Neisseria meningitidis Opc Invasin Binds to the Sulphated Tyrosines of Activated Vitronectin to Attach to and Invade Human Brain Endothelial Cells

Abstract

The host vasculature is believed to constitute the principal route of dissemination of Neisseria meningitidis (Nm) throughout the body, resulting in septicaemia and meningitis in susceptible humans. In vitro, the Nm outer membrane protein Opc can enhance cellular entry and exit, utilising serum factors to anchor to endothelial integrins; but the mechanisms of binding to serum factors are poorly characterised. This study demonstrates that Nm Opc expressed in acapsulate as well as capsulate bacteria can increase human brain endothelial cell line (HBMEC) adhesion and entry by first binding to serum vitronectin and, to a lesser extent, fibronectin. This study also demonstrates that Opc binds preferentially to the activated form of human vitronectin, but not to native vitronectin unless the latter is treated to relax its closed conformation. The direct binding of vitronectin occurs at its Connecting Region (CR) requiring sulphated tyrosines Y56 and Y59. Accordingly, Opc/vitronectin interaction could be inhibited with a conformation-dependent monoclonal antibody 8E6 that targets the sulphotyrosines, and with synthetic sulphated (but not phosphorylated or unmodified) peptides spanning the vitronectin residues 43–68. Most importantly, the 26-mer sulphated peptide bearing the cell-binding domain 45RGD47 was sufficient for efficient meningococcal invasion of HBMECs. To our knowledge, this is the first study describing the binding of a bacterial adhesin to sulphated tyrosines of the host receptor. Our data also show that a single region of Opc is likely to interact with the sulphated regions of both vitronectin and of heparin. As such, in the absence of heparin, Opc-expressing Nm interact directly at the CR but when precoated with heparin, they bind via heparin to the heparin-binding domain of the activated vitronectin, although with a lower affinity than at the CR. Such redundancy suggests the importance of Opc/vitronectin interaction in meningococcal pathogenesis and may enable the bacterium to harness the benefits of the physiological processes in which the host effector molecule participates.

Inhibition of the Membrane Attack Complex by Dengue Virus NS1 through Interaction with Vitronectin and Terminal Complement Proteins

“…Most pathogenic bacteria bind VN at either its N-terminal region (37), its central domain (containing HPX-like domains) (30), or the basic carboxy-terminal HBD-3 (38). Usually, bacterium-VN binding does not interfere with the VN domain involved in the inhibition of the C5b9 complex, thus allowing this complement regulator to remain active in inhibiting MAC formation.…”

Use of OmpU porins for attachment and invasion of Crassostrea gigas immune cells by the oyster pathogen Vibrio splendidus

“…Like OmpU, OMPs of intracellular pathogens can mediate adherence to host cells, stimulating host transduction pathways required for bacterial entry. One remarkable example is that of OpC from Neisseria meningitidis, which binds to human serum factors like activated vitronectin and to a lesser extent fibronectin to attach to and invade human brain endothelial cells (11). In these cells, fibronectin/ vitronectin serve as molecular bridges between the pathogen and the host RGD-recognizing αvβ3-integrin receptors.…”

“…As bacterial surface components, OMPs are both used by hosts for pathogen recognition and by pathogens for interaction with and invasion of host cells, serving as adhesion proteins (adhesins) (7)(8)(9) or invasion proteins (invasins) (10,11). OmpU is a major porin from the Vibrio species.…”

Pathogens Penetrating the Central Nervous System: Infection Pathways and the Cellular and Molecular Mechanisms of Invasion

“…Furthermore, the use of Opc-deficient mutant strains demonstrated that JNK signaling, but not p38 signaling, was mediated by Opc expression (192). A more recent study identified that Opc preferentially binds to activated vitronectin within human serum and that this interaction promotes N. meningitidis invasion of HBMECs (155). In vitro, the enhanced invasion of nonencapsulated N. meningitidis strains is thought to be due to the unmasking of Opc; however, the role of Opc in vivo has yet to be determined.…”