Postepy Biologii Komorki, vol. 32, 2005, issue 1

Summary: Helicobacter pylori is one of the most frequently observed pathogenic bacterium that colonizes the human stomach. Colonization of gastric mucosa is the main etiologic factor of the development of duodenal and gastric ulcer diseases and gastric adenocarcinoma. The spectrum of bacterial proteins, especially CagA antigen, cytotoxin VacA and BabA adhesin, are correlated with higher virulence of H. pylori strains. Differences in activities of cytotoxin VacA and CagA antigen are connected with polymorphisms observed in the genes which coded these proteins. However, the main role in pathogenesis of H. pylori infection might play specific interactions between H. pylori and gastric epithelial cell on the molecular level.

Key words: Helicobacter pylori; pathogen; virulence; ulcer disease; gastric cancer; vacuolization cytotoxin; adhesions; CagA antigen; protein interactions

Brefeldin A – An Insight Into the Functioning of the Membrane System of Plant Cells

Summary: The functioning of eukaryotic cells is strictly dependent on the proper vesicular traffic within the cell’s membrane system. Brefeldin A – a fungal toxin, disturbs this traffic, enabling an experimental insight into the organisation and co-operation of various elements of the system. Recently, BFA target proteins and sites of action have been identified. In this paper, we analyse the mechanism of BFA functioning and indicate those particular properties of the membrane system of plant cells that determine some of the reactions to BFA that are specific to plants. We demonstrate also, how the research into one of such reactions – the formation of BFA compartments has led to the discovery of novel aspects of endocytosis in plants. Finally, we identify implications, born from the recognition of the mechanisms of BFA action, for the modern concepts of molecular and cellular mechanisms of polar auxin transport.

Key words: brefeldin A, endocytosis, guanine nucleotide exchange factor, polar auxin transport, membrane system

Summary: Apoptosis is a natural process at reproductive age in women. It concerns granulosa and thecal cells. This process influences on the amount of ovarian follicles, luteal corpus sufficiency and on steroidogenesis and menopause. Apoptosis cause normal function and homeostasis of ovarian cells. Knowing the mechanism of apoptosis in human ovary to optimalize the management in endocrinologia disorders and neoplasmus.

Key words: ovary, apoptosis, inducing and inhibiting factors, caspases, menopausis

Summary: MicroRNAs (miRNAs) constitute a group of single-stranded, noncoding RNAs that regulate the expression of structural genes on post-transcriptional level. miRNAs are transcribed as several hundred-nucleotide pri-miRNAs. The mature, active form is only 21–23 nucleotides long and it binds target mRNAs containing antisense sequences. miRNA can either catalyze cleavage of mRNA that are perfectly base-paired to its sequence, or inhibit the translation of mRNAs that form an imperfect complex with the miRNA. Hundreds of miRNAs are described to date, which populate the genomes of plants and animals. They are necessary for crucial cellular and developmental processes. Some of them directly regulate the development; some affect programmed cell death (PCD), some at last are essential for signal transduction. miRNA expression profiles classify human cancers better than mRNA profiles what may be of big diagnostic and therapeutic value. This study presents the current understanding of miRNA biogenesis, regulatory mechanisms and the role that miRNAs exert in embryogenesis, hematopoiesis and oncogenesis.

Summary: Recent studies have underscored the importance of regulatory T cells (Treg) in the maintenance of immunological self-tolerance and in the prevention of autoimmune diseases. Regulatory T cells is heterogenic subpopulation of T cells, that is able to supress functions of effector cells during the immune response. Among them are natural (CD4+CD25+) and induced Treg (Tr1, Th3, CD4+CD25-) that gain their unique fenotype during the development in the thymus or in the periphery, respectively. CD25, CD45RO, CD152, GITR, LAG-3, several adhesion molecules, chemokine receptors as well as Toll-like receptors are detected on the surface of Treg. Mechanism of suppression used by natural Treg, although not completely understood, seems to depend more on the cell-cell contact than on cytokines (at least in vitro).

Summary: In this paper current knowledge concerning the role of mitochondria in plant programmed cell death (PCD) is presented. It has been already suggested that plant mitochondria, similarly to animal ones, can induce PCD. Senescence process in plants which engages PCD mechanisms involves transport and redistribution of metabolites what require energy generated in mitochondria. It seems therefore that PCD in plants might proceed in different way than animal apoptosis. It is still not clear whether mitochondrial permeability transition (MPT) and decrease of mitochondrial transmembrane potential (?¥_m) always take place in plants. Release of cytochrome c into cytosol and its inducible role in PCD in free-cell system in plants may suggest the existence of some common pathways of animal apoptosis and plant PCD. In spite of many results concerning induction of PCD during differentiation process, existing data do not elucidate the role of mitochondria in this process.

