Journal of Leukocyte Biology
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A more recent version of this article appeared on November 1, 2003

Published online before print July 22, 2003
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© by The Society for Leukocyte Biology
Journal of Leukocyte Biology, doi:10.1189/jlb.0203066

Received for publication February 11, 2003.
Revised June 13, 2003.
Accepted for publication June 29, 2003.

Article

Artificially controlled aggregation of proteins and targeting in hematopoietic cells

Hanna Rosén @, Ying Gao , Ellinor Johnsson , and Inge Olsson

Institution for Laboratory Medecine, Department of Hematology, Lund, Sweden

@ To whom correspondence should be addressed. E-mail: Hanna.Rosen{at}hematologi.lu.se.


  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 elastase (ELA)-(FKBP)3 with neutrophil ELA and (FKBP*)4-furin cleavage site (FCS)-human growth hormone (hGH) with a FCS and hGH were expressed in the myeloblastic 32D and the rat basophilic leukemia 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.

Key Words: secretory lysosomes • quality control






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