A cytosolic domain of the erythropoietin receptor contributes to endoplasmic reticulum-associated degradation.
The erythropoietin receptor (EPO-R) is the cellular target for erythropoietin (EPO), the primary hormone that mediates the proliferation of immature erythroblasts and their differentiation into mature erythrocytes. Unusual features of the EPO-R are its short half-life (t(1/2) 1-2 h), its degradation via multiple pathways and the fact that less than 1% of total cellular EPO-R molecules are found on the cell surface. The contribution of EPO-R structural determinants to the regulation of its intracellular metabolism is still unclear. The epidermal growth factor receptor (EGF-R), unlike the EPO-R, is efficiently transported to the cell surface and displays a much longer metabolic half-life. To determine which EPO-R cytosolic domains are involved in intracellular degradation, we studied chimeric receptor molecules constructed of EGF-R extracellular and transmembrane parts, linked to the full length or truncated cytosolic part of the EPO-R. The chimeras were expressed in transiently transfected COS 7 cells and stably expressed in Ba/F3 cells. Our experiments indicate that the cytosolic part of the EPO-R contains determinants that mark it for rapid degradation, in association with the endoplasmic reticulum (ER). This degradation was insensitive to brefeldin A and was inhibited by specific proteasomal inhibitors. A truncated EGF-R/EPO-R chimera containing only 50 amino acids of the EPO-R membrane-proximal cytosolic part was also rapidly degraded suggesting that these 50 amino acids are involved in receptor degradation.
Department of Cell Biology and Histology, Sackler Faculty of Medicine, Tel-Aviv University, Israel Institute of Life Science, Kurume University, Japan.
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Supino-Rosin
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Yoshimura
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Altaratz
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Neumann
D000818:Animals; D020126:Brefeldin A / Q000494:pharmacology; D019556:COS Cells; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D016296:Mutagenesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D017467:Receptors, Erythropoietin / Q000737:chemistry* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D013997:Time Factors
D011500:Protein Synthesis Inhibitors; D017467:Receptors, Erythropoietin; D011993:Recombinant Fusion Proteins; D020126:Brefeldin A; D066246:ErbB Receptors