Key words: plant mitochondria, programmed cell death, mitochondrial membrane potential

Summary: Endothelium is not only a layer of cells separating lumen of vessel from surrounding tissues. It begins to notice its role in many biological processes. This paper presents the role of endothelium and vessels in development, tissues and organs formation and maturation.

Peptidergic Modulation of Gonadotropin Subunit Gene Expression in the Anterior Pituitary of Female Rats

Summary: Transcription activity of genes encoding three gonadotropin subunits: (?, LH?,FSH?) depends on specific cis- and trans-acting regulatory elements located on their promoters. Gonadotropin releasing hormone (GnRH) is a crucial neurohormon stimulating these genes transcriptional activity. Pulsatile intracerebroventricular microinjections of GnRH, ?-endorphin, vasoactive intestinal peptide (VIP) and galanin in ovariectomized rats revealed their significant role in the modulation of gonadotropin subunits gene expression. LH? and FSH? mRNA expression were stimulated by low frequency GnRH pulses whereas ? subunit mRNA level was stimulated also by high frequency pulses. ?-endorphin reduced ??and LH? gene expression and diminished the stability of both mRNAs. VIP acting through its specific receptors reduced endogenous GnRH system activity and decreased both ? and LH? mRNA level in pituitary gland. Instead, galanin up-regulated GnRH receptor activity and exerted stimulatory effect on ? and LH? gene expression. Its effect depended on gonadal steroids and specific galanin receptors. FSH? gene expression was dependent both on GnRH and as well as on activin stimulation and both peptides were acting independently and synergistically. Peptidergic modulation (stimulatory or inhibitory) of endogenous GnRH system activity results in a significant changes of gonadotropin subunits mRNA content and, in consequence, may indirectly influence on gonadotropin biosynthesis activity in female rats.

Key words: gonadotropin genes expression, pituitary, GnRH, ?-endorphin, galanin, VIP, activin

Summary: For several decades, it has been assumed that plasminogen activation may play an important role in tumor invasion and metastasis. The basic idea is that plasminogen activators released from cancer cells catalyze the proteolytic conversion of the inactive zymogen plasminogen to the active proteinase plasmin, which in turn catalyzes degradation of proteins in basement membranes and extracellular matrix (ECM) and thus facilitates cancer cell invasion into the surrounding tissue. Studies have proved that plasminogen activation system also plays a role in processes connected with cancer cell-directed tissue remodelling. Examples of such processes are angiogenesis and desmoplasia, i.e. stimulation of fibroblast proliferation and extracellular matrix protein synthesis. In the text the structures of plasminogen activation system’s elements and theirs role in cancer cells adhesion, migration and invasion based on experiments in cell culture model systems are described. Moreover, processes in cancer tumor involving plasminogen activation system and the role of components’ expressions level in prognosis in selected human cancers are discussed.

Summary: Pests and plant pathogens are important reason of crops’ quality and productivity limitation. Chemical drugs and pesticides belong to the most common among the strategies used to restrict losses in agricultural production. However, agrophags frequently acquire the resistance towards these substances, even after short time of contact with them. The occurring resistance is a natural consequence of the continuous evolutionary processes influenced by the selective pression of pesticides. The resistance results from point mutations and, in consequence, the changes of target protein’s structure for pesticides or the functional changes of other proteins, for example enzymes. The matter of the mechanisms of pesticides’ action and the formation of resistance is very extensive, therefore in this paper only chosen molecular mechanisms, that influence the occurrence of resistance towards pesticides are discussed. Given examples had been restricted to the most common pests and plant pathogens – insects, fungi, pathogenic bacteria, as well as herbs.

Summary: In Arabidopsis thaliana more than 1300 genes (~5% of the proteome) encode components of the ubiquitin/26S proteasome pathway. Approximately 90% of these genes encode subunits of the E3 ubiquitin ligases, which confer substrate specificity to the ubiquitin/26S proteasome pathway. The plant E3 ubiquitin ligases comprise a large and diverse family of proteins or protein complexes containing a RING-finger, U-box domain or a HECT domain. Within the past several years, considerable progress has been achieved in understanding the role of protein degradation via the ubiquitin-proteasome pathway in hormone responses, self-incompatibility, photomorphogenesis and pathogen defenses.

Key words: proteolysis, ubiquitin, ubiquitin ligases, phytohormones, photomorphogenesis, self-incompatibility, pathogenesis