Receptors for human plasminogen on gram-negative bacteria

Abstract

A total of 188 strains representing 11 species of gram-negative bacteria were examined for the ability to interact with human plasminogen. Highly purified human plasminogen was labeled with 125I, and its uptake by different bacterial strains was measured. All 14 strains of Haemophilus influenzae and all 13 strains of Branhamella catarrhalis tested were positive with respect to plasminogen uptake. Also, eight species belonging to the family Enterobacteriaceae were tested, and of those, Proteus mirabilis demonstrated the most substantial uptake, with 28 of 39 strains taking up more than 10% of the plasminogen. Ten strains of Pseudomonas aeruginosa were also tested, of which seven showed uptake values higher than 10%. With H. influenzae and B. catarrhalis strains, Scatchard analysis indicated a two-phase receptor interaction, one more-avid receptor with a Kd of 6 to 8 nM and 2,000 to 2,500 sites per bacterium and a second receptor with a Kd of 50 to 80 nM and 9,000 sites per bacterium. With Pseudomonas aeruginosa strains, a single receptor interaction was detected with a Kd of 60 nM and the number of sites was estimated as 8,000 per bacterium. Scatchard analysis with strains of P. mirabilis indicated binding of a less-specific nature. However, plasminogen uptake by this species could be reduced by 50% by the addition of 2 mM unlabeled plasminogen. This estimate of Kd, as well as uptake studies with plasminogen fragments, suggests different properties of this receptor. With all receptor types, the addition of plasmin-aprotinin complex inhibited plasminogen uptake, which demonstrates that both forms of the molecule react with the same receptors. Plasminogen uptake could be eliminated by the addition of lysine or epsilon-aminocaproic acid, which suggests that the lysine-binding sites of the plasminogen molecule are involved in the receptor-ligand interaction.

Binding of tissue-type plasminogen activator (t-PA) to Neisseria meningitidis and Haemophilus influenzae

“…The ability to interact with plasminogen has been described for a wide range of bacterial organisms including both Gram-positive and Gram-negative species. Thus receptors for plasminogen/plasmin have been described on Streptococci groups A, C and G, Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, Neisseria meningitidis, Neisseri gonorrhoeae, Moraxella ( Branhamella) catarrhalis and Pseudomonas aeruginosa [13][14][15][16][17][18][19]. Also strains of Escherichia coli have been demonstrated to interact with plasminogen when cultivated under conditions allowing fimbrial expression [29,30].…”

“…When investigating different species we have been able to detect up to 50 000 binding sites for plasminogen per bacterium with K d values in the range of 20-200 nmol 1-1. In most cases the binding is mediated by lysine binding sites in the kringle 1-3 domains of the plasminogen molecule and can be completely blocked by low concentrations of the lysine analogue EACA [14][15][16][17][18][19]. Receptor associated plasminogen is activated to plasmin by t-PA and the speed of this t-PA mediated conversion is in fact enhanced up to 500-fold by the presence of purified plasminogen receptor molecules from H. influenzae [31].…”

“…Plasminogen binding structures have been described on several types of bacteria including both Gram-positive and Gram-negative species [13][14][15][16][17][18][19]. This group of plasminogen binding bacteria include highly pathogenic microorganisms such as streptococci groups A, C and G, Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae.…”

“…This group of plasminogen binding bacteria include highly pathogenic microorganisms such as streptococci groups A, C and G, Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae. With selected strains of these organisms we have been able to detect between 10 000 and 50 000 high affinity sites for plasminogen per bacterium [16,17,19]. In most cases plasminogen is bound to the receptor in its native state where it can become activated to plasmin by exogenous t-PA or alternatively, in the case of streptococci, by intrinsic streptokinase [20].…”

Interaction of clinical isolates of nonencapsulated Haemophilus influenzae with mammalian extracellular matrix proteins

“…We have previously demonstrated that also distinct nonencapsulated H. in£uenzae strains were able to adhere to the ECM and ECM components, like laminin, ¢bronectin and various collagens [15]. In addition to adherence to ECM components, nonencapsulated H. in£uenzae strains can bind plasminogen [16] that can be activated by tissue-type plasminogen activator (t-PA) [15,17]. Plasmin generated on nonencapsulated H. in£uenzae plasminogen receptors was demonstrated to degrade ECM components [15] and to potentiate bacterial penetration through a basement membrane preparation reconstituted on membrane ¢lters [15].…”