, we have now used synthetic oligonucleotides to probe a complementary DNA library, prepared from HUT-102 messenger RNA, for the presence of cDNA clones that might code for the IL-2 receptor. Two cDNA clones were isolated which had closely related DNA sequences. Interestingly, only one coded for an active receptor when transfected into COS-7 cells. This clone contained a 216-base pair (bp) insert that was not present in the other clone. The insert was flanked by an 8-bp direct repeat reminiscent of a transposable element, and appeared to code for a region of marked structural homology to the NH2-terminal region of the receptor molecule.

Amino Acid Sequence↗