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

Structural, Biochemical and Fuctional Characteristic of the Extraocular Muscles

Summary: Extraocular muscles are characterized by excellent neuromuscular control (one axon innervates about only 7 muscle fibres) which provides them high precision of eye movements and normal, binocular vision. In comparison to skeletal muscles extraocular, muscles are characterized by higher maximal shortening velocity and lower maximal isometric force, expressed by amount of force generated per cross sectional surface area unit. Besides of functional differences occurring between extraocular and skeletal muscles, molecular differences are present such as higher proportion of fast myosin heavy chain isoforms, specific myosin heavy chain isoforms: extraocular (MyHC-eom) and tonic myo-sin heavy chain isoforms (MyHC-sto), continuous expression of developmental isoforms (MyHC-emb i MyHC-pn), higher density of sarcoplasmic reticulum calcium ion pumps (SERCA) in extraocular muscle fibres. It is not clear why extraocular muscles, in contrary to skeletal muscles are preferentially spared in muscles diseases such as Duchenne’a or Becker muscular dystrophies and are preferentially susceptible to other diseases such as ocular myopathies. The causes of the differences in susceptibility to muscle diseases between skeletal and extraocular muscles remain unclear. They might be due to different ontogeny of this group of muscles. Extraocular muscles arise from unsegmented head mesoderm whereas skeletal muscles arise from segmented mesoderm.

Key words: skeletal muscles, extraocular muscles, myosin heavy chain isoforms

Translocation of Signaling Proteins is an Element of the Delayed Postischemic Neuronal Cell Death

Summary: Neuronal degeneration following transient global cerebral ischaemia develops from complex series of pathophysiological events that evolve in time and intracellular space. During both, the early and delayed, postischemic stages translocation of proteins to postsynaptic density (PSD) and mitochondria are probably associated with recovery or cell death in vulnerable brain regions. Early after the insult a significant increase in the amount of CamKII and PKC isoforms is observed in PSD. Sustained changes in protein kinases content in PSD may cause persistent alteration in synaptic transmission. In the time course of reperfusion the activation state of key signaling molecules changes. Western blot analysis of phosphorylated forms of protein kinases revealed persistent activation of JNK, being limited mostly to vulnerable CA1 region. On the contrary, activation of ERK, although observed transiently in both parts, was enhanced for a longer time in the abdominal, resistant part of hippocampus. Moreover, the amount of active JNK linked with mitochondria was significantly increased and preceded neuronal death in CA1. In parallel, the amount of pro-survival Raf-1 kinase decreased in mitochondria and proapoptotic Bad protein content was increased. Concomitantly, transient ischemia evokes biphasic cytochrome c release from mitochondria. Cytochrom c in cytoplasm may be involved in the activation of apoptosom, therefore cascade of caspases. Chasing a protein translocation in brain ischemia pathology this is a new research approach which might contribute to understand of the whole process and to search for a new points to prevent neuronal death.

Key words: brain ischemia, postsynaptic density, mitochondria, signal transduction pathways, neuronal degeneration, protein kinases

Plant Dynamin-Like Proteins – Insights into the Evolution of Division Machinery of Mitochondria and Plastids

Summary: Dynamin and dynamin-related proteins (DRP) participate in many processes essential for normal function of the cells and organisms. They were found both in animals and plants. In Arabidopsis thaliana 16 different dynamin-related proteins were identified that are grouped into six subfamilies. DRP1 and soybean fragmoplastin participate in the cell plate formation during cytokinesis. Two members of DRP2 subfamily display domain structure similar to mammalian classical dynamins and may be involved in endocytosis and membrane recycling via clathrin-coated vesicles. Dynamin-related pro-teins that are elements of mitochondrial and chloroplast division machinery were identified in Arabidopsis and red algae Cyanidioschyzon merolae. These organelles that are remnants of free-living endosymbiotic prokaryotes initially divided by similar mechanisms based on FtsZ ring of prokaryotic origin, PD/MD – of eukaryotic origin and dynamin ring. In the course of evolution this system was preserved only in chloroplasts and in mitochondria of lower eukaryotes like C. merolae. However, in mitochondria of animals, green plants and fungi the elements of prokaryotic mitochondrial machinery (FtsZ) were replaced by dynamin-like GTPases.

Key words: dynamin, dynamin-related proteins, Arabidopsis, mitochondria, chloroplasts, organelles division, phylogenesis

Summary: The article gives basic information on proteasome- and ubiquitin-dependent system of pro-tein degradation. The ubiquitination process of proteins designated for proteasomal breakdown and ubiquitin involvement in extraproteasomal cellular events is discussed. The article explains the structure of 20S, 26S and PA700 complexes, the role of immunoproteasomes in the immune response and proteasomal proteolysis independent of ubiquitination. Moreover, it gives the outline of proteasomal biogenesis and possible clinical application of proteasome inhibitors.

