Collapsin response mediator protein 4 enhances the radiosensitivity of colon cancer cells through calcium­mediated cell signaling.

Radiation therapy is an effective treatment against various types of cancer, but some radiation­resistant cancer cells remain a major therapeutic obstacle; thus, understanding radiation resistance mechanisms is essential for cancer treatment. In this study, we established radiation­resistant colon cancer cell lines and examined the radiation­induced genetic changes associated with radiation resistance. Using RNA­sequencing analysis, collapsin response mediator protein 4 (CRMP4) was identified as the candidate gene associated with radiation sensitivity. When cells were exposed to radiation, intracellular Ca2+ influx, collapse of mitochondrial membrane potential, and cytochrome c release into the cytosol were increased, followed by apoptosis induction. Radiation treatment­ or Ca2+ ionophore A23187­induced apoptosis was significantly inhibited in CRMP4­deficient cells, including radiation­resistant or CRMP4­shRNA cell lines. Furthermore, treatment of CRMP4­deficient cells with low levels (<5 µM) of BAPTA­AM, a Ca2+ chelator, resulted in radiation resistance. Conversely, Ca2+ deficiency induced by a high BAPTA­AM concentration (>10 µM) resulted in higher cell death in the CRMP4­depleted cells compared to CRMP4­expressing control cells. Our results suggest that CRMP4 plays an important role in Ca2+­mediated cell death pathways under radiation exposure and that CRMP4 may be a therapeutical target for colon cancer treatment.

Application of ultrasound treatment for improving the physicochemical, functional and rheological properties of myofibrillar proteins.

The aim of this study was to evaluate the impact of duration (10, 20 and 30min) and power (100 and 300W) of high-intensity ultrasound (20kHz) on physicochemical properties of beef myofibrillar proteins in order to investigate novel process for modification of its functional characteristics. Results showed that augmentation of duration and power of ultrasound led to enhance pH. Also, the water holding capacity and gel strength were improved by increasing pH. The highest value in pH, reactive sulfhydryl content, water holding capacity and gel strength was obtained in sample subjected to 30min of ultrasound at 300W. The particle size distribution of the proteins was decreased after ultrasound treatment because of the cavitation force of ultrasound waves. In this circumstance, an improvement of emulsifying properties can be obtained. Ultrasonic waves had significant effects on the rheological properties of myofibrillar proteins. Treated samples were more elastic and stiffer than control, although the inverse trend was observed after 30min treatment at each power. Finally, a reducing trend in viscosity was observed by increasing time and power of sonication. Ultrasonic treatment could successfully improve functional properties with effect on physicochemical properties of myofibrillar proteins.

Kinetic regime of aggregation of UV-irradiated glyceraldehyde-3-phosphate dehydrogenase from rabbit skeletal muscle.

The study of the kinetics of aggregation of UV-irradiated proteins has attracted considerable interest, since test systems based on aggregation of proteins denatured by UV radiation can be used for screening of the natural and artificial agents possessing chaperone-like activity (anti-aggregation activity). To provide the proper interpretation of the effects caused by the agents under study, the kinetic mechanism of the aggregation process should be established. In the present work the kinetic data on aggregation of UV-irradiated glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from rabbit skeletal muscle at 37 °C (O.I. Maloletkina et al. Biophys. Chem. 163-164 (2012) 11-20) have been analyzed. It has been shown that the stage of aggregate growth follows the first-order kinetics and the experimentally measured rate constant of the first order corresponds to heat-induced structural reorganization of UV-irradiated GAPDH containing concealed damage.

Label-free protein profiling of formalin-fixed paraffin-embedded (FFPE) heart tissue reveals immediate mitochondrial impairment after ionising radiation.

Qualitative proteome profiling of formalin-fixed, paraffin-embedded (FFPE) tissue is advancing the field of clinical proteomics. However, quantitative proteome analysis of FFPE tissue is hampered by the lack of an efficient labelling method. The usage of conventional protein labelling on FFPE tissue has turned out to be inefficient. Classical labelling targets lysine residues that are blocked by the formalin treatment. The aim of this study was to establish a quantitative proteomics analysis of FFPE tissue by combining the label-free approach with optimised protein extraction and separation conditions. As a model system we used FFPE heart tissue of control and exposed C57BL/6 mice after total body irradiation using a gamma ray dose of 3 gray. We identified 32 deregulated proteins (p≤0.05) in irradiated hearts 24h after the exposure. The proteomics data were further evaluated and validated by bioinformatics and immunoblotting investigation. In good agreement with our previous results using fresh-frozen tissue, the analysis indicated radiation-induced alterations in three main biological pathways: respiratory chain, lipid metabolism and pyruvate metabolism. The label-free approach enables the quantitative measurement of radiation-induced alterations in FFPE tissue and facilitates retrospective biomarker identification using clinical archives.

