Response of cell cycle proteins to neurotrophic factor and chemokine stimulation in human neuroglia

Increased expression of neurotrophins (e.g,, NGF, BDNF) and chemokines (e.g ., RANTES) has been observed in neurodegenerative diseases. We examined the effect of these factors on intracellular signaling cascades inducing cell cycle proteins p53, pRb, and E2F1 in human fetal mixed neuronal and glial c ells. Comparing neurotrophin- and chemokine-treated cultures with untreated controls showed altered subcellular localization and expression of hyperph osphorylated retinoblastoma protein (ppRb), E2F1, and p53. Using immunofluo rescent laser confocal microscopy, E2F1 and ppRb were detected exclusively in neuronal nuclei in control cultures while p53 was cytoplasmic in astrocy tes and nuclear in neurons. Following treatment with neurotrophins, E2F1 an d ppRb were observed in the cytoplasm of neurons, while p53 was observed in both neuronal and astrocytic nuclei. Similar findings were observed follow ing treatment with RANTES, Semiquantitative analysis using immunoblots show ed an increase in the amount of phosphorylated pRb in treated cultures. Ind uction of cell cycle proteins may play a role in neurodegeneration associat ed with neurotrophin and chemokine stimulation. (C) 2001 Academic Press.