Plant Signaling Peptides

Summary: Signaling peptides identified in plants are involved in communication between cells or organs. Until now, the five signaling peptides (SCR, CLAVATA3, phytosulfokine-a, systemin, ENOD40) have been found in plants. The SCR polypeptides are pollen ligands involved in activation of stigmatic receptors and initiation of a signal transduction cascade that leads to regulation of pollen hydratation. The CLAVATA3 is a small secreted polypeptide that plays a role in cell-cell communication in the shoot apical meristem. Phytosulfokine-a, a sulfated pentapeptide, promotes proliferation of plant cells in culture. Systemin, an oligopeptide released from wound site, systemically regulates the activation of over 20 defensive genes. The products of gene ENOD40 facilitate cell divisions in nodulation and differentiation of vascular bundles.

Key words: plant signaling peptides, SCR, CLAVATA3, phytosulfokine-a, systemin, ENOD40
 

The Outer Membrane Channels in Mitochondria Physiology

Summary: Pathways for molecule transport across the outer mitochondrial membrane are formed by ion channels. The transported molecules are not only metabolites exchanged between mitochondria and cytosol but also proteins imported into mitochondria. This review presents basic properties of the outer membrane channels and their role in mitochondria physiology. The existence of many factors influencing functional state of the outer membrane channels indicates that transport of a molecule across the outer membrane depends not only on its mass. Moreover, the functional complexity of the outer membrane channels suggests a significant role of the membrane not only in metabolic and energetic functions of mitochondria but also in their biogenesis as well as in cell physiology.

Key words: VDAC channel, the TOM complex channel, protein and metabolite transport.
 

Genetic Regulation of Copper Transport and Metabolism

Summary: The results obtained for many decades indicate that copper is an essential element for normal growth and metabolism of all living organisms. Both deficiency and excess of this element are harmful for plants and animals. That is why living organisms have developed a precise and genetically-controlled mechanism which regulates the concentration of this element in the cells. When the model organisms (bacteria, yeast) and mutants of higher animals, as well as human patients with genetic defect in copper metabolism were analysed, two groups of protein involved in copper transport and metabolism were found. Those proteins are: 1) two types of P-type ATPases necessery for maintaning cellular copper homeostasis in pro- and eucariotes. 2) metallochaperones, which bound the metal molecules and deliver to cellular organellas when the copper is incorporated into structure of the copper-dependent enzymes or nonenzymatic proteins.

Key words: copper metabolism, P-type ATPases, copper cations transport.
 

The Mechanism of Action and the Role of Oxytocin in the Oestrous Cycle

Summary: Oxytocin participates in the regulation of the oestrous cycle. The biosynthesis of hormone by different organs in females and structure of oxytocin receptor were described. The factors which regulate the biosynthesis and concentrations of oxytocin receptors in the tissues in the oestrous cycle were presented. It was shown the role of oxytocin during luteolysis in sheep, cows and sows. The influence of oxytocin on ovarian steroidogenesis and motility of uterus and oviduct was also presented.

Key words: oxytocin, oxytocin receptors, luteolysis.
 

Advance in Methods of Culturing Cells for Transplantology - Stem Cells

Summary: Stem cells raise an increasing interest for the sake of their potential significance in clinical medicine. Totipotent individual stem cells derived from early embryos are able to develop into a foetus. Pluripotent stem cells selected from adult organisms can differentiate into various tissue cell types and soon might be used in therapy. The development of methods of cell engineering can be expected to permit growth of tissues and organs in vitro and their later usage in transplantology. The article considers some latest achievements in the field of stem cells isolation and culture; the special attention is paid to stem cells present in cultures of human skin keratinocytes.

Key words: human stem cells, in vitro culture, transplantology
 

Sugar Regulation and Signaling in the Plant Cells

Summary: Sugars are not only the end products of photosynthesis, transporting forms and storage materials in some tissues, sugars also play regulatory function. Changes of sugar concentration in the tissue affect metabolic processes: photosynthesis, respiration, protein synthesis and nitrate assimilation. Changes in sugar content influence the expression of numerous genes. Sugars accumulated in the tissues often cause repression of photosynthetic genes while sugar starvation induce the same genes. Genes encoding enzymes involved in sucrose metabolism, eg. sucrose synthase, invertases and enzymes involved in starch synthesis, like ADP-glucose pyrophosphorylase, are induced by glucose and sucrose.

