Antianoikis effect of nuclear factor-kappaB through up-regulated expression of osteoprotegerin, BCL-2, and IAP-1.
Epithelial cells undergo a form of apoptosis termed anoikis when they lose extracellular attachments. We evaluated the role of transcription factor NF-kappaB in the regulation of anoikis susceptibility of intestinal epithelial cells. Culture of rat intestinal epithelial cells in suspension induced NF-kappaB activation, which blocked the anoikis of those cells, as assessed by internucleosomal DNA fragmentation and caspase-3 cleavage. Activation of NF-kappaB after the loss of extracellular attachments required focal adhesion kinase tyrosine 397 phosphorylation. This triggered a signaling cascade through phosphatidylinositol 3-kinase and AKT, to induce DNA binding of the RelA/p65 NF-kappaB polypeptide. NF-kappaB activated in this manner induced the up-regulated expression of a distinct program of genes that included osteoprotegerin, BCL-2, and IAP-1 (inhibitor of apoptosis protein-1). Chromatin immunoprecipitation experiments revealed that NF-kappaB directly regulated the promoters of these 3 genes. Knock-down of the expression of osteoprotegerin, BCL-2, or inhibitor of apoptosis protein-1 by RNA interference showed that these factors inhibit anoikis, and genetic reconstitution of their expression alone or in combination restored normal levels of anoikis to NF-kappaB-inactive intestinal epithelial cells. Together, these findings have identified the molecular components of a previously unrecognized antianoikis pathway in intestinal epithelial cells.
Toruner
Murat
M
Gastroenterology Research Unit and Molecular Medicine Program, Mayo Clinic, Rochester, Minnesota 55905, USA.
Fernandez-Zapico
Martin
M
Sha
Jing Jing
JJ
Pham
Linh
L
Urrutia
Raul
R
Egan
Laurence J
LJ
D000818:Animals; D023102:Anoikis; D018929:Cell Culture Techniques; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation; D006023:Glycoproteins / Q000378:metabolism*; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D053244:Osteoprotegerin; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D015854:Up-Regulation
D006023:Glycoproteins; D051034:Inhibitor of Apoptosis Proteins; D016328:NF-kappa B; D053244:Osteoprotegerin; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C506032:Tnfrsf11b protein, rat