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Characterization of CD200 Ectodomain Shedding
Karrie K Wong1, Fang Zhu1,2, Ismat Khatri2
1Institute of Medical Science, University of Toronto, Toronto, ON, Canada.
Plos One
|April 26, 2016
Summary
Soluble CD200 (sCD200), elevated in Chronic Lymphocytic Leukemia (CLL), is shed from cell surfaces. This shed sCD200 retains its functional extracellular domain, crucial for CD200 receptor interactions.
Area of Science:
- Immunology
- Molecular Biology
- Oncology
Background:
- Soluble CD200 (sCD200) is present in human plasma and elevated in Chronic Lymphocytic Leukemia (CLL).
- CLL cells constitutively release CD200, with partial attenuation by ADAM28 silencing.
Purpose of the Study:
- To investigate mechanisms of CD200 shedding beyond ADAM28.
- To biochemically analyze the shed form of CD200 (sCD200).
Main Methods:
- Biochemical analysis of sCD200 from purified CLL cells and transfected Hek293 cells.
- Antibody generation against extracellular or cytoplasmic CD200 regions.
- PMA stimulation to enhance shedding.
- Flow cytometry to monitor cell surface CD200 expression.
- Western blot analysis and functional studies with CD200R1 expressing cells.
Main Results:
- CD200 shedding is enhanced by PMA stimulation.
- Shed CD200 lacks the cytoplasmic domain but retains the functional extracellular domain.
- The shed extracellular domain is capable of binding to and phosphorylating CD200R.
Conclusions:
- Functionally active CD200 extracellular moiety is cleaved from cell surfaces via ectodomain shedding.
- This shedding mechanism contributes to elevated sCD200 levels in CLL.
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