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2017 ; 8
(ä): 1459
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Cystatin F Affects Natural Killer Cell Cytotoxicity
#MMPMID29180998
Peri?i? Nanut M
; Saboti? J
; ?vajger U
; Jewett A
; Kos J
Front Immunol
2017[]; 8
(ä): 1459
PMID29180998
show ga
Cystatin F is a cysteine peptidase inhibitor which, unlike other cystatin family
members, is targeted to endosomal/lysosomal compartments. It is synthesized as an
inactive disulfide-linked dimer which is then converted to an active monomer by
proteolytic cleavage of 15 N-terminal residues. Cystatin F has been suggested to
regulate the cytotoxicity of natural killer (NK) cells by inhibiting the major
granzyme convertases, cathepsins C and H. To test this hypothesis, we prepared
variants of cystatin F and analyzed their uptake, subcellular trafficking, and
peptidase inhibition, as well as their impact on the cytotoxicity of NK-92 cells
and primary NK cells. The N-glycosylation pattern is responsible for the
secretion, uptake, and subcellular sorting of cystatin F in HeLa and Hek293
cells, whereas the legumain binding site had no effect on these processes.
Active, N-terminally truncated, monomeric cystatin F can also be internalized by
recipient cells and targeted to endo/lysosomes, affecting also cells lacking the
activating peptidase. Cystatin F mutants capable of cell internalization and
trafficking through the endo/lysosomal pathway significantly decreased cathepsin
C and H activities, both in situ, following transfection and in trans, using
conditioned media. Further, incubation of IL-2 stimulated NK-92 and primary NK
cells with full-length and N-terminally truncated cystatin F mutants led to
suppression of their granule-mediated cytotoxicity. This effect was most
significant with the N-terminally truncated mutants. These results suggest that
cystatin F can be an important mediator within tumor microenvironment affecting
the cytotoxicity of NK cells and consequently antitumor immune response.