Binding and internalization of biotinylated interleukin-2 in human
lymphocytes
DK Peters and DH Norback
Department of Pathology, University of Wisconsin, Madison.
The binding, internalization, and fate of interleukin-2 (IL-2) were studied
in phytohemagglutinin (PHA)-activated human lymphocytes using biotinylated
recombinant IL-2 (rIL-2). Streptavidin adsorbed to 18-nm colloidal gold
beads (Au18-streptavidin) and streptavidin covalently bound to horseradish
peroxidase (HRP-streptavidin) were used to follow the movement of
biotinylated rIL-2 within cells over a 4-hour period. Results obtained from
either probe were similar. Biotinylated rIL-2 was taken up in coated pits,
transferred to a series of small uncoated vesicles and tubules in the
peripheral cytoplasm of the cell, then concentrated and sequestered in
uncoated vesicles, multivesicular bodies (MVB), and dense bodies (DB) in
the peripheral and juxtanuclear cytoplasm of the cell. Occasionally, MVB
containing Au18-streptavidin, or HRP-streptavidin, appear to have fused
with the plasma membrane of the cell. No labeling of the Golgi cisternae,
nuclear envelope, or nucleus was observed. Results from a competitive
receptor binding assay and a cell proliferation assay indicate that both
the affinity of rIL-2 for high affinity rIL-2 receptors and the
proliferative activity of rIL- 2 were negligibly affected by the
biotinylation procedure. These studies suggest that in activated
lymphocytes, IL-2 is bound to receptors on the cell surface, gathered in
coated pits, internalized by receptor-mediated endocytosis, concentrated in
the endosomal compartments, and delivered to lysosomes for degradation.
Volume 76,
Issue 1,
pp. 97-104,
07/01/1990
Copyright © 1990 by The American Society of Hematology
