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The fibronectin receptor on mammalian erythroid precursor cells: characterization and developmental regulation
Abstract:
The plasma membrane of murine erythro-leukemia (MEL) cells contains a 140-kD protein that binds specifically to fibronectin. A 125I-labeled 140-kD protein from surface-labeled uninduced MEL cells was specifically bound by an affinity matrix that contained the 115-kD cell binding fragment of fibronectin, and specifically eluted by a synthetic peptide that has cell attachment-promoting activity. The loss of this protein during erythroid differentiation was correlated with loss of cellular adhesion to fibronectin. Both MEL cells and reticulocytes attached to the same site on fibronectin as do fibroblasts since adhesion of erythroid cells to fibronectin was specifically blocked by a monoclonal antibody directed against the cell-binding fragment of fibronectin and by a synthetic peptide containing the Arg-Gly-Asp-Ser sequence found in the cell-binding fragment of fibronectin. Erythroid cells attached specifically to surfaces coated either with the 115-kD cell-binding fragment of fibronectin or with the synthetic peptide-albumin complex. Thus, the erythroid 140-kD protein exhibits several properties in common with those described for the fibronectin receptor of fibroblasts. We propose that loss or modification of this protein at the cell surface is responsible for the loss of cellular adhesion to fibronectin during erythroid differentiation.
Insights
Murine erythro-leukemia cells have a 140-kD protein that binds fibronectin. Its loss during differentiation correlates with reduced cell adhesion, suggesting a role in cell-fibronectin interactions.
Area of Science:
- Cell Biology
- Biochemistry
- Hematology
Background:
- Murine erythro-leukemia (MEL) cells express a 140-kD protein on their plasma membrane.
- This protein specifically binds to fibronectin, a key extracellular matrix protein.
Purpose of the Study:
- To investigate the role of the 140-kD protein in cellular adhesion to fibronectin during erythroid differentiation.
- To characterize the interaction between the 140-kD protein and fibronectin.
Main Methods:
- Surface labeling of MEL cells with 125I.
- Affinity chromatography using fibronectin fragments.
- Elution with synthetic peptides.
- Blocking adhesion with monoclonal antibodies and peptides.
Main Results:
- The 140-kD protein was specifically bound and eluted, confirming its interaction with the fibronectin cell-binding fragment.
- Loss of the 140-kD protein during erythroid differentiation correlated with decreased cellular adhesion to fibronectin.
- Erythroid cells and fibroblasts bind to the same site on fibronectin, indicated by blocking studies.
Conclusions:
- The erythroid 140-kD protein shares properties with the fibroblast fibronectin receptor.
- Loss or modification of this protein during erythroid differentiation likely causes the observed decrease in fibronectin adhesion.