Key words: proteasome, immunoproteasome, ubiquitin, proteolysis, PA700, PA28, proteasome inhibitors

Summary: In 1990s papers have been published suggesting the existence of an animal atrial natriuretic peptide (ANP) homologues in plant organisms. Multiple influence of egzogenic atrial natriuretic peptide into plant metabolism, growth and development has been showed. Plant ANP immunohomologues has been studied as well. However, the plant nucleotide or aminoacid sequence similar to the animal NP have not yet been published. The existence of plant NP homologues to the animal natriuretic peptides and genes encoding them was not established.

Key words: animal natriuretic peptides, receptors of natriuretic peptides, plant homologues of natriuretic peptides, expansins

Summary: Plant TGases, still unclassified, are widespread in higher and lower plants, in several plant organs and probably different isoforms are differently located in various cell compartments: chloro-plasts, mitochondria, cytoplasm, cell walls. They probably exert a mainly structural or conformational role; however, in chloroplasts and mitochondria their roles might be related to the organelles’ specific metabolisms. Transglutaminases appear related to growth (cell cycle, apical growth, seedling growth), differentiation, programmed cell death and stress.

The Influence of Opioids on Steroidogenesis in Granulosa and Theca Interna Cells from Porcine Ovarian Follicles; The Mechanism of Action of Opioid Agonist
FK 33-824

Summary: Opioid peptides belong to a group of agents, produced in porcine ovarian follicles, which effect functions of granulosa and theca interna cells. During short incubation of the cells with opioids (µ, ð or k agonists) inhibition of steroidogenesis prevails, while in the presence of LH, trophic agent for these cells (from large follicles), stimulation of steroid hormones under influence of opioids predominates. The mechanism of inhibitory action of opioids on follicular steroidogenesis was investigated using the agonist of mainly µ receptors, FK 33-824. Under influence of FK 33-824 it was found attenuation of adenylyl cyclase, protein kinases A and C activities in granulosa cells as well as phosphoinositide-specific phospholipase C, adenylyl cyclase, protein kinases A and C activities in theca interna cells.

Key words: pig, opioids, granulosa cells, theca interna cells, steroidogenesis, phosphoinositide-specific phospholipase C, adenylyl cyclase, protein kinase A, protein kinase C

Summary: Calcium ions are highly universal signaling molecules in cells and participate as integral components of many signal transduction pathways. Cell stimulation by various environmental and developmental cues induces an elevation in cytosolic calcium concentration. Generation of calcium signal engages numerous calcium channels. Their interaction with cellular Ca²⁺ removing mechanisms influences the shape and specificity of [Ca²⁺]_cyt. Spatio-temporal characteristics of calcium signal, termed as a calcium signature, encode information, which determine the form and shape of cellular physiological response. The subject of this publication is generation of a stimulus specific calcium signature and the way of encoding specificity in calcium signal to produce an appropriate physiological response of a cell.

Keywords: Ca²⁺-ATPases, calcium channels, [Ca²⁺]_cyt, calcium signature, Ca²⁺ sensors, calcium waves and oscillations, Ca²⁺/H⁺ cotransporters.

The Role of Apoptosis in Responsiveness to Allograft: Tolerance and Graft Rejection

Summary: Studies of a few last years give evidence for a role of apoptosis not only in graft rejection but also in induction of transplantation tolerance. Apoptosis – programmed cell death is an active process which refers to superflous and defective cells. For a responsiveness to allograft the most important are two mechanisms of apoptosis: AICD (activation induced cell death) which involves Fas/FasL engagement and PCD (passive cell death) – caused by cytokine withdrawal. Graft rejection is caused by genetic differences between a donor and a recipient. Allograft is damaged by effector cells including alloreactive lymphocytes T CD8+. These cells express FasL and could thereby induce apoptosis in Fas-positive graft cells. Participation of peripheral apoptosis in induction of transplantation tolerance depends on pool size of alloreactive lymphocytes – apoptosis is necessary to reduce the size of alloreactive T cells clone to be small enough to be controlled by immunoregulatory mechanism (“pool size” model). Apoptosis facilitates also the development of immunoregulation by antiinflamatory action and thereby suppression of immunostimulatory abilities of APC. Therapeutic strategies of the induction of transplantation tolerance by alloreactive lymphocyte deletion include macrochimerism, modification of FasL expression, costimulatory blockade, and anti-CD28 antibodies in the presence of IFN-g. Most of immunosuppressive drugs like CsA and FK506 possibly inhibit apoptosis by inhibition of T cell activation. It is quite likely that there are also regiments that induction of apoptosis contributes to their immunosuppressive activity, e.g. RAPA and MMF. Apoptosis of alloreactive lymphocyte T seems to be necessary to achieve transplantation tolerance. Not only does it reduce directly the quantity of cells attacking graft but it also facilitates the development of immunoregulation state.

