Lysyl oxidase inhibits ras-mediated transformation by preventing activation of NF-kappa B.
Lysyl oxidase (LO), which catalyzes the oxidation of lysine residues, was previously shown to have anti-oncogenic activity on ras-transformed cells. Since oncogenic Ras mediates transformation, in part, through the activation of the transcription factor nuclear factor-kappa B (NF-kappa B), we tested here the effects of LO on NF-kappa B activity. Expression of LO in ras-transformed NIH 3T3 cells led to decreased NF-kappa B binding and activity, as well as the expression of the NF-kappa B target gene c-myc. Importantly, ectopic expression of LO led to a dramatic decrease in colony formation by ras-transformed NIH 3T3 cells, a finding comparable to the expression of the I kappa B alpha dominant-negative mutant, which could be rescued by p65/p50 NF-kappa B subunit expression. LO was unable to directly inhibit the activity of ectopically expressed p65 and c-Rel NF-kappa B subunits, suggesting that LO affected an upstream signaling pathway(s) induced by Ras. Consistent with this hypothesis, LO expression decreased both the rate of I kappa B alpha turnover and the activities of IKK alpha and IKK beta. Moreover, the ectopic expression of a constitutively active version of either kinase reversed the negative effects of LO. Ras can induce NF-kappa B via both the phosphatidylinositol 3-kinase (PI3K)/Akt and Raf/MEK pathways. LO potently downregulated the PI3K and Akt kinases, while partially inhibiting MEK kinase activity. Expression of a constitutively activated, myristylated Akt or PDK1 was able to counteract the effect of LO on NF-kappa B, whereas constitutively activated Raf was only partially effective. Importantly, LO blocked membrane localization of Akt and PDK1 in Ras-transformed cells. Overall, these results strongly argue that the anti-oncogenic effects of LO on ras-mediated transformation are due to its ability to inhibit signaling pathways that lead to activation of NF-kappa B.
Jeay
Sébastien
S
Department of Biochemistry, Boston University Medical School, Boston, Massachusetts 02118, USA.
Pianetti
Stefania
S
Kagan
Herbert M
HM
Sonenshein
Gail E
GE
D016475:3T3 Cells; D000818:Animals; D002455:Cell Division / Q000235:genetics; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005799:Genes, Dominant; D017930:Genes, Reporter; D016259:Genes, myc / Q000502:physiology; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051379:Mice; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D008249:Protein-Lysine 6-Oxidase / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014162:Transfection
D004791:Enzyme Inhibitors; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins; D020930:MAP Kinase Kinase Kinases; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D008249:Protein-Lysine 6-Oxidase; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf; D016283:Proto-Oncogene Proteins p21(ras); C000606205:Nfkbia protein, mouse; C496564:Chuk protein, mouse; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse