Recombinant Analogs of a Novel Milk Pro-Apoptotic Peptide, Lactaptin, and Their Effect on Cultured Human Cells
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We recently isolated and characterized a human milk peptide, lactaptin, which induced apoptosis of cultured human MCF-7 cells. Lactaptin was identified as a proteolytic fragment of human kappa-casein. Here, we generated two recombinant analogs of the peptide, RL1 and RL2, containing truncated and complete amino acid sequences of lactaptin, respectively. Analogs were produced in E.coli, purified and assayed for biological activity on cultured human MCF-7 cells. RL1 was shown to induce only a small decrease in cell viability, whereas RL2 lowered the viability of MCF-7 cells by 60%. This reduction in MCF-7 cell viability was associated with apoptosis, which was indicated by phosphatidilserine externalization and caspase-7 activation. The viability of A549 and Hep-2 cells was also reduced by RL2, albeit to a lesser degree than seen with MCF-7 cells; this reduced viability was not accompanied by apoptosis. Non-malignant human mesenchymal stem cells (MSC) were completely resistant to RL2 action.
KeywordsApoptosis Human kappa-casein Lactaptin MCF-7
DNA fragmentation factor 45 kDa
Mesenchymal stem cells
Tumor necrosis factor alpha
This work was supported by a grant from the Russian Federal Agency for Science and Innovations, State contract # 02.512.11.2257, #02.522.12.2005 and by an Integration Grant from the Presidium of SB RAS № 18.