The elasticity of single kettin molecules using a two-bead laser-tweezers assay.

Kettin is a high molecular mass protein of insect muscle associated with thin filaments and alpha-actinin in the Z-disc. It is thought to form a link between thin and thick filaments towards its C-terminus, contributing significantly to passive sarcomere stiffness. Here the elastic properties were characterised by mechanical stretches on an antibody-delimited region of the single molecule using two independent optical traps capable of exerting forces up to 150 pN. Step-like events were observed in the force-extension relationships consistent with the unfolding of Ig domains at moderate force and refolding of these domains at significantly higher forces than have been observed for related modular proteins.

Modifications of human cardiac sodium channel gating by UVA light.

Voltage-gated Na(+) channels are membrane proteins responsible for the generation of action potentials. In this report we demonstrate that UVA light elicits gating changes of human cardiac Na+ channels. First, UVA irradiation hampers the fast inactivation of cardiac Nav1.5 Na(+) channels expressed in HEK293t cells. A maintained current becomes conspicuous during depolarization and reaches its maximal quasi steady-state level within 5-7 min. Second, the activation time course is slowed by UVA light; modification of the activation gating by UVA irradiation continues for 20 min without reaching steady state. Third, along with the slowed activation time course, the peak current is reduced progressively. Most Na(+) currents are eliminated during 20 min of UVA irradiation. Fourth, UVA light increases the holding current nonlinearly; this phenomenon is slow at first but abruptly fast after 20 min. Other skeletal muscle Nav1.4 isoforms and native neuronal Na(+) channels in rat GH(3) cells are likewise sensitive to UVA irradiation. Interestingly, a reactive oxygen metabolite (hydrogen peroxide at 1.5%) and an oxidant (chloramine-T at 0.5 mM) affect Na(+) channel gating similarly, but not identically, to UVA. These results together suggest that UVA modification of Na(+) channel gating is likely mediated via multiple reactive oxygen metabolites. The potential link between oxidative stress and the impaired Na(+) channel gating may provide valuable clues for ischemia/reperfusion injury in heart and in CNS.

Titin-based modulation of calcium sensitivity of active tension in mouse skinned cardiac myocytes.

We studied the effect of titin-based passive force on the length dependence of activation of cardiac myocytes to explore whether titin may play a role in the generation of systolic force. Force-pCa relations were measured at sarcomere lengths (SLs) of 2.0 and 2.3 microm. Passive tension at 2.3 microm SL was varied from approximately 1 to approximately 10 mN/mm(2) by adjusting the characteristics of the stretch imposed on the passive cell before activation. Relative to 2.0 microm SL, the force-pCa curve at 2.3 microm SL and low passive tension showed a leftward shift (pCa(50) [change in pCa at half-maximal activation]) of 0.09+/-0.02 pCa units while at 2.3 microm SL and high passive tension the shift was increased to 0.25+/-0.03 pCa units. Passive tension also increased pCa(50) at reduced interfilament lattice spacing achieved with dextran. We tested whether titin-based passive tension influences the interfilament lattice spacing by measuring the width of the myocyte and by using small-angle x-ray diffraction of mouse left ventricular wall muscle. Cell width and interfilament lattice spacing varied inversely with passive tension, in the presence and absence of dextran. The passive tension effect on length-dependent activation may therefore result from a radial titin-based force that modulates the interfilament lattice spacing.

[Regularities in the kinetic of photoactivation of lactate dehydrogenase by the action of UV light in different microenvironment]. / Kineticheskie zakonomernosti fotoaktivatsii laktatdegidrogenazy pod deistviem UF-izlucheniia v usloviiakh razlichnogo mikrookruzheniia.

The kinetics of photoinactivation of cardiac (H4) and muscular (M4) isoforms of lactate dehydrogenase irradiated by UV light (240-390 nm) in the free form and in the presence of sodium azide, D-mannitol, and serotonin was studied. It was shown that the decrease in the catalytic activity of both enzymes can be described by the kinetics of the first-order monomolecular reaction. The inactivation rate constant of lactate dehydrogenase M4 is considerably higher than that of lactate dehydrogenase H4, indicating a greater photochemical lability of the isoform M4. It was shown that sodium azide has a different protective action on the proteins studied. The irradiation of the muscular isoform in the presence of serotonin and D-mannitol did not change the character of the "dose-effect" curve and only led to a decrease in the photoinactivation rate constant of the protein.

