In-Gel 18O Labeling for Improved Identification of Proteins from 2-DE Gel Spots in Comparative Proteomic Experiments

Comparative proteomic analysis of lung tissue from guinea pigs with leptospiral pulmonary haemorrhage syndrome (LPHS) reveals a decrease in abundance of host proteins involved in cytoskeletal and cellular organization

Leptospiral pulmonary haemorrhage syndrome (LPHS) is a particularly severe form of leptospirosis. LPHS is increasingly recognized in both humans and animals and is characterized by rapidly progressive intra-alveolar haemorrhage leading to high mortality. The pathogenic mechanisms of LPHS are poorly understood which hampers the application of effective treatment regimes. In this study a 2-D guinea pig proteome lung map was created and used to investigate the pathogenic mechanisms of LPHS. Comparison of lung proteomes from infected and non-infected guinea pigs via differential in-gel electrophoresis revealed highly significant differences in abundance of proteins contained in 130 spots. Acute phase proteins were the largest functional group amongst proteins with increased abundance in LPHS lung tissue, and likely reflect a local and/or systemic host response to infection. The observed decrease in abundance of proteins involved in cytoskeletal and cellular organization in LPHS lung tissue further suggests that infection with pathogenic Leptospira induces changes in the abundance of host proteins involved in cellular architecture and adhesion contributing to the dramatically increased alveolar septal wall permeability seen in LPHS.

BIOLOGICAL SIGNIFICANCE

The recent completion of the complete genome sequence of the guinea pig (Cavia porcellus) provides innovative opportunities to apply proteomic technologies to an important animal model of disease. In this study, the comparative proteomic analysis of lung tissue from experimentally infected guinea pigs with leptospiral pulmonary haemorrhage syndrome (LPHS) revealed a decrease in abundance of proteins involved in cellular architecture and adhesion, suggesting that loss or down-regulation of cytoskeletal and adhesion molecules plays an important role in the pathogenesis of LPHS. A publically available guinea pig lung proteome map was constructed to facilitate future pulmonary proteomics in this species.

Quantification of Cry1Ab in genetically modified maize leaves by liquid chromatography multiple reaction monitoring tandem mass spectrometry using 18O stable isotope dilution

Cry1Ab is one of the most common Bacillus thuringiensis (Bt) proteins in genetically modified crops, which exhibits strong resistance against insect pests. In the present study, a sensitive and precise liquid chromatography stable isotope dilution multiple reaction monitoring tandem mass spectrometry (LC-SID-MRM-MS) assay was developed and validated to quantify the amount of Cry1Ab expression in transgenic maize leaves. The measurement of protein was converted to measurement of unique peptides to Cry1Ab protein. Two peptides unique to Cry1Ab were synthesized and labeled in H(2)(18)O to generate (18)O stable isotope peptides as internal standards. The validated method obtained superior specificity and good linearity. And the inter- and intra-day precision and accuracy for all samples were satisfactory. The results demonstrated Cry1Ab protein was 31.7 ± 4.1 μg g(-1) dry weight in Bt-176 transgenic maize leaves. It proved that the novel LC-SID-MRM-MS method was sensitive and selective to quantify Cry1Ab in the crude extract without time-consuming pre-separation or purification procedures.