Search

The U937 cell line is a monoblast-like cell line that can be induced to differentiate when treated with phorbol ester or a variety of other agents. Collagenase was detected in the media of U937 cell cultures after treatment with phorbol myristate acetate (PMA) at concentrations of 5 ng/mL or greater. In general, no collagenase was detected in the media of untreated cells. The induced collagenase cleaved native type I collagen into the 3/4 and 1/4-length fragments and showed the inhibition by ethylenediaminetetraacetic acid characteristic of the action of mammalian collagenases. Collagenase activity could be detected in the media of treated cells 12-18 h after the addition of PMA. Secretion of collagenase continued for 2-3 days after PMA addition. The production of collagenase by PMA-treated U937 cells was inhibited by actinomycin D and cycloheximide, suggesting that the induction of the enzyme is the result of de novo synthesis. The collagenase secreted by U937 cells induced with PMA has been purified 12-fold by using DEAE-Sephacel followed by wheat germ agglutinin-agarose chromatography. The apparent molecular mass of this U937 collagenase, determined by gel filtration chromatography on the partially purified enzyme, was 29-36 kilodaltons.

Complex mixtures of 2′,5′-oligoadenylates are formed in cells and tissues under several different circumstances, and methods for analyzing such mixtures are reviewed. Separation is achieved by high-performance liquid chromatography and quantitation by competition-binding assays, using three different types of antibodies or a specific binding protein, or by functional assay, using preparations of an endonuclease specifically activated by some of the 2′,5′-oligoadenylates. Representative results from three different biological systems are presented. The function of 2′,5′-oligoadenylates as activators of intracellular RNA degradation is discussed, along with the possibility that these compounds may serve as signals for other intracellular regulatory processes.

Polymorphonuclear leukocytes (PMNLs) store collagenase in an inactive form in secretory granules. The enzyme can be activated in vitro by limited proteolysis or by sulfhydryl-modifying agents such as N-ethylmaleimide (NEM). We have enriched NEM-activated collagenase 820-fold using granule isolation, gel filtration, and wheat germ agglutinin (WGA)-agarose chromatography. The use of WGA-agarose resulted in a 55-fold enrichment of collagenase in a single step with very little loss of activity. The chromatographic behavior of collagenase on other lectin matrices was explored and gave information about the type of complex asparagine-linked oligosaccharide found on collagenase isolated from PMNLs.