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Origin of a soluble truncated transferrin receptor
1Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
Blood
|May 1, 1993
Summary
Reticulocytes release transferrin receptors (TFR) during maturation. In sheep, this soluble TFR originates from exosomes, not the cell surface, and this exosome-mediated release may also occur in humans.
Area of Science:
- Cell Biology
- Molecular Biology
- Hematology
Background:
- Elevated reticulocytes lead to noncellular transferrin receptor (TFR) formation in circulation.
- In humans, released TFR is mostly truncated; in other species, it's full-length and exosome-associated.
Purpose of the Study:
- To investigate the origin of truncated transferrin receptor (TFR) in sheep reticulocytes.
- To determine if truncated TFR arises from cell surface cleavage or exosome cleavage.
- To explore the potential exosomal origin of truncated TFR in humans.
Main Methods:
- In vitro incubation of surface 125I-labeled sheep reticulocytes.
- Analysis of released receptor size and association with exosomes.
- Antibody probing for cytoplasmic domains on exosomes and plasma membranes.
Main Results:
- In sheep reticulocytes, 75% of released TFR is native-sized and exosome-associated; 25% is a truncated 80 kDa form.
- Native-sized TFR appears in exosomes before the truncated exofacial domain is detected in the medium.
- A 17 kDa peptide, recognized by anti-cytoplasmic domain antibodies, is found only in exosomes, not plasma membranes.
Conclusions:
- Truncated soluble transferrin receptor (TFR) in sheep originates from exosomes.
- Exosome formation is the primary mechanism for maturation-associated TFR loss in sheep.
- Findings suggest truncated TFR in humans may also originate from exosomes.