ZAK: a MAP3Kinase that transduces Shiga toxin- and ricin-induced proinflammatory cytokine expression.
Shiga toxins (Stxs) and ricin initiate damage to host cells by cleaving a single adenine residue on the alpha-sarcin loop of the 28S ribosomal RNA. This molecular insult results in a cascade of intracellular events termed the ribotoxic stress response (RSR). Although Stxs and ricin have been shown to cause the RSR, the mitogen-activated protein kinase kinase kinase (MAP3K) that transduces the signal from intoxicated ribosomes to activate SAPKinases has remained elusive. We show in vitro that DHP-2 (7-[3-fluoro-4-aminophenyl-(4-(2-pyridin-2-yl-5,6-dihydro-4H-pyrrolo[1,2-b]pyrazol-3-yl))]-quinoline), a zipper sterile-alpha-motif kinase (ZAK)-specific inhibitor, blocks Stx2/ricin-induced SAPKinase activation. Treatment of cells with DHP-2 also blocks Stx2/ricin-mediated upregulation of the proinflammatory cytokine interleukin-8 and results in a modest but statistically significant improvement in cell viability following Stx2/ricin treatment. Finally we show that siRNA directed against the N-terminus of ZAK diminishes Stx2/Ricin-induced SAPKinase activation. Together, these data demonstrate that a ZAK isoform(s) is the MAP3Kinase that transduces the RSR. Therefore, ZAKalpha and/or beta isoforms may act as potential therapeutic target(s) for treating Stx/ricin-associated illnesses. Furthermore, a small molecule inhibitor like DHP-2 may prove valuable in preventing the Stx/ricin-induced proinflammatory and/or apoptotic effects that are thought to contribute to pathogenesis by Stx-producing Escherichia coli and ricin.
Jandhyala
Dakshina M
DM
Division of Geographic Medicine and Infectious Disease Tufts-New England Medical Center, Boston, MA 02111, USA. djandhyala@tufts-nemc.org
Ahluwalia
Amrita
A
Obrig
Tom
T
Thorpe
Cheleste M
CM
D000368:Aged; D000818:Animals; D002460:Cell Line; D002648:Child; D002522:Chlorocebus aethiops; D016207:Cytokines / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D016209:Interleukin-8 / Q000276:immunology; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases; D020935:MAP Kinase Signaling System / Q000502:physiology; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011720:Pyrazoles / Q000378:metabolism; D011804:Quinolines / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012276:Ricin / Q000378:metabolism*; D022641:Shiga Toxin 2 / Q000378:metabolism*; D054323:Shiga-Toxigenic Escherichia coli / Q000378:metabolism / Q000472:pathogenicity; D014709:Vero Cells; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D016207:Cytokines; C501857:DHP-2 compound; D004791:Enzyme Inhibitors; D016209:Interleukin-8; D007527:Isoenzymes; D011720:Pyrazoles; D011804:Quinolines; D034741:RNA, Small Interfering; D022641:Shiga Toxin 2; D012276:Ricin; D011494:Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C413047:MAP3K20 protein, human