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O L Kon

Publications and source records attributed to O L Kon.

23 records · Page 2Linked to original sources
PubMed1983

An antiestrogen-binding protein in human tissues.

Although nonsteroidal antiestrogens of the triphenylethylene type are generally considered to act through the estrogen receptor, some observations suggest that estrogen target tissues may also contain a binding protein specific for these compounds. The data so far reported, however, are also consistent with ligand-induced changes in conformation or in the state of aggregation of the estrogen receptor. The studies reported here demonstrate the existence of a protein in human myometrial cytosol which binds 1-[4-(2-dimethylaminoethoxy)phenyl]1,2-diphenylbut-1(Z)-ene ([3H]tamoxifen) with high affinity (Kd = 2.3 X 10(-9) M). This protein exhibits striking specificity for nonsteroidal antiestrogens. Estradiol competes weakly for bound [3H]tamoxifen, while other estrogens and nonestrogenic steroid hormones do not compete at all. Sedimentation analysis and molecular sieve chromatography indicate that the antiestrogen-binding protein is a larger species than the estrogen receptor and elutes from DEAE-Sephacel at a lower KCl concentration (0.03 M) than the estrogen receptor (0.15 M). Differential thermal stability of the estrogen receptor and the antiestrogen-binding protein was demonstrable in the absence of added ligand. The antiestrogen-binding protein was ubiquitous, being present in many tissues where estrogen receptor was undetectable. These findings support the separate existence of an antiestrogen-binding protein.

Binding, Competitive↗
PubMed1980

Isolation and characterization of the estrogen receptor in hen oviduct: evidence for two molecular species.

Isolation of the estrogen receptor was undertaken for comparison with the progesterone receptor with respect to seasonal variations in receptor level and function and the specificity of nuclear binding sites in the hen oviduct. The estrogen receptor in the chick and hen oviduct has been only partially characterized, with conflicting or incomplete information on its properties. We have isolated a binding protein and have partially purified it by ammonium sulfate precipitation. The binding protein displays a single, high affinity class of sites (Kd similar to 10(-10) M) with a low capacity (35 fmol/mg protein) for 17beta-estradiol, shows a marked specificity for estrogenic compound, and is tissue specific. The protein sediments at approximately 8S in low salt and at approximately 4S in high salt conditions. The protein elutes from molecular sieve chromatography (agarose-0.5 m) in high salt conditions (0.3 M KCI) in a molecular weight range of approximately 60,000. DEAE chromatography and isoelectric focusing suggest that there are two molecular species, one focusing at pH 6.8 and the other at pH 7.3. Estrogen complexed to this protein will bind to nuclear acceptor sites in a cell-free assay in which free estrogen, estrogen bound to serum proteins, and [3H]estradiol receptor exchanged with a 100-fold excess of cold estradiol do not bind. Binding to nuclei is saturable and displaceable by an excess of nonradioactive estrogen receptor complexes under conditions of constant protein concentration. The above results represent the most detailed characterization to date of the cytosol estrogen receptor of hen oviduct This is the first demonstration of saturable, receptor-dependent, cell-free binding to target organ nuclei.

Animals↗
PubMedDate not supplied

Naked plasmid-mediated gene transfer to skeletal muscle ameliorates diabetes mellitus.

BACKGROUND: The ability of tissues to take up naked plasmid DNA in vivo suggests an approach for reconstituting systemic metabolic deficiencies without the disadvantages of viral vectors and lipid-DNA complexes. Plasmid-mediated gene transfer into skeletal muscle was investigated as a means of providing a therapeutic source of insulin. METHODS: Four plasmid constructs, each bearing a mouse furin cDNA transgene and rat proinsulin cDNA (modified for processing by furin) driven by four different promoters were injected into the calf muscles of male Balb/c mice. Insulin and C-peptide concentrations were measured by radio-immunoassays having minimal crossreactivity for proinsulin and partially processed proinsulin. RESULTS: Intramuscular insulin concentrations increased by up to 3.6-fold over controls seven days after single injections of CMV, beta-actin, hsp70 and myoglobin promoter constructs. The optimal dose for most constructs was 100 micrograms plasmid DNA. Intramuscular plasmid injection into streptozotocin-induced diabetic Balb/c mice raised plasma insulin and C-peptide concentrations, and reduced hyperglycaemia. Two injections (100 micrograms plasmid DNA each) caused higher plasma insulin concentrations and significantly reduced hyperglycemia in diabetic mice than a single injection. Best results were obtained when plasmid injections preceded induction of diabetes by 14 days. CONCLUSIONS: Skeletal muscle is a potentially useful platform for ectopic secretion of insulin using naked plasmid as a gene transfer vector. Injection at two sites 14 days before the onset of severe hyperglycemia is optimal. This approach could protect Type I diabetics from fatal ketoacidosis and enhance the action of agents that sensitize tissues to insulin in type II diabetes.

Animals↗