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The influence of artificially introduced N-glycosylation sites on the in vitro activity of Xenopus laevis erythropoietin.

ABSTRACT: Erythropoietin (EPO), the primary regulator of erythropoiesis, is a heavily glycosylated protein found in humans and several other mammals. Intriguingly, we have previously found that EPO in Xenopus laevis (xlEPO) has no N-glycosylation sites, and cross-reacts with the human EPO (huEPO) receptor despite low homology with huEPO. In this study, we introduced N-glycosylation sites into wild-type xlEPO at the positions homologous to those in huEPO, and tested whether the glycosylated mutein retained its biological activity. Seven xlEPO muteins, containing 1-3 additional N-linked carbohydrates at positions 24, 38, and/or 83, were expressed in COS-1 cells. The muteins exhibited lower secretion efficiency, higher hydrophilicity, and stronger acidic properties than the wild type. All muteins stimulated the proliferation of both cell lines, xlEPO receptor-expressing xlEPOR-FDC/P2 cells and huEPO receptor-expressing UT-7/EPO cells, in a dose-dependent manner. Thus, the muteins retained their in vitro biological activities. The maximum effect on xlEPOR-FDC/P2 proliferation was decreased by the addition of N-linked carbohydrates, but that on UT-7/EPO proliferation was not changed, indicating that the muteins act as partial agonists to the xlEPO receptor, and near-full agonists to the huEPO receptor. Hence, the EPO-EPOR binding site in X. laevis locates the distal region of artificially introduced three N-glycosylation sites, demonstrating that the vital conformation to exert biological activity is conserved between humans and X. laevis, despite the low similarity in primary structures of EPO and EPOR.

SUBMITTER: Nagasawa K

PROVIDER: S-EPMC4405594 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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The influence of artificially introduced N-glycosylation sites on the in vitro activity of Xenopus laevis erythropoietin.

Nagasawa Kazumichi K Meguro Mizue M Sato Kei K Tanizaki Yuta Y Nogawa-Kosaka Nami N Kato Takashi T

PloS one 20150421 4

Erythropoietin (EPO), the primary regulator of erythropoiesis, is a heavily glycosylated protein found in humans and several other mammals. Intriguingly, we have previously found that EPO in Xenopus laevis (xlEPO) has no N-glycosylation sites, and cross-reacts with the human EPO (huEPO) receptor despite low homology with huEPO. In this study, we introduced N-glycosylation sites into wild-type xlEPO at the positions homologous to those in huEPO, and tested whether the glycosylated mutein retained ...[more]

PMID: 25898205

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Project description:BackgroundA new type of influenza virus, known as type D, has recently been identified in cattle and pigs. Influenza D virus infection in cattle is typically asymptomatic; however, its infection in swine can result in clinical disease. Swine can also be infected with all other types of influenza viruses, namely A, B, and C. Consequently, swine can serve as a "mixing vessel" for highly pathogenic influenza viruses, including those with zoonotic potential. Currently, the only antiviral drug available targets influenza M2 protein ion channel is not completely effective. Thus, it is necessary to develop an M2 ion channel blocker capable of suppressing the induction of resistance to the genetic shift. To provide a basis for developing novel ion channel-blocking compounds, we investigated the properties of influenza D virus M2 protein (DM2) as a drug target.ResultsTo test the ion channel activity of DM2, the DNA corresponding to DM2 with cMyc-tag conjugated to its carboxyl end was cloned into the shuttle vector pNCB1. The mRNA of the DM2-cMyc gene was synthesized and injected into Xenopus oocytes. The translation products of DM2-cMyc mRNA were confirmed by immunofluorescence and mass spectrometry analyses. The DM2-cMyc mRNA-injected oocytes were subjected to the two-electrode voltage-clamp (TEVC) method, and the induced inward current was observed. The midpoint (Vmid) values in Boltzmann modeling for oocytes injected with DM2-cMyc RNA or a buffer were -152 and -200 mV, respectively. Assuming the same expression level in the Xenopus oocytes, DM2 without tag and influenza C virus M2 protein (CM2) were subjected to the TEVC method. DM2 exhibited ion channel activity under the condition that CM2 ion channel activity was reproduced. The gating voltages represented by Vmid for CM2 and DM2 were -141 and -146 mV, respectively. The reversal potentials observed in ND96 for CM2 and DM2 were -21 and -22 mV, respectively. Compared with intact DM2, DM2 variants with mutation in the YxxxK motif, namely Y72A and K76A DM2, showed lower Vmid values while showing no change in reversal potential.ConclusionThe M2 protein from newly isolated influenza D virus showed ion channel activity similar to that of CM2. The gating voltage was shown to be affected by the YxxxK motif and by the hydrophobicity and bulkiness of the carboxyl end of the molecule.

Dataset Information

The influence of artificially introduced N-glycosylation sites on the in vitro activity of Xenopus laevis erythropoietin.

Publications

The influence of artificially introduced N-glycosylation sites on the in vitro activity of Xenopus laevis erythropoietin.

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