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Alternative proteolytic processing of platelet membrane glycoprotein IIb
J C Loftus1, E F Plow, L K Jennings
1Research Institute of Scripps Clinic, Department of Immunology, La Jolla, California 92037.
The Journal of Biological Chemistry
|August 15, 1988
Summary
Platelet glycoprotein IIb undergoes primary cleavage near its light chain terminus. A minor fraction exhibits alternative cleavage, indicating dual processing sites for this crucial platelet receptor component.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Platelet membrane glycoprotein (GP) IIb-IIIa is a key receptor for adhesive proteins like fibrinogen.
- GPIIb is synthesized as a single chain and processed into heavy and light chains on the cell surface.
Purpose of the Study:
- To investigate alternative cleavage sites in the processing of platelet GPIIb.
- To characterize the processing heterogeneity of GPIIb using anti-peptide antibodies.
Main Methods:
- Utilized anti-peptide antibodies (anti-V43 and anti-V41) to probe GPIIb processing.
- Performed immunoblots and immunoprecipitation of surface-labeled platelets.
Main Results:
- Anti-V43 reacted with the heavy chain; anti-V41 reacted with the light chain.
- 97% of GPIIb light chains contained the V41 sequence, indicating primary cleavage site.
- Approximately 3% of GPIIb molecules showed alternative cleavage at both potential sites.
Conclusions:
- GPIIb is predominantly cleaved 12-15 amino acids upstream of the reported light chain terminus.
- A minor population of GPIIb molecules undergoes cleavage at an alternative site, suggesting dual processing pathways.