Characterization of a neuronal kappaB-binding factor distinct from NF-kappaB.
Transcription factors that bind kappaB enhancer elements have begun to garner wide attention in neurobiology. Data suggest that activation of kappaB-binding factors in neurons can be protective against various neurotoxins, but other data have connected NF-kappaB to cell death. In electrophoretic mobility shift assays of kappaB-binding activity, we have found that the predominant activity in rat brain tissue, in primary neurons, and in neuronal cell lines has a mobility inconsistent with that of bona fide NF-kappaB (RelA-p50 heterodimer). We have tentatively termed this activity neuronal kappaB-binding factor (NKBF). Competition assays with various DNA probes distinguished NKBF from NF-kappaB. Probes that efficiently bind the p50 homodimer were able to compete with a conventional NF-kappaB probe for NKBF binding, but NKBF did not react with antibodies to p50 (or any other known Rel family members). Furthermore, UV-crosslinking indicated that NKBF is composed of two polypeptides of 82 kDa and 27 kDa. Although NKBF activity can be elevated in a manner independent of new macromolecular synthesis, it does not appear to be modulated by IkappaB. Finally, no NF-kappaB was induced by glutamate in highly enriched neuronal cultures, although it was induced in neuron-glia cocultures. These data suggest that the primary kappaB-binding transcription factor in neurons is a novel protein complex distinct from NF-kappaB.
Moerman
A M
AM
Department of Geriatrics, University of Arkansas for Medical Sciences, J.L. McClellan Memorial Veterans Affairs Medical Center, 4300 W. Seventh St., Little Rock, AR 72205, USA.
Mao
X
X
Lucas
M M
MM
Barger
S W
SW
D000818:Animals; D001667:Binding, Competitive / Q000502:physiology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000032:analysis / Q000378:metabolism; D019281:Dimerization; D018698:Glutamic Acid / Q000494:pharmacology; D020672:I-kappa B Proteins; D016328:NF-kappa B / Q000032:analysis* / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000302:isolation & purification* / Q000378:metabolism; D009457:Neuroglia / Q000737:chemistry; D009474:Neurons / Q000737:chemistry* / Q000166:cytology / Q000187:drug effects; D015345:Oligonucleotide Probes; D051381:Rats; D017207:Rats, Sprague-Dawley; D014466:Ultraviolet Rays
D004268:DNA-Binding Proteins; C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D016328:NF-kappa B; D009419:Nerve Tissue Proteins; D015345:Oligonucleotide Probes; D018698:Glutamic Acid