Jasmonic Acid Induces Endoplasmic Reticulum Stress with Different Outcome in Cultured Normal and Tumor Epidermal Cells.

Plant hormones produce cytotoxic effect on human cells and can trigger the processes unrelated to cell death, e.g., biosynthetic system stress. The goal of this study was to investigate activation of the endoplasmic reticulum (ER) stress by jasmonic acid (JA) and to distinguish between the responses of cultured immortalized non-tumorigenic HaCaT cells and epidermoid carcinoma A431 cells to this plant hormone. JA was used in the concentration of 2 mM, as it suppressed cell proliferation in both cell lines. We analyzed expression of genes associated with the activation of ER stress (GRP78, ATF4, CHOP), the structure of the ER and Golgi complex, and synthetic processes in the HaCaT and A431 cell lines. JA induced expression of genes responsible for the activation of ER stress and caused hypertrophic changes in the Golgi complex in both cell lines. However, the patterns of gene expression in the HaCaT and A431 cells were different, and higher levels of involucrin synthesis were observed in A431 but not in HaCaT cells, suggesting that JA activated differentiation of the tumor A431 cells only. Therefore, JA induced ER stress in both cell lines, but the consequences of ER stress were different for the epidermal immortalized non-tumorigenic and tumor cells.

Interaction of early secretory pathway and Golgi membranes with microtubules and microtubule motors.

This review summarizes the data describing the role of cellular microtubules in transportation of membrane vesicles - transport containers for secreted proteins or lipids. Most events of early vesicular transport in animal cells (from the endoplasmic reticulum to the Golgi apparatus and in the opposite recycling direction) are mediated by microtubules and microtubule motor proteins. Data on the role of dynein and kinesin in early vesicle transport remain controversial, probably because of the differentiated role of these proteins in the movements of vesicles or membrane tubules with various cargos and at different stages of secretion and retrograde transport. Microtubules and dynein motor protein are essential for maintaining a compact structure of the Golgi apparatus; moreover, there is a set of proteins that are essential for Golgi compactness. Dispersion of ribbon-like Golgi often occurs under physiological conditions in interphase cells. Golgi is localized in the leading part of crawling cultured fibroblasts, which also depends on microtubules and dynein. The Golgi apparatus creates its own system of microtubules by attracting γ-tubulin and some microtubule-associated proteins to membranes. Molecular mechanisms of binding microtubule-associated and motor proteins to membranes are very diverse, suggesting the possibility of regulation of Golgi interaction with microtubules during cell differentiation. To illustrate some statements, we present our own data showing that the cluster of vesicles induced by expression of constitutively active GTPase Sar1a[H79G] in cells is dispersed throughout the cell after microtubule disruption. Movement of vesicles in cells containing the intermediate compartment protein ERGIC53/LMANI was inhibited by inhibiting dynein. Inhibiting protein kinase LOSK/SLK prevented orientation of Golgi to the leading part of crawling cells, but the activity of dynein was not inhibited according to data on the movement of ERGIC53/LMANI-marked vesicles.

Temperature dependence of the mean autodetachment lifetime of the p-benzoquinone molecular radical anion.

Experimental data previously published from this laboratory (Asfandiarov NL, Pshenichnyuk SA, Fokin AI, Nafikova EP. Chem. Phys. 2004; 298: 263), on the temperature dependence of the mean autodetachment lifetime of the p-benzoquinone molecular radical anion, were analyzed in the framework of a simple statistical model. This model is a simplification of the well-known semiempirical approach elaborated by Christophorou et al. (Christophorou LG, Hadjiantoniou A, Carter JG. J. Chem. Soc., Faraday Trans. II 1973; 69: 1722). Evaluation of the vibrational energy storage of the target molecule and anion was made in a quantum approximation following a published procedure (Matejcik S, Märk TD, Spanel P, Smith D, Jaffke T, Illenberger E. J. Chem. Phys. 1994; 102: 2516). The results obtained are in reasonable agreement with the experimental data.

Electron capture negative ion mass spectra of some typical matrix-assisted laser desorption/ionization matrices.

A series of seven typical matrix-assisted laser desorption/ionization (MALDI) matrices has been investigated by means of electron capture negative ion mass spectrometry (ECNI-MS). It has been shown that the most effective matrices form deprotonated negative ions predominantly in the low-energy region. Relative dissociative cross sections have been measured for all molecules under investigation. The relative integrated abundance of [M - H](-) ion formation in the series changes by four orders of magnitude. It has been shown that 2,5-DHB (gentisic acid), one of the most effective MALDI matrices, has maximal relative intensity of [M - H](-) formation at the energy approximately equal 0.8 eV. This result is in accordance with a finding of Frankevich and Zenobi [Book of Abstracts, Workshop-school "Mass spectrometry in chemical physics, bio-physics and environmental sciences", Zvenigorod, Russia, April, 25-26, 2002, p. 40] that a probable origin of negative ions in MALDI is the process of low-energy (0.5-1 eV) dissociative electron capture by matrix molecules.

Violation of frozen shell approximation in dissociative electron capture by halogenated anthraquinones.

A series of halogenated anthraquinone (AQ) derivatives has been studied by means of electron capture negative ion (NI) mass spectrometry (ECNI-MS). 1Cl-AQ and 2Br-AQ display dramatically steep positive temperature dependencies of Hal(-) ion abundance in the low electron energy region. Molecular NI intensity decreases rapidly with increasing temperature in the case of 1I-AQ. In the case of 2Br-AQ, a metastable NI peak (m/z 22.9) corresponding to the process BrAQ(-) --> Br(-) + AQ(0) was recorded. This means that the characteristic dissociation lifetime of the molecular NI Br-AQ(-) is at least approximately 25 micros at the energy approximately 0.67 eV in the low-temperature spectrum (T approximately 80 degrees C), and at the energy approximately 0.13 eV in the hot spectrum (T approximately 290 degrees C). Together with the observed temperature dependence of the 2Br-AQ curves of effective yield (CEY), this proves that this anion dissociates according to Coulson's model. The same halogen anion behavior is observed in the case of 1Cl-AQ. There are three consecutive stages in the process of molecular NI dissociation of Cl- and Br-substituted AQ, namely, electron capture into the empty pi-orbital by means of the shape resonance mechanism, followed by a radiationless transition into the ground electronic pi-state of the anion, as predicted by Compton in the case of the parabenzoquinone molecule, and, finally, a fluctuative dissociation of the molecular NI accompanied by the transition from the pi-term into the sigma-term, so-called predissociation. Calculations show reasonable agreement with the experimental data. In the case of 1I-AQ, an effect of inversion of empty levels in the process of electron capture by the molecule takes place, a violation of the so-called frozen shell approximation. The phenomenon found may be of significance not only in the case of ECNI-MS, but also in other experimental investigations using low-energy electron-molecule and ion-molecule collisions.

Electronic excitation as a mechanism of the ion selectivity filter.

A correlation between the character of pharmacological activity and the energies of electronic transitions in some biologically active molecules, affecting the nervous system, has been found. In order to explain the correlation, a new principle of the membrane ion selectivity filter has been suggested. The principle is based on the recombination process of a metal cation, passing through the filter, with an electron, when the energy quantum (equal to the metal ionization energy) is emitted. The amino acid residue group, performing the function of the channel filter, absorbs this quantum, transits itself into an electronically excited state, changes its conformation and lets, as a result, the cation pass. The process is possible only in that case when the amino acid residue group has a transition of the same energy, therefore not all of metals can pass through the filter. From the viewpoint of this conception, an active molecule acts because of its transition into an electronically excited state of the same energy and interfering, thereby, with the natural processes.