CD23 (FcepsilonRII) release from cell membranes is mediated by a membrane-bound metalloprotease

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• CD23, the low-affinity IgE receptor (FcepsilonRII), is a Type II extracellular protein found on B-cells, monocytes, and macrophages.
• Cleavage of CD23 from the cell surface generates soluble fragments involved in regulating IgE synthesis.

Purpose of the Study:

• To identify the protease responsible for cleaving CD23 from the cell surface.
• To characterize the mechanism and properties of the CD23-cleaving protease.

Main Methods:

• Development of an assay using purified CD23 and a neo-epitope antibody to detect cleavage products.
• Gel-filtration chromatography to determine the molecular mass of the protease.
• Inhibition assays using various protease inhibitors (metalloprotease, cysteine, serine, acid proteases).

Main Results:

• CD23 cleavage is mediated by a metalloprotease, not cysteine, serine, or acid proteases.
• The protease is an integral membrane protein with a functional molecular mass of approximately 63 kDa.
• The activity is inhibited by 1,10-phenanthroline, imidazole, and batimastat.
• Similar CD23-cleaving activity is found in various cell types, including those not expressing CD23.

Conclusions:

• A metalloprotease is responsible for the release of CD23 from the cell surface.
• This protease activity is conserved across different cell types.
• Understanding CD23 processing may offer insights into IgE regulation and related immune responses.