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PubMed1979

Translation of embryonic-chick tendon procollagen messenger ribonucleic acid in two cell-free protein-synthesizing systems.

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'.

Animals↗
PubMed1976

[The action of calcium on the step of collagen metabolism, catalyzed by procollagen-proline hydroxylase].

Calcium effects on procollagen-proline-hydroxylase activity of chick embryo tibias was studied. Serial preincubation of the natural substrate, the enzymatic preparation or the mixture of both with and without calcium showed that calcium decreased procollagen-prolin-hydroxylase affinity for procollagen, decreased the maximum velocity of the reaction by binding to the substrate and by increasing the thermosensitivity of the enzyme -- substrate complex. Calcium could also increase the maximum velocity by dissociation of an enzyme -- inhibitor ligand complex. The resulting decrease of the overall reaction rate has been discussed in the context of the relationship between collagen metabolism and calcium fixation during calcification.

Animals↗
PubMed1979

Structure of antigenic determinants in the N-terminal region of dermatosparactic sheep procollagen type I.

About half of the rabbit antisera raised against type-I procollagen, p alpha 1(I) chain or nonreduced procollagen peptides reacted in a radioimmunoassay with the reduced form of peptide Col 1, which comprises the whole non-collagenous region at the N-terminus of procollagen. Proteolytic fragments prepared from reduced peptide Col 1 were still effective inhibitors of the antibodies and allowed the localization of two antigenic determinants. The antigenically active regions have the sequences less than Glu-Glu-Glu-Gly-Gln-Gln-Glu and Gly-Asp-Thr-Gly-Pro-Arg, and are located at the N- and C-termini of the peptide respectively. Antibodies raised against reduced peptide Col 1 bind to a determinant localized in a different region of the peptide.

Amino Acid Sequence↗
PubMed1977

Hexamethylene bisacetamide induces morphologic changes and increased synthesis of procollagen in cell line from glioblastoma multiforme.

Addition to hexamethylene bisacetamide (diacetyldiaminohexane) to cultures of a malignant mesenchymal cell line derived from a human glioblastoma multiforme induces morphological changes and stimulates the synthesis of procollagen. The morphological changes include cell elongation, an increase of extracellular material with staining properties of collagen by light microscopy, and an increase in extracellular 220-A fibrils by electron microscopy. The rate of procollagen synthesis increased as much as 20-fold, and the ratio of type I:type III procollagen changed, with type I becoming the predominant form. The change in type I:type III ratio is similar to that seen in the maturation of normal fetal to adult connective tissue.

Acetamides↗
PubMed1979

Procollagen segment-long-spacing crystallites: their role in collagen fibrillogenesis.

Naturally occurring segment-long-spacing crystallites of procollagen collagen have been found in the culture medium of fibroblasts from chick embryo tendon, human skin, and dermatosparaxic calf skin; in whole-mount preparations of cultured human skin fibroblasts; in homogenates of lathyritic chick embryo tendon, cartilage, and cornea; and in a partially purified preparation of procollagen. Bundles of similar aggregates occurred within secretory vacuoles of collagen-synthesizing fibroblasts and chondrocytes. These observations suggest that fibroblasts and chondrocytes secrete procollagen assemblies that are stable in the extracellular environment. We propose that subsequent enzymatic processing is accompanied by direct incorporation of such structures into the assembling fibril, which then may be considered as an n X 67 nm staggered array of segment-long-spacing crystallites.

Animals↗
PubMed1977

Intermediates in the conversion of procollagen to collagen. Evidence for stepwise limited proteolysis of the COOH-terminal peptide extensions.

Intermediates in the conversion of procollagen to collagen were isolated from radioactively labeled chick cranial bones by ion-exchange chromatography. Cleavage of these proteins with vertebrate collagenase revealed that each of the several forms of these intermediates lacked NH2-terminal but retained COOH-terminal extensions. The chain composition of each intermediate was resolved by two-dimensional slab gel electrophoresis. The intermediates differed from each other in having sustained cleavages in zero, one or two pcalpha chains. The relative proportions of intermediates with different intact pcalpha chains, observed in conversion of procollagen, have enabled us to construct a detailed model of the stepwise limited proteolysis of procollagen.

