New Aminoacyl-tRNA Synthetase-like Protein in Insecta with an Essential Mitochondrial Function

Aminoacyl-tRNA synthetases (ARS) are modular enzymes that aminoacylate transfer RNAs (tRNA) for their use by the ribosome during protein synthesis. ARS are essential and universal components of the genetic code that were almost completely established before the appearance of the last common ancestor of all living species. This long evolutionary history explains the growing number of functions being discovered for ARS, and for ARS homologues, beyond their canonical role in gene translation. Here we present a previously uncharacterized paralogue of seryl-tRNA synthetase named SLIMP (seryl-tRNA synthetase-like insect mitochondrial protein). SLIMP is the result of a duplication of a mitochondrial seryl-tRNA synthetase (SRS) gene that took place in early metazoans and was fixed in Insecta. Here we show that SLIMP is localized in the mitochondria, where it carries out an essential function that is unrelated to the aminoacylation of tRNA. The knockdown of SLIMP by RNA interference (RNAi) causes a decrease in respiration capacity and an increase in mitochondrial mass in the form of aberrant mitochondria.     

ANG II induces apoptosis of human vascular smooth muscle via extrinsic pathway involving inhibition of Akt phosphorylation and increased FasL expression

In addition to well-documented vascular growth-promoting effects, ANG II exerts proapoptotic effects that are poorly understood. IGF-1 is a potent survival factor for human vascular smooth muscle cells (hVSMC), and its antiapoptotic effects are mediated via the IGF-1 receptor (IGF-1R) through a signaling pathway involving phosphatidylinositol 3-kinase and Akt. We hypothesized that there would be cross talk between ANG II proapoptotic effects and IGF-1 survival effects in hVSMC. To investigate ANG II-induced apoptosis and the potential involvement of IGF-1, we exposed quiescent and nonquiescent hVSMC to ANG II. ANG II induced apoptosis only in nonquiescent cells but stimulated hypertrophy in quiescent cells. ANG II-induced apoptosis was characterized by marked inhibition of Akt phosphorylation and stimulation of membrane Fas ligand (FasL) expression, caspase-8 activation, and a reduction in soluble FasL expression. Adenovirally mediated overexpression of Akt rescued hVSMC from ANG II-induced apoptosis. IGF-1R activation increased Akt phosphorylation and soluble FasL expression, and these effects were completely blocked by coincubating hVSMC with ANG II. In conclusion, ANG II-induced apoptosis of hVSMC is characterized by marked inhibition of Akt phosphorylation and stimulation of an extrinsic cell death signaling pathway via upregulation of membrane FasL expression, caspase-8 activation, and a reduction in soluble FasL expression. Furthermore, ANG II antagonizes the antiapoptotic effect of IGF-1 by blocking its ability to increase Akt phosphorylation and soluble FasL. These findings provide novel insights into ANG II-induced apoptotic signaling and have significant implication for understanding ANG II-induced remodeling in hypertension and atherosclerosis.     

Arterial compliance of rowers: implications for combined aerobic and strength training on arterial elasticity

Regular endurance exercise increases central arterial compliance, whereas resistance training decreases it. It is not known how the vasculature adapts to a combination of endurance and resistance training. Rowing is unique, because its training encompasses endurance- and strength-training components. We used a cross-sectional study design to determine arterial compliance of 15 healthy, habitual rowers [50 +/- 9 (SD) yr, 11 men and 4 women] and 15 sedentary controls (52 +/- 8 yr, 10 men and 5 women). Rowers had been training 5.4 +/- 1.2 days/wk for 5.7 +/- 4.0 yr. The two groups were matched for age, body composition, blood pressure, and metabolic risk factors. Central arterial compliance (simultaneous ultrasound and applanation tonometry on the common carotid artery) was higher (P < 0.001) and carotid beta-stiffness index was lower (P < 0.001) in rowers than in sedentary controls. There were no group differences for measures of peripheral (femoral) arterial stiffness. The higher central arterial compliance in rowers was associated with a greater cardiovagal baroreflex sensitivity, as estimated during a Valsalva maneuver (r = 0.54, P < 0.005). In conclusion, regular rowing exercise in middle-aged and older adults is associated with a favorable effect on the elastic properties of the central arteries. Our results suggest that simultaneously performed endurance training may negate the stiffening effects of strength training.     

A novel approach for screening immunogenic proteins in Penicillium marneffei using the DeltaAFMP1DeltaAFMP2 deletion mutant of Aspergillus fumigatus

Using serum from guinea-pigs immunized with a DeltaAFMP1DeltaAFMP2 deletion mutant of Aspergillus fumigatus to screen a cDNA library of A. fumigatus, we cloned a novel immunogenic 57-kDa protein in A. fumigatus. We also cloned its 55-kDa homologue in Penicillium marneffei, which was possibly related to amino acid biosynthesis and metabolism, with homologues present only in the subphylum Pezizomycotina of Ascomycota. The recombinant 55-kDa protein of P. marneffei reacted strongly with guinea-pig serum immunized with P. marneffei and with the sera of patients with P. marneffei infection. A similar approach could be applied to immunogenic protein screening in other microorganisms for serological diagnosis, epidemiological studies and the study of vaccines.     

Enantiomer separation of amino acids in immunoaffinity micro LC-MS

Chiral immunoaffinity microbore columns were directly interfaced with MS detection, and the effect of column length and temperature on the enantiomer separation of a number of underivatized aromatic and aliphatic amino acids was investigated utilizing an antibody chiral stationary phase that had been prepared by immobilizing a monoclonal anti-D-amino acid antibody onto silica. The stronger affinity of the antibody towards aromatic and bulky amino acids allowed separation of such analytes in a 0.75 x 150 mm column, while an increase in column length enabled separation of more weakly bound compounds. The strength of interaction between chiral selector and analytes could be modulated conveniently by lowering the temperature. For the first time, simultaneous enantiomer separation of mixtures of amino acids was achieved on antibody-based chiral stationary phases using extracted ion chromatograms.