Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.14.11.2 (prolyl hydroxylase)
 1,814 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Embryonic-chick tendon poly(A)-containing RNA was translated in the wheat-germ and mRNA-dependent rabbit reticulocyte-lysate systems. The ability of each system to synthesize polypeptides similar to pro-alpha chains of collagen was tested on the bases of electrophoretic mobility and susceptibility to highly purified bacterial collagenase. Very small amounts of polypeptides in the size range of pro-alpha chains were synthesized in the wheat-germ system, whereas efficient synthesis of two polypeptides similar to pro-alpha1 and pro-alpha2 chains was achieved in the reticulocyte lysate. The collagenous nature of the major high-molecular-weight products synthesized was demonstrated by their susceptibility to collagenase and ability to act as a substrate for purified collagen proline hydroxylase. Determinations of the relative amounts of these translation products suggest that the 2:1 ratio of pro-alpha1 and pro-alpha2 chains found in type I procollagen is reflected in proportional amounts of translatable mRNA for pro-alpha1 and pro-alpha2 chains. Comparisons of the electrophoretic mobilities of hydroxylated and unhydroxylated reticulocyte-lysate translation products were made with appropriate standards of hydroxylated and unhydroxylated procollagen polypeptides. The results suggest that, in common with a number of secreted proteins, procollagen is synthesized as pre-pro molecules consistent with the ;Signal Hypothesis'.
 ...
PMID:Translation of embryonic-chick tendon procollagen messenger ribonucleic acid in two cell-free protein-synthesizing systems. 22 70

Fibroblasts isolated by enzymic digestion of chick embryo tendons have previously been used to examine the kinetics for the secretion of procollagen (Kao, W. W.-Y., Berg, R. A., and Prockop, D. J. (1977) J. Biol. Chem. 252, 8391-8397). The results indicated that the kinetics approximated the sum of two first order processes with half-times of 14 and 115 min. Here, the same fibroblasts were incubated in the presence of 1.53 mM cis-4-hydroxyproline, an analogue of proline, or in the presence of 0.3 mM alpha,alpha'-dipyridyl, an inhibitor of prolyl hydroxylase, so that the cells synthesized procollagen which could not assume a triple helical conformation characteristic of procollagen. Measurements of the secretion of nonhelical procollagen indicated that the kinetics for secretion differed from the kinetics for the secretion of procollagen and approximated a single first order process with a half-time of approximately 130 min. The nonhelical procollagen synthesized and secreted in the presence of either cis-4-hydroxyproline or alpha,alpha'-dipyridyl consisted of disulfide-bonded pro gamma chains of type I procollagen. The results suggested that the intracellular nonhelical procollagen was present in a single metabolic pool and secretion from this pool occurred with a different rate-limiting step than for helical procollagen. Further results indicated that nonhelical procollagen had a high affinity for prolyl hydroxylase and the affinity for the enzyme was greatly reduced if the procollagen was allowed to assume the triple helical conformation characteristic of normal procollagen. The results are consistent with the hypothesis that the secretion of procollagen is influenced by its conformation-dependent interaction with prolyl hydroxylase or other post-translational enzymes.
 ...
PMID:Kinetics for the secretion of nonhelical procollagen by freshly isolated tendon cells. 57 Sep 70

Iron chelation has been shown previously to decrease collagen synthesis at a posttranslational level by inhibiting prolyl 4-hydroxylase, one of the key enzymes in collagen metabolism. On the other hand, recent in vivo studies of iron overload in rats suggest that iron could specifically activate collagen gene expression in liver tissues. These findings led us to investigate whether iron chelation might also affect collagen gene expression and posttranslational modification. Our data indicate that alpha,alpha'-dipyridyl, an iron chelator, at a concentration of 1 mmol/L, decreased steady-state levels of type I procollagen messenger RNA by 42% (p less than 0.001) without affecting beta-actin messenger RNA levels. Nuclear runoff studies demonstrated that transcription of the type I procollagen gene was unchanged by alpha,alpha'-dipyridyl. However, the turnover rate of type I procollagen messenger RNA was increased by 30%. This pretranslational inhibition of collagen synthesis was not due to decreased lipid peroxidation, because thiobarbituric acid-reactive substances were unchanged by alpha,alpha'-dipyridyl. However, cycloheximide totally abolished the effect, indicating that de novo protein synthesis was required.
 ...
PMID:Evidence that an iron chelator regulates collagen synthesis by decreasing the stability of procollagen mRNA. 173 31

