PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Factor II”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed1999

The mannose 6-phosphate/insulin-like growth factor-II receptor is a substrate of type V transforming growth factor-beta receptor.

The type V transforming growth factor beta (TGF-beta) receptor (TbetaR-V) is a ligand-stimulated acidotropic Ser-specific protein kinase that recognizes a motif of SXE/S(P)/D. This motif is present in the cytoplasmic domain of the mannose 6-phosphate/insulin-like growth factor-II (Man-6-P/IGF-II) receptor. We have explored the possibility that the Man-6-P/IGF-II receptor is a substrate of TbetaR-V. Purified bovine Man-6-P/IGF-II receptor was phosphorylated by purified bovine TbetaR-V in the presence of [gamma-32P]ATP and MnCl2 with an apparent Km of 130 nM. TGF-beta stimulated the phosphorylation of the Man-6-P/IGF-II receptor at 0 degrees C in mouse L cells overexpressing the Man-6-P/IGF-II receptor and in wild-type mink lung epithelial (Mv1Lu cells) metabolically labeled with [32P]orthophosphate. The in vitro and in vivo phosphorylation of the Man-6-P/IGF-II receptor occurred at the putative phosphorylation sites as revealed by phosphopeptide mapping and amino acid sequence analysis. TGF-beta stimulated Man-6-P/IGF-II receptor-mediated uptake (approximately 2-fold after 12 h treatment) of exogenous beta-glucuronidase in Mv1Lu cells and type II TGF-beta receptor (TbetaR-II)-defective mutant cells (DR26 cells) but not in type I TGF-beta receptor (TbetaR-I)-defective mutant cells (R-1B cells) and human colorectal carcinoma cells (RII-37 cells) expressing TbetaR-I and TbetaR-II but lacking TbetaR-V. These results suggest the Man-6-P/IGF-II receptor serves as an in vitro and in vivo substrate of TbetaR-V and that both TbetaR-V and TbetaR-I may play a role in mediating the TGF-beta-stimulated uptake of exogenous beta-glucuronidase.

Amino Acid Sequence↗
PubMed1990

Vitamin K1 levels and K1-dependent coagulation factors II and X in preterm and small-for-date neonates.

In 17 preterm neonates and 7 small-for-date neonates, all formula-fed, vitamin K-dependent coagulation factors II and X remained near 45% of adult values from the moment of birth until 28 days postnatally. Vitamin K1 levels, however, showed a remarkable rise from below the detection limit of 0.022 ng/ml in umbilical cord blood, to serum levels with a range of 0.99-7.29 ng/ml vitamin K1 on day 3, with a further rise on days 7 and 28 postnatally. Vitamin K1 (Konakion) parenterally given to a third group of four preterm neonates as a 1 mg dose resulted in very high serum levels of vitamin K1 (64.08-157.10 ng/ml), but without any significant increase in plasma levels of vitamin K-dependent coagulation factors II and X, compared to the group without any extra vitamin K1. It is concluded that in healthy preterm and small-for-date neonates no correlation is seen between serum levels of vitamin K1 and plasma levels of coagulation factors II and X. After administration of 1 mg Konakion no accelerated increase is seen in coagulation factor activities.

Factor X↗
PubMed2005

Effects of alpha-interferon on insulin-like growth factor-I, insulin-like growth factor-II and insulin-like growth factor binding protein-3 secretion by a human lung cancer cell line in vitro.

The aim of our study was to evaluate the effect of alpha-interferon (alpha-IFN) on cell growth and on the different IGF system components in a human non-small cell lung cancer line (Calu-6) in vitro. Our results confirm the release of IGF-I and IGF-II by these cells. The amount of IGF-II in conditioned media (10.25 +/- 3.95 nM/10(6) cells, mean +/- SE) was more than 10-fold higher than that of IGF-I. alpha-IFN treatment reduced IGF-II levels in the media, with a maximal effect between 1 and 10 U/ml (delta% of control: -31 and -55%, respectively, p < 0.05). IGF-I was significantly reduced at 0.5 U/ml (p < 0.01). No difference, however, was observed in IGF mRNA expression between untreated and alpha-IFN treated cells. An increase in IGF-I and IGF-II intracellular levels in alpha-IFN treated cultures was observed, suggesting that alpha-IFN can regulate the transfer of these peptides into the cells. Furthermore, IGF type-I and particularly type-lI receptor expression was increased after alpha-IFN treatment. IGFBP-3 was detected only in trace amounts in the conditioned media; however, it showed an increase after alpha-IFN treatment (+110% at 1 U/ml). IGFBP-3 mRNA expression showed a slight increase after treatment with 1 and 10 U/ml. alpha-IFN (1-10 U/ml) reduced the stimulatory effect of IGF-I on cell replication (p < 0.01), inhibited (p < 0.01) cell replication in untreated and in fetal calf serum (FCS)-stimulated cells, and increased apoptosis in Calu-6 cells. Our data suggest that alpha-IFN may exert its effects at the cellular level in part through modification of the local IGF system.

