An extracellular region of the erythropoietin receptor of the subterranean blind mole rat Spalax enhances receptor maturation.
Erythropoietic functions of erythropoietin (EPO) are mediated by its receptor (EPO-R), which is present on the cell surface of erythroid progenitors and induced by hypoxia. We focused on EPO-R from Spalax galili (sEPO-R), one of the four Israeli species of the subterranean blind mole rat, Spalax ehrenbergi superspecies, as a special natural animal model of high tolerance to hypoxia. Led by the intriguing observation that most of the mouse EPO-R (mEPO-R) is retained in the endoplasmic reticulum (ER), we hypothesized that sEPO-R is expressed at higher levels on the cell surface, thus maximizing the response to elevated EPO, which has been reported in this species. Indeed, we found increased cell-surface levels of sEPO-R as compared with mEPO-R by using flow cytometry analysis of BOSC cells transiently expressing HA-tagged EPO-Rs (full length or truncated). We then postulated that unique extracellular sEPO-R sequence features contribute to its processing and cell-surface expression. To map these domains of the sEPO-R that augment receptor maturation, we generated EPO-R derivatives in which parts of the extracellular region of mEPO-R were replaced with the corresponding fragments of sEPO-R. We found that an extracellular portion of sEPO-R, harboring the N-glycosylation site, conferred enhanced maturation and increased transport to the cell surface of the respective chimeric receptor. Taken together, we demonstrate higher surface expression of sEPO-R, attributed at least in part to increased ER exit, mediated by an extracellular region of this receptor. We speculate that these sEPO-R sequence features play a role in the adaptation of Spalax to extreme hypoxia.
Ravid
Orly
O
Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel-Aviv University, Ramat-Aviv 69978, Tel Aviv, Israel.
Shams
Imad
I
Ben Califa
Nathalie
N
Nevo
Eviatar
E
Avivi
Aaron
A
Neumann
Drorit
D
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D017467:Receptors, Erythropoietin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D046308:Spalax
D011134:Polysaccharides; D017467:Receptors, Erythropoietin