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Query: UNIPROT:P06889 (Mol)
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By raising monoclonal antibodies to the apical surface of Caco-2 cells we have identified a membrane protein (p100) that internalizes and recycles constitutively between the apical plasma membrane and endosomes in the apical cytoplasm. By applying tracers bound to the transferrin receptor, which internalizes and recycles back to the basolateral border, we demonstrate that the apical endosomes containing p100 include a subset of multivesticular bodies (MVB), which are also accessible to proteins arriving from the basolateral endosome. Tracers bound to EGF receptors and alpha-2-macroglobulin, which internalize from the basolateral border and are degraded, probably in lysosomes, also pass through the p100-containing MVB. These studies therefore suggest that the apical cytoplasm of Caco-2 cells contains a population of MVB capable of receiving membrane proteins trafficking in from both apical and basolateral borders and then routing them to a variety of cell surface and intracellular destinations. The differential distribution of apical and basolateral tracers within the 50-nm-diameter tubules connected to these p100-positive apical MVB suggests that the destination of proteins trafficking from the MVB back to apical and basolateral surfaces is determined by the tubules to which they gain access.
Mol Biol Cell 1995 May
PMID:Membrane protein trafficking through the common apical endosome compartment of polarized Caco-2 cells. 754 32

Activation of protein kinase C (PKC) by angiotensin II or 12-O-tetradecanoylphorbol-13-acetate (TPA) was associated with a mitogenic response in RIE-1 rat intestinal epithelial cells. However, whereas in control experiments using Swiss 3T3 cells TPA stimulated phosphorylation of the major PKC substrate, MARCKS, the agent did not induce the phosphorylation of any protein with the electrophoretic mobility pattern of MARCKS in RIE-1 cells. However, TPA was able to activate PKC in RIE-1 cells since the agent reduced ('transmodulated') 125I-EGF binding to the cells. The failure of TPA to induce phosphorylation of MARCKS in RIE-1 cells was due to the lack of expression of MARCKS protein and mRNA by these cells. MARCKS is not therefore required for mitogenic signalling via PKC in RIE-1 cells.
Biochem Mol Biol Int 1995 Apr
PMID:The myristoylated alanine-rich C-kinase substrate (MARCKS) is not required for mitogenic signalling via protein kinase C in cultured rat intestinal epithelial (RIE-1) cells. 754 20

Vero cell heparin-binding epidermal growth factor-like growth factor (HB-EGF) is synthesized as a 20- to 30-kDa membrane-anchored HB-EGF precursor (proHB-EGF). Localization and processing of proHB-EGF, both constitutive and 12-O-tetradecanoylphorbol 13-acetate (TPA)-inducible, was examined in Vero cells overexpressing recombinant HB-EGF (Vero H cells). Flow cytometry and fluorescence immunostaining demonstrated that Vero cell proHB-EGF is cell surface-associated and localized at the interface of cell to cell contact. Cell surface biotinylation and immunoprecipitation detected a 20- to 30-kDa heterogeneous proHB-EGF species. Vero H cell surface proHB-EGF turned over constitutively with a half-life of 1.5 h. Some of the 20- to 30-kDa cell surface-associated proHB-EGF was processed and a 14-kDa species of bioactive HB-EGF was released slowly, but most of the proHB-EGF was internalized, displaying a diffuse immunofluorescent staining pattern and accumulation of proHB-EGF in endosomes. Addition of TPA induced a rapid processing of proHB-EGF at a Pro148-Val149 site with a half-life of 7min. The TPA effect was abrogated by the protein kinase C inhibitors, staurosporine and H7. Kinetic analysis showed that loss of cell surface proHB-EGF is maximal at 30 min after addition of TPA and that proHB-EGF is resynthesized and the initial cell surface levels are regained within 12-24 h. Loss of cell surface proHB-EGF was concomitant with appearance of 14- and 19-kDa soluble HB-EGF species in conditioned medium. Vero H cell-associated proHB-EGF is a juxtacrine growth factor for EP170.7 cells in coculture. Processing of proHB-EGF resulted in loss of juxtacrine activity and a simultaneous increase in soluble HB-EGF paracrine mitogenic activity. It was concluded that processing regulates HB-EGF bioactivity by converting it from a cell-surface juxtacrine growth factor to a processed, released soluble paracrine growth factor.
Mol Biol Cell 1995 Aug
PMID:Phorbol ester induces the rapid processing of cell surface heparin-binding EGF-like growth factor: conversion from juxtacrine to paracrine growth factor activity. 757 12

