Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A strong mitogenic activity for fibroblastic cells has been found in serum-free medium of growth-arrested primary cultures of chicken embryo fibroblasts (CEF). This serum-free conditioned medium promoted growth of NIH/3T3 cells and primary as well as secondary cultures of CEF. The mitogenic activity was as potent as 5% serum. Half-maximum stimulation was obtained with 20% of the initial concentration of the conditioned medium. The activity eluted at high M(r) (1-2 x 10(5)) from a gel-filtration column under nondenaturing conditions and was trypsin insensitive and thiol insensitive. Treatment with acid or urea converted the mitogen to a low-molecular-mass form, which showed a delayed induction of DNA synthesis. Purification of this factor (10000-fold) to apparent homogeneity was achieved by preparative isoelectric focusing, gel filtration, reverse-phase HPLC and nonreducing SDS/PAGE. The factor, termed CEF-derived growth factor (CDGF) was a 32-kDa, disulfide-linked heterodimer of a 15-kDa and a 17-kDa subunit as judged by SDS/PAGE, with a pI of approximately 7 in 8 M urea. It exhibited partial stability towards heat treatment and was trypsin sensitive. CDGF was active only in its dimeric form and half-maximum stimulation of NIH/3T3 cells was obtained at approximately 10 pM. The mitogenic activity was not suppressible by an antibody neutralizing the activity of transforming growth factor beta 1, 2 and 3 (TGF-beta). The physico-chemical properties suggest that CDGF is not identical with one of the common growth factors like fibroblast growth factor, platelet-derived growth factor, epidermal growth factor, insulin-like growth factor, or TGF-beta but rather represents a novel type of growth factor.
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PMID:Isolation and characterization of a novel type of growth factor derived from serum-free conditioned medium of chicken embryo fibroblasts. 162 45

PC-3 human prostatic tumor sublines have been previously isolated which exhibit striking differences in their invasive and metastatic phenotypes. This work has been extended here to measure and compare the levels of kinesin, a microtubule-dependent translocator molecule, in the PC-3 sublines. Western blots, slot blots, radiolabeling, and immunoprecipitation analysis showed that kinesin was expressed in the highly invasive and metastatic sublines at levels which were elevated above the base-line levels observed in the parent PC-3 cells. In comparison, kinesin was not expressed in detectable amounts in the noninvasive cell lines. The conditioned medium of the metastatic PC-3 sublines contained a heat- and trypsin-sensitive protein which exhibited a dosage-dependent capacity to stimulate increased kinesin expression, type IV collagenase secretion, and invasion of Matrigel by the metastatic sublines. The noninvasive sublines failed to secrete a similar stimulatory factor(s) or respond to the conditioned medium of metastatic sublines. Various growth factors and cytokines tested (platelet-derived growth factor, epidermal growth factor, insulin-like growth factor, formylmethionineleucinephenylalanine) had no significant effect on either kinesin expression or protease secretion and invasion. Pertussis toxin blocked the stimulatory effects of the conditioned medium, but other agents known to interfere with adenylate cyclase pathways (i.e., cholera toxin, forskolin, 8-bromoadenosine) failed to block stimulation. The data show for the first time that kinesin, protease secretion, and the resulting invasion process may be regulated in a coordinated manner by an autocrine factor(s) which activates G-protein-dependent processes.
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PMID:Regulation of kinesin expression and type IV collagenase secretion in invasive human prostate PC-3 tumor sublines. 165 72

The ovarian granulosa cell has previously been shown to be a site of insulin-like growth factor (IGF) I production, reception, and action. It is the objective of this study to characterize in greater detail the soluble IGF binding activity released by this cell type. To this end, use was made of granulosa cells from immature diethylstilbestrol-treated rats. Serum-free media conditioned for 72 h by cultured untreated cells acquired polyethylene glycol (PEG)-precipitable [125I]IGF-I binding activity. The latter proved cell density-dependent, displaying a minimal inoculum requirement of less than or equal to 3 x 10(5) cells/culture. The daily elaboration of IGF-I binding activity appeared constant throughout the 72 h experimental period, the overall time-dependent accumulation of binding activity (over the same time period) proving virtually additive. Scatchard analysis of detailed competition studies with IGF-I suggests that the latter ligand binds to granulosa cell-derived IGF binding protein(s) (IGFBPs) with an apparent affinity of 3 x 10(-10) M. Qualitatively similar results were obtained when using [125I]IGF-II suggesting that the IGFBPs in question are not IGF-I-selective. In fact, specificity studies using either [125I]IGF-I or [125I]IGF-II revealed a rank order of competitive potencies compatible with that observed in other tissues so studied (IGF-II greater than IGF-I much greater than insulin). The proteinacious nature of the acid-stable IGF binding activity under study was indicated by its sensitivity to relatively low concentrations of cycloheximide, its apparent deactivation following repeated cycles of freezing and thawing, and its virtual elimination when subjected to boiling or trypsin treatment. Cycloheximide-induced blockade of protein biosynthesis also revealed that the IGF binding activity is subject to measurable turnover thereby suggesting that its accumulation represents the balance struck between synthetic and degradative processes. Western ligand blotting of sodium dodecyl sulfate-polyacrylamide gel electrophoresis-fractionated media revealed a non-glycosylated major band doublet of 28-29 kDa. A single minor IGFBP species represented by a 23 kDa band was also appreciated in some but not all experiments. Taken together, these findings document the ability of ovarian granulosa cells to secrete a heterogenous mix of low molecular weight, high-affinity IGF-selective binding species. As such, these observations are in keeping with the concept of a complete intraovarian IGF system replete with ligands, receptors, and soluble binding activity.
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PMID:Ovarian granulosa cell-derived insulin-like growth factor (IGF) binding proteins: release of low molecular weight, high-affinity IGF-selective species. 171 Jan 90

