Extracellular Activities of Human Granzymes
Situated in secretory granules of cytotoxic cells, granzymes are essential for induction of target cell apoptosis with perforin. However, since cytotoxic cells constitutively secrete a portion of their synthesized granzymes, these proteases could mediate extracellular functions independently of their role in the lytic event. Thrombin has been shown to function as an activation molecule by cleaving its receptor. We hypothesize that granzymes may act similarly. In this report, we show that purified human granzyme A can induce human lung fibroblasts to produce IL6 and IL8. Cytokine induction is abrogated by treating the serine protease with the suicide serine protease inhibitor 3,4-dichloroisocoumarin. Other fibroblast lines as well as epithelial cells produced cytokines in response to granzyme A. Our data suggest that granzyme A can function as an activation molecule with potentially important immunoregulatory functions.
Sower
LE
Department of Microbiology and Immunology, University of Texas Medical Branch, 3.162 Medical Research Building, 11th and Mechanic, Galveston, Texas, 77555-1019
Klimpel
GR
Hanna
W
Froelich
CJ