Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The insulin-like growth factor-II (IGF-II)/Mannose 6-P receptor (Man 6-P) is a multifunctional receptor that binds two unrelated ligands, IGF-II and lysosomal enzymes that contain Man 6-P recognition markers. Although this receptor has been extensively characterized in mammalian cells, binding of radiolabeled IGF-II to this receptor in avian cells and tissues has not been reported. In the present study, we demonstrate that chick embryo fibroblasts (CEFs) bind and internalize lysosomal enzymes in a Man 6-P-inhibitable fashion, and possess a protein immunologically related to the mammalian IGF-II/Man 6-P receptor that binds lysosomal enzymes with Man 6-P recognition markers but does not bind IGF-II. 1) When lysates of biosynthetically labeled CEFs were affinity-purified on beta-galactosidase-Sepharose, an approximately 250 kilodalton protein was observed in the Man 6-P eluate but not in the Glc 1-P or mannose eluates, that was precipitated by antisera to purified rat and bovine IGF-II/Man 6-P receptors, but not by nonimmune serum. 2) When CEFs were incubated with [35S]proteins enriched in lysosomal enzymes, Man 6-P inhibited binding (0 C) and uptake (34 C) in a dose-dependent fashion. Binding was unchanged in the absence of divalent cations. At low sugar concentrations, binding and uptake were inhibited selectively by Man 6-P and the conformationally similar sugar phosphate, Fru 1-P, a specificity similar to that of mammalian cation-independent Man 6-P receptors. 3) When affinity-purified lysates from biosynthetically labeled CEFs were incubated with antiserum to the rat IGF-II/Man 6-P receptor, a 245 kilodalton protein was immunoprecipitated from lysates that had been affinity purified on beta-galactosidase-Sepharose but not after purification on IGF-II-Sepharose. By contrast, a truncated IGF-II/Man 6-P receptor, presumably internalized from the fetal bovine serum used to feed the cells, was purified from lysates of unlabeled CEFs on IGF-II-Sepharose. Thus, CEFs possess a cation-independent Man 6-P receptor that is similar in size and immunological reactivity to the mammalian IGF-II/Man 6-P receptor, and binds and internalizes lysosomal enzymes but, unlike the mammalian receptor, does not bind IGF-II.
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PMID:The chick embryo fibroblast cation-independent mannose 6-phosphate receptor is functional and immunologically related to the mammalian insulin-like growth factor-II (IGF-II)/man 6-P receptor but does not bind IGF-II. 184 80

The insulin-like growth factor-II/mannose 6-phosphate receptor which targets acid hydrolases to lysosomes, has two different binding sites, one for the mannose 6-phosphate (Man-6-P) recognition marker on lysosomal enzymes and the other for insulin-like growth factor-II (IGF-II). We have asked whether IGF-II can regulate the cellular uptake of the lysosomal enzyme 125I-beta-galactosidase by modulating the binding of 125I-beta-galactosidase to the IGF-II/Man-6-P receptor. We first isolated high affinity 125I-beta-galactosidase by affinity chromatography on an IGF-II/Man-6-P receptor-Sepharose column. Specific uptake (mannose 6-phosphate-inhibitable) of 125I-beta-galactosidase in BRL 3A2 rat liver cells and in rat C6 glial cells was 3.7-4.8 and 4.0-8.0% of added tracer, respectively. The cell-associated 125I-beta-galactosidase in the uptake experiments largely represented internalized radioligand as measured by acid or mannose 6-phosphate washing. The uptake of 125I-beta-galactosidase was inhibited by an antiserum (No. 3637) specific for the IGF-II/Man-6-P receptor. Low concentrations of IGF-II also inhibited the uptake of 125I-beta-galactosidase. Maximal concentrations of IGF-II inhibited uptake by 73 +/- 8% (mean +/- S.D.) in C6 cells and by 77 +/- 6% in BRL 3A2 cells compared to the level of inhibition by mannose 6-phosphate. The relative potency of IGF-II, IGF-I, and insulin (IGF-II much greater than IGF-I; insulin, inactive) were characteristic of the relative affinities of the ligands for the IGF-II/Man-6-P receptor. IGF-II also partially inhibited the binding of 125I-beta-galactosidase to C6 and BRL 3A2 cells at 4 degrees C and inhibited the binding to highly purified IGF-II/Man-6-P receptor by 58 +/- 14%. We conclude that IGF-II inhibits the cellular uptake of 125I-beta-galactosidase and that this inhibition is partly explained by the ability of IGF-II to inhibit binding of 125I-beta-galactosidase to the IGF-II/Man-6-P receptor.
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PMID:Insulin-like growth factor-II (IGF-II) inhibits both the cellular uptake of beta-galactosidase and the binding of beta-galactosidase to purified IGF-II/mannose 6-phosphate receptor. 253 55