The insulin-like growth factor-II (IGF-II) and lysosomal enzymes containing a mannose-6-phosphate (M6P) recognition site bind to different sites of the same receptor molecule. We have observed that M6P increases the receptor-mediated uptake of IGF-II into IM-9 cells. We now confirm this phenomenon in a different line, the H-35 rat hepatoma cells, and present additional characterization of the underlying mechanisms. When incubated in the presence of radiolabeled IGF-II, H-35 cells accumulated, in a time-dependent fashion, radioactivity that was resistant to removal by trypsin digestion at 15 C, indicating that it was endocytosed. In the presence of 3 mM M6P, endocytosed counts were approximately 2-fold higher after 5 min of incubation, an enhancement that peaked at 10 min, then declined, but was still evident after 40 min (1.5-fold). The rate of release of cell-associated IGF-II, degraded or intact, as measured in a chase experiment, was not affected by M6P. These observations indicate that M6P increased accumulation of IGF-II by accelerating its rate of endocytosis rather than by interfering with IGF-II degradation or with the recycling of intact hormone-receptor complexes to the cell surface. Electrophoresis after affinity cross-linking of labeled cells demonstrated that the enhancement in radioactivity could be located at a molecular size of approximately 250 kDa, corresponding to IGF-II-receptor complexes. Preincubation with M6P did not significantly alter the specific binding of IGF-II to the cell surface of H-35 cells, as measured by a binding assay at 4 C. Finally, pretreatment with cycloheximide for up to 8 h, to remove all newly synthesized lysosomal enzymes bound to the M6P/IGF-II receptor, did not affect IGF-II endocytosis beyond what could be accounted for by some loss of receptor, suggesting that the observed effect of M6P is due to the binding of M6P itself to the receptor and not to displacement of lysosomal enzymes. We conclude that simultaneous occupancy of the M6P/IGF-II receptor by ligands on both binding sites enhances its rate of endocytosis.
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PMID:Effects of mannose-6-phosphate on receptor-mediated endocytosis of insulin-like growth factor-II. 216 4

Receptor-mediated endocytosis may represent an important mechanism whereby peptide hormones exert their biological effects. The ability of recombinant insulin-like growth factor (IGF)-I to be internalized by cultured cells was evaluated in BRL-3A2 cells, a rat liver-derived cell line which lacks insulin receptors. Since recombinant IGF-I does not bind to the Type II IGF receptor, all specific binding of 125I-IGF-I in BRL-3A2 cells represents binding to the Type I receptor. Exposure of BRL-3A2 cells to IGF-I resulted in a rapid 50% downregulation of Type I IGF receptors. Only one-half of these binding sites were sensitive to treatment with trypsin, a phenomenon which indicates that the peptide and its receptor were internalized after the cells were exposed to IGF-I. In conclusion, these experiments demonstrate that IGF-I can be internalized by cultured cells via the Type I IGF receptor, and suggest that IGF hormone action may be exerted by receptor-mediated endocytosis.
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PMID:Insulin-like growth factor-I is internalized after binding to the type I insulin-like growth factor receptor. 253 84

