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From the Department of Pediatrics, Case Western Reserve University
School of Medicine, Cleveland, OH; and the Department of Rheumatology
and Immunology, Brigham and Women's Hospital, Boston, MA.
Polymorphonuclear neutrophils (PMN) contain multiple
distinct secretory compartments that are sequentially mobilized during cell activation. Complement receptor type 1 (CR1) is a marker for a
readily mobilizable secretory vesicle compartment, which can undergo
exocytic fusion with the plasma membrane independently of secretion of
traditional granule contents. The basis for the formation of these
distinct compartments is incompletely understood. Primary and secondary
granules are generated directly from the Golgi complex during different
stages of development of the cell, obviating the need for sorting
signals for proper packaging of their constituents. To determine
whether the secretory vesicles are formed in a similar manner, we
studied a stable rat basophilic leukemia cell line (RBL-CR1)
transfected with a plasmid containing the cDNA of human CR1 driven by a
viral promoter. The CR1 was present primarily intracellularly in small
vesicles resembling the CR1 storage pools in resting PMN. Activation of
RBL-CR1 resulted in translocation of intracellular CR1 to the plasma
membrane, with mobilization requirements different from those of the
classical RBL granules. Thus, in RBL-CR1, continuously synthesized CR1
is stored and upregulated in much the same way as in PMN. This suggests that differential timing of gene expression is not essential for proper
storage of CR1 and that other sorting mechanisms are involved, which
can be studied in RBL-transfectants.
Blood, Vol. 92 No. 1 (July 1), 1998:
pp. 300-309
This article has been cited by other articles:
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| Copyright © 1998 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
