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Rommel MGE, Hoerster K, Milde C, Schenk F, Roser L, Kohlscheen S, Heinz N, Modlich U. Signaling properties of murine MPL and MPL mutants after stimulation with thrombopoietin and romiplostim. Exp Hematol 2020; 85:33-46.e6. [PMID: 32417303 DOI: 10.1016/j.exphem.2020.04.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 04/24/2020] [Accepted: 04/29/2020] [Indexed: 01/01/2023]
Abstract
Thrombopoietin (THPO) and its receptor myeloproliferative leukemia virus oncogene (MPL) regulate hematopoietic stem cell (HSC) quiescence and maintenance, but also megakaryopoiesis. Thrombocytopenias or aplastic anemias can be treated today with THPO peptide mimetics (romiplostim) or small-molecule THPO receptor agonists (e.g., eltrombopag). These THPO mimetics were designed for human application; however, many preclinical studies are performed in murine models. We investigated the activation of wild-type murine MPL (mMPL) by romiplostim. Romiplostim stimulated AKT, ERK1/2, and STAT5 phosphorylation without preference for one of these pathways, however, with a four- to fivefold lower phosphorylation intensity at high concentration. Faster internalization of mMPL after romiplostim binding could be one explanation of reduced signaling. In vitro megakaryocyte differentiation, proliferation, and maturation by romiplostim was less efficient compared with stimulation with mTHPO. We further dissected mMPL signaling by lentiviral overexpression of mMPL mutants with tyrosine (Y)-to-phenylalanine (F) substitutions in the distal cytoplasmic tyrosines 582 (Y582F), 616 (Y616F), and 621 (Y621F) individually and in combination (Y616F_Y621F) and in truncated receptors lacking 53 (Δ53) or 69 (Δ69) C-terminal amino acids. Mutation at tyrosine residue Y582F caused a gain-of-function with baseline activation and increased ERK1/2 phosphorylation upon stimulation. In agreement with this, proliferation in Y582F-32D cells was increased, yet did not rescue in vitro megakaryopoiesis from Mpl-deficient cells. Y616F and Y621F mutated receptors exhibited strongly impaired ERK1/2 and decreased AKT signaling and conferred reduced proliferation to 32D cells upon mTHPO stimulation but a partial correction of immature megakaryopoiesis in vitro.
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Affiliation(s)
- Marcel G E Rommel
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | - Keven Hoerster
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany; Institute for Transfusion Medicine, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Christian Milde
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | - Franziska Schenk
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | - Luise Roser
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | - Saskia Kohlscheen
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | - Niels Heinz
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | - Ute Modlich
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany.
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