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Title: Regulation of osteosarcoma EGF receptor affinity by phorbol ester and cyclic AMP

We studied the binding and degradation of 125I-labeled epidermal growth factor (EGF) by UMR-106 osteosarcoma cells and the regulation of EGF receptor affinity for EGF by the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and by treatments that raise intracellular levels of cyclic AMP. Cell surface binding of (125I)EGF to A431 cells reached a plateau after a 30 minute incubation at 37 degrees C but was undetectable in UMR-106 cells. Degradation of (125I)EGF proceeded at a 50-fold higher rate in A431 cells on a per cell basis, but receptor-bound (125I)EGF was internalized and degraded at a 3.5-fold higher rate by UMR-106 cells on a per receptor basis. At 4 degrees C, (125I)EGF labeled a single class of surface binding sites in the UMR-106 cell. Treatment with TPA at 37 degrees C reduced subsequent cell surface binding of (125I)EGF at 4 degrees C a maximum of 80% with an IC50 of 1.25 ng/ml. Maximal TPA reduction of (125I)EGF binding was observed within 5-15 minutes and was due to a reduction in the affinity of cell surface receptors of (125I)EGF without a change in receptor density. Pretreatment of the cells for 4 h with 30 microM forskolin, 1 mM isobutylmethylxanthine (IBMX) plus 30 microM forskolin,more » or 1 mM IBMX plus 100 ng/ml parathyroid hormone (PTH) attenuated the loss in (125I)EGF binding caused by a subsequent dose of 10 ng/ml of TPA by 17% (p less than 0.0005), 39% (p less than 0.0002), and 35% (p less than 0.002), respectively.« less
Authors:
;  [1]
  1. (Emory Univ. Department of Medicine, Atlanta, GA (USA))
Publication Date:
OSTI Identifier:
5512366
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Bone and Mineral Research; (USA); Journal Volume: 4:2
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; 59 BASIC BIOLOGICAL SCIENCES; AMP; BIOCHEMICAL REACTION KINETICS; GROWTH FACTORS; RECEPTORS; PHORBOL ESTERS; BIOLOGICAL EFFECTS; AFFINITY; IODINE 125; MAN; OSTEOSARCOMAS; PARATHORMONE; PHOSPHOLIPIDS; TRACER TECHNIQUES; ANIMALS; BETA DECAY RADIOISOTOPES; CARCINOGENS; DAYS LIVING RADIOISOTOPES; DISEASES; ELECTRON CAPTURE RADIOISOTOPES; ESTERS; HORMONES; INTERMEDIATE MASS NUCLEI; IODINE ISOTOPES; ISOTOPE APPLICATIONS; ISOTOPES; KINETICS; LIPIDS; MAMMALS; MEMBRANE PROTEINS; MITOGENS; NEOPLASMS; NUCLEI; NUCLEOTIDES; ODD-EVEN NUCLEI; ORGANIC COMPOUNDS; ORGANIC PHOSPHORUS COMPOUNDS; PEPTIDE HORMONES; PRIMATES; PROTEINS; RADIOISOTOPES; REACTION KINETICS; SARCOMAS; SKELETAL DISEASES; VERTEBRATES 560300* -- Chemicals Metabolism & Toxicology; 550201 -- Biochemistry-- Tracer Techniques