melitten and Leukemia--Erythroblastic--Acute

The complement membrane attack complex (MAC), the cytolytic granule protein of cytotoxic lymphocytes perforin, the streptococcal exotoxin streptolysin O (SLO), and the bee venom polypeptide melittin utilize a similar mechanism to incorporate into cell membranes, induce a Ca2+ influx and a rise in intracellular Ca2+ concentration, and produce cell lysis. At sublytic concentrations, these proteins trigger several cellular activities, including protein phosphorylation and synthesis. We have recently demonstrated that human leukemic cells treated with sublytic doses of human complement become more resistant to lytic complement doses. The study has now been extended to include three other pore-formers: murine perforin, SLO and melittin. As shown here, sublytic MAC induces in the K562 human erythroleukemic cells protection from lytic perforin, and vice versa, sublytic perforin induces protection from complement. Also, sublytic SLO and melittin increase resistance of K562 cells to lytic complement and perforin doses. The capacity of Ca2+ ionophores to induce resistance to the lytic proteins has been examined. Exposure of K562 cells to sublytic concentrations of ionomycin or A23187 for 1 h at 37 degrees C confers on them resistance to complement- and perforin-mediated lysis. The protective effects of the ionophores can be abrogated by chelation of extracellular Ca2+ and by inhibition of RNA or protein synthesis in the cells. These results indicate the following: 1) nucleated cells exposed to sublytic complement MAC, perforin, SLO, or melittin may become resistant to the four pore-formers. Physiologically, this may be regarded as an immunologic tachyphylaxis. 2) Ca2+ influx induced by these pore-formers is an essential and sufficient factor to produce this tachyphylaxis.

Topics: Bacterial Proteins; Calcium; Complement Membrane Attack Complex; Cytotoxicity, Immunologic; Humans; Leukemia, Erythroblastic, Acute; Melitten; Membrane Glycoproteins; Perforin; Pore Forming Cytotoxic Proteins; Streptolysins; Tumor Cells, Cultured

Melittin, the hydrophobic polypeptide from bee venom, sufficiently destabilizes the plasma membrane of cultured cells to allow cell disruption in the absence of detergents with minimal homogenization. Nuclei are thus isolated in high yield with intact nuclear membranes and high transcriptional activity.

Topics: Bee Venoms; Cell Membrane; Cell Nucleus; Hydrolysis; Leukemia, Erythroblastic, Acute; Leukemia, Experimental; Melitten; Membrane Lipids; Membrane Proteins; Nuclear Envelope; Solubility; Transcription, Genetic