Cloning and sequencing of the human type II insulin-like growth factor (IGF) receptor cDNA revealed an 80% deduced amino acid sequence homology with the bovine cation-independent mannose 6-phosphate (Man-6-P) receptor, suggesting identity of the two receptors (Morgan, D. O., Edman, J. C., Standring, D. N., Fried, V. A., Smith, M. C., Roth, R. A., and Rutter, W. J. (1987) Nature 329, 301-307). We have performed biochemical experiments that support this proposal. Rat liver type II IGF receptor, purified by the conventional method of IGF-II affinity chromatography, bound quantitatively to a beta-galactosidase affinity column and was eluted with Man-6-P. Bovine liver Man-6-P receptor, prepared by the conventional method of affinity chromatography on phosphomannan-Sepharose, bound IGF-II with high affinity (Kd = 1 nM). Affinity cross-linking of 125I-IGF-II to the Man-6-P receptor and analysis by sodium dodecyl sulfate-gel electrophoresis showed that beta-galactosidase, but not Man-6-P, inhibited the formation of the 250-kDa 125I-IGF-II-receptor complex. The inhibition by beta-galactosidase was prevented by coincubation with Man-6-P. 125I-IGF-II did not bind to the 46-kDa cation-dependent Man-6-P receptor. For immunologic studies we purified type II IGF receptors and Man-6-P receptors in parallel from rat placental membranes using either IGF-II- or beta-galactosidase affinity chromatography. A panel of five antisera that previously had been raised against either type II IGF receptor or Man-6-P receptor behaved identically toward type II IGF receptor versus Man-6-P receptor in ligand blocking and immunoprecipitation assays. Our data support the conclusion that the type II IGF receptor and the cation-independent Man-6-P receptor are the same protein and that the IGF-II and Man-6-P-binding sites are distinct.
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PMID:Biochemical evidence that the type II insulin-like growth factor receptor is identical to the cation-independent mannose 6-phosphate receptor. 296 21

The binding of 125I-labeled insulin-like growth factor-II (125I-IGF-II) to luminal and basolateral membrane vesicles isolated from pars convoluta and the straight part (pars recta) of rabbit proximal tubule was investigated. Analyses of the binding data by use of the general stoichiometric binding equation revealed, that in all preparations IGF-II was bound to one high-affinity binding site and other sites with lower affinities. The specificity of the high-affinity 125I-IGF-II binding to the membrane vesicles assessed by displacement by unlabeled IGF-II, IGF-I and insulin showed that IGF-I displaced 125I-IGF-II in the range 22.5-47.9 nM (IC50) whereas insulin did not effect 125I-IGF-II binding at all. beta-Galactosidase inhibited the 125I-IGF-II binding with half-maximal inhibition of 20-30 nM beta-galactosidase. D-Mannose 6-phosphate increased the binding of 125I-IGF-II and reversed the inhibitory effect of beta-galactosidase. Analyses of 125I-IGF-II binding curves in the presence of beta-galactosidase or D-mannose 6-phosphate demonstrated that none of these compounds changed the binding affinity of 125I-IGF-II for the membrane vesicles. The IGF-II/M6P receptor content in the luminal membranes was in the range 0.21-0.34 pmol IGF-II/M6P receptor per mg protein and very low compared to 2.27-2.86 pmol IGF-II/M6P receptor per mg protein in basolateral membranes.
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PMID:IGF-II receptors in luminal and basolateral membranes isolated from pars convoluta and pars recta of rabbit proximal tubule. 771 11

