Endocytosis of GPI-linked membrane folate receptor-alpha
| Autor: | Rijnboutt, S, Jansen, G, Posthuma, G, Hynes, J B, Schornagel, J H, Strous, G J |
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| Přispěvatelé: | Rheumatology, CCA - Cancer biology and immunology, CCA - Imaging and biomarkers, CCA - Cancer Treatment and quality of life, AII - Inflammatory diseases |
| Jazyk: | angličtina |
| Rok vydání: | 1996 |
| Zdroj: | Journal of Cell Biology, 132(1-2), 35-47. Rockefeller University Press Rijnboutt, S, Jansen, G, Posthuma, G, Hynes, J B, Schornagel, J H & Strous, G J 1996, ' Endocytosis of GPI-linked membrane folate receptor-alpha ', Journal of Cell Biology, vol. 132, no. 1-2, pp. 35-47 . |
| ISSN: | 0021-9525 |
| Popis: | GPI-linked membrane folate receptors (MFRs) have been implicated in the receptor-mediated uptake of reduced folate cofactors and folate-based chemotherapeutic drugs. We have studied the biosynthetic transport to and internalization of MFR isoform alpha in KB-cells. MFR-alpha was synthesized as a 32-kD protein and converted in a maturely glycosylated 36-38-kD protein 1 h after synthesis. 32-kD MFR-alpha was completely soluble in Triton X-100 at 0 degree C. In contrast, only 33% of the 36-38-kD species could be solubilized at these conditions whereas complete solubilization was obtained in Triton X-100 at 37 degrees C or in the presence of saponin at 0 degree C. Similar solubilization characteristics were found when MFR-alpha at the plasma membrane was labeled with a crosslinkable 125I-labeled photoaffinity-analog of folic acid as a ligand. Triton X-100-insoluble membrane domains containing MFR-alpha could be separated from soluble MFR-alpha on sucrose flotation gradients. Only Triton X-100 soluble MFR-alpha was internalized from the plasma membrane. The reduced-folate-carrier, an integral membrane protein capable of translocating (anti-)folates across membranes, was completely excluded from the Triton X-100-resistant membrane domains. Internalized MFR-alpha recycled slowly to the cell surface during which it remained soluble in Triton X-100 at 0 degree C. Using immunoelectron microscopy, we found MFR-alpha along the entire endocytic pathway: in clathrin-coated buds and vesicles, and in small and large endosomal vacuoles. In conclusion, our data indicate that a large fraction, if not all, of internalizing MFR-alpha bypasses caveolae. |
| Databáze: | OpenAIRE |
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