Comparative membrane proteome analysis of three Borrelia species

The versatility of the surface of Borrelia, the causative agent of Lyme borreliosis, is very important in host-pathogen interactions allowing bacteria to survive in ticks and to persist in a mammalian environment. To identify the surface proteome of Borrelia, we have performed a large comparative proteomic analysis on the three most important pathogenic Borrelia species, namely B. burgdorferi (strain B31), B. afzelii (strain K78), and B. garinii (strain PBi). Isolation of membrane proteins was performed by using three different approaches: (i) a detergent-based fractionation of outer membrane proteins; (ii) a trypsin-based partial shedding of outer cell surface proteins; (iii) biotinylation of membrane proteins and preparation of the biotin-labelled fraction using streptavidin. Proteins derived from the detergent-based fractionation were further sub-fractionated by heparin affinity chromatography since heparin-like molecules play an important role for microbial entry into human cells. All isolated proteins were analysed using either a gel-based liquid chromatography (LC)-MS/MS technique or by two-dimensional (2D)-LC-MS/MS resulting in the identification of 286 unique proteins. Ninety seven of these were found in all three Borrelia species, representing potential targets for a broad coverage vaccine for the prevention of Lyme borreliosis caused by the different Borrelia species.     

Measurement of Monosaccharides and Conversion of Glucose to Acetate in Anoxic Rice Field Soil

Degradation of glucose has been implicated in acetate production in rice field soil, but the abundance of glucose, the temporal change of glucose turnover, and the relationship between glucose and acetate catabolism are not well understood. We therefore measured the pool sizes of glucose and acetate in rice field soil and investigated the turnover of [U-¹⁴C]glucose and [2-¹⁴C]acetate. Acetate accumulated up to about 2 mM during days 5 to 10 after flooding of the soil. Subsequently, methanogenesis started and the acetate concentration decreased to about 100 to 200 μM. Glucose always made up >50% of the total monosaccharides detected. Glucose concentrations decreased during the first 10 days from 90 μM initially to about 3 μM after 40 days of incubation. With the exception at day 0 when glucose consumption was slow, the glucose turnover time was in the range of minutes, while the acetate turnover time was in the range of hours. Anaerobic degradation of [U-¹⁴C]glucose released [¹⁴C]acetate and ¹⁴CO₂ as the main products, with [¹⁴C]acetate being released faster than ¹⁴CO₂. The products of [2-¹⁴C]acetate metabolism, on the other hand, were ¹⁴CO₂ during the reduction phase of soil incubation (days 0 to 15) and ¹⁴CH₄ during the methanogenic phase (after day 15). Except during the accumulation period of acetate (days 5 to 10), approximately 50 to 80% of the acetate consumed was produced from glucose catabolism. However, during the accumulation period of acetate, the rate of acetate production from glucose greatly exceeded that of acetate consumption. Under steady-state conditions, up to 67% of the CH₄ was produced from acetate, of which up to 56% was produced from glucose degradation.     

RAGE mediates amyloid-beta peptide transport across the blood-brain barrier and accumulation in brain

Amyloid-beta peptide (Abeta) interacts with the vasculature to influence Abeta levels in the brain and cerebral blood flow, providing a means of amplifying the Abeta-induced cellular stress underlying neuronal dysfunction and dementia. Systemic Abeta infusion and studies in genetically manipulated mice show that Abeta interaction with receptor for advanced glycation end products (RAGE)-bearing cells in the vessel wall results in transport of Abeta across the blood-brain barrier (BBB) and expression of proinflammatory cytokines and endothelin-1 (ET-1), the latter mediating Abeta-induced vasoconstriction. Inhibition of RAGE-ligand interaction suppresses accumulation of Abeta in brain parenchyma in a mouse transgenic model. These findings suggest that vascular RAGE is a target for inhibiting pathogenic consequences of Abeta-vascular interactions, including development of cerebral amyloidosis.