In primary cultures of rat preadipocytes (PA) isolated from epididymal or perirenal depots, rat serum is more effective than other animal sera (fetal calf, newborn calf, human, horse, rabbit, cat, sheep, goat, dog, pig) in promoting adipogenic conversion, biochemical differentiation, and mitogenesis. Only mouse serum is comparable to rat serum. This activity is attributable to a specific growth factor (preadipocyte stimulating factor, PSF). An assay for PSF in rat serum was devised using PA from perirenal fat of 3-month-old Fischer 344 rats grown first to confluence in FCS for 8 days and then for the next 3 days in test serum, followed by measurement of triglyceride (TG) and glycerol-3-phosphate dehydrogenase (GPDH). Rat serum induces dose-dependent rapid cell division, which coincides with accumulation of TG and increase of GPDH; for routine quantitation, TG is assayed. The biochemical characteristics of PSF in serum are as follows: stable at 4 degrees C for up to 1 year; inactivated at 100 degrees C (80% loss, 30 min) but stable at 56 degrees C for 1 hr; stable at pH 2-12; non-dialyzable; completely resistant to pepsin, trypsin, and chymotrypsin but destroyed by pronase and subtilisn; stable to DTT and periodate; and m.w. between 68 kDa (Sephacryl-300) and 58 kDa (Sephacryl-300 in 5 M urea). PSF activity is greater in serum from Wistar than from Fischer 344 rats, while activity of serum from Zucker obese (fa/fa) rats is at least as great as that from Wistar rats and, like serum of rats made obese by feeding a high-fat, high-carbohydrate diet, is not suppressed. PSF activity is not due to insulin, insulin-like growth factor-1 (IGF-1), growth hormone, glucocorticoids, or combinations of these hormones. PSF activity was not seen with a number of growth factors including colony-stimulating factor (CSF-1), GM-CSF, interleukins 1, 2, and 3, neuroleukin, tumor necrosis factor, and others. PSF is distinct from the low molecular weight (4-8 kDa) differentiation factor present in rat serum, FCS, and human serum that promotes the adipogenic conversion and cellular differentiation of 3T3-L1, 3T3-F442A, and Ob17 cells. PSF appears to be a new differentiation factor for rat preadipocytes, has properties suggestive of a highly glycosylated protein, and may be highly species specific.
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PMID:Preadipocyte stimulating factor in rat serum: evidence for a discrete 63 kDa protein that promotes cell differentiation of rat preadipocytes in primary cultures. 268 98

Type I insulin-like growth factor (IGF-I) stimulated high density lipoprotein (HDL)-promoted progesterone production by swine granulosa cells cultured under serum-free conditions in vitro. In the presence of pure human IGF-I (50 ng/ml), the half-maximally effective concentration of swine HDL was 16 micrograms/ml (67% confidence limits; 15-17 micrograms/ml) after 2 days of exposure to this growth factor, 5.4 (2.6-9.8) micrograms/ml after 4 days, and 3.8 (1.2-4.8) micrograms/ml after 6 days. Maximal progesterone production increased approximately 10-fold in the presence of IGF-I and HDL on day 2, 125-fold on day 4, and 330-fold on day 6. The facilitative action of IGF-I on HDL-supported progesterone biosynthesis was accompanied by time-dependent stimulatory effects of IGF-I on trypsin-releasable HDL, trypsin-resistant cell-associated HDL, and degraded HDL (P less than 0.01). Moreover, incubation of swine granulosa cells with [3H]cholesteryl oleate-labeled HDL demonstrated that IGF-I exerted a time-dependent stimulatory effect on [3H]free cholesterol and [3H]cholesteryl ester accumulation in granulosa cells, and significantly augmented the secretion of [3H]progesterone (separated by two-dimensional TLC). In addition to the ability of IGF-I to amplify the cellular acquisition of radiolabeled sterol, this growth factor also increased the total mass of cellular cholesteryl ester and total cellular cholesterol as measured by microfluorometric assay (P less than 0.01). We conclude that IGF-I facilitates the effective delivery of HDL-derived sterol substrate into the steroidogenic pool of ovarian cells. Such observations offer an additional role for the differentiative actions of this somatomedin in the expression of full steroidogenic potential by granulosa-luteal cells.
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PMID:Insulin-like growth factor type I (somatomedin-C) stimulates high density lipoprotein (HDL) metabolism and HDL-supported progesterone biosynthesis by swine granulosa cells in vitro. 272 57

The extracts from rat submandibular glands (SMGs) induced erythroid differentiation of K-562. The activity was non-dialysable and abolished by heat, trypsin or 2-mercaptoethanol. Follistatin, which neutralizes the erythroid differentiation factor (EDF), had no effects on this activity. Analysis by gel chromatography and polyacrylamide gel electrophoresis-isoelectric focussing showed that the characteristics of this substance were different from those of erythropoietin, TGF-beta 1, EDF, stem cell factor and insulin-like growth factor-1. These results suggest the presence of a novel substance in rat SMGs which induces erythroid differentiation of K-562.
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PMID:The extracts from rat submandibular glands induce the erythroid differentiation of K-562 cells. 759 52

