The lipid raft proteome ofBorrelia burgdorferi

Abstract

Eukaryotic lipid rafts are membrane microdomains that have significant amounts of cholesterol and a selective set of proteins that have been associated with multiple biological functions. The Lyme disease agent, Borrelia burgdorferi, is one of an increasing number of bacterial pathogens that incorporates cholesterol onto its membrane, and form cholesterol glycolipid domains that possess all the hallmarks of eukaryotic lipid rafts. In this study, we isolated lipid rafts from cultured B. burgdorferi as a detergent resistant membrane (DRM) fraction on density gradients, and characterized those molecules that partitioned exclusively or are highly enriched in these domains. Cholesterol glycolipids, the previously known raft-associated lipoproteins OspA and OpsB, and cholera toxin partitioned into the lipid rafts fraction indicating compatibility with components of the DRM. The proteome of lipid rafts was analyzed by a combination of LC-MS/MS or MudPIT. Identified proteins were analyzed in silico for parameters that included localization, isoelectric point, molecular mass and biological function. The proteome provided a consistent pattern of lipoproteins, proteases and their substrates, sensing molecules and prokaryotic homologs of eukaryotic lipid rafts. This study provides the first analysis of a prokaryotic lipid raft and has relevance for the biology of Borrelia, other pathogenic bacteria, as well as for the evolution of these structures. All MS data have been deposited in the ProteomeXchange with identifier PXD002365 (http://proteomecentral.proteomexchange.org/dataset/PXD002365).

A Helicobacter pylori Homolog of Eukaryotic Flotillin Is Involved in Cholesterol Accumulation, Epithelial Cell Responses and Host Colonization

“…Amongst these predicted cytoplasmic proteins are HP0248 and UreA (HP0073) (Figure 1B, Phadnis et al, 1996). Similar findings were reported in a proteomic study on B. burgdorferi DRMs in which the majority (63%) of the proteins found in those fractions were predicted to be associated with the bacterial membrane, however, some cytoplasmic proteins were also detected (Toledo et al, 2015). …”

Borrelia burgdorferi HtrA: evidence for twofold proteolysis of outer membrane protein p66

“…However, the distribution of the merged labeling was not uniform, as the distribution of HtrA was more clustered than p66, which was more dispersed. This result is in agreement with the proteome analysis of he lipid rafts (Toledo et al ., ) in which HtrA was found enriched 116‐fold in lipid rafts, whereas p66 was enriched only 1.67‐fold. Therefore, the distribution of both proteins in the membrane of B. burgdorferi is expected to be different, as the IFA indicated.…”

Cholesterol lipids and cholesterol-containing lipid rafts in bacteria

“…An analysis of DRM proteins provided a potential lipid raft proteome for B. burgdorferi (37). DRM and non-DRM fractions were characterized by liquid chromatography MS/MS or multidimensional protein identification technology (MudPIT) MS. DRM-associated proteins were identified that are involved in biological functions such as motility, chemotaxis and signaling, suggesting that lipid rafts in Borrelia could play many important roles in its life cycle (37).…”

“…DRM and non-DRM fractions were characterized by liquid chromatography MS/MS or multidimensional protein identification technology (MudPIT) MS. DRM-associated proteins were identified that are involved in biological functions such as motility, chemotaxis and signaling, suggesting that lipid rafts in Borrelia could play many important roles in its life cycle (37). Acylation was identified as one of the properties targeting proteins to lipid rafts, with the acylated proteins OspA, OspB (as also seen in previous studies), and BB_0323 being especially highly enriched in DRM.…”