This study documents evolutionary modifications in the expression patterns of the sea urchin EGF I and EGF III genes, which encode a family of extracellular matrix proteins, the fibropellins. We show that the sea urchin apical lamina, a macromolecular extracellular matrix that surrounds the sea urchin embryo and is made up of the fibropellins, has been conserved through at least 250 million years of echinoid evolution. The contribution of different fibropellin family members to this structure has, however, changed over the course of sea urchin phylogeny, and between two congeneric species that exhibit different developmental modes. Mapping the evolutionary history of the EGF genes on a cladogram of relationships among sea urchins reveals that EGF I is present in all echinoids examined, while EGF III appears to have arisen by duplication and divergence from EGF I during the radiation of a suborder of the camarodont sea urchins some 35-45 million years ago. Alterations in the temporal expression patterns of these genes as well as the loss of one of the two EGF I transcripts and encoded protein are coincident with the evolution of a direct-developing larval form in Heliocidaris erythrogramma. H. erythrogramma and its congener Heliocidaris tuberculata, which develops via a typical echinopluteus larva, shared a common ancestor about 10 million years ago. The differences in fibropellin representation within the apical lamina of the various taxa indicate that a homologous embryonic structure can undergo substantial changes in composition during its evolutionary history.
J Mol Evol 1995 Jul
PMID:Evolution of the fibropellin gene family and patterns of fibropellin gene expression in sea urchin phylogeny. 760 87

The crucial role played by androgens in the growth of prostatic carcinoma is now well established. However, the mechanisms of this proliferative action are still poorly understood. Experiments have been performed to clarify: (1) the metabolism of androgens in prostatic tumor cells; and (2) the role played by locally produced growth factors in the autocrine regulation of prostatic tumor cell proliferation and the possible regulation exerted by testosterone (T) on the activity of these factors. These studies have been performed by utilizing the human androgen-responsive prostatic cancer LNCaP cell line. (1) By incubating LNCaP cells with different 14C-labeled androgenic precursors, it has been shown that all the major key enzymes involved in the metabolism of androgens (5 alpha-reductase, 17 beta-hydroxysteroid-oxidoreductase, 3 alpha- and 3 beta-hydroxysteroid-oxidoreductases) are present and active in these cells. In particular, the 5 alpha-reductase, which converts T and delta 4 to DHT and 5 alpha-A respectively, seems to be more active when delta 4 is the substrate, suggesting a preference for this precursor. (2) The hypothesis that LNCaP cells might produce LHRH (or a LHRH-like peptide) has been verified by RT-PCR, performed in the presence of a pair of specific oligonucleotide primers. A cDNA band of the expected size (228 bp), which specifically hybridized with a 32P-labeled LHRH oligonucleotide probe, has been obtained in LNCaP cells. To clarify the possible role played by this factor in the regulation of tumor growth, LNCaP cells, cultured in steroid-free conditions, have been treated with a LHRH antagonist; the treatment resulted in a significant increase of cell proliferation. Taken together, these data indicate that a LHRH (or LHRH-like) growth modulatory system is expressed in LNCaP cells and plays an inhibitory role in the regulation of tumor cell proliferation. This system seems to be regulated in a negative way by steroids. Growth factors endowed with stimulatory activity, such as EGF and TGF alpha, have also been shown to be produced by LNCaP cells. The present studies show that the immunoprecipitation of the EGF receptor with a specific monoclonal antibody (Ab225) reveals a protein band of the expected size (170 kDa) which is phosphorylated even in basal conditions. Moreover, the treatment of LNCaP cells, cultured in serum-free conditions, either with a monoclonal antibody against the EGF receptor, or with immunoneutralizing antibodies against EGF and TGF alpha, results in a significant decrease of cell proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)
J Steroid Biochem Mol Biol 1995 Jun
PMID:Growth of the androgen-dependent tumor of the prostate: role of androgens and of locally expressed growth modulatory factors. 762 87

