title: Comprehensive Spatial Analysis of the Borrelia burgdorferi Lipoproteome Reveals a Compartmentalization Bias toward the Bacterial Surface.
abstract: The Lyme disease spirocheteBorrelia burgdorferiis unique among bacteria in its large number of lipoproteins that are encoded by a small, exceptionally fragmented, and predominantly linear genome. Peripherally anchored in either the inner or outer membrane and facing either the periplasm or the external environment, these lipoproteins assume varied roles. A prominent subset of lipoproteins functioning as the apparent linchpins of the enzootic tick-vertebrate infection cycle have been explored as vaccine targets. Yet, most of theB. burgdorferilipoproteome has remained uncharacterized. Here, we comprehensively and conclusively localize theB. burgdorferilipoproteome by applying established protein localization assays to a newly generated epitope-tagged lipoprotein expression library and by validating the obtained individual protein localization results using a sensitive global mass spectrometry approach. The derived consensus localization data indicate that 86 of the 125 analyzed lipoproteins encoded byB. burgdorferiare secreted to the bacterial surface. Thirty-one of the remaining 39 periplasmic lipoproteins are retained in the inner membrane, with only 8 lipoproteins being anchored in the periplasmic leaflet of the outer membrane. The localization of 10 lipoproteins was further defined or revised, and 52 surface and 23 periplasmic lipoproteins were newly localized. Cross-referencing prior studies revealed that the borrelial surface lipoproteome contributing to the host-pathogen interface is encoded predominantly by plasmids. Conversely, periplasmic lipoproteins are encoded mainly by chromosomal loci. These studies close a gap in our understanding of the functional lipoproteome of an important human pathogen and set the stage for more in-depth studies of thus-far-neglected spirochetal lipoproteins.IMPORTANCEThe small and exceptionally fragmented genome of the Lyme disease spirocheteBorrelia burgdorferiencodes over 120 lipoproteins. Studies in the field have predominantly focused on a relatively small number of surface lipoproteins that play important roles in the transmission and pathogenesis of this global human pathogen. Yet, a comprehensive spatial assessment of the entire borrelial lipoproteome has been missing. The current study newly identifies 52 surface and 23 periplasmic lipoproteins. Overall, two-thirds of theB. burgdorferilipoproteins localize to the surface, while outer membrane lipoproteins facing the periplasm are rare. This analysis underscores the dominant contribution of lipoproteins to the spirochete's rather complex and adaptable host-pathogen interface, and it encourages further functional exploration of its lipoproteome.
authors.affiliation: Department of Microbiology, Molecular Genetics & Immunology, University of Kansas School of Medicine, Kansas City, Kansas, USA.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Dowdell
authors.affiliation: Department of Microbiology, Molecular Genetics & Immunology, University of Kansas School of Medicine, Kansas City, Kansas, USA.
authors.forename: Maxwell D
authors.initials: MD
authors.lastname: Murphy
authors.affiliation: Department of Microbiology, Molecular Genetics & Immunology, University of Kansas School of Medicine, Kansas City, Kansas, USA.
authors.forename: Christina
authors.initials: C
authors.lastname: Azodi
authors.affiliation: Proteomics Center, Stowers Institute for Medical Research, Kansas City, Missouri, USA.
authors.forename: Selene K
authors.initials: SK
authors.lastname: Swanson
authors.affiliation: Proteomics Center, Stowers Institute for Medical Research, Kansas City, Missouri, USA.
authors.forename: Laurence
authors.initials: L
authors.lastname: Florens
authors.affiliation: Department of Microbiology, Molecular Genetics & Immunology, University of Kansas School of Medicine, Kansas City, Kansas, USA shiyongchen@hotmail.com wzueckert@kumc.edu.|School of Life Sciences, Qingdao Agricultural University, Shandong, China.
authors.forename: Shiyong
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Microbiology, Molecular Genetics & Immunology, University of Kansas School of Medicine, Kansas City, Kansas, USA shiyongchen@hotmail.com wzueckert@kumc.edu.
authors.forename: Wolfram R
authors.initials: WR
authors.lastname: Zückert
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D025065:Borrelia burgdorferi / Q000235:genetics / Q000378:metabolism*; D000939:Epitopes; D004926:Escherichia coli / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D015723:Gene Library; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism*; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport
chemical_list: D001426:Bacterial Proteins; D000939:Epitopes; D008074:Lipoproteins; D008565:Membrane Proteins
keywords: cell envelope; lipoproteins; localization; membrane biogenesis; membrane proteins; outer membrane; protein secretion; proteomics; spirochetes; surface proteins