Transforming growth factor alpha in arterioles: cell surface processing of its precursor by elastases.

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Transforming growth factor alpha (TGF alpha) is a mitogen derived from a membrane-bound precursor.
• Elastase-like proteases are implicated in the cleavage and release of TGF alpha.

Purpose of the Study:

• To investigate if polymorphonuclear (PMN) leukocytic elastase can process cell surface TGF alpha precursors.
• To determine the bioactivity of TGF alpha released by PMN elastase.
• To explore the role of PMN elastase in TGF alpha processing in arterioles.

Main Methods:

• Transfection of NR6 cells with rat TGF alpha cDNA.
• Zinc-inducible expression of TGF alpha precursor in 1B2 transfectant cells.
• Western blot analysis to detect TGF alpha release after elastase treatment.
• Mitogenic assays to assess the bioactivity of released TGF alpha.

Main Results:

• PMN leukocytic elastase and pancreatic elastase released bioactive TGF alpha from the cell surface precursor.
• Fixed cells prevented basal release but allowed elastase-mediated processing.
• Other proteases like cathepsin G and trypsin did not process the TGF alpha precursor.

Conclusions:

• PMN leukocytic elastase can cleave membrane-bound TGF alpha precursors, releasing bioactive TGF alpha.
• This finding suggests a novel function for PMN elastase in wound healing processes.
• TGF alpha localization in arterioles and PMN elastase activity point to a potential role in vascular smooth muscle cell regulation.