[alpha-Actinin-4 and p65/RelA subunit of NF-kappaB transcription factor are co-localized and migrate together into the nucleus in EGF-stimulated A431 cell].

The NF-kappaB/Rel family of transcription factors in mammalian cells regulates inducible transcription of a large number of genes in response to diverse stimuli. Despite a great number of publications on this subject, little is known about precise NF-kappaB localization in the cytoplasm. As previously demonstrated, in normal rat fibroblast and human epidermoid carcinoma A431 cells p65/RelA subunit of NF-kappaB is co-localized in the cytoplasm with actin structures. However, the mechanism of NF-kappaB interaction with actin remains unclear. We have investigated localization of p65/RelA subunit NFkappaB and alpha-actinin isoforms during cell activation by epidermal growth factor (EGF). Using confocal microscopy, we have shown that alpha-actinin-4 and p65/RelA subunit of NF-kappaB transcription factor are co-localized in A431 cells. Cell treatment with EGF leads to translocation of the proteins to membrane ruffles, and eventually to migration into the nucleus. Pretreatment of A431 cells with cytochalasin D or wortmannin prior to EGF treatment increases p65/RelA and alpha-actinin-4 accumulation in nuclear extracts. Co-localization of alpha-actinin-4 with p65/RelA subunit of NF-kappaB was found in nuclei isolated from stimulated cells. These results support the notion that actin cytoskeleton reorganization and alpha-actinin-4 are involved in NF-kappaB signaling.