Placental lactogen (PL) stimulates amino acid transport, DNA synthesis, and insulin-like growth factor production in isolated fetal fibroblasts and myoblasts. To clarify the mechanisms by which PL exerts its effects in fetal tissues, we have examined the binding and processing of PL and its receptor in cultured ovine fetal skin fibroblasts. Fetal sheep fibroblasts bound ovine PL (oPL) with high affinity (Kd, 0.2 nM) and ovine (o) GH (Kd, 1.6 nM) and oPRL (Kd, > 200 nM) with lower affinities, as recently reported. Maximal specific binding of oPL was noted after a 24-h incubation at 4 C. When fibroblasts were incubated with [125I]oPL at 4 C and then warmed to 37 C, the radiolabeled hormone was internalized within 2-4 min. Most of the internalized hormone, however, was recycled rapidly to the cell surface by 6-10 min and released intact by retroendocytosis into the incubation medium. Of the small amount of remaining internalized radioligand, approximately 50% appeared to be degraded, as assessed by solubility in trichloracetic acid. To directly examine the cellular processing of receptor proteins, we used the membrane-impermeant cross-linking reagent bis-(sulfosuccinimidyl)suberate (BS3) to detect oPL-binding sites confined to the cell surface. These studies detected a specific oPL-receptor complex with a mol wt of 130 kilodaltons, suggesting that the mol wt of the membrane receptor is 108 kilodaltons. At 37 C, oPL-receptor complexes were internalized rapidly, reducing cell surface binding activity to 25% of the initial values within 4 min. oPL receptor activity reappeared on the cell surface at 6 min, suggesting receptor recycling, but declined precipitously during the ensuing 30 min, reflecting receptor processing and turnover. After proteolysis of surface receptors with trypsin, binding activity was recovered fully during a 12- to 24-h incubation in serum-containing medium. Recovery of surface receptors was blocked by cyclohexamide (2 microM), suggesting that repopulation of receptors depends upon new protein synthesis. Specific binding of PL was 1.5- to 5-fold higher in cells preincubated in medium containing dexamethasone (0.1 microM), suggesting that glucocorticoids may regulate expression of the fetal PL receptor. These studies provide insight into the cellular mechanisms by which the fetus may regulate its sensitivity and response to PL.
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PMID:Placental lactogen-binding sites in isolated fetal fibroblasts: characterization, processing, and regulation. 838 82

Partial-thickness defects evolving in mature articular cartilage do not heal spontaneously. This type of defect was created in the articular cartilage of adult rabbits and Yucatan minipigs, and the effects of chondroitinase ABC or trypsin, fibrin clots, and mitogenic growth factors on the healing process were examined histologically at intervals ranging from one to forty-eight weeks. The effect of chondroitinase ABC or trypsin was examined initially. Articular cartilage contains macromolecules, including proteoglycans, which render the surfaces of this tissue, and of partial-thickness defects within it, antiadhesive. Chondroitinase ABC digests the glycosaminoglycan chains of cartilage proteoglycans, and trypsin degrades their core proteins. To test the hypothesis that mesenchymal cells may be prevented from adhering to and migrating over the surfaces of partial-thickness defects by proteoglycans, we removed a superficial layer of these macromolecules from the surface of the defect with use of one of these enzymes. The treatment evoked an increase in the coverage of the defect surface with mesenchymal cells; when combined with the local application of a mitogenic growth factor (basic fibroblast growth factor, transforming growth factor-beta 1, epidermal growth factor, insulin-like growth factor-1, or growth hormone), the coverage was more extensive but mesenchymal cells did not extend into and completely fill the volume of the defect. When the surface of the defect was treated with chondroitinase ABC and the cavity of the defect was filled with a fibrin clot to furnish a matrix or scaffolding for the migration of cells therein, there was migration and proliferation of cells throughout the volume of the defect but at a low population density. Mesenchymal cells remodeled the deposited fibrin matrix, which was replaced by a loose fibrous connective tissue. When defects that had been treated with chondroitinase ABC were filled with a fibrin clot containing a mitogenic growth factor, mesenchymal cells filled the entire cavity of the defect, and the density of the cells was greatly increased, particularly when transforming growth factor-beta 1 was used. Histological studies revealed a continuous layer of mesenchymal cells extending from the synovial membrane across the superficial tangential zone of normal articular cartilage into the defect, indicating that the cells that were recruited for the repair process were of synovial origin. At forty-eight weeks, the entire cavity of the defect remained filled with a fibrous connective tissue.
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PMID:Repair of partial-thickness defects in articular cartilage: cell recruitment from the synovial membrane. 864 29


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