Interferon heterogeneity resulting from differences in glycosylation.

Area of Science:

• Biochemistry
• Immunology
• Molecular Biology

Background:

• Interferons (IFNs) are crucial cytokines involved in antiviral and immune responses.
• Mouse interferons, particularly alpha and beta types, are known to display size heterogeneity.
• Understanding the structural basis of this heterogeneity is key to elucidating IFN function.

Purpose of the Study:

• To investigate the structural basis for the observed size heterogeneity in mouse interferons.
• To determine the role of glycosylation in the size variation of interferon polypeptides.
• To analyze interferon synthesis in the presence and absence of glycosylation.

Main Methods:

• Mouse C-243 cells were induced with Newcastle disease virus (NDV) for interferon synthesis.
• Cells were metabolically labeled with 35S-methionine.
• Immunoprecipitation followed by gel electrophoresis was used to analyze interferon size.
• Tunicamycin was used to inhibit glycosylation.
• Interferon mRNA was analyzed in a cell-free system.

Main Results:

• Interferons produced in induced cells showed significant size heterogeneity, ranging from 24,000 to 35,000 daltons.
• In tunicamycin-treated cells (inhibited glycosylation), two major interferon bands appeared at 15,000 and 18,000 daltons.
• The synthesis of these smaller interferon forms was confirmed to be directed by interferon mRNA in a cell-free system.
• These results indicate that glycosylation significantly contributes to the size heterogeneity of mouse interferons.

Conclusions:

• The size heterogeneity of mouse interferons (alpha, beta) is primarily attributed to variations in their carbohydrate moieties.
• Glycosylation plays a critical role in determining the apparent molecular weight of interferon polypeptides.
• The core interferon polypeptide sizes are smaller than previously observed due to glycosylation.