Antineoplastic Agents↗
PubMed1985

Mitogenic activity of glia maturation factor. Interaction with insulin and insulin-like growth factor-II.

The mitogenic activity of glia maturation factor (GMF) was tested on sparse-cultured cells. GMF stimulates the growth rate of normal astroblasts and fibroblasts grown in the presence of fetal calf serum (FCS), and raises the saturation density of the cells over what is imposed by the corresponding serum concentrations. GMF has no mitogenic effect in the complete absence of serum. The mitogenicity of GMF is also demonstrable in defined media where certain serum components are present. In particular, GMF in combination with the defined medium N2 partially mimics the proliferative effect of serum alone. Insulin, an ingredient of N2, can substitute for the complete N2 formula. Insulin-like growth factor-II (IGF-II), in turn, can substitute for insulin. The interaction of GMF with insulin or IGF-II can be demonstrated in a sequential manner, suggesting that GMF is a competence factor. Since insulin is required at a concentration well above the physiologic serum level, and must be used at a dose 1000 times higher than IGF-II, we suspected that insulin acts on IGF-II receptors. This was substantiated by the demonstration of IGF-II receptors and the absence of detectable insulin receptors on the astroblasts. The combined effect of IGF-II and GMF mimics the combined effect of 10% FCS and GMF, in both growth rate and saturation density.

Animals↗
PubMed1989

Circadian rhythms of blood clotting time and coagulation factors II, VII, IX and X in rats.

The 24-hr variations in clotting times and vitamin K-dependent blood coagulation factors were studied in rats kept on a 12-hr light-dark cycle (light on: 0600-1800 hours). Clotting times were determined under a binocular microscope by measuring the time required for the formation of the first fibrin thread. Factors II, VII and X were analyzed by the prothrombin test while the factor IX was quantified using the activated partial thromboplastin time assay. Results indicated that the clotting times were significantly longer during the dark (activity) period with a peak at 1:00 and a trough at 17:00. Similarly, a variation was found in factor activity levels: prothrombin (II), factor VII and factor X had higher activities during the light span (rest period). The highest activities found at 13:00 and 09:00 were statistically different from the minimum activity levels obtained at 21:00. Factor IX did not show a significant circadian variation.

Animals↗
PubMed1996

Expression of insulin-like growth factor-II and insulin-like growth factor binding proteins during Caco-2 cell proliferation and differentiation.

The components of the insulin-like growth factor (IGF) axis and their roles in regulating proliferation and differentiation of the human colon adenocarcinoma cell line, Caco-2, have been investigated. Caco-2 cells proliferated in serum-free medium at 75% the rate observed in medium containing 10% fetal bovine serum. IGF-I (10 nM) increased Caco-2 cell growth in serum-free medium, but not to the rate seen with serum. Multiple IGF-II mRNA species were produced by Caco-2 cells, but IGF-I mRNA was undetectable. Secretion of radioimmunoassayable IGF-II corresponded with steady-state levels of IGF-II mRNA, neither of which was observed to change markedly over the course of 16 days of Caco-2 cell differentiation. Levels of sucrase-isomaltase mRNA, a marker for enterocytic differentiation, increased 12-fold between days 5 and 16 of culture. Northern blotting of total RNA and ligand blot and immunoblot analyses of serum-free conditioned medium revealed that Caco-2 cells produce several IGF binding proteins (IGFBPs), including IGFBP-2, -3, and -4, as well as a 31,000 M(r) species that was not identified. The pattern of IGFBP secretion changed dramatically during Caco-2 cell differentiation: IGFBP-3 and IGFBP-2 increased 8.5-fold and 5-fold, respectively, whereas IGFBP-4 and the 31,000 M(r) species decreased 43% and 90%. Caco-2 cell clones stably transfected with a human IGFBP-4 cDNA construct exhibited a 60% increase in steady-state level of IGFBP-4 mRNA, and secreted twice as much IGFBP-4 protein as controls. Moreover, IGFBP-4-overexpressing cells proliferated at only 25% the rate of control cells in serum-free medium, in conjunction with a 70% increase in expression of sucrase-isomaltase. In summary, these studies indicate that a complex IGF axis is involved in autocrine regulation of Caco-2 cell proliferation and differentiation.

Caco-2 Cells↗
PubMed1992

Parental imprinting: potentially active chromatin of the repressed maternal allele of the mouse insulin-like growth factor II (Igf2) gene.

The mouse insulin-like growth factor II (Igf2) gene, which is located on distal chromosome 7 (Chr7), has been shown previously to undergo tissue-specific parental imprinting. This imprinting results in expression of Igf2 from the paternally inherited chromosome and repression of the maternally inherited allele in most tissues of the developing embryo. We are using embryos with the maternal duplication and paternal deficiency of distal Chr7 to characterize the mechanism that underlies repression of the maternal allele. We show that the chromatin of the 5' region of the repressed Igf2 allele is potentially active for transcription rather than heterochromatic. In particular, a CpG island that comprises one of the two strong promoters is unmethylated at both parental alleles, and DNase I hypersensitive sites in and around the strong promoters are consistently present on both parental chromosomes. In agreement with the chromatin state, primary transcripts from the maternal Igf2 allele have been detected at low but significant levels. These findings differ from observations in other instances of imprinting, namely, X-chromosome inactivation and transgene imprinting in mice. Although no parent-specific differences were detected in either DNA methylation or sensitivity to nucleases at these promoters, we have observed parental methylation differences in a region several kilobases upstream of the first exon. The differential activity of the parental Igf2 alleles could be achieved through epigenetic modifications situated outside the promoters or by subtle and yet unidentified modifications at the promoters.

Alleles↗
PubMed1989

Coordinate expression of insulin-like growth factor II and its receptor during muscle differentiation.

The role of polypeptide growth factors in promoting muscle differentiation is uncharacterized. We have used a fusing skeletal muscle cell line, C2, to examine the endogenous expression of one peptide, insulin-like growth factor II (IGF-II), and its receptor during differentiation. The synthesis of IGF-II is low during proliferation of myoblasts; IGF-II mRNA can be detected only through use of a highly sensitive solution-hybridization assay. Competition binding studies reveal that the IGF-II receptor is similarly nonabundant in myoblasts. During differentiation IGF-II mRNA rises rapidly. A nearly 4-fold increase is seen within 16 hr of onset of the differentiation process, and levels are 25 times higher than those in myoblasts by 96 hr, when myotubes have formed and muscle-specific alpha-actin mRNAs are synthesized. IGF-II accumulates in conditioned culture medium with similar kinetics. The expression of IGF-II receptors on the cell surface increases almost 6-fold 24 hr after the onset of differentiation and remains high. These studies suggest that IGF-II and its receptor are coordinately regulated during myogenic differentiation in C2 cells and that IGF-II may be an autocrine factor for skeletal muscle.

Amino Acid Sequence↗
PubMed2004

[Pregnancy-associated venous thrombosis in women with hereditary heterozygous factor V Leiden and/or factor II gene mutations].

The risk of venous thromboembolism (VTE) in pregnant women with heterozygous factor V Leiden and/or heterozygous factor II 20210A gene mutations is poorly documented, and the need for prophylaxis is therefore controversial. We retrospectively studied 208 women with hereditary thrombophilia (heterozygous FV Leiden and/or factor II gene mutations), who had a total of 406 full-term pregnancies, including 10 with thromboprophylaxis. The ante- and post-partum incidence of VTE was significantly higher in women with both mutations (17.8 %) than in women with FII gene mutation alone (6.2%) p = 0.003. In contrast, there was no significant difference between women with FV+FII mutation and those with FV mutations alone (10%). Thus, the two most common hereditary risk factors for thrombophilia seem to have an additive rather than a synergistic effect on the antepartum/post-partum risk of VTE. In contrast, a previous history of VTE before pregnancy in women with both the FV and the FII gene mutations was associated with a very high risk of VTE (50%). The incidence of VTE was higher during the post-partum period than the ante-partum period. There was no significant difference in the incidence of fetal loss in the three groups, but this was not a primary endpoint. These results, obtained in a single center, have implications for VTE prophylaxis. Routine use of LMWH is not indicated during pregnancy in asymptomatic women with a single mutation. In contrast, it is justified throughout pregnancy in women with both mutations and a history of venous thrombosis. Regarding asymptomatic women with both mutations, the need for prophylaxis during part or all of the pregnancy should be weighed up on an individual basis. In the post-partum period, there is a consensus on the use of LMWH for 6 weeks in women with single or dual mutations associated with thrombophilia.

