Specific sensitivity of CD43 to neutrophil elastase

Area of Science:

• Immunology
• Cell Biology
• Proteomics

Background:

• CD43 (sialophorin, leukosialin) is a sialylated membrane protein on leukocytes with antiadhesive properties.
• It is believed to prevent cell surface interactions, protecting circulating leukocytes.
• Neutrophil elastase was recently implicated in the loss of extracellular CD43.

Purpose of the Study:

• To investigate the susceptibility of CD43 to cleavage by neutrophil elastase.
• To determine the specificity and sites of CD43 cleavage by neutrophil elastase.
• To explore the potential physiological and pathological roles of CD43 cleavage.

Main Methods:

• Flow cytometry was used to assess CD43 cleavage by various proteases.
• Western blotting was employed to identify CD43 fragments after elastase treatment.
• Enzymatic removal of sialic acid was performed to investigate its effect on cleavage.

Main Results:

• Neutrophil CD43 is cleaved by low levels of neutrophil elastase (half-maximal cleavage at 5 µg/mL), but not by pancreatic elastase.
• Other neutrophil proteases like proteinase-3 and cathepsin-G showed minimal or no CD43 cleavage.
• CD43 isoforms on T-lymphoid cells were equally sensitive to neutrophil elastase.
• Western blots revealed CD43 is cleaved at two sites, releasing the distal ~40% of the molecule.
• Cleavage was specific for CD43, with minimal effect on other surface proteins, except for P-selectin glycoprotein ligand-1 and CD16.
• Sialic acid removal did not enhance CD43 cleavage by neutrophil elastase.

Conclusions:

• Neutrophil elastase specifically cleaves CD43 on various leukocytes.
• The cleavage occurs at defined sites, releasing a significant portion of the extracellular domain.
• The sensitivity, specificity, and abundance of neutrophil elastase suggest a significant physiological or pathological role in leukocyte function.