Postepy Biologii Komorki, vol. 27, 2000, nr 2

Summary: A pathway of auxin action, from perception to response, has not been completely defined, as yet. However, there are now good evidences that auxin-binding protein ABP1, which is associated with a membrane docking protein is a G-protein-coupled receptor. The signal transduction pathway appear to involve activation of phospholipase A2 leading to the production of lipid second messengers which activate the plasma membrane H+-ATPase by a protein kinase-dependent mechanism. Increasing evidences now suggest that MAP kinase pathway is involved in mediating auxin responses. Studies of the auxin mutants (axr1, tir1, sur1) of Arabidopsis thaliana have focused attention on the role of ubiquitin-mediated cell cycle regulation in auxin response.
Changes in the transcription of specific auxin-responsive genes are among the earliest responses to applied auxin. The Aux/IAA genes are the best-studied family of early auxin-response genes. Several results suggest that at least some of the Aux/IAA proteins are involved in controlling transcription. Functional analysis of several auxin-specific promoters identified a number of functionally defined auxin response elements (AuxREs) and auxin response domains (Aux RDs). A family of transcription factors, referred to as auxin-response factors (ARFs), has been identified and shown to bind to auxin-response elements.

Key words: auxin, auxin binding proteins, auxin transduction pathway, auxin responsive genes, auxin response factors

Molecular characterisation of mitochondrial DNA of fall rye (Secale cereale L.)

Summary: In this paper current knowledge state about mitochondrial genome in rye is presented. General description of the character of mitochondrial DNA from rye, mitochondrial DNA in cytoplasmic male sterility (cms) lines, organization of the 18S and 5S ribosomal RNA genes in the mitochondrial genome of rye and also DNA – polymerase type B – related reading frame (pol-r) were described.

The pacemaking cells in the gastrointestinal tract — structure-function relationships

Summary: Electrical slow action potentials named slow waves are generated by the specialized pacemaking cells present within the gastrointestinal wall. This phenomenon is the basis for the so-called miogenic control of motor activity and the aforementioned cells are identified as the interstitial cells of Cajal. However, the pacemaking function is ascribed solely to the cells of type I and IV, while the cells of types II, III and also of type IV are believed to conduct the electrical signals from the intramural ganglionic neurons to the smooth muscle cells. The similarity of the interstitial cells of Cajal to other cells, especially to the neurons, fibroblasts or myocytes accomplishes their precise identification.

Key words: interstitial cells of Cajal, gastrointestinal tract, pacemaker, slow waves

Cytokines and signal transduction mechanisms: IL-6-type cytokines as a model system

Summary: Cytokines play an important role in defining the fate of cells, such as proliferation, differentiation or death. Distinct responses of target cells to cytokines are determined by specific signal transduction events. The group of interleukin-6-type cytokines comprises also: interleukin-11 (IL-11), oncostatinM (OSM), leukemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF) and cardiotrophin-I (CT-I). IL-6-type cytokines use pl30 as a common b chain of their multimeric receptor complexes. Binding of the ligands leads to the activation of Jak tyrosine kinases, which in tum phosphorylate intracellular part of the receptor and initiate various signal transduction events mediated by STAT factors, SHP-2 phosphatase or Src-family kinases. The signalization by Jak/STAT pathway is negatively regulated by dephosphorylation or synthesis of the specific inhibitors like PIAS or SOCS/SSI/JAB. The outcome ofthe signal transduction seems to be an effect of the interplay among the contradictory signaling pathways simultanously activated via cytokine receptor.