Amino Acids↗
PubMed1978

Translation of chick calvarial procollagen messenger RNA'S by a messenger RNA dependent reticulocyte lysate.

A method was developed for the extraction of RNA from chick embryo calvaria which should be generally applicable to other connective tissues. Total RNA prepared by this method was translated by a mRNA-dependent reticulocyte lysate into discrete pro alpha chains. Several criteria were used to identify these translation products, including (1) preferential labeling with [3H]proline, (2) appropriate migration on sodium dodecyl sulfate-polyacrylamide gels, (3) selective sensitivity to collagenase digestion, and (4) specific precipitability by two different antisera against procollagen. Data from the immunoprecipitation experiments indicated that the majority of the pro alpha chains contained the carboxy-terminal antigenic determinants. These results demonstrate that this translation system can be used as an assay for intact procollagen mRNAs and as a source of in vitro synthesized pro alpha chains for future structural analysis.

Animals↗
PubMed1979

Procollagen processing. Limited proteolysis of COOH-terminal extension peptides by a cathepsin-like protease secreted by tendon fibroblasts.

An enzymatic activity, capable of removing the COOH-terminal extensions of type I chick procollagen, has been demonstrated in embryonic chick tendons and in cultured tendon fibroblasts utilizing two new methods of analysis. The protease was purified by a combination of ultrafiltration concanavalin A affinity chromatography and gel filtration. The isolated protein has an apparent Mr of 43,000 by gel filtration and sodium dodecyl sulfate gel electrophoresis. The enzyme shows a major pH optimum at 4.2 and is susceptible to inhibitors such as pepstatin and leupeptin; it therefore seems related to the cathepsins. The possibility that this enzyme plays a role in the limited proteolytic processing of procollagen is discussed.

Animals↗
PubMed1978

Chinese hamster lung cell polysomes direct the synthesis of a single molecular weight species of procollagen alpha chains.

Polysomes prepared from cultured Chinese hamster lung cells direct the synthesis of procollagen alpha chains in an heterologous cell-free system containing the postribosomal supernatant fraction prepared from wheat germ. Total protein synthesis requires both subcellular components and an exogenous energy source, and is inhibited by the antibiotics puromycin and aurin tricarboxylic acid. The ratio of collagenase-digestible to nondigestible material produced depends upon the wheat germ and not the polysome level in the reaction. Under optimal conditions, a significant fraction of the total product migrates on denaturing sodium dodecyl sulfate-polyacrylamide gels as a single molecular weight collagenase-digestible species corresponding in size to the procollagen alpha chain (Mr approximately equal to 170,000). Approximately one-third of this high molecular weight material represents products whose synthesis results from cell-free mRNA initiation, and no distinct product larger than the 170,000-dalton material is observed. These studies confirm the initial observation that collagen represents one of the major gene products of Chinese hamster lung cells and demonstrate the usefulness of this cell line for the study of mammalian collagen biosynthesis.

Animals↗
PubMed1979

Beta-turns in nascent procollagen are sites of posttranslational enzymatic hydroxylation of proline.

The selective hydroxylation of proline residues in nascent procollagen chains by prolyl hydroxylase (EC 1.14.11.2) can be understood in terms of the conformational feature of the -Pro-Gly-segments in linear peptides and globular proteins. The folded beta-turn conformation in such segments appears to be the conformational requirement for proline hydroxylation. The available data on the hydroxylation of native and synthetic substrates of prolyl hydroxylase are explained on the basis of the extent of beta-turn formation in them. Taken in conjunction with the conformational features of the hydroxyproline residue, our results bring out the conformational reason for the posttranslational proline hydroxylation which, it is proposed, leads to the "straightening" of the beta-turn segments into the linear triple-helical conformation.

Hydroxyproline↗
PubMed2025

Pitavastatin, Procollagen Pathways, and Plaque Stabilization in Patients With HIV: A Secondary Analysis of the REPRIEVE Randomized Clinical Trial.