Deciphering the complex interactions of the various components of the insulin-like growth factor (IGF) system [IGF-I and -II peptides, type I and II IGF receptors, and IGF-binding proteins (IGFBPs)] is important for our understanding of cell growth regulation. We report here that IGF-II can enhance IGF-I-stimulated cell proliferation independent of direct IGF-II interaction with type I or II IGF receptors. Human fibroblasts cultured in serum-free medium for 40 h were relatively resistant to the mitogenic effects of added IGF-I. However, preexposure of the cultures to low concentrations of IGF-II enhanced IGF-I action several-fold. IGF-II by itself had no stimulatory effect and did not influence [Gln3,Ala4,Tyr15,Leu16]IGF-I or insulin-stimulated DNA synthesis. IGF-II did not directly interact with type I IGF receptors, as [Leu27]IGF-II, an IGF-II analog that does not bind type I IGF receptors, could mimic IGF-II's potentiating effect. Type II IGF receptors also were not involved because 1) [Gln6,Ala7,Tyr18,Leu19,Leu27]IGF-II, an analog with normal receptor binding, had no effect; and 2) beta-galactosidase, a competitive inhibitor of IGF-II receptor binding, did not influence IGF-II potentiation of IGF-I action. Enhanced cell responsiveness to IGF-I appears to be due to IGF-II-induced changes in pericellular IGFBP-3 and IGFBP-4. These data support the hypothesis that IGF-II can potentiate the action of IGF-I by disrupting the IGFBP barrier at the cell surface, thereby increasing IGF-I availability for type I IGF receptor interaction.
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PMID:Insulin-like growth factor-II enhancement of human fibroblast growth via a nonreceptor-mediated mechanism. 801 94

As a consequence of parental imprinting in mice, the paternal allele encoding insulin-like growth factor-II (IGF-II) is expressed, whereas the maternal allele is silent in most tissues. To examine whether cis-acting sequences involved in imprinting are located in the vicinity of the Igf-2 gene, we have constructed mouse transgenic lines and studied the expression of a 30 kb rat Igf-2 transgene, in which the coding region has been replaced with the lacZ reporter sequence. Chromatin position effects and/or absence of long-range regulatory elements seem to have affected tissue-specific expression in the transgenic mice. However, in one of six expressing lines, staining of embryos for beta-galactosidase activity was detected in a minor subset of tissues normally transcribing the endogenous homolog, but only when the transgene was transmitted paternally. This transgene was integrated into mouse chromosome 19, which is apparently free of imprinted loci. Although the possibility that the Igf-2 transgene was inserted into an as yet unidentified imprinted locus is discussed, a more likely interpretation of our results is that the transgene carries at least a portion of its own imprinting signal, because it consists of the genomic sequences of a locus already known to be imprinted and maintains the correct imprinting mode.
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PMID:Parental imprinting of an Igf-2 transgene. 839 16

Elevated insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1) mRNA in senescent human mammary epithelial cells suggested that the IGFBP-3 gene product may inhibit cell proliferation. To test this hypothesis, we used a retroviral vector to express IGFBP-rP1 cDNA in the IGFBP-rP1-deficient MCF-7 breast cancer cell line. Compared with control vector-transduced cells, cumulative cell numbers for IGFBP-rP1-transduced polyclonal or clonal cell cultures were reduced by 39 and 74%, respectively, after 1 week. Medium conditioned by IGFBP-rP1-producing cultures reduced cumulative cell numbers in parental MCF-7 cultures by 20% compared with medium from cultures of a control vector-transduced cell line. Nuclear fragmentation analysis and cell proliferation assays completed in the presence of the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone excluded apoptosis as the responsible mechanism. The percentage of cells containing senescence-associated beta-galactosidase activity was doubled compared with control cell cultures. Flow cytometry analysis indicated that twice as many noncycling cells were present in the IGFBP-rP1-transduced MCF-7 cell cultures compared with controls. These findings indicate that IGFBP-rP1 is an inhibitor of MCF-7 breast cancer cell proliferation and may act via a cellular senescence-like mechanism.
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PMID:Insulin-like growth factor binding protein-related protein 1 inhibits proliferation of MCF-7 breast cancer cells via a senescence-like mechanism. 1206 44

