Neutrophil elastase sorting involves plasma membrane trafficking requiring the C-terminal propeptide.

Area of Science:

• Cell Biology
• Protease Function
• Protein Trafficking

Background:

• Neutrophil elastase (NE) is stored in primary granules/secretory lysosomes.
• NE pro-peptides regulate its activation and localization.
• The C-terminal pro-peptide's function in NE trafficking remained undefined.

Purpose of the Study:

• To investigate the role of the NE C-terminal pro-peptide in NE trafficking.
• To determine if the C-terminal pro-peptide influences NE localization to the plasma membrane.

Main Methods:

• Expressed wild-type NE and a C-terminal deletion mutant (NE/Delta248-267) in rat basophilic leukemia (RBL) cells.
• Utilized antibody ligation and cell-surface biotinylation techniques.
• Analyzed protein targeting in RBL cells and normal granulopoietic precursor cells.

Main Results:

• Both wild-type NE and the mutant were targeted to secretory lysosomes.
• Proform of NE was targeted to the plasma membrane and internalized.
• Targeting to the plasma membrane required the C-terminal pro-peptide; the mutant bypassed this pathway.

Conclusions:

• A subset of NE is targeted to the plasma membrane and undergoes endocytosis.
• This plasma membrane targeting and internalization is dependent on the C-terminal NE pro-peptide.
• The C-terminal pro-peptide has a defined role in regulating NE cellular localization.