Summary: The knowledge concerning cell surface markers and immunophenotypes of lymphocytes in different animal species opens possibilities in veterinary laboratory diagnostics. The human CD antigens do not always correspond to surface markers found on animal lymphocytes. Therefore, a close follow-up on research developments on new CD antigens and their corresponding monoclonal antibodies is important in veterinary laboratory diagnostics. A detailed description of known ruminant CD antigens is available. Thorough knowledge of clusters of differentiation is particularly important in the ruminant due to emerging diseases and difficulties in eliminating the already existing ones. Ruminant lymphocytes make up 45-75% of the total leukocyte population. CD45 is the common leukocyte antigen, however, it is absent from ruminant WC1⁺ lymphocytes and monocytes. Ruminant T cells are mainly identified by the TCR molecule, with TCR-1 (g and d) making up 60% of all T cells. Other T cell surface antigens are CD1, CD2, CD5, CD4, CD6, CD8 and WC1. In the ruminant, the CD4/CD8 index in peripheral blood is 1,53 and in milk it is 0,85, but fluctuates during lactation. WC1⁺ (CD4^-CD8^- TCR gd^-) lymphocytes account for 40% of the total T cell population in young ruminants. Cell surface bound IgM and other molecules not related to those found on human lymphocytes such as WC3 (CD21-like), WC4 (CD19), WC6 (present on B and CD2⁺ cells but not on WC1 and thymocytes) and WC10 (on B and CD2⁺ cells but not present on monocytes, granulocytes and WC1 cells). Activation markers on both T and B cells are IL-2R (expressed after TCR-ab⁺ activation) and CD25 (highly expressed on WC1). CD1, CD45 isoforms and L-selectin receptors act as cell maturation markers. The immunophenotype of bovine peripheral blood NK cells is CD4^-CD5^-
CD6^-WC1^- while that of LAK cells is CD2⁺CD4^-CD8^-.

Summary: Endothelial cells play a critical role in blood circulation and hemostasis, in arteriosclerosis, inflamation and cancer progression. Low cellular turnover, and migration and proliferation capacity in response to specific stimuli are characteristic features of endothelial cells. High endothelial venules in lymph nodes are the type of endothelium specialised in lymphocyte circulation. E selectin and other endothelium specific adhesive molecules called addressins, initiate process of leukocytes' adhesion to the vascular wall. Under influence of chemokines activated leukocytes adhere firmly and finaly transmigrate through the vascular wall to the surronding tissues. The knowlege of adhesive molecules and their activators/inhibitors, participating in the process, would possibly allow a specific antiadhesive therapy of inflamatory and neoplastic diseases.

Key words: Endothelial cell phenotype, adhesive molecules, adhesion, transmigration.

Summary: Sister chromatid cohesion is essential for accurate chromosome segregation in the cell cycle. Recently a cohesin complex has been identified, required for establishing and maintaining mitotic cohesion up to the metaphase to anaphase transition. A few proteins inducing and regulating cohesin complex destrucion have also been identified: APC - a Pds1p - anaphase inhibitor, and Es1p - separine, directly influencing cohesin destruction.

Key words: mitosis, multisubunit protein - ubiquitin ligase , chromosomes, chromatids, cohesion

Krzysztof PTAK, Marian H. LEWANDOWSKI, Roger MONTEAU

Neurokinins and their receptors

Summary: Neurokinins are a group of peptide compounds occurring in the nervous system of mammals. They are characterized by a common sequence of four amino acids at the C-terminal of a peptide chain. The neurokinins include substance P (SP), neurokinin A (NKA) and neurokinin B (NKB). The neurokinins bind to their specific receptors NK1, NK2 and NK3. An amino acid sequence of these receptors is over 65 per cent homologous. SP is a ligand of the NK1 receptor, NKA - of the NK2 receptor, and NKB - of the NK3 receptor. Each of them is simultaneously an agonist of neurokinin receptors of every type. The neurokinin receptors are linked to the G proteins which produce an effect on different effector system of secondary transmitters by which these neuropeptides depolarize the postsynaptic membrane of a nerve cell. The depolarization is connected with inactivation of potassium current. Synaptic terminals containing neurokinins and neurokinin receptors occur at early stages of embryogenesis. All these findings permit a hypothesis that neurokinins are engaged in differentiation and development of neurones.

Key words: neurokinins, neuropeptides, transmembrane receptors, substance P, tachykinins

[Postepy Biologii Komorki 2000; 27: 273�286]