Lysine residues are key residues in many cellular processes, in part due to their ability to accept a wide variety of post-translational modifications. In the present study, we identify the EPO-R [EPO (erythropoietin) receptor] cytosolic lysine residues as enhancers of receptor function. EPO-R drives survival, proliferation and differentiation of erythroid progenitor cells via binding of its ligand EPO. We mutated the five EPO-R cytosolic lysine residues to arginine residues (5KR EPO-R), eliminating putative lysine-dependent modifications. Overexpressed 5KR EPO-R displayed impaired ubiquitination and improved stability compared with wt (wild-type) EPO-R. Unexpectedly, fusion proteins consisting of VSVGtsO45 (vesicular stomatitis virus glycoprotein temperature-sensitive folding mutant) with wt or 5KR EPO-R cytosolic domains demonstrated delayed glycan maturation kinetics upon substitution of the lysine residues. Moreover, VSVG-wt EPO-R, but not VSVG-5KR EPO-R, displayed endoplasmic reticulum-associated ubiquitination. Despite similar cell-surface EPO-binding levels of both receptors and the lack of EPO-induced ubiquitination by 5KR EPO-R, the lysine-less mutant produced weaker receptor activation and signalling than the wt receptor. We thus propose that EPO-R cytosolic lysine residues enhance receptor function, most probably through ubiquitination and/or other post-translational modifications.
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Research Article|
March 29 2011
Cytosolic lysine residues enhance anterograde transport and activation of the erythropoietin receptor
Liron Yosha;
Liron Yosha
1Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Ramat-Aviv, Tel-Aviv 69978, Israel
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Orly Ravid;
Orly Ravid
1Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Ramat-Aviv, Tel-Aviv 69978, Israel
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Nathalie Ben-Califa;
Nathalie Ben-Califa
1Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Ramat-Aviv, Tel-Aviv 69978, Israel
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Drorit Neumann
Drorit Neumann
1
1Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Ramat-Aviv, Tel-Aviv 69978, Israel
1To whom correspondence should be addressed (email histo6@post.tau.ac.il).
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Publisher: Portland Press Ltd
Received:
November 16 2010
Revision Received:
January 20 2011
Accepted:
February 03 2011
Accepted Manuscript online:
February 03 2011
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2011 Biochemical Society
2011
Biochem J (2011) 435 (2): 509–518.
Article history
Received:
November 16 2010
Revision Received:
January 20 2011
Accepted:
February 03 2011
Accepted Manuscript online:
February 03 2011
Citation
Liron Yosha, Orly Ravid, Nathalie Ben-Califa, Drorit Neumann; Cytosolic lysine residues enhance anterograde transport and activation of the erythropoietin receptor. Biochem J 15 April 2011; 435 (2): 509–518. doi: https://doi.org/10.1042/BJ20101876
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