The soluble interleukin-6 receptor is generated by shedding

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• The interleukin-6 receptor (IL-6R) is crucial for IL-6 signaling.
• The IL-6R consists of a ligand-binding subunit (gp80) and a signal-transducing subunit (gp130).
• Soluble forms of IL-6R can modulate IL-6 activity.

Purpose of the Study:

• To investigate the mechanism of soluble gp80/IL-6R generation.
• To identify the signaling pathways regulating gp80 shedding.
• To determine the biological activity of shed gp80.

Main Methods:

• Transient expression of human gp80/IL-6R in COS-7 cells.
• Metabolic labeling and protein purification.
• N-terminal sequencing.
• Treatment with phorbol esters (PMA) and protease inhibitors.
• Co-transfection with protein kinase C (PKC) expression plasmid.
• Analysis of shedding from transfected cells and human monocytes.

Main Results:

• A soluble form of gp80/IL-6R was identified and purified from COS-7 cells.
• Shedding of gp80 was significantly induced by PMA, indicating PKC regulation.
• Co-transfection with PKC plasmid enhanced gp80 shedding.
• Protease inhibitors did not prevent shedding, suggesting a novel protease.
• Shed gp80 specifically bound IL-6 and exhibited biological activity.
• PMA treatment of human monocytes induced shedding of soluble gp80.

Conclusions:

• The release of gp80 from COS-7 cells is a specific, PKC-regulated shedding process.
• A novel protease is likely involved in gp80 shedding.
• PKC-regulated shedding is the physiological mechanism for generating soluble IL-6R.
• The shed soluble IL-6R retains biological activity and can bind IL-6.