Activation of ryanodine receptors by flash photolysis of caged Ca2+.

Flash photolysis of DM-nitrophen generates an extremely large [Ca2+] transient ("Ca2+ spike") at the start of each Ca2+ "step." The Ca2+ spike greatly increases the speed of activation of the ryanodine receptor channel ("supercharging") and could be responsible for apparent channel adaptation.

[The effect of ionizing radiation on human muscle tissue]. / Vliianie ioniziruiushchei radiatsii na myshechnuiu tkan' cheloveka.

The effect of ionizing radiation (gamma-irradiation of 60Co, doses from 10 Gy to 15 kGy) on human muscle tissue was studied using a biopsy material. Destructive alterations in muscle proteins were observed beginning from the dose of 1.0 kGy: appearance of new protein fractions with molecular mass 68-160 kDa and 18-36 kDa. Resistance of muscle proteins to the trypsin effect was unaltered, while the rate of pronase-induced hydrolysis was slightly increased, about 1.2-fold. Content of water and biomechanical properties of the tissue were unaltered, but the modulus of elasticity was decreased approximately 3-fold after treatment with maximal doses of the ionizing radiation used.

The effect of photogenerated site-directed free radicals on surface dihydropyridine binding sites identified with photoaffinity probe (-)-[3H]-azidopine on cultured monkey renal cells.

With the use of the photoactivable dihydropyridine (DHP)-type calcium (Ca2+ channel antagonist (-)-[3H]-azidopine, a specific photoaffinity probe for Ca2+ channels, we tested the hypothesis of the existence of a separate subsite in the DHP receptor region on native polarized, stimulated depolarized and UV irradiated green monkey renal (GMR) cells preincubated with selected DHPs. Our results demonstrate that specific binding of (-)-[3H]-azidopine on GMR cells is of high affinity, stereoselective and dependent mainly on the inactivation of the membrane bound Ca2+ channel. Preincubation of the GMR cells with the DHP Ca2+ channel agonist BAY-K-8644 significantly reduced specific photolabeling. The site-directed free radicals generated after UV irradiation in DHP-preincubated renal cells inactivated Ca2+ channels and did not significantly affect the specific photoincorporation of (-)-[3H]-azidopine. (+)-Niguldipine, a DHP with the voluminous substituent on the DHP ring, significantly reduced the photolabeling. Low affinity labeling was partially prevented in (+)-nimodipine and (+)-niguldipine preincubated photoirradiated cells. The results strongly support the existence of central and peripheral subsites of the DHP region on GMR cells, with the former incorporating on photoactivation the intrinsically photoactive DHPs and with the latter labeled with a side chain bearing nitrene-generating photoreactive group, the photoaffinity probe, (-)-[3H]-azidopine.

Radiation-induced increase in the release of amino acids by isolated, perfused skeletal muscle.

Local exposure of the hindquarter of the rat to 15 Gy of gamma-radiation resulted, 4-6 h after irradiation, in an increased release of amino acids by the isolated, perfused hindquarter preparation, 70 per cent of which is skeletal muscle. This increase in release involves not only alanine and glutamine which are synthesized to a large extent de novo in muscle, but also those amino acids which are not metabolized by muscle and, therefore, released in proportion to their occurrence in muscle proteins. Because metabolic parameters and content of energy-rich phosphate compounds in muscle remain unchanged, it is unlikely that general cellular damage is the underlying cause of the radiation-induced increase in amino acid release. The findings strongly favour the hypothesis that the increased availability of amino acids results from enhanced protein breakdown in skeletal muscle which has its onset shortly after irradiation. This radiation-induced disturbance in protein metabolism might be one of the pathogenetic factors in the aetiology of radiation myopathy.

[Ultrastructure of skeletal muscle tissue of microwave damaged chick embryos]. / Ul'trastruktura skeletnoi myshechnoi tkani kurinykh émbrionov pri mikrovolnovom porazhenii.

The effect of ultrahigh-frequency energy of electromagnetic field of low intensity on certain morphometric indices of intracellular organoids and on cellular ultrastructure were studied in the developing skeletal muscular tissue of chick embryos. In the skeletal muscles of irradiated embryos a limited cellular destruction, structural disorders in myonic organoids were revealed. Reactive-recovery processes manifested themselves in hyperplasy and hypertrophy of organoids, in activation of protein synthesis, in increasing amount of myosatellites. At early stages after irradiation peripheral mitochondria are subjected to greater changes. After hatching, central mitochondria in myons suffer more. Quantitative changes in myonic organoids and degree of their destruction seem to depend on.a peculiar differentiation of the muscular tissue, blood supply and innervation of the muscle as an organ.