Proteomic studies of human and other vertebrate muscle proteins

Seasonal changes in atrophy-associated proteins of the sonic muscle in the big-snout croaker, Johnius macrorhynus (Pisces, Sciaenidae), identified by using a proteomic approach

In most sciaenids, males possess sonic muscles and produce sound through the contraction of these muscles and amplification of the swim bladder. The sonic muscles in some fishes exhibit seasonal changes in size. For example, they are hypertrophic in the spawning season, and atrophic in the non-spawning months. The protein profiles of the sonic muscle, red muscle, and white muscle in the Johnius macrorhynus were shown by two-dimensional electrophoresis (2-DE) and were compared to reveal differential protein expressions. About 80 up-regulated protein spots in the sonic muscle, and 30 spots related to six contractile proteins (fast muscle myosin heavy chain, skeletal alpha actin, alpha actin cardiac, tropomyosin, myosin light chain 2, and myosin light chain 3), four energy metabolic enzymes (enolase, acyl-CoA synthetase, creatine kinase, and cytochrome P450 monooxygenase), and two miscellaneous proteins (DEAD box protein and cyclin H) were identified. Seasonal hypertrophy and atrophy of the sonic muscles related to the reproductive cycle were verified in male big-snout croaker. The contents of some proteins were significantly different in the muscles under these conditions. The levels of cytochrome P450 monooxygenase, fast muscle myosin heavy chain, DEAD box proteins, isocitrate dehydrogenase, and creatine kinase were up-regulated in the hypertrophic muscle, but the levels of alpha actin cardiac, myosin light 2, and myosin light 3 were lower than in the atrophic muscle. Potential reasons for these differences in protein expression related to physiological adaptation are discussed.

Identification of cysteine, methionine and tryptophan residues of actin oxidized in vivo during oxidative stress

Increased levels of reactive oxygen species (ROS) cause oxidative stress and are believed to play a key role in the development of age-related diseases and mammalian aging in general by oxidizing proteins, lipids, and DNA. In this study, we have investigated the effects of ROS on actin in an established rat model of acute oxidative stress using short-term X-ray irradiation. Relative to the control, the actin functions studied in vitro were reduced for (i) actin polymerization to a minimum of 33% after 9 h and (ii) actin activated Mg(2+)-ATPase activity of myosin to 55% after 9 h. At 24 h, the activities had partially recovered to 64 and 80% of the control sample, respectively. The underlying oxidative modifications were also studied at the molecular level. The content of reactive carbonyl-groups increased 4-fold within the studied 24 h period. Among the five cysteine residues of actin, Cys(239) and Cys(259) were oxidized to sulfenic (Cys-SOH), sulfinic (Cys-SO(2)H), or sulfonic (Cys-SO(3)H) acids by increasing amounts over the time periods studied. The content of methionine sulfoxides also increased for 15 of the 16 methionine residues, with Met(44), Met(47), and Met(355) having the highest sulfoxide contents. Met(82) was also further oxidized to the sulfone. Among the four tryptophan residues present in actin, only Trp(79) and Trp(86) appeared to undergo oxidation. The relative contents of hydroxy-tryptophan, N-formyl-kynurenine, and kynurenine increased after irradiation, reaching a maximum in the 9 h sample.

Proteomic analysis of human skeletal muscle (m. vastus lateralis) proteins: identification of 89 gene expression products

Proteins from bioptates and autoptates of human skeletal muscle m. vastus lateralis were separated by O'Farrell two-dimensional gel electrophoresis (2DE). MALDI-TOF MS and MS/MS enabled identification of 89 protein spots as expression products of 55 genes. A modification of the O'Farrell's method including non-equilibrium electrophoresis in a pH gradient allowed detection--among major sarcomeric, mitochondrial, and cytosolic proteins--of several proteins, such as PDZ- and LIM domain-containing ones (pI > 8.70), fragments of known proteins, and a stable complex of heavy and light ferritin chains. The data underlie further studies of human skeletal muscle proteins in terms of molecular mechanisms of some physiological and pathological processes.

Reversible and irreversible modifications of skeletal muscle proteins in a rat model of acute oxidative stress

Oxidative stress caused by an imbalance of the production of "reactive oxygen species" (ROS) and cellular scavenging systems is known to a play a key role in the development of various diseases and aging processes. Such elevated ROS levels can damage all components of cells, including proteins, lipids and DNA. Here, we study the influence of highly reactive ROS species on skeletal muscle proteins in a rat model of acute oxidative stress caused by X-ray irradiation at different time points. Protein preparations depleted for functional actin by polymerization were separated by gel electrophoresis in two dimensions by applying first non-reductive and then reductive conditions in SDS-PAGE. This diagonal redox SDS-PAGE revealed significant alterations to intra- and inter-molecular disulfide bridges for several proteins, but especially actin, creatine kinase and different isoforms of the myosin light chain. Though the levels of these reversible modifications were increased by oxidative stress, all proteins followed different kinetics. Moreover, a significant degree of protein was irreversibly oxidized (carbonylated), as revealed by western blot analyses performed at different time points.

