casein-kinase-ii and staurosporine-aglycone

Monocytes encounter basement membranes and interact with laminins while crossing the vascular barrier. It is known that these cells possess ecto-protein kinase activity on their surface. Several proteins of the extracellular matrix can be phosphorylated by ectokinases. Therefore, it has been hypothesized that monocyte ectokinases could phosphorylate laminins and influence their biological properties. In order to test the above hypothesis, we used intact human monocytes and adenosine triphosphate labeled with radioactive phosphate at the third phosphate ([gamma-32P]-ATP) to phosphorylate laminin-1. Autoradiography after sodium dodecyl sulphate polyacrylamyde gel electrophoresis (SDS-PAGE) electrophoresis indicated phosphorylation of laminin-1 on the beta and/or gamma chains. After phosphorylation, phosphoserine could be detected on Western blots by a specific monoclonal antibody. Phosphorylation was not detected when monocytes were pre-treated with trypsin and was inhibited by a specific ecto-protein kinase inhibitor (K252b). Laminin phosphorylation was also inhibited by heparin, a known inhibitor of casein kinase II and by pretreatment of monocytes by a monoclonal anti-casein kinase II antibody. Heparin binding, cell attachment and proliferation, and monocyte migration were enhanced on the phosphorylated laminin-1 as compared to the non-phosphorylated controls. These data indicate that laminin-1 can be phosphorylated by monocyte casein kinase II type ectokinase. This phosphorylation influences important functions of laminin and therefore could provide an additional means for the interaction of monocytes with basement membranes.

Topics: Anticoagulants; Basement Membrane; Carbazoles; Casein Kinase II; Cells, Cultured; Enzyme Inhibitors; Heparin; Humans; Indole Alkaloids; Laminin; Monocytes; Phosphorylation; Protein Kinases

We studied the properties of the ectokinase activity on the outer cell surfaces of RBL-2H3 cells and examined the phosphorylation of exogenous substrates to clarify the substrate specificity of the ectokinases on RBL-2H3 cells. Among the several protein substrates tested, casein was the most strongly phosphorylated with [gamma-32P]ATP, and the net incorporation of 32P into casein was 0.65 pmol P/50 microg/10(6) cells. Casein kinase II peptide was also phosphorylated with [gamma-32P]ATP. The phosphorylation of casein and casein kinase II peptide was almost completely inhibited by the addition of 3 microg/ml of cell-impermeable K252b. Phosphorylation of casein and casein kinase II peptide was also observed by [gamma-32P]GTP. Western blot analysis using anti-casein kinase II antibody revealed a 44-kDa casein kinase band in the membrane fraction and Fc epsilonRI complexes. The immunofluorescence microscopic analysis using anti-casein kinase II antibody showed the existence of casein kinase II on the surface of the cells. This is the first report about the existence of ectokinase on mast cells.

Topics: Animals; Basophils; Carbazoles; Casein Kinase II; Cell Membrane; Cell Membrane Permeability; Indole Alkaloids; Mast Cells; Membrane Proteins; Phosphorylation; Protein Binding; Protein Kinase Inhibitors; Protein Kinases; Protein Serine-Threonine Kinases; Rats; Receptors, IgE; Substrate Specificity; Tumor Cells, Cultured

We investigated the antiviral mechanisms of K-252a, a broad non-specific protein kinase inhibitor which was isolated from Nocardiopsis sp. and its derivative (KT5926), against vesicular stomatitis virus (VSV) replication in BHK-21 cells. Although K-252a (5 microM) and KT5926 (15 microM) similarly suppressed the viral primary and secondary transcriptions and genomic RNA synthesis in vivo, the inhibitory mechanisms did not seem to be the same; phosphorylation of the viral NS protein was suppressed by K-252a, which might account for the decreased viral RNA synthesis caused by K-252a. On the other hand, KT5926, being known to preferentially inhibit myosin light chain kinase (MLCK), had little effect on NS protein phosphorylation. Cellular casein kinase II, which is believed to be involved in the phosphorylation of the N-terminal side (domain I) of NS protein, was not inhibited at all by KT5926 even at 15 microM under in vitro assay conditions, and was only weakly inhibited by K-252a at 1 to 10 microM. Neither inhibitor seemed to directly affect viral protein synthesis, but affected it indirectly as a secondary effect of reduced viral RNA synthesis. These results suggest that both the KT5926-sensitive and the KT5926-resistant but K-252a-sensitive functions are involved in the essential processes of viral RNA synthesis. The KT5926-sensitive function(s) might not be involved in the NS protein phosphorylation, but may participate in some other way in the process of virus replication. On the other hand, the KT5926-resistant, K-252a-sensitive function(s) are probably involved in NS protein phosphorylation. The possible nature of those functions is discussed.

Topics: Alkaloids; Animals; Antiviral Agents; Autoradiography; Carbazoles; Casein Kinase II; Cell Line; Cricetinae; Electrophoresis, Polyacrylamide Gel; Enzyme Inhibitors; Indole Alkaloids; Indoles; Myosin-Light-Chain Kinase; Protein Kinase C; Protein Serine-Threonine Kinases; RNA, Viral; Transcription, Genetic; Vesicular stomatitis Indiana virus; Viral Plaque Assay; Viral Proteins; Virus Replication

Extracellular adenosine triphosphate (ATPo) has been suggested to play a role in lymphocyte effector functions. Recently, it has been suggested that MgATP2- may be the molecular species which is involved in modulating the lytic interaction between cytotoxic T-lymphocytes (CTL) and their target cells. In this study, we provide evidence that ATPo mediates the phosphorylation of extracellular proteins on T-lymphocytes through the action of ectoprotein kinases. The ectophosphorylation is temperature-dependent, supported by Mg2+ and Mn2+, and both ATP and GTP, whereas kinase activity and/or substrates were removed by pretreatment of intact lymphocytes with trypsin. We show the presence of extracellular ATP/GTP-binding sites, indicating the presence of ectoenzymes on intact lymphocytes. The major ectoprotein kinase was identified as a casein kinase II-like protein kinase and could be inhibited by heparin, whereas its activity was enhanced by spermine. The ectoprotein kinase showed remarkable substrate specificity, phosphorylating the serum protein vitronectin, but not fibronectin. In experiments with the cell-impermeable protein kinase inhibitor K-252b, we demonstrate the possible functional importance of ectoprotein kinase in CTL-mediated cytotoxicity, i.e., target cell death was completely blocked by K-252b without affecting intracellular phosphorylation. These results suggest that ectoprotein phosphorylation may possibly be an important event in immunologically relevant cell-cell interactions.

Topics: Adenosine Triphosphate; Animals; Carbazoles; Casein Kinase II; Cations; Cell Membrane; Cytotoxicity Tests, Immunologic; Cytotoxicity, Immunologic; Enzyme Inhibitors; Guanosine Triphosphate; Indole Alkaloids; Membrane Proteins; Mice; Phosphorylation; Protein Kinase Inhibitors; Protein Kinases; Protein Serine-Threonine Kinases; Substrate Specificity; T-Lymphocytes, Cytotoxic