Regulation of c-Rel nuclear localization by binding of Ca2+/calmodulin.
The NF-kappa B/Rel family of transcription factors participates in the control of a wide array of genes, including genes involved in embryonic development and regulation of immune, inflammation, and stress responses. In most cells, inhibitory I kappa B proteins sequester NF-kappa B/Rel in the cytoplasm. Cellular stimulation results in the degradation of I kappa B and modification of NF-kappa B/Rel proteins, allowing NF-kappa B/Rel to translocate to the nucleus and act on its target genes. Calmodulin (CaM) is a highly conserved, ubiquitously expressed Ca(2+) binding protein that serves as a key mediator of intracellular Ca(2+) signals. Here we report that two members of the NF-kappa B/Rel family, c-Rel and RelA, interact directly with Ca(2+)-loaded CaM. The interaction with CaM is greatly enhanced by cell stimulation, and this enhancement is blocked by addition of I kappa B. c-Rel and RelA interact with CaM through a similar sequence near the nuclear localization signal. Compared to the wild-type protein, CaM binding-deficient mutants of c-Rel exhibit increases in both nuclear accumulation and transcriptional activity on the interleukin 2 and granulocyte macrophage colony-stimulating factor promoters in the presence of a Ca(2+) signal. Conversely, for RelA neither nuclear accumulation nor transcriptional activity on these promoters is increased by mutation of the sequence interacting with CaM. Our results suggest that CaM binds c-Rel and RelA after their release from I kappa B and can inhibit nuclear import of c-Rel while letting RelA translocate to the nucleus and act on its target genes. CaM can therefore differentially regulate the activation of NF-kappa B/Rel proteins following stimulation.
Antonsson
Asa
A
Department of Molecular Biology, Umeå University, 901 87 Umeå, Sweden.
Hughes
Kate
K
Edin
Sofia
S
Grundström
Thomas
T
D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D019281:Dimerization; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D007376:Interleukin-2 / Q000235:genetics; D019169:Jurkat Cells / Q000187:drug effects; D008969:Molecular Sequence Data; D009154:Mutation; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D021381:Protein Transport / Q000187:drug effects; D020569:Proto-Oncogene Proteins c-rel / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D051996:Transcription Factor RelA
D002147:Calmodulin; D020672:I-kappa B Proteins; D007376:Interleukin-2; D016328:NF-kappa B; D020569:Proto-Oncogene Proteins c-rel; D051996:Transcription Factor RelA; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium