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p180, a novel recycling transmembrane glycoprotein with restricted cell type expression
C M Isacke1, P van der Geer, T Hunter
1Department of Biochemistry, Imperial College of Science and Technology, University of London, England.
Molecular and Cellular Biology
|June 1, 1990
Summary
A novel 180-kilodalton (kDa) protein, p180, functions as a recycling receptor on human fibroblast cell surfaces. This transmembrane glycoprotein is internalized and recycled, with restricted expression in mesodermal cells.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- A 180-kilodalton (kDa) protein, designated p180, was identified using monoclonal antibodies against human fibroblast cell surface proteins.
- p180 is a transmembrane glycoprotein with both cell surface and intracellular membrane localization.
Purpose of the Study:
- To characterize the localization, dynamics, and biochemical properties of the p180 protein.
- To investigate the potential function of p180 as a cell surface receptor.
Main Methods:
- Monoclonal antibody binding studies using 125I-Fab' fragments.
- Immunoblot analysis with polyclonal antiserum.
- Biochemical characterization including N-terminal sequencing.
- Immunoaffinity chromatography and gel filtration for protein purification.
- Confocal microscopy for colocalization studies.
Main Results:
- p180 is found on both plasma membrane (10-30%) and intracellular membranes (70-90%).
- p180 undergoes rapid internalization from the cell surface at 37°C, followed by recycling.
- The protein concentrates in coated pits on the cell surface and is found in endosomes intracellularly, colocalizing with the transferrin receptor.
- p180 exhibits restricted expression in fibroblast cultures and mesodermal tissues.
- Biochemical analysis reveals a transmembrane glycoprotein with a phosphorylated cytoplasmic domain.
Conclusions:
- p180 is a novel recycling receptor with highly restricted expression in fibroblast-like cells.
- Its localization and dynamic behavior suggest a role in cellular transport and signaling.