The role of hexokinase, sugar transporters and other components in sugar signaling in plant cell is discussed in this review.

Key words: gene expression, glucose, hexokinase, metabolism regulation, sugar signaling, sucrose.
 

Chloroplast Proteases

Summary: A controlled degradation of proteins is intimately involved in regulatory mechanisms of many different cell functions, including cell cycle, differentiation, protein targeting and sorting and a programmed cell death. It is about fifteen years that the role of the degradation of specific proteins in mechanisms behind chloroplast biogenesis and adaptation to everchanging environmental stimuli was recognized as well. It also became evident that the proteases responsible for the degradation of chloroplast proteins are located inside the chloroplast themselves. As a result at the moment most investigated chloroplast proteases can be operationally divided into three categories: 1) the ones responsible for a proteolytic processing of precursor forms of chloroplast proteins; 2) the ones catalysing degradative processing put into motion in response to changing incident photon flux density and temperature; 3) the ones degradaing the proteins that are damaged or otherwise abnormal, the unassembled subunits of protein complexes and mistargeted proteins. The data regarding current awareness in relation to intrachloroplast compartmentation of defined proteases, their structure (including structural homology to bacterial enzymes), functional properties and expression pattern as determined by changing ontogenetical and enviromental context is summarised below.

Keywords: protease, catalytic domain, Clp, FtsH, DegP, chloroplast, stroma, thylakoid membrane, thylakoid lumen, chloroplast envelope, transit peptide.
 

Specification of the Germ-Line Cells in Invertebrates and Vertebrates. The Function of the Germ Plasm

Summary: In many invertebrates and vertebrates the specification of germ cells depends on the germ cell fate determinant which is called the germ plasm. During development the germ plasm segregates to the prospective germ line blastomeres and eventually to the primordial germ cells. At the ultrastructural level, the germ plasm contains a number of constant components: mitochondria, elements of rough endoplasmic reticulum, Golgi complexes and characteristic structures termed germinal granules. Various RNAs and proteins are localized either in the germ plasm matrix or on the germinal granules. We discuss the role of the germ plasm components and the methods of interference with its function.

Key words: Primordial germ cells, oocytes, RNA localization, embryogenesis
 

The Peripheral Benzodiazepine Receptor

Summary: Benzodiazepines are the most widely used therapeutic drugs because of their sedative and anxiolytic effects mediated through GABAA receptors located in the central nervous system. Another recognition site for these drugs termed the peripheral-type benzodiazepine receptor (PRB) has been found in peripheral tissues (outside the nervous system) and glial cells in the brain. PRB is comprised in part by a 18 kDa protein. This protein is present in the outer mitochondrial membrane and is likely to associate with the VDAC channel and adenine nucleotide carrier. A definitive role of PRB has not been elucidated but strong evidence indicates that this receptor plays an important role in steroid biosynthesis, mechanism affecting mitochondrial respiration, proliferation, calcium flow, cellular immunity, malignancy and apoptosis. The tissue distribution of PRB shows a distinct cell-specific pattern of expression. The receptor levels are regulated in a tissue dependent manner by hormonal regulation and stress.

Key words: peripheral benzodiazepine receptor, benzodiazepine
 

Neuronal Calcium Sensors

Summary: Calcium ion is a key intracellular messenger molecule. Its action is mediated by the calcium-binding proteins. Among them, still growing group are homologous "EF-hand" proteins, discovered during last ten years and constituting a family called Neuronal Calcium Sensors. The family consists of recoverins, frequenins, GCAPs, and VILIPs. They all share such features as a specific structure and occurrence in certain neurons what suggests that they play a strictly determined role there. However, the function of most members of the NCS family has not been explained yet, and it still remains a matter of investigations. In this review we present the actual knowledge concerning this interesting and important group of proteins.

Key words: calcium, calcium-binding proteins, neuronal calcium sensors, signal transduction