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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Phospholipase A(2)-independent Ca(2+) entry and subsequent apoptosis induced by melittin in human MG63 osteosarcoma cells.

Melittin, a peptide from bee venom, is thought to be a phospholipase A(2) activator and Ca(2+) influx inducer that can evoke cell death in different cell types. However, the effect of melittin on cytosolic free Ca(2+) concentration ([Ca(2+)](i)) and viability has not been explored in human osteoblast-like cells. This study examined whether melittin altered [Ca(2+)](i) and killed cells in MG63 human osteosarcoma cells. [Ca(2+)](i) changes and cell viability were measured by using the fluorescent dyes fura-2 and WST-1, respectively. Melittin at concentrations above 0.075 muM increased [Ca(2+)](i) in a concentration-dependent manner. The Ca(2+) signal was abolished by removing extracellular Ca(2+). Melittin-induced Ca(2+) entry was confirmed by Mn(2+) quenching of fura-2 fluorescence at 360 nm excitation wavelength which was Ca(2+)-insensitive. The melittin- induced Ca(2+) influx was unchanged by modulation of protein kinase-C activity with phorbol 12-myristate 13-acetate (PMA) and GF 109203X, or inhibition of phospholipase A(2) with AACOCF(3) and aristolochic acid; but was substantially inhibited by blocking L-type Ca(2+) channels. At concentrations of 0.5 muM and 1 muM, melittin killed 33% and 45% of cells, respectively, via inducing apoptosis. Lower concentrations of melittin failed to kill cells. The cytotoxic effect of 1 muM melittin was completely reversed by pre-chelating cytosolic Ca(2+) with BAPTA. Taken together, these data showed that in MG63 cells, melittin induced a [Ca(2+)](i) increase by causing Ca(2+) entry through L-type Ca(2+) channels in a manner independent of protein kinase-C and phospholipase A(2) activity; and this [Ca(2+)](i) increase subsequently caused apoptosis.[1]

References

  1. Phospholipase A(2)-independent Ca(2+) entry and subsequent apoptosis induced by melittin in human MG63 osteosarcoma cells. Chu, S.T., Cheng, H.H., Huang, C.J., Chang, H.C., Chi, C.C., Su, H.H., Hsu, S.S., Wang, J.L., Chen, I.S., Liu, S.I., Lu, Y.C., Huang, J.K., Ho, C.M., Jan, C.R. Life Sci. (2007) [Pubmed]
 
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