title: Artificially controlled aggregation of proteins and targeting in hematopoietic cells.
abstract: The targeting mechanisms for granule proteins in hematopoietic cells are largely unknown. Aggregation is believed to be important for protein sorting-for-entry and sorting-by-retention in endocrine and neuroendocrine cells. We asked whether artificially induced multimerization/aggregation of chimeric proteins could affect their sorting in hematopoietic cells. A system was used that permits ligand-controlled intracellular oligomerization of hybrid proteins containing the FK506-binding protein (FKBP). The hybrid proteins ELA-(FKBP)3 with neutrophil elastase (ELA) and (FKBP*)4-FCS-hGH with a furin cleavage site (FCS) and human growth hormone (hGH) were expressed in the myeloblastic 32D and the rat basophilic leukemia (RBL-1) hematopoietic cell lines. ELA alone is normally targeted to secretory lysosomes. However, the hybrid proteins and ligand-induced aggregates of them were constitutively secreted and not targeted. The hGH that was released at the FCS in (FKBP*)4-FCS-hGH was also constitutively secreted. We conclude that protein multimerization/aggregation per se is not enough to facilitate sorting-for-entry to secretory lysosomes in hematopoietic cells and that improperly folded proteins may be eliminated from sorting by constitutive secretion.
authors.affiliation: Department of Hematology, Lund, Sweden. Hanna.Rosen@hematologi.lu.se
authors.forename: Hanna
authors.initials: H
authors.lastname: Rosen
authors.forename: Ying
authors.initials: Y
authors.lastname: Gao
authors.forename: Ellinor
authors.initials: E
authors.lastname: Johnsson
authors.forename: Inge
authors.initials: I
authors.lastname: Olsson
mesh_terms: D000818:Animals; D002449:Cell Aggregation / Q000502:physiology*; D002458:Cell Fractionation; D002460:Cell Line; D015471:Leukemia, Basophilic, Acute; D019272:Leukocyte Elastase / Q000493:pharmacokinetics*; D051379:Mice; D008954:Models, Biological; D020033:Protein Isoforms / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000493:pharmacokinetics; D013347:Subcellular Fractions / Q000378:metabolism; D022021:Tacrolimus Binding Proteins / Q000493:pharmacokinetics*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D019272:Leukocyte Elastase; D022021:Tacrolimus Binding Proteins