Targeted deletion of MKK4 gene potentiates TNF-induced apoptosis through the down-regulation of NF-kappa B activation and NF-kappa B-regulated antiapoptotic gene products.
MAPK kinase 4 (MKK4) is a dual-specificity kinase that activates both JNK and p38 MAPK. However, the mechanism by which MKK4 regulates TNF-induced apoptosis is not fully understood. Therefore, we used fibroblasts derived from MKK4 gene-deleted (MKK4-KO) mice to determine the role of this kinase in TNF signaling. We found that when compared with the wild-type cells, deletion of MKK4 gene enhanced TNF-induced apoptosis, and this correlated with down-regulation of TNF-induced cell-proliferative (COX-2 and cyclin D1) and antiapoptotic (survivin, IAP1, XIAP, Bcl-2, Bcl-x(L), and cFLIP) gene products, all regulated by NF-kappaB. Indeed we found that TNF-induced NF-kappaB activation was abrogated in MKK4 gene-deleted cells, as determined by DNA binding. Further investigation revealed that TNF-induced I kappaB alpha kinase activation, I kappaB alpha phosphorylation, I kappaB alpha degradation, and p65 nuclear translocation were all suppressed in MKK4-KO cells. NF-kappaB reporter assay revealed that NF-kappaB activation induced by TNF, TNFR1, TRADD, TRAF2, NIK, and I kappaB alpha kinase was modulated in gene-deleted cells. Overall, our results indicate that MKK4 plays a central role in TNF-induced apoptosis through the regulation of NF-kappaB-regulated gene products.
Sethi
Gautam
G
Cytokine Research Laboratory, Department of Experimental Therapeutics, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Ahn
Kwang Seok
KS
Xia
Dianren
D
Kurie
Jonathan M
JM
Aggarwal
Bharat B
BB
D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000276:immunology*; D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D002460:Cell Line; D019938:Cyclin D1 / Q000096:biosynthesis / Q000235:genetics; D051546:Cyclooxygenase 2 / Q000096:biosynthesis / Q000235:genetics; D015536:Down-Regulation / Q000235:genetics / Q000276:immunology*; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology / Q000276:immunology; D017353:Gene Deletion; D018390:Gene Targeting; D048670:MAP Kinase Kinase 4 / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000096:biosynthesis / Q000235:genetics; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000096:biosynthesis / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
D051017:Apoptosis Regulatory Proteins; D016328:NF-kappa B; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D014409:Tumor Necrosis Factor-alpha; D019938:Cyclin D1; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D048670:MAP Kinase Kinase 4; D020780:Matrix Metalloproteinase 9