Biosynthetic processing of human interleukin-2 receptor (Tac antigen)

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• The T-cell surface receptor for interleukin-2 (IL-2R) plays a crucial role in immune responses.
• Understanding the biosynthetic pathway of IL-2R is essential for comprehending T-cell activation and function.

Purpose of the Study:

• To investigate the post-translational modifications involved in the biosynthesis of the human T-cell interleukin-2 receptor (IL-2R).
• To characterize the precursor and mature forms of IL-2R and identify the biochemical changes during its maturation.

Main Methods:

• Metabolic and cell surface radiolabeling of cultured human T-cell line MT-1.
• Immunoprecipitation using a monoclonal anti-receptor antibody (anti-Tac).
• Analysis by one- and two-dimensional polyacrylamide gel electrophoresis.

Main Results:

• The nascent IL-2R precursor (Mr ~40,000) is post-translationally modified to the mature IL-2R (Mr 60,000-65,000) within 2-4 hours.
• Maturation involves a significant increase in molecular weight due to glycosylation (glucosamine, galactose) and an acidic shift in isoelectric point from sialic acid addition.
• Monensin treatment blocked IL-2R maturation, and fatty acid attachment was identified as a modification step.

Conclusions:

• The biosynthesis of IL-2R involves complex post-translational modifications, including glycosylation, sialylation, and fatty acid attachment.
• These modifications are critical for generating the functional mature IL-2R on the T-cell surface.
• The study provides insights into the intermediate steps and reactions governing IL-2R precursor maturation.