Key words: apoptosis, transplantation tolerance, graft rejection, deletion, T lymphocytes

Summary: The human proto-oncogene BCL-6, encodes transcriptional repressor that is necessary for germinal-center formation, T cell dependent antibody responses, regulation of B cell differentiation, and B-cell receptor signaling modulation. High expression of BCL6 is detected in GC B cells, but not in pre-GC B cells or in more differentiated memory or plasma cells. It performs a function as a potent transcriptional repressor of various target genes, but the precise function of BCL6 in these processes is unclear. In B cell lymphomas, structural alterations of the BCL6 promoter region, including chromosome translocation and somatic hypermutation present the most prevalent genetic lesion, especially in diffuse large cell lymphoma. BCL-6 is suggested as an important factor in lymphomagenesis.

Molecular Factor in Reproduction; the Role and Characteristics of Antisperm Antibodies

Summary: Infertility is estimated to affect one of every five Polish couples in the reproductive age. Antisperm antibodies (ASA) are considered to be the main cause for immunological infertility, but it is still relatively little known about the specific mechanisms that elicit development of auto- and isoimmune reactions in humans. Antibodies directed to sperm antigens can be detected in serum of men and women, but also in reproductive tract secretions such as seminal fluid, where they can be bound to the sperm surface. Free ASA can be also found in cervical mucus, peritoneal, oviductal and follicular fluids of women. Presence of ASA may impair sperm fertilization capacity through various effects, interfering with pre- as well as post-fertilization stages of the reproductive process. They may affect sperm motility, sperm penetration to cervical mucus, the acrosome reaction, sperm binding to zona pellucida, sperm-oocyte fusion and embryo cleavage. The detailed identification and characterization of the auto- and isoimmune reactive sperm antigens would be useful in understanding the mechanisms underlying the immunological infertility. Moreover, a precise knowledge on the sperm antigens would provide more accurate diagnostic approaches and treatment options.

Summary: Human ovarian cyclic function is a complex process. Ovarian failure can lead to a loss of not only female hormonal function, which depends on cyclic changes of gonadotropin levels, but to the absence of oocytes. Whereas there are numerous factors associated with ovarian dysfunction and de-creased female fertility, the autoimmune mechanisms have been put forward by several investigators. In ovarian pathology, such as idiopathic infertility, premature ovarian failure and polycystic ovarian syndrome, immunological etiology has been suggested. Special interest has been focused on antiovarian autoantibodies directed to multiple targets, including cellular elements and oocyte-related antigens. However, the exact role of ovarian autoimmunity in these disorders still remains controversial. There are also some conflicting reports on association of antiovarian antibodies with repeated attempts of in vitro fertilization (IVF) procedures. Antiovary autoimmunization may be induced by repeated stimulation and puncture of ovarian follicles, probably due to the releasing of altered, immunogenic proteins from the internal layers of ovary. Since, autoimmunity plays an important role in ovarian disorders and infertility, therefore there is an increased need for identification of the specific antigens and development of standardized tests enabling a diagnosis and providing a basis for therapy.

Summary: Blood cells are exposed to any agent absorbed or injected into the bloodstream, even those rapidly metabolised and extracted. Although anucleated, blood platelets are highly organized cells, rich in different types of organelles. They respond to small amounts of circulating molecules by secreting a number of active compounds stored in specific granules. That«s the reason blood platelets are used as pharmacological model for new drugs evaluation for many years. The use of platelets as models has not only been confined to coagulation assay but also has extended to other cell types like: neuronal cells and vascular smooth muscle cells. This review presents the main information about structure of blood platelets, their activation, methods for monitoring of their function and using platelets as pharmacological model.

Key words: platelets, platelet receptors, platelet function assays, pharmacological model

Summary: During the last two decades treatment based on selective stimulation of immune system has became a promising anti-neoplastic strategy, testing in several clinical centers all over the world. Vaccination with dendritic cells previously exposed to tumor antigens seems to be one of the most attractive approaches of immunotherapy. Dendritic cell-based vaccines were tested in many early phase clinical trials in patients with solid tumors, including malignant melanoma. There are also several reports on effectiveness of this therapeutic approach in patients with hematological malignancies, especially malignant lymphomas and multiple myeloma. In this review we summarize theoretical rationale and the ways of preparation of dendritic cell vaccines as well as results of their use in clinical trials with different types of malignancy.

Key words: dendritic cells, immunotherapy, vaccines, neoplastic diseases, leukemias, lymphomas