The Inactivation Mechanism of Low Molecular Weight Phosphotyrosine-protein Phosphatase by H2O2

Low molecular weight phosphotyrosine-protein phosphatase (LMW-PTP) shares no general sequence homology with other PTPs, although it has an active site sequence motif CXXXXXR and a reaction mechanism identical to those of all PTPs. The main function of this enzyme is the down-regulation of platelet-derived growth factor and insulin receptors. Both human LMW-PTP isoenzymes are inactivated by H2O2. The enzymes are protected from inactivation by Pi, a competitive inhibitor, suggesting that the H2O2 reaction is directed to active site. Analysis of free thiols performed on the inactivated enzymes demonstrates that only two out of the eight LMW-PTP cysteines are modified. Time-course high performance liquid chromatography-electrospray mass spectrometry, together with specific radiolabeling and tryptic fingerprint analyses, enables us to demonstrate that H2O2 causes the oxidation of Cys-12 and Cys-17 to form a disulfide bond. Because both residues are localized into the active site region, this modification inactivates the enzyme. Fluorescence spectroscopy experiments suggest that the fold of the enzyme is modified during oxidation by H2O2. Because a physiological concentration of H2O2 produces enzyme inactivation and considering that the activity is restored by reduction with low molecular weight thiols, we suggest that oxidative stress conditions and other processes producing hydrogen peroxide regulate the LMW-PTP in the cell

Chronic lactate exposure promotes cardiomyocyte cytoskeleton remodelling

We investigated the effect of growing on lactate instead of glucose in human cardiomyocyte assessing their viability, cell cycle activity, oxidative stress and metabolism by a proteomic and metabolomic approach. In previous studies performed on elite players, we found that adaptation to exercise is characterized by a chronic high plasma level of lactate. Lactate is considered not only an energy source but also a signalling molecule and is referred as “lactormone”; heart is one of the major recipients of exogenous lactate. With this in mind, we used a cardiac cell line AC16 to characterize the lactate metabolic profile and investigate the metabolic flexibility of the heart. Interestingly, our data indicated that cardiomyocytes grown on lactate (72 h) show change in several proteins and metabolites linked to cell hypertrophy and cytoskeleton remodelling. The obtained results could help to understand the effect of this metabolite on heart of high-performance athletes

Chronic Training Induces Metabolic and Proteomic Response in Male and Female Basketball Players: Salivary Modifications during In-Season Training Programs

The aim of this study was to characterize the salivary proteome and metabolome of highly trained female and male young basketball players, highlighting common and different traits. A total of 20 male and female basketball players (10 female and 10 male) and 20 sedentary control subjects (10 female and 10 male) were included in the study. The athletes exercised at least five times per week for 2 h per day. Saliva samples were collected mid-season, between 9:00 and 11:00 a.m. and away from sport competition. The proteome and metabolome were analyzed by using 2DE and GC–MS techniques, respectively. A computerized 2DE gel image analysis revealed 43 spots that varied in intensity among groups. Between these spots, 10 (23.2%) were differentially expressed among male athletes and controls, 22 (51.2%) between female basketball players and controls, 11 spots (25.6%) between male and female athletes, and 13 spots (30.2%) between male and female controls. Among the proteins identified were Immunoglobulin, Alpha-Amylase, and Dermcidin, which are inflammation-related proteins. In addition, several amino acids, such as glutamic acid, lysine, ornithine, glycine, tyrosine, threonine, and valine, were increased in trained athletes. In this study, we highlight that saliva is a useful biofluid to assess athlete performance and confirm that the adaptation of men and women to exercise has some common features, but also some different sex-specific behaviors, including differential amino acid utilization and expression of inflammation-related proteins, which need to be further investigated. Moreover, in the future, it will be interesting to examine the influence of sport-type on these differences