Thrombopoietin and erythropoietin activate inside-out signaling of integrin and enhance adhesion to immobilized fibronectin in human growth-factor-dependent hematopoietic cells

A. Gotoh, A. Ritchie, H. Takahira, Hal Broxmeyer

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Abstract

Erythropoietin (EPO) and thrombopoietin (c-MPL ligand; TPO) are structurally similar cytokines and support respectively, the proliferation and differentiation for erythroid and megakaryocytic lineages, as well as more primitive progenitors. We studied the effect of these cytokines on the induction of adhesion of human growth-factor-dependent hematopoietic cells to immobilized fibronectin, which is a main component of the extracellular matrix in the bone marrow. MO7ER cells that are genetically engineered to express human EPO receptor and MO7e cells that express endogenous c-MPL were used. Stimulation with either TPO or EPO induced rapid increases in adhesion of MO7ER cells to fibronectin without apparent change of expression of integrins. Experiments with inhibitory monoclonal antibodies (mAbs) demonstrated that CD41, which has been reported to be involved in TPO-induced adhesion of megakaryocytic cells, is not responsible for this enhanced adhesion. Anti-β1 integrin mAb inhibited adhesion completely, while inhibition by anti-α4 integrin mAb and anti-α5 integrin mAb was partial. Combination of anti-α4 mAb plus anti-α5 mAb completely abolished adhesion, as did anti-β1 mAb, suggesting that the adhesion is mediated by both α4β1 and α5β1 integrins. Experiments using inhibitors suggested that ligand binding followed by activation of intracellular tyrosine kinases along with PI3-kinase activation is required. After stimulation of MO7ER cells with either TPO or EPO, fibronectin-attached cells, but not cells in suspension, showed tyrosine phosphorylation of focal adhesion kinase, which plays a central role in integrin-mediated signaling. These data suggest that TPO and EPO might be involved in homing/migration to the bone marrow microenvironment by hematopoietic cells that express corresponding receptors.

Original languageEnglish
Pages (from-to)207-213
Number of pages7
JournalAnnals of Hematology
Volume75
Issue number5-6
DOIs
StatePublished - Nov 1997

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Hematopoietic Cell Growth Factors
Thrombopoietin
Erythropoietin
Fibronectins
Integrins
Cell Adhesion
Bone Marrow
Cytokines
Erythropoietin Receptors
Ligands
Cellular Microenvironment
Focal Adhesion Protein-Tyrosine Kinases
Phosphatidylinositol 3-Kinases
Protein-Tyrosine Kinases
Extracellular Matrix
Tyrosine
Suspensions
Monoclonal Antibodies
Phosphorylation

ASJC Scopus subject areas

  • Hematology

Cite this

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title = "Thrombopoietin and erythropoietin activate inside-out signaling of integrin and enhance adhesion to immobilized fibronectin in human growth-factor-dependent hematopoietic cells",
abstract = "Erythropoietin (EPO) and thrombopoietin (c-MPL ligand; TPO) are structurally similar cytokines and support respectively, the proliferation and differentiation for erythroid and megakaryocytic lineages, as well as more primitive progenitors. We studied the effect of these cytokines on the induction of adhesion of human growth-factor-dependent hematopoietic cells to immobilized fibronectin, which is a main component of the extracellular matrix in the bone marrow. MO7ER cells that are genetically engineered to express human EPO receptor and MO7e cells that express endogenous c-MPL were used. Stimulation with either TPO or EPO induced rapid increases in adhesion of MO7ER cells to fibronectin without apparent change of expression of integrins. Experiments with inhibitory monoclonal antibodies (mAbs) demonstrated that CD41, which has been reported to be involved in TPO-induced adhesion of megakaryocytic cells, is not responsible for this enhanced adhesion. Anti-β1 integrin mAb inhibited adhesion completely, while inhibition by anti-α4 integrin mAb and anti-α5 integrin mAb was partial. Combination of anti-α4 mAb plus anti-α5 mAb completely abolished adhesion, as did anti-β1 mAb, suggesting that the adhesion is mediated by both α4β1 and α5β1 integrins. Experiments using inhibitors suggested that ligand binding followed by activation of intracellular tyrosine kinases along with PI3-kinase activation is required. After stimulation of MO7ER cells with either TPO or EPO, fibronectin-attached cells, but not cells in suspension, showed tyrosine phosphorylation of focal adhesion kinase, which plays a central role in integrin-mediated signaling. These data suggest that TPO and EPO might be involved in homing/migration to the bone marrow microenvironment by hematopoietic cells that express corresponding receptors.",
author = "A. Gotoh and A. Ritchie and H. Takahira and Hal Broxmeyer",
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AU - Gotoh, A.