Proteomic Identification of Altered Proteins in Skeletal Muscle During Chronic Potassium Depletion: Implications for Hypokalemic Myopathy

Prolonged potassium depletion is a well-known cause of myopathy. The pathophysiology of hypokalemic myopathy, however, remains unclear. We performed a gel-based, differential proteomics study to define altered proteins in skeletal muscles during chronic potassium depletion. BALB/c mice were fed with normal chow (0.36% K+) or K+-depleted (KD) diet (<0.001% K+) for 8 weeks (n = 5 in each group). Left gastrocnemius muscles were surgically removed from each animal. Histopathological examination showed mild-degree infiltration of polymornuclear and mononuclear cells at the interstitium of the KD muscles. Extracted proteins were resolved with two-dimensional electrophoresis (2-DE), and visualized with Coomassie Brilliant Blue R-250 stain. Quantitative intensity analysis revealed 16 up-regulated protein spots in the KD muscles, as compared to the controls. These differentially expressed proteins were subsequently identified by peptide mass fingerprinting and by quadrupole time-of-flight tandem mass spectrometry (Q-TOF MS/MS). Most of the altered proteins induced by chronic potassium depletion were muscle enzymes that play significant roles in several various metabolic pathways. Other up-regulated proteins included myosin-binding protein H, alpha-B Crystallin, and translationally controlled tumor protein (TCTP). These findings may lead to a new roadmap for research on hypokalemic myopathy, to better understanding of the pathophysiology of this medical disease, and to biomarker discovery.

Polymorphism of delta3,5-delta2,4-dienoyl-coenzyme A isomerase (the ECH1 gene product protein) in human striated muscle tissue

Two polymorphic variants of the ECH1 gene product protein (delta3,5-delta2,4-dienoyl-coenzyme A isomerase) have been revealed by proteomics methods in samples of human striated muscle tissue. These variants are identical in molecular weight (29.7 kD) but different in pI values (6.57 and 6.75) and in amino acid substitution (41 E-->A) confirmed by mass spectrometry. The same type of polymorphism has been detected in samples of different tissues of the same person, so these variants are considered (also based on other data) to be allelic. The rates of these alleles in two representative cohorts of Moscow and Minsk residents are similar.

Concentrations of glycolytic enzymes and other cytosolic proteins in the diffusible fraction of a vertebrate muscle proteome

We used a novel microvolumetric technique based on protein diffusion to characterize the subproteome of muscle that consists of diffusible proteins, including those involved in cell metabolism. Muscle fiber segments were mechanically demembranated under mineral oil and transferred into drops of relaxing solution. After the fiber segment was depleted of diffusible proteins, the content of each drop and residual segment was analyzed by one-dimensional polyacrylamide gel electrophoresis. Proteins were identified through peptide mass fingerprinting and quantified using purified protein standards. Ten of the most abundant cytosolic proteins, distinguished by their ability to readily diffuse out of the skinned fiber, were glycolytic enzymes whose concentrations ranged from 2.6+/-1.0 g liter-1 (phosphoglucose isomerase) to 12.8+/-1.1 g liter-1 fiber volume (pyruvate kinase). The concentrations of the other five most abundant cytosolic proteins were as follows: glycogen phosphorylase, 6.0+/-2.3 g liter-1; phosphoglucose mutase, 2.2+/-0.2 g liter-1; adenylate kinase, 1.6+/-1.3 g liter-1; phosphocreatine kinase, 6.6+/-2.6 g liter-1; and parvalbumin, 0.7+/-0.4 g liter-1. Given the molecular weight and subunit number of each enzyme, the combined concentration of the 15 most abundant cytosolic proteins was 82.3 g liter-1; the volume fraction was 0.093. The large volume fraction of diffusible proteins favors nonspecific interactions and associations, particularly if the glycolytic enzymes and diffusible phosphocreatine kinase are restricted to the I-band as previous studies suggest. The relative molar concentration of glycolytic enzymes is roughly consistent with a stoichiometry of 1:2 for enzymes catalyzing the hexose and triose sugar reactions, respectively, a stoichiometry that may favor metabolic channeling of intermediates during glycolysis. Our results indicate that subcellular fractionation of muscle proteins, in which cytosolic constituents are distinguished by their ability to diffuse readily from demembranated cells, is a promising microvolumetric technique that allows conclusions to be drawn about native protein-protein interactions based on concentration and stoichiometry.