Biochemistry (Moscow) (v.83, #7)

Abstract—Here we present new approaches to better understanding multidrug resistance (MDR) development in cancer cells, such as identification of components of a complex process of MDR evolution. Recent advances in the studies of MDR are discussed: 1) chemotherapy agents might be involved in the selection of cancer stem cells resulting in the elevated drug resistance and enhanced tumorigenicity; 2) cell–cell interactions have a great effect on the MDR emergence and evolution; 3) mechanotransduction is an important signaling mechanism in cell–cell interactions; 4) proteins of the ABC transporter family which are often involved in MDR might be transferred between cells via microvesicles (epigenetic MDR regulation); 5) proteins providing cell-to-cell transfer of functional P-glycoprotein (MDR1 protein) via microvesicles have been investigated; 6) P-glycoprotein may serve to regulate apoptosis, as well as transcription and translation of target genes/proteins. Although proving once again that MDR is a complex multi-faceted process, these data open new approaches to overcoming it.
Keywords: multidrug resistance; cell–cell interactions; epigenetic regulation; microvesicles

UVB radiation (290-320 nm) causes diverse effects in plant cells that vary with the fluence rate of exposure. High fluence rates of UVB radiation cause damage to DNA and formation of reactive oxygen species in mitochondria and chloroplasts, which lead to oxidation of membrane proteins and lipids and inhibition of cellular functions. In response to oxidative stress, mitochondrial transmembrane potential dissipates, resulting in cytochrome c release and activation of metacaspases. This leads to the apoptosis-like cell death. The signaling mechanism based on UVB DNA damage includes check-point activation, cell-cycle arrest, and finally programmed cell death with characteristic DNA fragmentation and morphological hallmarks typical of apoptotic cells. Recently, it was shown that among the components of this signaling mechanism the transcriptional factor SOG1 (suppressor of gamma response 1) plays a key role in regulation of programmed cell death in plants. In contrast to its damaging effects, UVB radiation at low fluence rates can act as a regulatory signal that is specifically perceived by plants to promote acclimation and survival in sunlight. The protective action of UVB is based on expression of various genes, including those encoding flavonoid synthesis enzymes that provide a UVB-absorbing sunscreen in epidermal tissues and DNA photorepair enzymes. These processes are mediated by the UVB photoreceptor UVR8, which has been recently characterized at the molecular level. Now progress is made in uncovering the UVR8-mediated signaling path-way mechanism in the context of UVB photon perception and revealing the biochemical components of the early stages of light signal transduction. In this review, attention is focused on the achievements in studying these UVB-induced signaling processes.
Keywords: UVB radiation; signaling mechanisms; plants; cell death; photoprotection

The only pathway for the synthesis of essential amino acids in vertebrates is reversible transamination of their keto analogs with glutamic acid. At the same time, it is commonly accepted that such essential amino acids as lysine and threonine are not involved in transamination and, therefore, cannot be synthesized from their keto analogs. However, using radio-labeled isotopes, synthesis of threonine was demonstrated in rat liver and in a reaction mixture containing chicken liver threonine dehydrogenase. In the review, we discuss why threonine is an essential amino acid in mammals and birds based on the pathways of threonine biosynthesis in these two classes of vertebrates.
Keywords: threonine; NAD; acetyl-CoA; threonine dehydrogenase; threonine dehydratase

