Constitutive NF-kappa B activity in neurons

Area of Science:

• Neuroscience
• Molecular Biology
• Immunology

Background:

• Nuclear factor kappa B (NF-kappa B) is typically an inducible transcription factor found in a latent cytoplasmic form.
• Constitutive nuclear NF-kappa B activity has been reported primarily in immune cells.
• The human immunodeficiency virus type 1 (HIV-1) promoter shows high activity in brain regions of transgenic mice.

Purpose of the Study:

• To investigate the presence and activity of NF-kappa B in neurons.
• To determine if neurons exhibit constitutive NF-kappa B activity.
• To explore the implications of neuronal NF-kappa B activity for brain function and HIV-1 pathogenesis.

Main Methods:

• Primary neuronal cultures from rat hippocampus and cerebral cortex.
• Luciferase reporter gene assays driven by the HIV-1 long terminal repeat.
• Indirect immunofluorescence and confocal laser microscopy.
• Electrophoretic mobility shift assays (EMSA).
• Analysis of NF-kappa B subunits p50 and RelA (p65).

Main Results:

• Primary neuronal cultures demonstrated high constitutive expression of the HIV-1 reporter gene, dependent on NF-kappa B binding sites.
• Coexpression of I kappa B-alpha abolished reporter gene activity, confirming NF-kappa B's role.
• NF-kappa B subunits p50 and RelA (p65) were detected in neuronal nuclei.
• Constitutive NF-kappa B DNA-binding activity was found in neuronal nuclei in vivo.
• Nuclear NF-kappa B immunostaining was observed in a subset of neurons in the mouse brain.

Conclusions:

• Neurons possess constitutively active NF-kappa B in their nuclei.
• This neuronal NF-kappa B activity may play a role in normal brain function and neuronal differentiation.
• Constitutive NF-kappa B activity in neurons could explain the high activity of the HIV-1 enhancer in the brain, relevant to AIDS dementia complex.