TNF-alpha mediated transport of NF-kappaB to the nucleus is independent of the cytoskeleton-based transport system in non-neuronal cells.
In unstimulated cells, proteins of the nuclear factor kappaB (NF-kappaB) transcription factor family are sequestered in the cytoplasm through interactions with IkappaB inhibitor proteins. Tumor necrosis factor alpha (TNF-alpha) activates the degradation of IkappaB-alpha and the nuclear import of cytoplasmic NF-kappaB. Nuclear localization of numerous cellular proteins is mediated by the ability of the cytoskeleton, usually microtubules, to direct their perinuclear accumulation. In a former study we have shown that activated NF-kappaB rapidly moves from distal processes in neurons towards the nucleus. The fast transport rate suggests the involvement of motor proteins in the transport of NF-kappaB. Here we address the question how NF-kappaB arrives at the nuclear membrane before import in non-neuronal cells, i.e., by diffusion alone or with the help of active transport mechanisms. Using confocal microscopy imaging and analysis of nuclear protein extracts, we show that NF-kappaB movement through the cytoplasm to the nucleus is independent of the cytoskeleton, in the three cell lines investigated here. Additionally we demonstrate that NF-kappaB p65 is not associated with the dynein/dynactin molecular motor complex. We propose that cells utilize two distinct mechanisms of NF-kappaB transport: (1) signaling via diffusion over short distances in non-neuronal cells and (2) transport via motor proteins that move along the cytoskeleton in neuronal processes where the distances between sites of NF-kappaB activation and nucleus can be vast.
Institut für Neurobiochemie Universität Witten/Herdecke, Stockumer Str. 10, D-58448 Witten, Germany.
Ilja
I
Mikenberg
Darius
D
Widera
Aljoscha
A
Kaus
Barbara
B
Kaltschmidt
Christian
C
Kaltschmidt
D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism*; D006801:Humans; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism*; D008954:Models, Biological; D009474:Neurons / Q000166:cytology*; D021381:Protein Transport / Q000187:drug effects; D053778:Thiazolidines / Q000494:pharmacology; D051996:Transcription Factor RelA / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D019086:Bridged Bicyclo Compounds, Heterocyclic; D053778:Thiazolidines; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D016159:Tumor Suppressor Protein p53; C037068:latrunculin B