Adolescent↗
PubMed1987

Purification and characterization of a unique high molecular weight form of insulin-like growth factor II.

A form of insulin-like growth factor II (IGF-II) with a mol wt of 15,000 has been purified to homogeneity from human Cohn fraction IV1-4. This protein has an amino-terminal sequence through the first 28 residues that is identical to 7.5K IGF-II. The amino acid composition of 15K IGF-II, however, indicates that its carboxyl-terminal region may be different from that predicted from the analysis of IGF-II cDNA clones. The affinities of 15K IGF-II for receptors on rat placental membranes and for an IGF-binding protein that was isolated from the medium of cultured buffalo rat liver cells were similar to those of the 7.5K form of the growth factor. A best-fit analysis of data from the binding of the two mol wt forms of IGF-II to receptors on rat placental membranes by the LIGAND program was consistent with a model in which 7.5K and 15K IGF-II bound to one site with Kd values of 0.27 +/- 0.03 and 0.38 +/- 0.04, respectively. There was an indication that 15K IGF-II also bound to a second low affinity site on the membrane. In mitogenesis assays performed on human fibroblasts isolated from the skin of two fetuses of an early gestational age, 15K IGF-II stimulated the incorporation of [3H]thymidine into DNA at a half-maximal concentration, i.e. ED50, of 5.7 and 5.0 nM. In these experiments, the ED50 values for 7.5K IGF-II were 8.7 and 15 nM.

Amino Acid Sequence↗
PubMed1985

Identification of a peptide fragment from the carboxyl-terminal extension region (E-domain) of rat proinsulin-like growth factor-II.

A fragment of the carboxyl-terminal extension region (E-peptide) of rat proinsulin-like growth factor-II has been purified from medium conditioned by cultured BRL-3A rat liver cells. The fragment, identified by microsequence analysis, was discovered in a biologically active fraction of insulin-like growth factor II (IGF-II). The fragment begins at position 117 in pro-IGF-II, two amino acids downstream from an Arg-Arg potential prohormone processing site. A synthetic analogue of the E-peptide at high concentrations stimulates [3H]thymidine incorporation in NIL8 hamster cells, raising the possibility that the E-peptide might bind with low affinity to a mitogen receptor. Peptides from the E-regions of pro-IGF-I and pro-IGF-II should be useful for development of radioimmunoassays for measurement of the somatic production of IGF-I and IGF-II, analogous to the radioimmunoassay for the insulin C-peptide.

Amino Acid Sequence↗
PubMed1993

Insulin-like growth factor II in follicular fluid of the patients with in vitro fertilization and embryo transfer.

OBJECTIVE: To investigate whether insulin-like growth factor II (IGF-II) is present in follicular fluids (FF) and whether IGF-II in FF plays an important role on human ovarian function. DESIGN, SETTING, PATIENTS: Insulin-like growth factor II concentrations were measured using an RIA technique in 46 samples of human FF obtained from 20 patients who were undergoing IVF and ET. The distribution profiles of unsaturated IGF-II binding protein were also investigated. Moreover, the effect of IGF-II on steroidogenesis by cultured granulosa cells (GCs) obtained simultaneously in the IVF-ET program was investigated. RESULTS: The IGF-II levels in FF (92.7 +/- 7.5 nmol/L) were approximately eight times greater than those of IGF-I (11.4 +/- 1.0 nmol/L), and significant positive correlations were observed between these IGFs in FF. By Sephadex G-150 gel-chromatography of FF, two apparent peaks of unsaturated IGF-II binding protein could be detected in the high molecular weight (MW) (150 kd) and low MW (approximately 36 to 38 kd) regions. Additionally, IGF-II dose dependently increased the release of P and E2 from the cultured human GCs. CONCLUSIONS: These findings suggest that the large quantity of IGF-II in FF may play possibly some roles in the ovarian steroidogenesis.

Adult↗
PubMed2000

Soluble insulin-like growth factor II/mannose 6-phosphate receptor inhibits DNA synthesis in insulin-like growth factor II sensitive cells.

