IL-32α down-regulates β2 integrin (CD18) expression by suppressing PU.1 expression in myeloid cells

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• CD18 is crucial for leukocyte adhesion to the endothelium.
• Interleukin-32 alpha (IL-32α) is implicated in inflammatory processes.
• Understanding IL-32α's regulatory mechanisms is vital for immune cell function.

Purpose of the Study:

• To elucidate the mechanism by which IL-32α down-regulates CD18 expression.
• To investigate the role of transcription factors PU.1, STAT3, and C/EBPα in this process.
• To explore the interaction between IL-32α, STAT3 phosphorylation, and downstream gene regulation.

Main Methods:

• PMA stimulation of THP-1 and K562 cells.
• Analysis of CD18 and PU.1 expression levels.
• Western blotting for STAT3 S727 phosphorylation.
• Chromatin immunoprecipitation to assess transcription factor binding.
• Reporter assays to evaluate promoter activity.

Main Results:

• IL-32α decreased CD18 expression by suppressing PU.1 transcription.
• IL-32α induced prolonged STAT3 S727 phosphorylation.
• IL-32α-mediated STAT3 phosphorylation promoted C/EBPα association, inhibiting PU.1 promoter activity.
• STAT3 S727 phosphorylation is essential for C/EBPα interaction.

Conclusions:

• IL-32α down-regulates CD18 expression through a pathway involving STAT3 S727 phosphorylation and C/EBPα association.
• This mechanism ultimately suppresses PU.1 expression, affecting leukocyte adhesion.
• Findings provide insights into the molecular regulation of immune cell adhesion by IL-32α.