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C A Towle

Publications and source records attributed to C A Towle.

14 recordsLinked to original sources
PubMed1992

Alternatively spliced annexin XI transcripts encode proteins that differ near the amino-terminus.

Annexins are a family of structurally related calcium-dependent phospholipid binding proteins. We recently described a new member of this family, bovine annexin XI [1]. Two kinds of cDNAs were identified corresponding to annexin XI mRNA variants A and B, which are generated by alternative splicing of identical primary transcripts. Annexin XI isoforms are predicted to differ at the amino-terminus, suggesting that they may have distinct biological roles.

Amino Acid Sequence↗
PubMed1992

Identification of a novel mammalian annexin. cDNA cloning, sequence analysis, and ubiquitous expression of the annexin XI gene.

Annexins (or lipocortins) are a family of at least 10 structurally related calcium- and phospholipid-binding proteins. Each protein consists of a conserved core domain having four (or eight) repeats of a segment approximately 70 amino acids in length and a nonconserved, usually short, amino-terminal domain. To date, amino acid sequences for eight distinct mammalian annexins have been predicted from cDNAs. This report describes an additional member of this family, bovine annexin XI, identified by cDNA cloning and sequence analysis. The 503-amino acid deduced protein consists of a core domain of four annexin repeats and a long amino-terminal domain rich in glycine, proline, and tyrosine. This novel annexin gene is expressed in a wide variety of tissues and isolated cells in culture.

Amino Acid Sequence↗
PubMed1991

Cartilage synthesizes the serine protease inhibitor PAI-1: support for the involvement of serine proteases in cartilage remodeling.

The work described here demonstrates the synthesis by human articular cartilage of plasminogen activator inhibitor-1 (PAI-1), a potent inhibitor of the serine protease tissue plasminogen activator (tPA). We also present data demonstrating an increase in PAI-1 messenger ribonucleic acid (mRNA) in chondrocytes exposed to the cytokine interleukin-1 (IL-1). Interestingly, this elevation of steady-state mRNA levels does not appear to result in an increase in synthesis of PAI-1 protein. Northern blot analysis reveals that of the two mRNA species (3.4 kb, 2.4 kb) previously reported for PAI-1, only the larger species (3.4 kb) appears to be synthesized by chondrocytes. Our data demonstrate the IL-1-stimulated production by cartilage of tissue plasminogen activator. We also show evidence for the presence of plasminogen in cartilage. A scheme is presented indicating the probable importance of the serine proteases (tPA and plasminogen) and PAI-1 in cartilage degradation.

Blotting, Northern↗
PubMed1987

Regulation of cartilage remodeling by IL-1: evidence for autocrine synthesis of IL-1 by chondrocytes.

Evidence is presented for the synthesis of Interleukin-1 (IL-1) by joint synovial tissue and chondrocytes. Purified preparations of mouse and human recombinant forms of this factor stimulate the synthesis of a secretory protease by cartilage. The IL-1 stimulated chondrocyte protease is capable of converting latent collagenase to its active form. Other proteases such as trypsin and the mercurial aminophenyl mercuric acetate will not activate collagenase in the absence of this protease. Evidence is presented showing that chondrocytes synthesize IL-1 suggesting autocrine control of cartilage matrix turnover.

Animals↗
PubMed1986

Expression of IL-1 genes in human and bovine chondrocytes: a mechanism for autocrine control of cartilage matrix degradation.

In this report we describe the presence of interleukin-1 activity in medium conditioned by bovine articular cartilage. Preparations partially purified by Sephacryl S200 chromatography (Mr 18000-25000) stimulate murine thymocyte proliferation in the lymphocyte activation factor assay. Furthermore, the factor(s) activate cartilage tissue to secrete a protease which is essential for the activity of purified synovial collagenase. We also demonstrate the presence of mRNA coding for IL-1 alpha and beta in human articular chondrocytes and conclude that the human monocytic and chondrocytic mRNAs are identical. Our results demonstrating cartilage expression of IL-1 genes suggest the possibility of an autocrine mechanism whereby chondrocyte production of matrix degrading proteases is initiated by chondrocyte derived IL-1.

Adult↗
PubMed1986

Purification and characterization of collagenase activator protein synthesized by articular cartilage.

We have isolated an activator of collagenase from medium conditioned with articular cartilage. The activity is contained in an acidic protein appearing as a doublet band of Mr 57,000 and 56,000 on sodium dodecyl sulfate polyacrylamide gels. Both components of the doublet have identical isoelectric points as demonstrated by gel electrophoresis. Purified synovial collagenase has a high dependence on the presence of this factor for activity. Other known activators of latent proteolytic enzymes such as trypsin and mercurials will stimulate collagenase but only if activator protein is present. The activator protein is itself a latent metalloprotease because in the presence of p-aminophenylmercuric acetate and calcium it will digest casein. The caseinase activity and collagenase activation activity have identical heat inactivation profiles, both being stable to a temperature of 60 degrees C and partially inactivated at 80 degrees C. The synthesis of the activator is localized in the superficial zone of articular cartilage.

