Insect peptide CopA3-induced protein degradation of p27Kip1 stimulates proliferation and protects neuronal cells from apoptosis

Abstract

We recently demonstrated that the antibacterial peptide, CopA3 (a D-type disulfide dimer peptide, LLCIALRKK), inhibits LPS-induced macrophage activation and also has anticancer activity in leukemia cells. Here, we examined whether CopA3 could affect neuronal cell proliferation. We found that CopA3 time-dependently increased cell proliferation by up to 31 ± 2% in human neuroblastoma SH-SY5Y cells, and up to 29 ± 2% in neural stem cells isolated from neonatal mouse brains. In both cell types, CopA3 also significantly inhibited the apoptosis and viability losses caused by 6-hydroxy dopamine (a Parkinson disease-mimicking agent) and okadaic acid (an Alzheimer's disease-mimicking agent). Immunoblotting revealed that the p27Kip1 protein (a negative regulator of cell cycle progression) was markedly degraded in CopA3-treated SH-SY5Y cells. Conversely, an adenovirus expressing p27Kip1 significantly inhibited the antiapoptotic effects of CopA3 against 6-hydroxy dopamine- and okadaic acid-induced apoptosis, and decreased the neurotropic effects of CopA3. These results collectively suggest that CopA3-mediated protein degradation of p27Kip1 may be the main mechanism through which CopA3 exerts neuroprotective and neurotropic effects.

Keywords: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; 6-OHDA; 6-hydroxy dopamine; Apoptosis; Caspase-3; Cell proliferation; Cell viability; Insect peptide; MNSCs; MTT; Mouse neural stem cells; Neuronal cells; Neuroprotective activity; Neurotropic factor; OA; mouse neural stem cells; okadaic acid; p27Kip1.