Prep1/Pbx2 complexes regulate CCL2 expression through the -2578 guanine polymorphism.

Area of Science:

• Neuroimmunology
• Molecular Genetics
• Inflammation Biology

Background:

• CC-chemokine ligand 2 (CCL2) is a key chemoattractant for monocytes in inflammation.
• Increased CCL2 expression is linked to inflammatory diseases, including HIV-associated dementia (HIV-D).
• The -2578 G polymorphism in the CCL2 promoter is associated with elevated CCL2 and HIV-D pathogenesis, but its mechanism is unclear.

Purpose of the Study:

• To elucidate the molecular mechanism by which the -2578 G polymorphism regulates CCL2 expression in astrocytes.
• To model the role of the -2578 G polymorphism in CCL2 gene regulation under basal and inflammatory conditions.

Main Methods:

• In silico analysis to identify potential transcription factor binding sites.
• Reporter gene assays using CCL2 promoter constructs with different alleles (-2578 G vs. A).
• Electrophoretic mobility shift assays (EMSAs) to assess protein-DNA interactions.

Main Results:

• The -2578 G allele creates a consensus binding site for the transcriptional regulator complex Prep1/Pbx2.
• Prep1/Pbx2 preferentially binds to the -2578 G allele compared to the A allele.
• Under unstimulated conditions, the G allele exhibits lower basal promoter activity than the A allele.
• Upon IL-1β stimulation, both G and A alleles show equal transcriptional activation, indicating the -2578 region's influence is context-dependent.
• Promoters with the -2578 G allele show a higher fold induction of CCL2 expression upon stimulation.

Conclusions:

• The -2578 G polymorphism influences CCL2 regulation by modulating Prep1/Pbx2 binding and fold induction during inflammation.
• Individuals homozygous for the -2578 G allele may exhibit hyper-responsive CCL2 phenotypes during inflammatory periods.
• This finding provides a molecular basis for the association between the -2578 G allele and inflammatory disease pathogenesis, such as HIV-D.