AU - Ritchie, A.

AU - Takahira, H.

AU - Broxmeyer, Hal

PY - 1997/11

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N2 - Erythropoietin (EPO) and thrombopoietin (c-MPL ligand; TPO) are structurally similar cytokines and support respectively, the proliferation and differentiation for erythroid and megakaryocytic lineages, as well as more primitive progenitors. We studied the effect of these cytokines on the induction of adhesion of human growth-factor-dependent hematopoietic cells to immobilized fibronectin, which is a main component of the extracellular matrix in the bone marrow. MO7ER cells that are genetically engineered to express human EPO receptor and MO7e cells that express endogenous c-MPL were used. Stimulation with either TPO or EPO induced rapid increases in adhesion of MO7ER cells to fibronectin without apparent change of expression of integrins. Experiments with inhibitory monoclonal antibodies (mAbs) demonstrated that CD41, which has been reported to be involved in TPO-induced adhesion of megakaryocytic cells, is not responsible for this enhanced adhesion. Anti-β1 integrin mAb inhibited adhesion completely, while inhibition by anti-α4 integrin mAb and anti-α5 integrin mAb was partial. Combination of anti-α4 mAb plus anti-α5 mAb completely abolished adhesion, as did anti-β1 mAb, suggesting that the adhesion is mediated by both α4β1 and α5β1 integrins. Experiments using inhibitors suggested that ligand binding followed by activation of intracellular tyrosine kinases along with PI3-kinase activation is required. After stimulation of MO7ER cells with either TPO or EPO, fibronectin-attached cells, but not cells in suspension, showed tyrosine phosphorylation of focal adhesion kinase, which plays a central role in integrin-mediated signaling. These data suggest that TPO and EPO might be involved in homing/migration to the bone marrow microenvironment by hematopoietic cells that express corresponding receptors.

AB - Erythropoietin (EPO) and thrombopoietin (c-MPL ligand; TPO) are structurally similar cytokines and support respectively, the proliferation and differentiation for erythroid and megakaryocytic lineages, as well as more primitive progenitors. We studied the effect of these cytokines on the induction of adhesion of human growth-factor-dependent hematopoietic cells to immobilized fibronectin, which is a main component of the extracellular matrix in the bone marrow. MO7ER cells that are genetically engineered to express human EPO receptor and MO7e cells that express endogenous c-MPL were used. Stimulation with either TPO or EPO induced rapid increases in adhesion of MO7ER cells to fibronectin without apparent change of expression of integrins. Experiments with inhibitory monoclonal antibodies (mAbs) demonstrated that CD41, which has been reported to be involved in TPO-induced adhesion of megakaryocytic cells, is not responsible for this enhanced adhesion. Anti-β1 integrin mAb inhibited adhesion completely, while inhibition by anti-α4 integrin mAb and anti-α5 integrin mAb was partial. Combination of anti-α4 mAb plus anti-α5 mAb completely abolished adhesion, as did anti-β1 mAb, suggesting that the adhesion is mediated by both α4β1 and α5β1 integrins. Experiments using inhibitors suggested that ligand binding followed by activation of intracellular tyrosine kinases along with PI3-kinase activation is required. After stimulation of MO7ER cells with either TPO or EPO, fibronectin-attached cells, but not cells in suspension, showed tyrosine phosphorylation of focal adhesion kinase, which plays a central role in integrin-mediated signaling. These data suggest that TPO and EPO might be involved in homing/migration to the bone marrow microenvironment by hematopoietic cells that express corresponding receptors.

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