Proteomics: delivering new routes to drug discovery - Part 1

iTRAQ-Based Proteomic Analysis Reveals Recovery of Impaired Mitochondrial Function in Ischemic Myocardium by Shenmai Formula

Shenmai formula (SM) has been a traditional medicinal remedy for treating cardiovascular diseases in China for 800 years; however, its mechanism of action remains unclear. To explore the mechanism underlying cardioprotective effects of SM, iTRAQ-based proteomic approach was applied to analyze protein of myocardium in rats with myocardial ischemic injury. Upon treatment with SM and its two major components Red ginseng (RG) and Radix Ophiopogonis (OP), 101 differentially expressed proteins were filtered from a total of 712 detected and annotated proteins. They can be classified according to their locations and functions, while most of them are located in intracellular organelle, participating in cellular metabolic process. The functions of them are mostly associated with mitochondrial oxidative phosphorylation/respiration. The differentially expressed proteins were validated by liquid chromatography-tandem mass spectrometry and Western blotting (ATP5D, NDUFB10, TNNC1). Further in vitro experiments found that SM could attenuate hypoxia induced impairment of mitochondrial membrane potential and cellular ATP concentration in neonatal rat ventricular myocytes. Interestingly, the result of quantitative mitochondrial biogenesis assays revealed that SM had dominant positive effects on the maximum respiration, ATP-coupled respiration, and spare capacity of mitochondria in response to hypoxia. Hence, our findings suggest that SM promotes mitochondrial function to protect cardiomyocytes against hypoxia, which provides a possible illustration for conventional botanical therapy on a molecular level.

Protein denaturation and protein:drugs interactions from intrinsic protein fluorescence measurements at the nanolitre scale

Protein stability and ligand-binding affinity measurements are widely required for the formulation of biopharmaceutical proteins, protein engineering and drug screening within life science research. Current techniques either consume too much of often precious biological or compound materials, in large sample volumes, or alternatively require chemical labeling with fluorescent tags to achieve measurements at submicrolitre volumes with less sample. Here we present a quantitative and accurate method for the determination of protein stability and the affinity for small molecules, at only 1.5-20 nL optical sample volumes without the need for fluorescent labeling, and that takes advantage of the intrinsic tryptophan fluorescence of most proteins. Coupled to appropriate microfluidic sample preparation methods, the sample requirements could thus be reduced 85,000-fold to just 10(8) molecules. The stability of wild-type FKBP-12 and a destabilizing binding-pocket mutant are studied in the presence and absence of rapamycin, to demonstrate the potential of the technique to both drug screening and protein engineering. The results show that 75% of the interaction energy between FKBP-12 and rapamycin originates from residue Phe99 in the binding site.