Identification of a 47 kDa fibronectin‐binding protein expressed by Borrelia burgdorferi isolate B31

Abstract

SummaryThe attachment of pathogenic microorganisms to host cells and tissues is often mediated through the expression of surface receptors recognizing components of the extracellular matrix (ECM). Here, we investigate the ability of Borrelia spirochaetes to bind the ECM constituent, fibronectin. Borrelia lysates were separated by SDS-PAGE, transferred to nitrocellulose and probed with alkaline phosphatase-labelled fibronectin (fibronectin-AP). Five of six Borrelia species and four of eight B. burgdorferi sensu lato isolates expressed one or more fibronectin-binding proteins. Borrelia burgdorferi isolate B31 expressed a 47 kDa (P47) fibronectin-binding protein that was localized to the outer envelope based on susceptibility to proteinase K. The interaction of P47 with fibronectin was specific, and the region of fibronectin bound by P47 mapped to the gelatin/collagen binding domain. P47 was purified by affinity chromatography, digested with endoproteinase Lys-C, and the peptide fragments analysed by liquid chromatography/tandem mass spectroscopy. A search of protein databases disclosed that the P47 peptide mass profile matched that predicted for the bbk32 gene product of B. burgdorferi isolate B31. The bbk32 gene was cloned into Escherichia coli, and the ability of recombinant BBK32 to bind fibronectin and inhibit the attachment of B. burgdorferi was demonstrated. The identification of BBK32 as a receptor for fibronectin binding may enhance our understanding of the pathogenesis and chronic nature of Lyme disease.

Overexpression of CsrA (BB0184) Alters the Morphology and Antigen Profiles ofBorrelia burgdorferi

“…6D) and DbpA (Fig. 6E), which are well-characterized adhesins mediating adherence of B. burgdorferi to fibronectin (64,75) and decorin (39), respectively. In addition, there was increased expression of BBA64 in ES25 while there was little or no expression of this lp54-encoded protein in both the parental control strain and MSK5 when these strains are propagated in BSK-II medium at pH 7.6 and 32°C.…”

“…Differential gene expression plays a critical role in the transmission, colonization, and dissemination of B. burgdorferi in mammalian hosts. Several of these open reading frames (ORFs) include mediators that provide a selective advantage to B. burgdorferi by enhancing its ability to adhere to host matrices (24,39,64) and to evade the mediators of innate and adaptive immunity (16,26,48,89), as well as other deleterious physiological processes encountered in its hosts (27). A number of studies have determined the significance of alterations of surface lipoproteins in response to these signals, and the molecular mechanisms responsible for these changes are beginning to be understood (41,86).…”

Inhibition of Borrelia burgdorferi-Tick Interactions In Vivo by Outer Surface Protein A Antibody

“…As one example, B. burgdorferi express outer surface protein (Osp) 3 A in the tick gut, and then down-regulate OspA and up-regulate OspC during engorgement and early infection within mammals (8 -11). During mammalian infection, decorin binding protein A and BBK32 (a fibronectin binding protein) appear to have a role in adherence of B. burgdorferi to the extracellular matrix, and several other Ags are preferentially produced by the spirochete in the vertebrate (12,13). In addition, B. burgdorferi undergo antigenic variation involving specific loci such as the vls gene cluster, and this may also contribute to immune evasion and spirochete persistence (14).…”

Biology of Infection with Borrelia burgdorferi

“…Among the B. burgdorferi proteins that bind ECM components are DbpA and DbpB, which bind decorin [145], BBK32, which binds fibronectin [146], Bgp, which binds proteoglycans [147], and P66, which binds integrins [148]. These proteins may help B. burgdorferi migrate through mammalian tissue and persist in joints and skin, where the spirochetes may be inaccessible to circulating antibodies.…”