The Regulatory Role of NAD in Human and Animal Cells by V. A. Kulikova; D. V. Gromyko; A. A. Nikiforov (800-812).
Nicotinamide adenine dinucleotide (NAD) and its phosphorylated form NADP are the major coenzymes in the redox reactions of various essential metabolic pathways. NAD+ also serves as a substrate for several families of regulatory proteins, such as protein deacetylases (sirtuins), ADP-ribosyltransferases, and poly(ADP-ribose) polymerases, that control vital cell processes including gene expression, DNA repair, apoptosis, mitochondrial biogenesis, unfolded protein response, and many others. NAD+ is also a precursor for calcium-mobilizing secondary messengers. Proper regulation of these NAD-dependent metabolic and signaling pathways depends on how efficiently cells can maintain their NAD levels. Generally, mammalian cells regulate their NAD supply through biosynthesis from the precursors delivered with the diet: nicotinamide and nicotinic acid (vitamin B3), as well as nicotinamide riboside and nicotinic acid riboside. Administration of NAD precursors has been demonstrated to restore NAD levels in tissues (i.e., to produce beneficial therapeutic effects) in preclinical models of various diseases, such as neurodegenerative disorders, obesity, diabetes, and metabolic syndrome.
Keywords: NAD; metabolism; deacetylation; ADP-ribosylation; biosynthesis

Involvement of Mitochondria in Neurodegeneration in Multiple Sclerosis by M. S. Kozin; O. G. Kulakova; O. O. Favorova (813-830).
Functional disruption and neuronal loss followed by progressive dysfunction of the nervous system underlies the pathogenesis of numerous disorders defined as “neurodegenerative diseases”. Multiple sclerosis, a chronic inflammatory demyelinating disease of the central nervous system resulting in serious neurological dysfunctions and disability, is one of the most common neurodegenerative diseases. Recent studies suggest that disturbances in mitochondrial functioning are key factors leading to neurodegeneration. In this review, we consider data on mitochondrial dysfunctions in multiple sclerosis, which were obtained both with patients and with animal models. The contemporary data indicate that the axonal degeneration in multiple sclerosis largely results from the activation of Ca2+-dependent proteases and from misbalance of ion homeostasis caused by energy deficiency. The genetic studies analyzing association of mitochondrial DNA polymorphic variants in multiple sclerosis suggest the participation of mitochondrial genome variability in the development of this disease, although questions of the involvement of individual genomic variants are far from being resolved.
Keywords: neurodegenerative diseases; neurodegeneration; mitochondria; multiple sclerosis; haplogroup; single nucleotide polymorphism

Structure of the K82 Capsular Polysaccharide from Acinetobacter baumannii LUH5534 Containing a d-Galactose 4,6-Pyruvic Acid Acetal by A. A. Kasimova; J. J. Kenyon; N. P. Arbatsky; A. S. Shashkov; A. V. Popova; Y. A. Knirel; R. M. Hall (831-835).
Type K82 capsular polysaccharide (CPS) was isolated from Acinetobacter baumannii LUH5534. The structure of a linear tetrasaccharide repeating unit of the CPS was established by sugar analysis along with one- and two-dimensional 1H and 13C NMR spectroscopy. Proteins encoded by the KL82 capsule gene cluster in the genome of LUH5534 were assigned to roles in the synthesis of the K82 CPS. In particular, functions were assigned to two new glycosyltransferases (Gtr152 and Gtr153) and a novel pyruvyltransferase, Ptr5, responsible for the synthesis of D-galactose 4,6-(R)-pyruvic acid acetal.
Keywords: Acinetobacter baumannii ; capsular polysaccharide structure; pyruvic acid acetal; K locus; genetics of capsule biosynthesis

It is shown that differentiation of mouse mortality curves (number of animals that died at a certain age plotted versus their lifespan) results in the appearance of eight clearly distinguished clusters of peaks corresponding to increased mortality rates. Smoothing of the original mortality curves and subsequent transformation of the differential mortality curves according to the Gompertz model makes the peaks and the corresponding clusters less pronounced and drives the logarithm of the force mortality curve toward a straight line. The positions of the clusters on the lifespan axis (expressed in days) were calculated as weighted means by dividing the sum of the products of multiplication of the peak heights and their position on the lifespan axis by the sum of the peak heights within a cluster. To prove that the peaks and their clusters are not random, we have demonstrated that the positions of the clusters on the lifespan axis do not depend on the extent of mortality curve smoothing or the group of mice analyzed.
Keywords: lifespan; mice; differential mortality curves; peak clusters; Gompertz model

