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Calnexin is associated with and induced by overexpressed human complement protein C2
Hiroshi Tsukamoto1, Albert Tousson, Antonella Circolo
1Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama-Birmingham, Birmingham, Alabama 35294-0005, USA.
The Anatomical Record
|May 2, 2002
Summary
Complement protein C2 interacts with calnexin, a chaperone protein, leading to calnexin upregulation. This interaction is crucial for C2
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Complement protein C2 is vital for the classical and lectin pathways.
- Previous studies showed C2 accumulates in the ERGIC and a mutant C2Delta(17) is retained in the ER.
Purpose of the Study:
- To investigate the interaction between C2 and calnexin.
- To understand the mechanism of calnexin upregulation in response to C2 expression.
Main Methods:
- Immunofluorescence microscopy to assess colocalization.
- Biosynthetic labeling and immunoprecipitation to confirm physical association.
- Treatment with castanospermine to analyze the role of glycosylation.
Main Results:
- Calnexin colocalizes and physically associates with both wild-type C2 and C2Delta(17).
- Expression of C2 leads to calnexin upregulation, independent of castanospermine's effect on translocation.
- Factor B, similar to C2, also upregulates calnexin, unlike C3 or factor D.
Conclusions:
- Calnexin interacts with C2, influencing its cellular localization.
- Calnexin upregulation by C2 or factor B may be triggered by shared structural features or high glycan content.
- This interaction highlights a novel aspect of complement protein regulation.