Four phosphorylation sites have been identified in the chicken progesterone receptor. Two of these sites exhibit basal phosphorylation which is enhanced upon treatment with hormone and two of the sites are phosphorylated in response to hormone. Mutation of one of these hormone dependent sites, Ser530 to Ala530, causes a decrease in transcriptional activation at low concentrations of hormone, but the activity is unaffected at high concentrations. However, the hormone binding of the mutant is unaffected suggesting that phosphorylation of Ser530 plays a role in facilitating the response of the receptor to low concentrations of hormone. The chicken progesterone receptor can be activated by modulators of kinases in the absence of hormone. The finding that signals initiated by tyrosine phosphorylation (through treatment with EGF) or through the dopamine receptor suggests that there are multiple means of activating chicken progesterone receptor. In contrast, the human progesterone receptor does not exhibit ligand independent activation; however, its activity in the presence of the agonist R5020 is enhanced by treatment with 8-Br-cAMP, an activator of protein kinase A, and treatment with 8-Br-cAMP causes the antagonist, RU486, to act as an agonist.
J Steroid Biochem Mol Biol 1995 Jun
PMID:Phosphorylation and progesterone receptor function. 762 2

The Marfan syndrome (MFS) is an autosomal dominant heritable disorder of connective tissue. Variable and pleiotropic clinical features are observed in the skeletal, ocular, and cardiovascular systems. The most severe end of the phenotypic spectrum of this disorder comprises a group of patients usually diagnosed at birth, who have a life expectancy of little more than a year. To distinguish this group of patients from those with classical MFS, we refer to them as neonatal Marfan syndrome (nMFS). These infants usually die of congestive heart failure rather than aortic aneurysmal disease, the most frequent cause of morbidity and mortality in classical MFS. Defects in fibrillin, an elastin-associated microfibrillar glycoprotein, are now known to cause both the classical and neonatal forms of MFS. Here we report the recurrent mis-splicing of fibrillin (FBN1) exon 32, a precursor EGF-like calcium binding domain, in two unrelated infants with nMFS. The mis-splicing, in one patient, was due to an A-->T transversion at the -2 position of the consensus acceptor splice site; while that in the second patient was caused by a G-->A transition at the +1 position of the donor splice site. Characterization of FBN1 mutations in individuals at the most severe end of the Marfan syndrome spectrum should provide greater understanding of the multiple domains and regions of fibrillin.
Hum Mol Genet 1995 Apr
PMID:Recurrent mis-splicing of fibrillin exon 32 in two patients with neonatal Marfan syndrome. 763 9