The soluble form of the insulin-like growth factor II (IGF-II)/mannose 6-P (IGF-II/M6P) receptor is released by cells in culture and circulates in the serum. It retains its ability to bind IGF-II and blocks IGF-II-stimulated DNA synthesis in isolated rat hepatocytes. Because these cells are not normally stimulated to divide by IGF-II in vivo, the effect of soluble IGF-II/M6P receptor on DNA synthesis has been further investigated in two cell lines sensitive to IGF-II; mouse 3T3(A31) fibroblasts, stimulated by low levels of IGF-II following priming by epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) and Buffalo rat liver (BRL) cells, which secrete IGF-II and proliferate in the absence of exogenous growth factors. Soluble IGF-II/M6P receptor (0.2-2.0 microgram/ml) purified from a rat hepatoma cell line inhibited DNA synthesis (determined by dThd incorporation) in both cell lines. Basal DNA synthesis was very low in serum-free 3T3 cells, but high in serum-free BRL cells, possibly as a result of autocrine IGF-II production. The inhibitory effect was reversible in cells preincubated with soluble receptor prior to incubation with growth factors and could also be overcome by excess IGF-II. Soluble receptor was more potent in IGF-II-stimulated 3T3 cells and serum-free BRL cells than in BRL cells incubated with serum. Mean inhibition by four preparations of soluble receptor (1 microgram/ml) was 34.7% +/- 4.4% in BRL cells stimulated with fetal calf serum (FCS) (5%) compared to 54.8% +/- 4.2% in serum-free BRL cells (P = 0.05) and 60.6% +/- 6.5% (P = 0.02) in 3T3 cells stimulated by PDGF, EGF, and IGF-II. Soluble receptor had no effect on DNA synthesis in 3T3 cells stimulated with IGF-I. These results demonstrate that soluble receptor, at physiological concentrations, can block proliferation of cells by IGF-II and could therefore play a role in blocking tumor growth mediated by IGF-II.

Animals↗
PubMed1998

An insulin-like growth factor II (IGF-II) affinity-enhancing domain localized within extracytoplasmic repeat 13 of the IGF-II/mannose 6-phosphate receptor.

Insulin-like growth factor II (IGF-II) and phosphomannosylated glycoproteins bind to distinct sites on the same receptor, the IGF-II/mannose 6-phosphate receptor (IGF2R). Analysis of truncated receptors (minireceptors) has been used to map the IGF-II binding site within the receptor's extracytoplasmic domain, which consists of 15 homologous repeats. A minireceptor consisting of repeat 11 contained the minimal elements for binding IGF-II, but with 5- to 10-fold lower relative binding affinity than the full-length receptor. We hypothesized that the complete, high-affinity IGF-II binding site is formed by interaction between the primary site in repeat 11 and a putative affinity-enhancing domain. To determine the minimum portion of the IGF2R's extracytoplasmic domain needed for expression of high-affinity IGF-II binding, a nested set of FLAG epitope-tagged minireceptors encompassing repeats 11 through 15 was prepared and transiently expressed in 293T cells. Minireceptors containing repeats 11-13 or 11-15 exhibited high affinity, comparable to the full-length receptor (IC50 = 1-2 nM), whereas constructs containing repeat 11 only or repeats 11-12 did not (IC50 = 10-20 nM). These data suggested that the affinity-enhancing domain is located within repeat 13, which contains a unique 43-residue insert that has approximately 50% sequence identity to the type II repeat of fibronectin. Although a repeat 13 minireceptor did not bind IGF-II on its own, an 11-13 minireceptor containing a deletion of the 43-residue insert exhibited low IGF-II binding affinity (IC50 = 10-20 nM). Expression of mutant receptors from a full-length IGF2R construct bearing a deletion of the 43-residue insert was very low relative to wild type. Depletion assays using IGF-II-Sepharose showed that the mutant receptor had lower affinity for IGF-II than the wild-type receptor. This study reveals that two independent receptor domains are involved in the formation of a high-affinity binding site for IGF-II, and that a complete repeat 13 is required for high-affinity IGF-II binding.

Binding Sites↗
PubMed1994

Characterization of the linked ovine insulin and insulin-like growth factor-II genes.