Increased expression of mac25/insulin-like growth factor binding-protein related protein-1 (IGFBP-rP1) in human breast and prostate epithelial cell lines results in the suppression of tumor growth. CDNA expression array analysis revealed increased manganese superoxide dismutase (SOD-2) expression in the mac25/IGFBP-rP1-transfected M12 human prostate cancer cell line compared to M12 control cells. SOD-2 has been postulated to be a tumor suppressor. SOD-2 was also increased in LNCaP cells stably transfected with mac25/IGFBP-rP1, but not in mac25/IGFBP-rP1-transfected PC-3 cells. Mac25 LNCaP cells had a marked decrease in tumor growth in nude mice compared to controls, but there was no difference in tumor growth in mac25 PC-3 cells compared to control. Phosphorylated Erk and Akt were increased in the M12 and LNCaP transfected mac25/IGFBP-rP1 cells but not PC-3 mac25. Inhibition of PI-3 kinase results in a marked decrease in viability of the M12-mac25 cells compared to M12 controls. Cells treated with H(2)O(2) result in an increase in phospho-ERK. Transfection of SOD-2 in M12 cells markedly decreased tumor growth, apoptosis, G1 delay in the cell cycle, and expression of senescence associated beta-galactosidase. These results suggest that one of the downstream mediators of the senescence-associated tumor suppression effect of mac25/IGFBP-rP1 is SOD-2.
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PMID:Increased manganese superoxide dismutase (SOD-2) is part of the mechanism for prostate tumor suppression by Mac25/insulin-like growth factor binding-protein-related protein-1. 1259 89

The signaling pathway of insulin/insulin-like growth factor/phosphatidylinositol-3 kinase/Akt/forkhead transcription factors is known to control life span and senescence in organisms ranging from yeast to mice. The FOXO family of forkhead transcription factors, FOXO1, FOXO3a, and FOXO4, play a critical role in this signal transduction pathway. However, the impact of FOXO3a activation on life span of primary cultured human dermal fibroblasts (HDFs) is unknown. To investigate the role of FOXO3a in the regulation of cellular senescence, we prepared FOXO3a-siRNA stable HDFs. We found that the down-regulation of FOXO3a RNA and protein in HDFs induced many senescent phenotypes, including changes in cell morphology, increases in population doubling times, senescence-associated beta-galactosidase staining and the cellular reactive oxygen species, and up-regulation of p53/p21 protein expression. Our data provide evidence of the key role of FOXO3a transcription factor as a mediator of cellular senescence in HDFs, and suggest that the mechanism of senescence is conserved in HDFs.
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PMID:Down-regulation of a forkhead transcription factor, FOXO3a, accelerates cellular senescence in human dermal fibroblasts. 1574 Dec 76

Insulin/insulin-like growth factor (IGF) signaling pathways are among the most conserved processes in aging in organisms ranging from yeast to mammals. Previously, using cDNA microarray technology, we reported that expression of IGF-binding protein 3 (IGFBP3), one of the IGF-binding proteins, was increased with age in human dermal fibroblasts. In this study, the role of IGFBP3 on cellular senescence was studied in human umbilical vein endothelial cells (HUVEC). The expression levels of IGFBP3 mRNA and protein were increased in HUVECs with age. Knockdown of IGFBP3 in old cells with IGFBP3 short hairpin RNA (shRNA) retrovirus resulted in the partial reduction of a variety of senescent phenotypes, such as changes in cell morphology, and decreases in population doubling times and senescence-associated beta-galactosidase (SA-beta-gal) staining. Down-regulation of IGFBP3 rescued the growth arrest induced by p53 overexpression in young HUVECs. In contrast, up-regulation of IGFBP3 in young cells and prolonged IGFBP3 treatment accelerated cellular senescence, confirmed by cell proliferation and SA-beta-gal staining. The FOXO3a (forkhead box O3a) protein level was increased in old IGFBP3 shRNA cells. The treatment of young HUVECs with IGFBP3 repressed the levels of FOXO3a protein. Furthermore, calorie restriction reduced IGFBP3 protein levels, which were found to be increased with age in the rat liver and serum. These results suggest that IGFBP3 might play an important role in the cellular senescence of HUVECs as well as in vivo aging.
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PMID:Regulation of replicative senescence by insulin-like growth factor-binding protein 3 in human umbilical vein endothelial cells. 1763 17


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