The biochemical and morphological consequences of procollagen prolyl 4-hydroxylase inhibition by pyridine-2,4-dicarboxylic acid (2,4-PDCA) and its diethyl ester (diethyl-2,4-PDC) were studied in chick-embryo calvaria, which predominantly synthesize type I collagen. Half-maximal inhibition of tissue hydroxyproline formation required 650 microM-2,4-PDCA, whereas the Ki with respect to chicken prolyl 4-hydroxylase in vitro was 2 microM. In contrast, half-maximal inhibition was caused by 10 microM-diethyl-2,4-PDC in the intact calvaria, although chicken prolyl 4-hydroxylase in vitro was not inhibited even at 1 mM. The collagenous material produced in the presence of diethyl-2,4-PDC showed an altered 'melting' profile and a lowering of the transition temperature by 10 degrees C, indicating misalignment and thermal instability of its triple-helical structure. Amount and electrophoretic mobility of procollagen type I chains were increased in a dose-dependent manner. The amounts of partially processed species and alpha-chains were decreased, without change in mobility. This marked effect on procollagen-collagen conversion in the intact calvaria suggests that the underhydroxylated collagenous material generated in the presence of diethyl-2,4-PDC is resistant to or acts as endogenous secondary inhibitor of type I procollagen N-proteinase. Electron microscopy of treated calvaria cells showed dilated rough endoplasmic reticulum and numerous phagolysosomes, indicating intracellular retention and lysosomal degradation of the newly synthesized underhydroxylated collagenous material. In summary, these results identify 2,4-PDCA and diethyl-2,4-PDC as the first prolyl 4-hydroxylase-directed inhibitor/proinhibitor pair that affects intra- and extra-cellular events during collagen formation.
 ...
PMID:Inhibition of prolyl hydroxylation and procollagen processing in chick-embryo calvaria by a derivative of pyridine-2,4-dicarboxylate. Characterization of the diethyl ester as a proinhibitor. 185 Sep 89

Dimethylnitrosamine-induced liver damage, which leads to hepatic failure and death of the animal, was prevented by treatment with malotilate. The accumulation of collagen and the morphologic changes caused by dimethylnitrosamine, such as inflammatory cell accumulation and fibrosis, were also prevented by this drug. Malotilate drastically reduced the increases in the amount of type I procollagen alpha 2-chain mRNA and activities of the enzymes prolyl 4-hydroxylase and galactosylhydroxylysyl glucosyltransferase, which are early events in liver fibrosis preceding the deposition of collagen. Even when started 14 days after dimethylnitrosamine induction, malotilate treatment was able to reduce liver damage. We suggest that the effect of malotilate is a result of the inhibition of inflammation.
 ...
PMID:Preventive effect of malotilate on dimethylnitrosamine-induced liver fibrosis in the rat. 291 82