The ovine insulin-like growth factor-II (oIGF-II) gene is comprised of 9 exons that span approximately 25 kb. Approximately 750 nucleotides upstream of oIGF-II exon 1 are the three exons of the ovine insulin gene that are transcribed in the same direction as oIGF-II. The genomic organization and expression of the oIGF-II gene is similar to that of the human IGF-II gene. Four putative promoters direct the transcription of six 5' noncoding exons (1, 3, 4, 5, 6, and 7), which are alternatively spliced to the shared exons 8, 9, and 10. An ovine exon comparable to human exon 2 has not been identified. Multiple transcription initiation sites were identified for exons 1 and 6 by primer extension analysis. Using a reverse transcriptase polymerase chain reaction (RT-PCR) assay, exon 1 and 3 transcripts were shown to be expressed in adult but not fetal liver. In addition, a novel transcript, which contained exon 1 spliced directly to exon 8, was detected in adult liver. Exon 4 transcripts were not detected in either fetal or adult liver, whereas exon 6 and 7 transcripts were detected in both fetal and adult liver. Exon 5 transcripts were also expressed in both fetal and adult liver, which is in contrast to the tumor cell-specific expression of human exon 5. Like the human and rodent genes, the regulation of expression of the oIGF-II gene is under complex control.

Alternative Splicing↗
PubMed1988

Structure of the receptor for insulin-like growth factor II: the puzzle amplified.

The insulin-like growth factor II (IGF-II) is a polypeptide hormone with structural homologies to insulin and insulin-like growth factor I (IGF-I). In contrast to these other hormones, the in vivo function of IGF-II is not known. Although IGF-II can stimulate a broad range of biological responses in isolated cells, these responses have usually been found to be mediated by the insulin and IGF-I receptors. Recently, the receptor for IGF-II was found to also be the receptor for mannose-6-phosphate. Since this latter receptor has been implicated in targeting of lysosomal enzymes, the question is now raised of whether the same protein can also mediate metabolic responses to IGF-II.

Animals↗
PubMed1995

Does the overexpression of pro-insulin-like growth factor-II in transfected human embryonic kidney fibroblasts increase the secretion of lysosomal enzymes?

Insulin-like growth factor-II (IGF-II) and lysosomal enzymes bearing the mannose 6-phosphate (Man6P) recognition marker, bind to two distinct binding sites of the IGF-II/M6P receptor. The two classes of ligands reciprocally modulate the binding of the other class of ligand to the receptor [Kiess, W., Thomas, C. L., Greenstein, L., Lee, L., Sklar, M. M., Rechler, M. M., Sahagian, G. G. & Nissley, S. P. (1989) J. Biol. Chem. 264, 4710-4714]. We asked whether or not overexpression of pro-IGF-II by cells in culture leads to missorting of lysosomal enzymes. Human embryonal kidney fibroblasts were transfected with the full-length human IGF-II cDNA or a control cDNA. Solution hybridization/RNase protection experiments using a human IGF-II riboprobe showed that two transfectants expressed large quantities of IGF-II mRNA, whereas the non-transfected cells did not. The analysis of conditioned media revealed that these cells secrete approximately 0.15 micrograms and 1.0 micrograms immunoreactive IGF-II/ml and 22 x 10(6) cells and 24 x 10(6) cells within 24 hours. Immunoreactive IGF-II was shown by Western blotting to represent 17-kDa pro-IGF-II. The amount of the lysosomal enzyme, beta-hexosaminidase, was approximately twofold increased in the conditioned media from pro-IGF-II overexpressing cells compared with control media, as shown by Western-blot analysis and immunoprecipitation of media extracts of metabolically labeled cells. The synthesis rate of beta-hexosaminidase was not affected by pro-IGF-II overexpression. In addition, the basal amount of another newly synthesized lysosomal enzyme, the cathepsin D precursor, was also twofold higher in pro-IGF-II overexpressing cells than in control cells. In contrast, the surface binding and cellular uptake rate of a Man6P-containing neoglycoprotein did not differ between the cell lines. The results indicate that the overexpression of pro-IGF-II doubles the secretion and/or reduces the re-uptake of beta-hexosaminidase and cathepsin D to approximately 20% of the total synthesized enzymes in human embryonal kidney fibroblasts compared to control cells. We hypothesize that, in cells synthesizing high amounts of pro-IGF-II, the growth factor may modulate the targeting of a portion of lysosomal enzymes, mainly by partially enhancing the secretion of newly synthesized enzymes and, in addition, possibly by affecting the re-uptake mechanism.

Cathepsin D↗