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

Disturbances of the Asymmetry of Phosphatidylserine in the Cell Membrane – The Latest Data

Summary: The maintenance of transbilayer lipid asymmetry is essential for normal cell membrane function and homeostasis of organisms. Even though many articles appeared about loss of transmembrane phospholipid asymmetry, constantly come out new data about this interesting occurrence. The most noteworthy are studies about phosphatidylserine (PS) externalization in apoptosis. This article present the latest data about the redistribution of PS on the surface of the cells.

Recent Developments on Myotropic Neuropeptidesin Insects: Tachykinins, Sulfakinins and FMRF-Amide-Related Peptides

Summary: In insects, neuropeptides are important messenger molecules which influence on developmental, reproductive and behavioural processes. In the past few years large number of new neuropeptides has been identified from insects. They can act as transmitters, modulators and classical hormones and often exhibit pleiotropic functions including myotropic activity. We summarize the current knowledge on primary structures and physiological functions of three different groups of myotropic neuropeptides in insects: tachykininrelated peptides, sulfakinins and FMRF-amiderelated peptides. Peptides from this groups revealed homology to other invertebrates and vertebrates peptides.

Key words: insects, myotropic neuropeptides, tachykininrelated peptides, sulfakinins, FMRF-amide-related peptides.

Opioid System and Innate Immunity – Comparative Studies I. Opioids and Opioids Receptors

Summary: Existence of the opioid receptors, prohormones and peptides is recorded both in invertebrates and vertebrates. The comparative molecular studies of nucleotide and amino acid sequences rose a hypothesis that all opioid prohormones originated by a duplication of proenkephalin gene. Probably, as a first originated proopiomelanocortin, then pronociceptin and after the third and last duplication prodynorphin. Proopiomelanocortin is the prohormon for adrenocorticotropin and melanocyte stimulating hormone, lipotropins and ß-endorphin. From proenkephalin originate leu- and met-enkephalin, met-enkephalin-Arg6-Gly7-Leu8, met-enkephalin-Arg6-Phe7 and peptides E and F. Prodynorphin is a precursor for dynorphins and neoendorphins. Moreover, in last years atypical opioid peptides (endomorphins, nociceptins, hemorphins and casomorphins) were discovered. Those peptides are the natural ligands for opioid receptors. There are four types of opioid receptors: MOR, DOR, KOR and NOR. Comparative analysis of sequence similarities of opioid receptors indicated that they are highly conserved and confirmed supposed evolution order from KOR, trough DOR, till to the youngest MOR receptors. Moreover, it was indicated that in stress conditions animal body could also produce opiates – opioid alkaloids, including morphine.

Opioid System and Innate Immunity – Comparative Studies II. Opioids and Inflammation

Summary: Homeostasis is critically dependent on communication between the immune, endocrine and nervous systems, and also the opioid system. Opioids can affect immune processes directly through the activation of opioid receptors on leukocytes or indirectly through the stimulation of the corticosteroid and catecholamine release. Leukocytes can also synthesize and release opioid peptides, which act as analgesic factors during inflammatory process. Many data indicate that opioids are also immunomodulators, and can affect leukocyte migration, killing activity and apoptosis. The comparative studies of invertebrates and vertebrates indicate that the opioid system is strongly conserved. Moreover, it has been proposed that opioids arose as antibacterial and immunomodulatory peptides and that the analgesic properties were developed later in evolution, when the nervous system become more complicated and the pain appeared to be an alerting process. The present work is a review of the papers concerning the connection between opioids and innate immunity, in particular inflammatory reactions.

Summary: Plants have evolved various strategies to cope with common in nature phosphorus deficiency. Efficient inorganic phosphate (Pi) acquisition and distribution system within the plant and between cellular compartments is the most important of them. Amount and variety of transporters involved in this process indicates the complicity of Pi transport system in plants. In this work membrane transporters involved in Pi acquisition from soil (Pht1), Pi transport from root to shoot (Pht2) are characterized. Some proteins which seem to take part, or regulate this process, are also described. Moreover, Pi translocators involved in Pi distribution within a plant cell (Pht3, pPT) are characterized.

Summary: Cells have evolved mechanism to get rid of nonfunctional or potentially deleterious proteins that are coded by mRNA with premature translation termination or mRNA without stop codon. The pathway of degradation of such mRNA have been described in mammals, flies, nematodes, yeast and plants. The degradation steps as well as factors involved in are not identical in different species. The general way of recognition of aberrant transcripts depends on spatial relationship between ribosome components and ribonucleoproteins bound to the 3’UTR sequence. Moreover, protein factors involved in degradation can participate in additional processes like cell cycle regulation, replication or RNA interference. The control of mRNA quality in prokaryotes is performed by tmRNA that works both as tRNA and mRNA. tmRNA recognizes ribosomes stalled by transcripts without stop codon and continues the synthesis of truncated proteins in trans-translation process. In consequence ribosomes are reactivated and aberrant transcript and protein are triggered for decay.

Summary: There are many hypotheses on the increase of male infertility. The phenomenon is believed to be connected with the presence of substances with hormonal activity – xenoestrogens in human environment. The substances are divided into two groups: man made substances and components occurring naturally – phytoestrogens. Steroids influence not only male and female reproductive systems but also development and function of another tissue. Therefore, this is very important to list of substances with hormonal activity, their potency of acting, the way of expositions. Moreover, there exist the need to define safe doses for human and to recognize effects of chronic exposition.

Molecular Mechanisms of the Therapeutic Activity of Rituximab – The Monoclonal Antibody Against CD20 Antigen

Summary: Rituximab is a chimeric monoclonal antibody directed against CD20 antigen. This molecule is expressed only on the surface of B lymphocytes, it is present neither on precursor cells nor on plasma cells. CD20 antigen is not internalized nor shed. Infusion of rituximab evokes rapid B-cell depletion. It is caused mainly due to complement activation and antibody-dependent cellular cytotoxicity. Furthermore, rituximab acts synergistically with standard chemotherapy, sensitizing cells to apoptosis, via inhibition of the expression of Bcl-2 protein. Rituximab has been registered for the treatment of non-Hodgkin’s lymphoma, but its indications are still expanding. Currently it is also approved in the treatment of rheumatoid arthritis, however it is also used in other autoimmune disease as well as in transplantology. On the basis of success of rituximab new drugs are being made against CD20 antigen. These are, among others: monoclonal antibodies conjugated with radioisotopes, completely human monoclonal antibodies or small peptides (mimotops), which are designed to induce the response of the immune system against CD20 antigen.

Summary: The ImageStream technology was developed as a novel tool for multiparameter cell analysis. The system fully integrates the features of flow cytometry and fluorescent microscopy combined with a modern system of image analysis. Similarly to flow cytometry, the ImageStream allows analyzing of a large number of cells according to their fluorescent features and provides statistical analysis of these objects. Additionally, allows detailed morphometric analysis of cells based of their images collected during acquisition as well as correlation of various morphometric and photometric features of the cells. Simply, the ImageStream system is a flow cytometer collecting images of cells during their acquisition that allows their further multiparameter analysis. The innovative features of the instrument create multitude possible applications of the system, especially for experiments where flow cytometry does not provide enough information about analyzed cells. The aim of this article is to introduce brief information about the system to scientists working with various systems of image analysis or flow cytometry. The article summarizes basic information about the features of ImageStream system as well as its possible applications.

Summary: a-Synuclein (ASN) is richly abundant in the central nervous system, particulary in presynaptic terminals. Among many functions, ASN plays a crucial role in regulation of dopaminergic system. In physiological conditions, soluble ASN is involved in maintenance of dopamine (DA) homeostasis in the central nervous system. This protein regulates DA level and biosynthesis by inhibition of the tyrosine hydroxylase. It also influences DA storage and release from synaptic vesicles as well as DA uptake by its transporter (DAT). These mechanisms play a role in the maintenance of proper DA concentration at nerve terminals, which protects against its uncontrolled conversion and formation of highly reactive oxidative radicals. In PD the level of cytoplasmic ASN is decreased due to its aggregation and accumulation in the form of Lewy bodies. Aggregated ASN looses its physiological functions and the ability to control the intracellular DA concentration. Excessive accumulation of this neurotransmitter in cytoplasm favours the production of toxic free radicals that may damage proteins, lipids and DNA, which, in consequence, leads to neurodegeneration.

Summary: Heterochromatin fraction called „constitutive” and euchromatin differ in respect of DNA types (tandem repeats vs coding/unique sequences) and in epigenetic modifications, i.e. in methylation of DNA, H3 and H4 histones and in acetylation of the latter two. These modifications result in permanent heterochromatin condensation. On the other hand, during the past decade, it has been well documented that gene expression in euchromatin is affected by its reversible condensation resulting from epigenetic modifications of DNA and H3 and H4 histones characteristic of heterochromatin with simultaneous histone modifications specific for euchromatin. These data imply that the term “heterochromatinisation” should bo replaced with “euchromatin condensation”.

Key words: heterochromatin, euchromatin, facultative heterochromatin, H3, H4 histones, methylation, acetylation

The Genetic and Molecular Basis of Root Hair Development in Arabidopsis thaliana

Summary: Root hairs are cylindrical in shape outgrowths of root epidermis. They are characterized by the tip growth which relies on the deposition of new components of cell membrane and cell wall at the tip of the growing hair. The main role of root hairs is to extend the root surface, uptake of water and mineral soils. They are responsible for building interactions with soil microorganisms, and in some species, they synthesize and secrete bioherbicides. The development of root hairs is a complex process that involves many proteins, enzymes and cellular structures. It can be divided into several phases: formation of rhizodermis pattern, initiation of root hair development by bulge formation, transition to the tip growth and the tip growth itself. Up to date, several dozens of genes involved in root hair formation have been described and about 40 of them were characterized at the molecular level. Among them, there are genes encoding transcription factors, cell wall components and variety of enzymes, including kinases family and GTPases. Many of proteins are involved in cell signaling, cytoskeletal dynamics or vesicular trafficking. Plant hormones, mainly ethylene and auxin play also an important role in root hair development. Although the type of root hair growth is rather distinctive among the plant cells, many biochemical pathways that lead to their development are universal, and because of the relative ease of their observation, root hairs can serve as a good model of plant cell differentiation. The paper presents a comprehensive review on the genetic and molecular control of root hair development in a model plant Arabidopsis thaliana.

Key words: root hairs, Arabidopsis thaliana, cell differentiation, tip growth