Recent clinical observations have suggested that retinoids, which are in frequent use in dermatology, can affect the connective tissue metabolism in skin and other tissues. In this study, we examined the effects of several retinoids on the metabolism of collagen by human skin fibroblasts in culture. Incubation of cultured fibroblasts with all-trans-retinoic acid or 13-cis-retinoic acid, in 10(-5) M or higher concentrations, markedly reduced the procollagen production, as measured by synthesis of radioactive hydroxyproline. The effect was selective in that little, if any, inhibition was noted in the incorporation of [3H]leucine into the noncollagenous proteins, when the cells were incubated with the retinoids in 10(-5) M concentration. Similar reduction in procollagen production was noted with retinol and retinal, whereas an aromatic analogue of retinoic acid ethyl ester (RO-10-9359) resulted in a slight increase in procollagen production in these cultures. The reduction in procollagen production by all-trans-retinoic acid was accompanied by a similar reduction in pro alpha 2(I) of type I procollagen specific messenger RNA (mRNA), as detected by dot blot and Northern blot hybridizations. Hybridizations with human fibronectin and beta-actin specific DNA probes indicated that the levels of the corresponding mRNAs were not affected by the retinoids, further suggesting selectivity in the inhibition of procollagen gene expression. Further control experiments indicated that all-trans-retinoic acid, under the culture conditions employed, did not affect the posttranslational hydroxylation of prolyl residues, the mannosylation of newly synthesized procollagen, the specific radioactivity of the intracellular prolyltransfer RNA pool, or DNA replication. All-trans-retinoic acid also elicited a reduction in trypsin-activatable collagenase, but not in the activity of prolyl hydroxylase or an elastaselike neutral protease in the fibroblast cultures. Incubation of three fibroblast lines established from human keloids with all-trans-retinoic acid or 13-cis-retinoic acid also resulted in a marked reduction in procollagen production. The results, therefore, suggest that further development of retinoids might provide a novel means of modulating collagen gene expression in patients with various diseases affecting the connective tissues.
 ...
PMID:Modulation of procollagen gene expression by retinoids. Inhibition of collagen production by retinoic acid accompanied by reduced type I procollagen messenger ribonucleic acid levels in human skin fibroblast cultures. 298 6

Keloids are histologically characterized by an abundance of the extracellular matrix of connective tissue. In the present study, we examined the connective tissue composition of keloids, and analyzed the details of collagen metabolism utilizing fibroblast cultures established from keloid tissue. Quantitative connective tissue analyses indicated that collagen was the predominant extracellular matrix component in keloids. The ratio of genetically distinct collagens type I/III was significantly increased, as compared to normal human skin. Collagen biosynthesis was measured in fibroblast cultures by the formation of radioactive hydroxyproline: 5 of 9 keloid cell cultures studied demonstrated increased procollagen production in comparison to age-, sex-, and passage-matched control skin fibroblast lines, while the remaining 4 cell lines were within the control range. Keloid fibroblast cultures which were high collagen producers also demonstrated elevated prolyl hydroxylase activity. The mechanisms of increased procollagen production in fibroblast cultures were first examined by assaying the abundance of type I procollagen-specific mRNA utilizing dot blot hybridizations with a pro alpha 2(I)-chain-specific cDNA. The type I procollagen mRNA levels were significantly increased in 4 keloid fibroblast lines, and a good correlation between the mRNA levels and the rate of procollagen production in the same cultures was noted. These observations suggest regulation of the collagen gene expression on the transcriptional level. The catabolic pathway of collagen metabolism in fibroblast cultures was examined by determining the degradation of newly synthesized procollagen polypeptides through assay of radioactive hydroxyproline in small-molecular-weight peptide fragments. In 3 keloid cell cultures, the degradation of newly synthesized collagen polypeptides was below the range of normal controls. These findings suggest that a reduced degradation of newly synthesized polypeptides might contribute to the accumulation of procollagen in some keloid fibroblast cultures. The results of this study suggest two possible mechanisms for deposition of collagen in keloid lesions in vivo: first, the growth of the lesions may result from a localized loss of control of the extracellular matrix production by fibroblasts; secondly, reduced degradation of the newly synthesized procollagen polypeptides may contribute to collagen deposition in some keloids.
 ...
PMID:Biochemical composition of the connective tissue in keloids and analysis of collagen metabolism in keloid fibroblast cultures. 399 89

