Presynaptic CK2 promotes synapse organization and stability by targeting Ankyrin2

The precise regulation of synapse maintenance is critical to the development and function of neuronal circuits. Using an in vivo RNAi screen targeting the Drosophila kinome and phosphatome, we identify 11 kinases and phosphatases controlling synapse stability by regulating cytoskeletal, phospholipid, or metabolic signaling. We focus on casein kinase 2 (CK2) and demonstrate that the regulatory (β) and catalytic (α) subunits of CK2 are essential for synapse maintenance. CK2α kinase activity is required in the presynaptic motoneuron, and its interaction with CK2β, mediated cooperatively by two N-terminal residues of CK2α, is essential for CK2 holoenzyme complex stability and function in vivo. Using genetic and biochemical approaches we identify Ankyrin2 as a key presynaptic target of CK2 to maintain synapse stability. In addition, CK2 activity controls the subcellular organization of individual synaptic release sites within the presynaptic nerve terminal. Our study identifies phosphorylation of structural synaptic components as a compelling mechanism to actively control the development and longevity of synaptic connections.     

Preadapted for invasiveness: do species traits or their plastic response to shading differ between invasive and non‐invasive plant species in their native range?

Aim Species capable of vigorous growth under a wide range of environmental conditions should have a higher chance of becoming invasive after introduction into new regions. High performance across environments can be achieved either by constitutively expressed traits that allow for high resource uptake under different environmental conditions or by adaptive plasticity of traits. Here we test whether invasive and non‐invasive species differ in presumably adaptive plasticity. Location Europe (for native species); the rest of the world and North America in particular (for alien species). Methods We selected 14 congeneric pairs of European herbaceous species that have all been introduced elsewhere. One species of each pair is highly invasive elsewhere in the world, particularly so in North America, whereas the other species has not become invasive or has spread only to a limited degree. We grew native plant material of the 28 species under shaded and non‐shaded conditions in a common garden experiment, and measured biomass production and morphological traits that are frequently related to shade tolerance and avoidance. Results Invasive species had higher shoot–root ratios, tended to have longer leaf‐blades, and produced more biomass than congeneric non‐invasive species both under shaded and non‐shaded conditions. Plants responded to shading by increasing shoot–root ratios and specific leaf area. Surprisingly, these shade‐induced responses, which are widely considered to be adaptive, did not differ between invasive and non‐invasive species. Main conclusions We conclude that high biomass production across different light environments pre‐adapts species to become invasive, and that this is not mediated by plasticities of the morphological traits that we measured.     

Energetics of enzyme catalysis. II. Oversaturation, case diagrams, reversible and irreversible behaviour

Most enzymes react in vivo under reversible conditions where the substrate and product concentrations are not far removed from equilibrium values. Under these conditions when the concentration of substrate is increased, in addition to the usual unsaturated and saturated behaviour we find a third type of kinetic regime at high substrate concentration-oversaturation. In this regime the rate limiting transition state involves interconversion of free enzyme forms. For a one substrate/one product enzyme, case diagrams can be constructed which depict the kinetic behaviour as a function of substrate and product concentrations. Six different cases are found and are discussed with the relevant free energy profiles. A systematic procedure is described for the investigation and construction of the case diagram.     

M241 (CD1) expression on B lymphocytes

The human thymus leukemia-like antigens (CD1a-c) consist of three similar glycoproteins found on subpopulations of normal thymocytes, T cell acute leukemias, and cutaneous dendritic cells. The CD1c antigen recognized by the M241 monoclonal antibody was detected on the circulating mononuclear cells of three children with severe combined immunodeficiency disease (SCID). Two-color immunofluorescence analysis demonstrated that M241 expression (43 to 95%) was limited to cells expressing the B cell-restricted antigens B4 (CD19), B1 (CD20), and surface immunoglobulin. To confirm M241 expression on normal cells of the B lineage rather than aberrant expression limited to SCID B cells, its expression was demonstrated serologically and biochemically on purified B cells from spleen, tonsil, and peripheral blood. Parallel analyses with monoclonal antibodies NA1/34 and 4A76 demonstrated that the CD1a and CD1b molecules were negative on all B cells that were studied. It has been hypothesized that the CD1 molecules represent the human counterpart of the murine thymus leukemia antigens due to their similar size, limited tissue distribution, and association with beta 2-microglobulin. This study suggests that a subset of CD1 antigens detected by M241 (CD1c) may represent a human analog of a murine Qa antigen due to its extended distribution on normal peripheral B cells.     

A synthetic peptide homologous to the envelope proteins of retroviruses inhibits monocyte-mediated killing by inactivating interleukin 1

The synthetic peptide CKS-17 has homology to a highly conserved region of the immunosuppressive retroviral envelope protein P15E, to envelope proteins of HTLV I, II, III, and to that encoded by an endogeneous C-type human retroviral DNA. CKS-17 inhibits the immune response of lymphocytes and the respiratory burst of human monocytes. Because P15E-related antigens are present in human malignant cell lines and cancerous effusions, we sought to determine the effect of CKS-17 on monocyte-mediated tumor cell lysis. Lysis of A375 tumor cells by lymphokine or lipopolysaccharide-activated human monocytes was inhibited by 10 microM CKS-17 (control, 79%; CKS-17-treated, 19%). Another synthesized peptide, CS-2, which has partial homology to CKS-17, failed to block monocyte-mediated killing. Thus, the inhibition by CKS-17 appeared to be specific. Because interleukin 1 (IL-1) is a cytocidal factor produced by activated monocytes, we also investigated the effect of CKS-17 on IL-1 production by monocytes and on direct IL-1-mediated cytotoxicity. CKS-17 did not block production or secretion of IL-1 by lipopolysaccharide- or interferon-gamma-activated monocytes. However, the direct cytocidal activity of both recombinant IL-1 alpha and IL-1 beta against A375 tumor cells was blocked by CKS-17. The cytotoxic activity of IL-1 was inhibited by CKS-17 if (a) IL-1 was preincubated with CKS-17 for 1 hr at 37 degrees C or (b) the A375 cells were incubated with CKS-17 for 1 hr prior to the addition of IL-1. CKS-17 also blocked IL-1-induced proliferation of murine thymocytes, the D10 T cell line, and an IL-1-responsive astrocytoma cell line. These data suggest that CKS-17 may be a potent inhibitor of IL-1.