The capacities of relatively nontoxic lipopolysaccharide (LPS) from Rhodobacter capsulatus PG and highly potent LPS from Salmonella enterica serovar Typhimurium to evoke proinflammatory cytokine production have been compared in vivo. Intravenous administration of S. enterica LPS at a relatively low dose (1 mg/kg body weight) led to upregulation of TNF-α, IL-6, and IFN-γ production by non-sensitized CD-1 mice. LPS from R. capsulatus PG used at a four-times higher dose than that from S. enterica elicited production of almost the same amount of systemic TNF-α; therefore, the doses of 4 mg/kg LPS from R. capsulatus PG and 1 mg/kg LPS from S. enterica were considered to be approximately equipotential doses with respect to the LPS-dependent TNF-α production by CD-1 mice. Rhodobacter capsulatus PG LPS was a weaker inducer of the production of TNF-α, IL-6, and IFN-γ, as compared to the equipotential dose of S. enterica LPS. Administration of R. capsulatus PG LPS before S. enterica LPS decreased production of IFN-γ, but not of TNF-α and IL-6, induced by S. enterica LPS. Rhodobacter capsulatus PG LPS also suppressed IFN-γ production induced by S. enterica LPS when R. capsulatus PG LPS had been injected as little as 10 min after S. enterica LPS, but to a much lesser extent. Rhodobacter capsulatus PG LPS did not affect TNF-α and IL-6 production induced by the equipotential dose of S. enterica LPS. In order to draw conclusion on the endotoxic activity of particular LPSs, species-specific structure or arrangement of the animal or human immune systems should be considered.
Keywords: LPS; lipid A; Rhodobacter capsulatus ; Salmonella enterica ; CD-1 mice; cytokines; TNF-α; IL-6; IFN-γ

A Novel Fluorescent GFP Chromophore Analog-Based Dye for Quantitative PCR by A. A. Stakheev; D. Yu. Ryazantsev; Yu. K. Zvezdina; M. S. Baranov; S. K. Zavriev (855-860).
This is the first report describing the possibility of using a green fluorescent protein chromophore synthetic analog, P-HOBDI-BF2, as a fluorescent dye for a linear hydrolysis probe used in qPCR. The study was carried out on a system for detection of the plant pathogenic fungus Fusarium avenaceum using a plasmid containing translation elongation factor 1α fragment as a template. To estimate fluorogenic properties of P-HOBDI-BF2, 6-FAM-and BDP-FL-labeled probes were used. It was demonstrated that a synthetic dye based on the P-HOBDI-BF2 chromophore can be used for labeling hydrolysis probes for qPCR, but fluorescence increase levels for P-HOBDI-BF2-labeled probes were slightly lower than those for 6-FAM-labeled ones. At the same time, the sensitivity of P-HOBDI-BF2-based assays remained high, and this fact together with acceptable fluorescence levels suggests that this dye can be considered as an efficient alternative for reporters traditionally used for fluorescence detection in the FAM channel.
Keywords: quantitative PCR; fluorophore; probe; green fluorescent protein; fluorescence increase

Erratum to: “Rhamnose-Containing Cell Wall Glycopolymers from Rathayibacter toxicus VKM Ac-1600 and “Rathayibacter tanaceti” VKM Ac-2596” by A. S. Shashkov; E. M. Tul’skaya; A. S. Dmitrenok; G. M. Streshinskaya; N. V. Potekhina; S. N. Senchenkova; N. F. Piskunkova; L. V. Dorofeeva; L. I. Evtushenko (861-861).
On p. 725 in section Acknowledgments instead of:This work was supported by the Russian Science Foundation (project No. 14-50-00126) and the Russian Foundation for Basic Research (project No. 13-04-00447).Should read:This work was supported by the Russian Science Foundation (project No. 14-50-00126: structural studies, optical and NMR spectroscopy experiments, interpretation of spectra) and the Russian Foundation for Basic Research (project No. 13-04-00447: obtaining biomass of actinobacteria under study, microbiological control, obtaining cell walls and isolation of glycopolymer preparations and their primary chemical analysis).