IMPORTANCE: In a mechanistic substudy of the Randomized Trial to Prevent Vascular Events in HIV (REPRIEVE) randomized clinical trial, pitavastatin reduced noncalcified plaque (NCP) volume, but specific protein and gene pathways contributing to changes in coronary plaque remain unknown. OBJECTIVE: To use targeted discovery proteomics and transcriptomics approaches to interrogate biological pathways beyond low-density lipoprotein cholesterol (LDL-C), relating statin outcomes to reduce NCP volume and promote plaque stabilization among people with HIV (PWH). DESIGN, SETTING, AND PARTICIPANTS: This was a post hoc analysis of the double-blind, placebo-controlled, REPRIEVE randomized clinical trial. Participants underwent coronary computed tomography angiography (CTA), plasma protein analysis, and transcriptomic analysis at baseline and 2-year follow-up. The trial enrolled PWH from April 2015 to February 2018 at 31 US research sites. PWH without known cardiovascular diseases taking antiretroviral therapy and with low to moderate 10-year cardiovascular risk were eligible. Data analyses were conducted from October 2023 to February 2024. INTERVENTION: Oral pitavastatin calcium, 4 mg per day. MAIN OUTCOMES AND MEASURES: Relative change in plasma proteomics, transcriptomics, and noncalcified plaque volume among those receiving treatment vs placebo. RESULTS: Among 558 individuals (mean [SD] age, 51 [6] years; 455 male [82%]) included in the proteomics assessment, 272 (48.7%) received pitavastatin and 286 (51.3%) received placebo. After adjusting for false discovery rates, pitavastatin increased abundance of procollagen C-endopeptidase enhancer 1 (PCOLCE), neuropilin 1 (NRP-1), major histocompatibility complex class I polypeptide-related sequence A (MIC-A) and B (MIC-B), and decreased abundance of tissue factor pathway inhibitor (TFPI), tumor necrosis factor ligand superfamily member 10 (TRAIL), angiopoietin-related protein 3 (ANGPTL3), and mannose-binding protein C (MBL2). Among these proteins, the association of pitavastatin with PCOLCE (a rate-limiting enzyme of collagen deposition) was greatest, with an effect size of 24.3% (95% CI, 18.0%-30.8%; P&#x2009;<&#x2009;.001). In a transcriptomic analysis, individual collagen genes and collagen gene sets showed increased expression. Among the 195 individuals with plaque at baseline (88 [45.1%] taking pitavastatin, 107 [54.9%] taking placebo), changes in NCP volume were most strongly associated with changes in PCOLCE (%change NCP volume/log2-fold change&#x2009;=&#x2009;-31.9%; 95% CI, -42.9% to -18.7%; P&#x2009;<&#x2009;.001), independent of changes in LDL-C level. Increases in PCOLCE related most strongly to change in the fibro-fatty (<130 Hounsfield units) component of NCP (%change fibro-fatty volume/log2-fold change&#x2009;=&#x2009;-38.5%; 95% CI, -58.1% to -9.7%; P&#x2009;=&#x2009;.01) with a directionally opposite, although nonsignificant, increase in calcified plaque (%change calcified volume/log2-fold change&#x2009;=&#x2009;34.4%; 95% CI, -7.9% to 96.2%; P&#x2009;=&#x2009;.12). CONCLUSIONS AND RELEVANCE: Results of this secondary analysis of the REPRIEVE randomized clinical trial suggest that PCOLCE may be associated with the atherosclerotic plaque stabilization effects of statins by promoting collagen deposition in the extracellular matrix transforming vulnerable plaque phenotypes to more stable coronary lesions. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02344290.

Humans↗
PubMed1976

[Research on subcellular localization of procollagen proline hydroxylase from chick embryo liver (author's transl)].

Subcellular fractionation by differential centrifugation was used to study protocollagen proline hydroxylase (EC 1.14.11.2) localization from chick embryo liver. The fractions have been characterized by marker enzymes and electron microscopy. By these methods, it was observed that procollagen-proline-hydroxylase is concentrated in the microsomal fraction which is sedimented at 145 000 X g in 250 mM sucrose.

Animals↗
PubMed1975

Ascorbate increases the synthesis of procollagen hydroxyproline by cultured fibroblasts from chick embryo tendons without activation of prolyl hydroxyla.

An improved procedure was developed to extract prolyl hydroxylase from tendon cells of chick embryos with detergent, and improved assays were developed for both the activity of the enzyme and the amount of enzyme protein. Freshly isolated tendon cells were found to contain approx. 100 mug of enzyme protein per 10(8) cells and 40-50% of the enzyme protein was active. When the cells were cultured, they were found to contain the same amount of enzyme protein but only 15-20% of the enzyme protein was active. Gel filtration of cell extracts indicated that the active form of prolyl hydroxylase in freshly isolated tendon cells and incultured tendon cells had the same apparent size and the same activity per mug of immunoreactive protein as enzyme which was shown to be a tetramer. The inactive form was found to have about the same apparent size as subunits of the enzyme. When freshly isolated cells were incubated for 2 h in the presence of 40 mug per ml of ascorbate, there was a slight increase in the rate of hydroxyproline synthesis. In cultured cells, ascorbate at a concentration of 40 mug per ml caused a 2-fold increase in the rate of hydroxyproline synthesis within 30 min. However, ascorbate did not icrease the activity of prolyl hydroxylase in extracts from either cell system. Therefore it appears that the influence of ascorbate on synthesis of procollagen hydroxyproline by the cells studied here must be ascribed to a cofactor effect on the hydroxylation reaction similar to that observed with purified enzyme, and it does not involve "activation" of inactive enzyme protein to active enzyme as has been observed in cultures of L-929 and 3T6 mouse fibroblasts.

Animals↗
PubMed1978

Collagen biosynthesis by cultured Chinese hamster lung cells. Cell-free synthesis of procollagen alpha chains.

Cell-free extracts from the HTl clone of cultured Chinese hamster lung cells efficiently promote the incorporation of proline into newly synthesized material, 50% of which is digestible to small peptides by highly purified bacterial collagenase. The synthesis of the these products occurs under optimal protein synthesis conditions and is inhibited by puromycin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the cell-free synthesized material reveals a major collagenase sensitive peak (20% of the total product) at mol wt 165 000 which is reflected by a collagenase sensitive material of similar size in the culture medium. Two additional collagenase digestible species (mol wt 95000 and 65000), each having a corresponding secreted product, are generated by the cell-free system. These results are consistent with the concept that procollagen is formed by the association of three individually translated pro alphachains. The data further constitute the report of a highly active homologous cell-free system capable of pro alpha chain biosynthesis derived from a cultured cell line that is a practical source for pro alphachain biosynthesis derived from a cultured cell line that is a practical source for proalpha chain mRNA as well as a unique system for elucidating regulatory mechanisms involved in collagen biosynthesis.

Cell Line↗
PubMed1976

Characterization of procollagen synthesized by matrix-free cells isolated from chick embryo tendons.

The genetic type and molecular structure of the precursor forms of collagen synthesized by matrix-free tendon cells isolated from 17-day old chick embryos were examined by chromatographic and electrophoretic techniques. The [14C]proline-labeled collagenous proteins secreted by the cells resolved on diethylaminoethylcellulose into two peaks, A and B. Both peaks contained type I collagenous proteins since on chromatography on carboxymethylcellulose, after limited pepsin proteolysis, both peaks contained alpha1 and alpha2 chains of collagen in a 2:1 ratio, and cyanogen bromide peptide maps of the 14C-labeled protein in both peaks were similar to cyanogen bromide peptide maps derived from authentic type I collagen. Enzymatic digestion with purified mammalian collagenase demonstrated that the collagen precursor in peak B contained noncollagenous peptide extensions at both the amino- and carboxy-terminal ends of the molecule, while peak A had only carboxy-terminal extension peptides. Although both the amino- and carboxy-terminal extensions incorporated radioactive cystine, only the carboxy-terminal extensions contained interchain disulfide bonds. The carboxy-terminal extensions were also shown to incorporate radioactive tryptophan. Since most of the precursor forms of collagen recovered in the incubation medium chromatographed in peak B, it is concluded that matrix-free tendon cells secrete only type I procollagen with extension peptides at both the amino- and carboxy-terminal ends of the molecule.

Animals↗