Publications

The Streptococcus gordonii cell surface glycoprotein GspB mediates high-affinity binding to distinct sialylated carbohydrate structures on human platelets and salivary proteins. GspB is glycosylated in the cytoplasm of S. gordonii and is then transported to the cell surface via a dedicated transport system that includes the accessory Sec components SecA2 and SecY2. The means by which the GspB preprotein is selectively recognized by the accessory Sec system have not been characterized fully. GspB has a 90-residue amino-terminal signal sequence that displays a traditional tripartite structure, with an atypically long amino-terminal (N) region followed by hydrophobic (H) and cleavage regions. In this report, we investigate the relative importance of the N and H regions of the GspB signal peptide for trafficking of the preprotein. The results show that the extended N region does not prevent export by the canonical Sec system. Instead, three glycine residues in the H region not only are necessary for export via the accessory Sec pathway but also interfere with export via the canonical Sec route. Replacement of the H-region glycine residues with helix-promoting residues led to a decrease in the efficiency of SecA2-dependent transport of the preprotein and a simultaneous increase in SecA2-independent translocation. Thus, the hydrophobic core of the GspB signal sequence is responsible primarily for routing towards the accessory Sec system.

Although certain markers of inflammation and hemostasis are elevated in persons at risk of future cardiovascular events, data assessing the relation between inflammatory and hemostatic markers of vascular risk and race/ethnicity are limited. Thus, in a cross-sectional analysis of the Women's Health Study (WHS), baseline soluble intercellular adhesion molecule-1 (ICAM-1), homocysteine, and fibrinogen were measured in 23,687 women without a history of cardiovascular disease. In 22,677 white, 242 Hispanic, 428 black, and 340 Asian women, the distribution of median ICAM-1 levels was significantly lower in black (311.9 ng/ml, interquartile range [IQR] 220.1 to 380.0) and Asian (312.7 ng/ml, IQR 267.3 to 362.3) women than white (343.1 ng/ml, IQR 301.9 to 394.9) and Hispanic (351.9 ng/ml, IQR 305.9 to 404.2) women (p <0.001). Although homocysteine was marginally lower in Asian women (p = 0.05), fibrinogen was higher in black women than their counterparts. After controlling for body mass index, hypertension, diabetes, smoking, alcohol use, family history of myocardial infarction, education, hormone use, and lipids, ICAM-1 remained significantly lower in black and Asian women. Meanwhile, homocysteine was lower in Asian women and fibrinogen remained higher in black women than their counterparts. In conclusion, this cross-sectional analysis shows that baseline fibrinogen, ICAM-1, and homocysteine vary by self-reported race/ethnicity.

RATIONALE

Mechanical ventilation with high tidal volumes leads to increased permeability, generation of inflammatory mediators, and damage to alveolar epithelial cells (ATII).

OBJECTIVES

To identify changes in the ATII proteome after two different ventilation strategies in rats.

METHODS

Rats (n = 6) were ventilated for 5 hours with high- and low tidal volumes (VTs) (high VT: 20 ml/kg; low VT: 6 ml/kg). Pooled nonventilated rats served as control animals. ATII cells were isolated and lysed, and proteins were tryptically cleaved into peptides. Cellular protein content was evaluated by peptide labeling of the ventilated groups with (18)O. Samples were fractionated by cation exchange chromatography and identified using electrospray tandem mass spectrometry. Proteins identified by 15 or more peptides were statistically compared using t tests corrected for the false discovery rate.

MEASUREMENTS AND MAIN RESULTS

High Vt resulted in a significant increase in airspace neutrophils without an increase in extravascular lung water. Compared with low-VT samples, high-VT samples showed a 32% decrease in the inositol 1,4,5-trisphosphate 3 receptor (p < 0.01), a 34% decrease in Na(+), K(+)-ATPase (p < 0.01), and a significantly decreased content in ATP synthase chains. Even low-VT samples displayed significant changes, including a 66% decrease in heat shock protein 90-beta (p < 0.01) and a 67% increase in mitochondrial pyruvate carboxylase (p < 0.01). Significant differences were found in membrane, acute phase, structural, and mitochondrial proteins.

CONCLUSIONS

After short-term exposure to high-VT ventilation, significant reductions in membrane receptors, ion channel proteins, enzymes of the mitochondrial energy system, and structural proteins in ATII cells were present. The data supports the two-hit concept that an unfavorable ventilatory strategy may make the lung more vulnerable to an additional insult.