Three possible mechanisms are considered to account for the variations of post-translational modifications in different collagen types. 1) The cells have different amounts of post-translational modifying enzymes, 2) the rate of prolylhydroxylation of different procollagen types is varied, and 3) the rate of chain association of pro-alpha chains of different collagen types is modulated. In an attempt to examine the three possibilities, we have determined the activities of prolyl hydroxylase and lysyl hydroxylase, and we have examined the kinetics of the secretion of procollagens and the kinetics of pro-gamma chain formation of different procollagen types in matrix-free cells isolated from tissues of 17-day-old chick embryos. Type II collagen synthesized by cartilage cells contains more hydroxylysine than type I collagen synthesized by tendon and cornea cells. It was found, however, that cartilage cells contain significantly less lysyl hydroxylase than tendon and cornea cells. In contrast, we found only a small difference in the amount of prolyl hydroxylase in tendon, cornea, and cartilage cells. The secretion of type I procollagen by tendon and cornea cells can be described by two first order processes. In contrast, the secretion of type II procollagen by cartilage cells, type IV procollagen by lens cells, and type V procollagen by cornea cells can be described by single first order processes. Examination of the formation of pro-gamma components of procollagen types I and II revealed that it occurs via intermediate dimers of two pro-alpha chains. The formation or pro-gamma(I) chains in tendon and cornea cells is about three times faster than the formation of pro-gamma(II) chains in cartilage cells. These results are consistent with the hypothesis that the rate of association of pro-alpha chains regulates the synthesis of procollagens with different degrees of post-translational modifications.
 ...
PMID:Mechanism for the regulation of post-translational modifications of procollagens synthesized by matrix-free cells from chick embryos. 630 52

We evaluated collagen synthetic activity, which plays an important role in wound healing, following experimental filtration surgery in rabbits. Collagen synthetic activity was measured by immunohistochemistry for prolyl 4-hydroxylase beta-subunit and type I procollagen. Trabeculectomy was performed on albino rabbit eyes, with the filtering site harvested on postoperative days 1, 4, 7, 14, and 28. Samples were fixed with 10% buffered formalin for 12 hours and prepared for paraffin section, and each antigen was detected in filtering site tissue using avidin-biotinylated peroxidase complex. Immunoreaction of prolyl 4-hydroxylase beta-subunit or type I procollagen increased from day 4 to 14 and markedly decreased at day 28. These findings show that prolyl 4-hydroxylase and type I procollagen are markedly produced almost simultaneously, and collagen synthetic activity following filtration surgery continues for over 14 days in the process of wound healing.
 ...
PMID:[Collagen synthetic activity following filtration surgery in rabbits]. 788 25

Doxorubicin is an antiproliferative agent, that also inhibits prolyl 4-hydroxylase in vitro. We evaluated the effects of doxorubicin and mitomycin C (MMC) on the proliferation of human Tenon's capsule fibroblasts and the secretion of type I collagen in these cells to explore the potential use of doxorubicin as an antifibrotic agent after glaucoma filtering surgery. Standard immunoassays were used to determine the concentrations of type I procollagen COOH-terminal peptide (PIP), laminin and vitronectin receptor in conditioned media and cell lysates in the presence or absence of doxorubicin or MMC. The mitotic activity and viability of these cells were also determined. Cellular ultrastructure was evaluated by transmission electron microscopy. Doxorubicin and MMC decreased the cellular viability, the mitotic activity, and the production of the peptides measured. The inhibition of PIP secretion into the culture medium was higher in doxorubicin-treated cultures than in MMC-treated cultures at the tested concentrations (5-100 microM). The decrease in PIP levels in cell lysates was less in doxorubicin-treated culture (25 microM) than in MMC-treated culture (25 microM), suggesting that procollagen synthesis and secretion might be attenuated by doxorubicin. Ultrastructural studies revealed increased numbers of lysosomes in the cytoplasm of doxorubicin-treated cells relative to MMC-treated cells. Doxorubicin and MMC reduced cell viability and inhibited the proliferation and synthesis of PIP, laminin, and vitronectin receptor peptide. Inhibitory effects of doxorubicin on PIP secretion were more potent than those of MMC. Doxorubicin may be useful for inhibiting the fibrotic response at the site of ocular filtering surgery.
 ...
PMID:In vitro effects of doxorubicin and mitomycin C on human Tenon's capsule fibroblasts. 915 35


1 2 Next >>