Plasminogen Binding and Activation by Mycoplasma fermentans

Abstract

The binding of plasminogen to Mycoplasma fermentans was studied by an immunoblot analysis and by a binding assay using iodine-labeled plasminogen. The binding of 125 I-labeled plasminogen was inhibited by unlabeled plasminogen, lysine, and lysine analog -aminocaproic acid. Partial inhibition was obtained by a plasminogen fragment containing kringles 1 to 3 whereas almost no inhibition was observed with a fragment containing kringle 4. Scatchard analysis revealed a dual-phase interaction, one with a dissociation constant Mycoplasmas (class Mollicutes) are wall-less prokaryotes widely distributed in nature. Most mycoplasmas are parasites, exhibiting strict host and tissue specificities, and almost all of them are bound to the surface of the host cell (22, 24). Human pathogen Mycoplasma fermentans was isolated from the urogenital tract several decades ago (25). The interest in this organism has recently increased because of its possible role in the pathogenesis of rheumatoid arthritis and reports indicating that this organism may function as a cofactor accelerating the progression of human immunodeficiency virus disease (17, 23).Plasminogen (Pg) is a 92-kDa plasma glycoprotein. This protein is activated in vivo to the serine protease plasmin by urokinase-type and tissue-type Pg activators (uPA and tPA, respectively) by cleavage of a single peptide bond (R 561 -V 562 ) yielding two chains that remain connected by two disulfide bridges (26). Plasmin participates in several physiological and pathophysiological processes such as fibrinolysis, pericellular proteolysis, tissue penetration of cancer cells, and neuronal cell death (19,21,26). The active domain of Pg is located in the COOH terminal of the molecule, whereas the NH 2 terminal contains five characteristic triple-loop structures (kringles) that mediate the interaction of Pg with a variety of ligands such as fibrin, the ␣ 2 -plasmin inhibitor, etc. (21). This interaction is between lysine-binding sites in the kringles and exposed COOH-terminal lysines in the ligands (26). Therefore, lysine or lysine analogs such as ε-aminocaproic acid (εACA) mimic COOH-terminal lysine by inhibiting the interaction.Many eucaryotic cells express surface structures that interact with Pg, and specific receptors have been described (21). Recently it became evident that Pg is also capable of interacting with receptors on several prokaryotic organisms, including both gram-positive (4, 15, 18, 34) and gram-negative bacteria (12,13,20,32,33). In the present study we extend the group of bacteria capable of binding Pg to include the wall-less M. fermentans and show that Pg interacts with two surface proteins of this organism. The association of Pg with M. fermentans greatly enhances its uPA-associated activation. The possible role of Pg binding in M. fermentans-host interactions is discussed. MATERIALS AND METHODSOrganisms and growth conditions. M. fermentans strain PG-18 was used throughout the study. In some experiments strains M-52, M-32, AOU, and Z-62 (kindly provided by P. Hannan, Sur...

A Processed Multidomain Mycoplasma hyopneumoniae Adhesin Binds Fibronectin, Plasminogen, and Swine Respiratory Cilia

“…Plasminogen binding ability has been reported widely among bacterial pathogens, including Mycoplasma fermentans and Mycoplasma sp. bovine group 7 (34,36,37). P116 is the first M. hyopneumoniae plasminogenbinding protein to be described.…”

“…The C-terminal lysine in P116, isolation of M. hyopneumoniae in deep tissues (35) and previous studies describing the interaction of the broad spectrum protease plasminogen with Mycoplasma species (36,37) led us to investigate the capacity of M. hyopneumoniae and P116 to bind plasminogen. M. hyopneumoniae was found to bind porcine plasminogen in a saturable and dose-dependent manner (Fig.…”

Mycoplasma Removal from Cell Culture Using Antimicrobial Photodynamic Therapy

“…In mycoplasmas, Mycoplasma fermentans, which frequently contaminates cell culture, 18 and Mycoplasma penetrans are known to have invasive properties. 19,20 Recently, O'Riordan et al 21 have reported that 50% of intracellular Mycobacterium bovis were killed using aPDT, compared with extracellular bacteria, when they are cocultured with macrophages, suggesting that aPDT may be applicable to killing intracellular bacteria. However, there are still few reports on the application of aPDT for killing intracellular bacteria, and further studies are needed to develop a method that is able to completely remove the mycoplasmas that have host cell-invasive properties from the contaminated cells.…”

Contamination of Tissue Cultures by Mycoplasmas

“…This organism, which contains a 65-kDa fibronectin binding protein, binds selectively immobilized fibronectin [23]. The finding that M. fermentans binds plasminogen (Plg) and in the presence of urokinase-type Plg activated (uPA) internalization was apparent (26,27), indicates that the ability of M. fermentans to invade host cell stems from its potential to bind and activate Plg to plasmin, a protease with broad substrate specificity. Plg and uPA are two proteins that play an important role in the invasion of several human malignant tumors [28], therefore it is not surprising that the same system stimulates M. fermentans invasion.…”