We have shown previously that transforming growth factor beta 1 (TGF-beta 1) is antimitotic for human fetal adrenal (HFA) cells in vitro and that this effect can be partially blocked by adrenocorticotropic hormone (ACTH). In the present study, we sought to determine whether ACTH might interfere with TGF-beta 1 action by means of reducing TGF-beta 1 binding to adrenal cells. We incubated adrenal cells with 50 pM 125I-labeled TGF-beta 1 for 15 min to 3 h at 4 degree C and found that the binding of 125I-labeled TGF-beta 1 increased with time and could be inhibited in a dose-dependent manner by non-labeled TGF-beta 1 (0.05-10 nM), but not with other relevant cytokines: IL6, TNF alpha,IGF-I, IGF-II, TGF-alpha, and EGF. Pretreatment of HFA cells with ACTH (0.009-900 nM) for 4-24 h significantly increased specific 125I-labeled TGF-beta 1 binding compared to that in untreated cells; maximal increases in binding were achieved with 0.9 nM ACTH. This effect of ACTH could be mimicked by treatment of adrenal cells with dibutyryl cAMP (1 mM) or forskolin (10 microM). Scatchard analysis of data from ACTH-treated cells suggest the presence of two populations of TGF-beta 1 binding sites with different affinity and capacity of binding for the ligand.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1995 Apr 01
PMID:Receptor binding of transforming growth factor-beta by human fetal adrenal cells. 766 78

Hypervascularity, focal necrosis, persistent cerebral edema, and rapid cellular proliferation are key histopathologic features of glioblastoma multiforme (GBM), the most common and malignant of human brain tumors. By immunoperoxidase and immunofluorescence, we definitively have demonstrated the presence of vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFr) in five out of five human glioma cell lines (U-251MG, U-105MG, D-65MG, D-54MG, and CH-235MG) and in eight human GBM tumor surgical specimens. In vitro experiments with glioma cell lines revealed a consistent and reliable relation between EGFr activation and VEGF production; namely, EGF (1-20 ng/ml) stimulation of glioma cells resulted in a 25-125% increase in secretion of bioactive VEGF. Conditioned media (CM) prepared from EGF-stimulated glioma cell lines produced significant increases in cytosolic free intracellular concentrations of Ca2+ ([Ca2+]i) in human umbilical vein endothelial cells (HUVECs). Neither EGF alone or CM from glioma cultures prepared in the absence of EGF induced [Ca2+]i increases in HUVECs. Preincubation of glioma CM with A4.6.1, a monoclonal antibody to VEGF, completely abolished VEGF-mediated [Ca2+]i transients in HUVECs. Likewise, induction by glioma-derived CM of von Willebrand factor release from HUVECs was completely blocked by A4.6.1 pretreatment. These observations provide a key link in understanding the basic cellular pathophysiology of GBM tumor angiogenesis, increased vascular permeability, and cellular proliferation. Specifically, EGF activation of EGFr expressed on glioma cells leads to enhanced secretion of VEGF by glioma cells. VEGF released by glioma cells in situ most likely accounts for pathognomonic histopathologic and clinical features of GBM tumors in patients, including striking tumor angiogenesis, increased cerebral edema and hypercoagulability manifesting as focal tumor necrosis, deep vein thrombosis, or pulmonary embolism.
Mol Biol Cell 1993 Jan
PMID:Epidermal growth factor stimulates vascular endothelial growth factor production by human malignant glioma cells: a model of glioblastoma multiforme pathophysiology. 768 Feb 47

Human benign prostatic hyperplasia (BPH) samples were analyzed to evaluate the presence of immunoreactive epidermal growth factor (irEGF) and EGF receptor (EGFR). In all BPH samples examined both peptide and its receptor were present. Scatchard analysis of binding data of [125I]EGF showed two classes of binding sites with high and low affinity. Intratissular irEGF concentrations showed a significant inverse linear correlation with EGFR levels. Two groups of samples can be identified: the first showing high irEGF concentrations and low levels of EGF binding sites; the second low irEGF and high concentrations of EGFR. The simultaneous presence of EGF and its receptor in BPH samples indicates that this growth factor may act in an autocrine/paracrine manner in human prostatic tissue. The inverse relationship between EGF and the two sites of EGFR lead one to hypothesize that EGF itself could play a central role in determining receptor cell surface availability.
J Steroid Biochem Mol Biol 1993 Oct
PMID:Relationship between epidermal growth factor and its receptor in human benign prostatic hyperplasia. 769 39


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