Cell density-dependent increase in the level of protease-resistant prion protein in prion-infected Neuro2a mouse neuroblastoma cells.

Cells persistently infected with prions continuously produce protease-resistant prion protein (PrP-res). Here, we show that the PrP-res level in prion-infected Neuro2a (N2a) neuroblastoma cells decreased to 50% of their initial level over the first 48 h and then recovered by 96 h after seeding. The level of cellular prion protein (PrP(C)) also appeared to fluctuate, but did not influence the fluctuation of the PrP-res level.

Characterization of prion susceptibility in Neuro2a mouse neuroblastoma cell subclones.

In this study, we established Neuro2a (N2a) neuroblastoma subclones and characterized their susceptibility to prion infection. The N2a cells were treated with brain homogenates from mice infected with mouse prion strain Chandler. Of 31 N2a subclones, 19 were susceptible to prion as those cells became positive for abnormal isoform of prion protein (PrP(Sc)) for up to 9 serial passages, and the remaining 12 subclones were classified as unsusceptible.

Insect cytokine growth-blocking peptide triggers a termination system of cellular immunity by inducing its binding protein.

Growth-blocking peptide (GBP) is a 25-amino acid cytokine found in lepidopteran insects that possesses diverse biological activities such as stimulation of immune cells (plasmatocytes), cell proliferation, and larval growth regulation. We found another novel function of GBP that induces a hemolysis of another class of blood cells (oenocytoids). In the lysate of oenocytoids we identified a GBP-binding protein that shows a specific affinity for GBP.