title: Granule targeting of soluble tumor necrosis factor (TNF) receptor expressed during granulopoietic maturation in murine bone marrow cells.
abstract: In this experiment, we explored the potential of secretory lysosomes of hematopoietic cells to act as vehicles for immunomodulatory protein delivery at an inflammation site. We investigated whether exogenous soluble TNF-receptor 1 (sTNFR1) could be expressed in primary hematopoietic progenitor cells and become targeted for storage and secretion during granulopoietic differentiation. An sTNFR1 construct with a transmembrane domain (tm) and a cytosol sorting signal (Y) taken from CD63, was retrovirally transduced to lineage-negative murine hematopoietic bone marrow stem/progenitor cells. This process was followed by cytokine-driven granulopoietic maturation. The sTNFR1-tm-Y was found to be synthesized in precursor cells and to persist in mature granulocytes and monocytes/macrophages. Immunofluorescence-localization studies showed a granule pattern of sTNFR1-tm-Y in both precursor and mature granulocytes and secretion to phagosomes after ingestion of bacteria. Immunoelectron microscopy revealed co-localization between the sTNFR1-tm-Y and the primary (azurophil) granule marker myeloperoxidase. Collectively, our results demonstrated granule targeting, storage, and secretion of exogenous sTNFR1-tm-Y constitutively expressed during normal granulopoietic differentiation. These findings support the concept of using storage organelles of circulating hematopoietic cells as vehicles for targeting sites of inflammation with immunoregulatory agents.
authors.affiliation: Department of Hematology, C14, BMC, SE-221 84 Lund, Sweden.
authors.forename: Ying
authors.initials: Y
authors.lastname: Gao
authors.forename: Hans
authors.initials: H
authors.lastname: Tapper
authors.forename: Jero
authors.initials: J
authors.lastname: Calafat
authors.forename: Inge
authors.initials: I
authors.lastname: Olsson
authors.forename: Markus
authors.initials: M
authors.lastname: Hansson
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000378:metabolism*; D000068800:Etanercept; D006098:Granulocytes / Q000166:cytology* / Q000378:metabolism; D007074:Immunoglobulin G / Q000378:metabolism*; D051379:Mice; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*
chemical_list: D007074:Immunoglobulin G; D018124:Receptors, Tumor Necrosis Factor; D000068800:Etanercept