Artificially controlled aggregation of proteins and targeting in hematopoietic cells.
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.
Rosen
Hanna
H
Department of Hematology, Lund, Sweden. Hanna.Rosen@hematologi.lu.se
Gao
Ying
Y
Johnsson
Ellinor
E
Olsson
Inge
I
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
D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D019272:Leukocyte Elastase; D022021:Tacrolimus Binding Proteins