Structural and biophysical studies of the human IL-7/IL-7Ralpha complex
Craig A McElroy1, Julie A Dohm, Scott T R Walsh
1Department of Molecular and Cellular Biochemistry, College of Medicine, Comprehensive Cancer Center, Ohio State University, 467 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210, USA.
Structure (London, England : 1993)
|January 15, 2009
Summary
Interleukin-7 (IL-7) receptor alpha (IL-7Ralpha) binding to IL-7 is significantly enhanced by glycosylation, increasing affinity 300-fold. This glycosylation mechanism is unique among gamma(c) family receptors and offers therapeutic targets.
Area of Science:
- Immunology
- Molecular Biology
- Structural Biology
Background:
- Interleukin-7 (IL-7) and its receptor alpha subunit (IL-7Ralpha) form a complex with the gamma(c) receptor, essential for T and B cell development and homeostasis.
- The IL-7/IL-7Ralpha complex initiates signaling cascades critical for adaptive immunity.
Purpose of the Study:
- To investigate the role of glycosylation in modulating the binding affinity between IL-7 and IL-7Ralpha.
- To elucidate the structural basis for IL-7Ralpha's interaction with IL-7 and the impact of glycosylation.
- To understand the implications of SCID mutations in IL-7Ralpha.
Main Methods:
- X-ray crystallography was used to determine the structures of IL-7 in complex with both glycosylated and unglycosylated IL-7Ralpha.
- Binding kinetics were measured to quantify the affinity changes due to glycosylation.
- Structural comparisons were performed to analyze the binding interfaces and the location of SCID mutations.
Main Results:
- Glycosylation of IL-7Ralpha enhances its binding affinity to IL-7 by approximately 300-fold, primarily due to an accelerated on-rate.
- Glycosylation does not directly participate in the IL-7 binding interface.
- Severe Combined Immunodeficiency (SCID) mutations in IL-7Ralpha are located outside the IL-7 binding interface, suggesting they cause protein folding defects.
Conclusions:
- Glycosylation is a critical post-translational modification that uniquely regulates IL-7Ralpha binding affinity within the gamma(c) receptor family.
- The structural insights gained provide a molecular understanding of IL-7 signaling and identify potential targets for therapeutic intervention in IL-7-related immune disorders.
- Understanding the impact of SCID mutations on IL-7Ralpha folding is crucial for diagnosing and potentially treating these immune deficiencies.
