The Complement Binding and Inhibitory Protein CbiA of Borrelia miyamotoi Degrades Extracellular Matrix Components by Interacting with Plasmin(ogen).

Ngoc T. T. Nguyen,Florian Röttgerding,Gayatri Devraj,Yi-Pin Lin,Peter Kraiczy,Arno Koenigs

doi:10.3389/fcimb.2018.00023

Abstract

The emerging relapsing fever spirochete Borrelia (B.) miyamotoi is transmitted by ixodid ticks and causes the so-called hard tick-borne relapsing fever or B. miyamotoi disease (BMD). More recently, we identified a surface-exposed molecule, CbiA exhibiting complement binding and inhibitory capacity and rendering spirochetes resistant to complement-mediated lysis. To gain deeper insight into the molecular principles of B. miyamotoi-host interaction, we examined CbiA as a plasmin(ogen) receptor that enables B. miyamotoi to interact with the serine protease plasmin(ogen). Recombinant CbiA was able to bind plasminogen in a dose-dependent fashion. Moreover, lysine residues appear to play a crucial role in the protein-protein interaction as binding of plasminogen was inhibited by the lysine analog tranexamic acid as well as increasing ionic strength. Of relevance, plasminogen bound to CbiA can be converted by urokinase-type plasminogen activator (uPa) to active plasmin which cleaved both, the chromogenic substrate S-2251 and its physiologic substrate fibrinogen. Concerning the involvement of specific amino acids in the interaction with plasminogen, lysine residues located at the C-terminus are frequently involved in the binding as reported for various other plasminogen-interacting proteins of Lyme disease spirochetes. Lysine residues located within the C-terminal domain were substituted with alanine to generate single, double, triple, and quadruple point mutants. However, binding of plasminogen to the mutated CbiA proteins was not affected, suggesting that lysine residues distant from the C-terminus might be involved in the interaction.

Highlights

Borrelia (B.) miyamotoi, an emerging relapsing fever spirochete, is transmitted by hard-bodied, ixodid ticks and causes systemic infections accompanied with symptoms similar to relapsing fever, including headache, fatigue, chills, myalgia, arthralgia, nausea, and high-grade fever with possible relapses (Platonov et al, 2011; Molloy et al, 2015; Jobe et al, 2016; Stone and Brissette, 2017) leading to the description of a new entity termed hard tick-borne relapsing fever (HTBRF) or B. miyamotoi disease (BMD) (Krause and Barbour, 2015; Telford et al, 2015)
Microtiter plates were coated with recombinant CbiA (5 μg/ml) and binding of plasminogen was detected by a specific antibody
The plasminogen-binding BBA70 protein of B. burgdorferi (Koenigs et al, 2013) served as a positive and DbpA of B. burgdorferi as a negative control protein while BSA was used as a control for unspecific binding

Summary

Introduction

Borrelia (B.) miyamotoi, an emerging relapsing fever spirochete, is transmitted by hard-bodied, ixodid ticks and causes systemic infections accompanied with symptoms similar to relapsing fever, including headache, fatigue, chills, myalgia, arthralgia, nausea, and high-grade fever with possible relapses (Platonov et al, 2011; Molloy et al, 2015; Jobe et al, 2016; Stone and Brissette, 2017) leading to the description of a new entity termed hard tick-borne relapsing fever (HTBRF) or B. miyamotoi disease (BMD) (Krause and Barbour, 2015; Telford et al, 2015). B. miyamotoi occurs sympatrically with spirochetes belonging to the Borrelia burgdorferi sensu lato complex in Asia (Fukunaga et al, 1995), North America (Scoles et al, 2001; Barbour et al, 2009), and Europe (Richter et al, 2003) and can be potentially co-transmitted during the blood meal by the same tick that carries multiple vector-borne pathogens, e.g., Borrelia spp., Anaplasma phagocytophilum, and Babesia microti. CbiA, a complement-inhibitory protein, has been identified that interacts with complement in multiple ways, binding distinct complement components including key complement regulator Factor H (FH), C3, C3b, C4b, and C5 and thereby terminating activation of distinct complement pathways (Röttgerding et al, 2017)

Objectives

Methods

Results

Conclusion