| First Author | Chang NS | Year | 2002 |
| Journal | J Biol Chem | Volume | 277 |
| Issue | 12 | Pages | 10323-31 |
| PubMed ID | 11799106 | Mgi Jnum | J:75464 |
| Mgi Id | MGI:2176657 | Doi | 10.1074/jbc.M106607200 |
| Citation | Chang NS (2002) The Non-ankyrin C Terminus of Ikappa Balpha Physically Interacts with p53 in Vivo and Dissociates in Response to Apoptotic Stress, Hypoxia, DNA Damage, and Transforming Growth Factor-beta 1-mediated Growth Suppression. J Biol Chem 277(12):10323-31 |
| abstractText | Transforming growth factor beta (TGF-beta1) suppresses the growth of mink lung Mv1Lu epithelial cells, whereas testicular hyaluronidase abolishes the growth inhibition. Exposure of Mv1Lu cells to TGF-beta1 rapidly resulted in down-regulation of cytosolic IkappaBalpha and hyaluronidase prevented this effect, suggesting a possible role of IkappaBalpha in the growth regulation. Ectopic expression of wild-type and dominant negative IkappaBalpha prevented TGF-beta1-mediated growth suppression. Nonetheless, the blocking effect of IkappaBalpha is not related to regulation of NF-kappaB function by its N-terminal ankyrin-repeat region (amino acids 1-243). Removal of the PEST (proline-glutamic acid-serine-threonine) domain-containing C terminus (amino acids 244-314) abolished the IkappaBalpha function, and the C terminus alone blocked the TGF-beta1 growth-inhibitory effect. Co-immunoprecipitation by anti-p53 antibody using Mv1Lu and other types of cells, as well as rat liver and spleen, revealed that a portion of cytosolic IkappaBalpha physically interacted with p53. In contrast, Mdm2, an inhibitor of p53, was barely detectable in the immunoprecipitates. The cytosolic p53 small middle dotIkappaBalpha complex rapidly dissociated in response to apoptotic stress, etoposide- and UV-mediated DNA damage, hypoxia, and TGF-beta1-mediated growth suppression. Also, a rapid increase in the formation of the nuclear p53 small middle dotIkappaBalpha complex was observed during exposure to etoposide and UV. In contrast, TGF-beta1-mediated promotion of fibroblast growth failed to mediate p53 small middle dotIkappaBalpha dissociation. Mapping by yeast two-hybrid showed that the non-ankyrin C terminus of IkappaBalpha physically interacted with the proline-rich region and a phosphorylation site, serine 46, in p53. Deletion of serine 46 or alteration of serine 46 to glycine abolished the p53 small middle dotIkappaBalpha interaction. Alteration to threonine retained the binding interaction, suggesting that serine 46 phosphorylation is involved in the p53 small middle dotIkappaBalpha complex formation. Functionally, enhancement of p53 apoptosis was observed when p53 and IkappaBalpha were transiently co-expressed in cells. Together, the IkappaBalpha small middle dotp53 complex plays an important role in responses involving growth regulation, apoptosis, and hypoxic stress. |