Animals↗
PubMed1986

Stimulation of the synthesis of collagenase activator protein in cartilage by a factor present in synovial-conditioned medium.

We have purified a low molecular weight protein from medium conditioned by calf synovium with physical and biological properties similar to the leukocyte cytokine interleukin 1 (IL-1). The factor is active in stimulating the synthesis (three- to fivefold) of collagenase activator protein (CAP) by the surface (1-2 mm) of articular cartilage while CAP synthesis in the deeper zones of articular cartilage is not affected. Recombinant mouse IL-1 and commercially available purified human IL-1 are also capable of stimulating cartilage to synthesize and secrete CAP. The synthesis of other proteins, including collagenase, appeared to be unaffected by either the synovial factors or the human and mouse IL-1.

Animals↗
PubMed1985

Stress-induced proteins in chondrocytes from patients with osteoarthritis.

Recent studies have shown that a specific set of proteins is produced by a variety of cells after the application of some forms of stress, including heat shock. Human chondrocytes isolated from cartilage with moderate to severe osteoarthritis synthesize at least 1 of these stress proteins (Mr 70,000) at physiologic temperature (37 degrees C), whereas chondrocytes isolated from non-pathologic cartilage synthesize this protein only in response to incubation at temperatures above 39 degrees C. The active synthesis of this protein (SP-70) at 37 degrees C is positively correlated with the severity of osteoarthritis and can be a characteristic indicator of this degenerative disease. We identified the active synthesis of stress proteins after incubating the cartilage tissue in medium containing 35S-methionine and separating the cell-associated proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The radioactive proteins were visualized by autoradiography. Analysis of the longevity of cell-associated proteins was determined by pulsing the tissue with 35S-methionine, and after different periods of chase in medium, the proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Specific proteins bands were then excised, and the radioactivity was determined by liquid scintillation counting.

Autoradiography↗
PubMed1985

Induction of heat-shock protein synthesis in chondrocytes at physiological temperatures.

Induction of heat-shock protein (HSP) synthesis is demonstrated in cultured calf-chondrocytes at temperatures shown to occur in normal human cartilage during experiments subjecting intact cadaverous hip joints to the parameters of level walking. A 70,000 MW heat-shock protein (HSP-70) is synthesized by chondrocytes at temperatures above 39 degrees C, while induction of synthesis of a 110,000 MW HSP only occurs at temperatures of 45 degrees C or greater. These differences in critical temperatures for induction, and data showing differences in kinetics of induction and repression of synthesis, suggest that there are differences in the mechanism of induction of the two HSPs. The duration of HSP synthesis and inhibition of synthesis of normal cellular proteins is directly proportional to the duration and magnitude of the temperature rise. Possible relationships between these new findings and the initiation and progression of degenerative joint disease are discussed.

Animals↗
PubMed1984

Insulin promoted decrease in the phosphorylation of protein synthesis initiation factor eIF-2.

Insulin stimulates cellular protein synthesis in calf chondrocytes in suspension culture. This enhanced synthetic activity is seen in association with a decrease in phosphorylation of the alpha subunit of protein synthesis initiation factor eIF-2. [32P] associated with the alpha subunit is reduced approximately 50% by insulin treatment of chondrocytes incubated in [32P] containing media. Identical or closely located amino acids in the eIF-2 alpha subunit are phosphorylated by the chondrocyte kinase(s) and the rabbit reticulocyte hemin regulated kinase as indicated by comparative peptide fragment analysis of [32P] labeled alpha subunits.

Animals↗
PubMed1982

Characterisation of human articular cartilage link proteins from normal and osteoarthritic cartilage.

Proteoglycan link proteins were isolated from human articular cartilage obtained from normal and osteoarthritic femoral heads and purified to homogeneity employing a method previously described by this laboratory. The link proteins were analysed for amino acid composition, molecular weight on sodium dodecyl sulphate polyacrylamide gels, and ability to stabilise proteoglycan aggregates. The results of these studies were compared with those obtained with bovine link proteins. Two link proteins were identified in the purified fraction from normal and osteoarthritic human cartilage with apparent molecular weights of 54 000 (link 1) and 48 000 (link 2). Functionally the link proteins, isolated from osteoarthritic and normal cartilage, were indistinguishable as measured by their ability to stabilise aggregate. The amino acid compositions of normal and osteoarthritic link proteins were also found to be similar to each other but significantly different from the amino acid composition reported for the bovine link proteins. The quantities of these proteins in extracts from normal and diseased tissue were similar, as was the ratio of link protein 1 to link protein 2.

Aged↗