IkappaBalpha degradation is not a requirement for the X-ray-induced activation of nuclear factor kappaB in normal rat astrocytes and human brain tumour cells.
OBJECTIVE
To investigate the mechanism of NFkappaB activation by X-rays in normal primary rat astrocytes.


METHODS
Primary cultures of type I astrocytes generated from the cortex of neonatal rats were exposed to X-rays with and without various kinase inhibitors and a protease inhibitor. The nuclear or cytoplasmic protein extracts were collected at specified times after treatment and analysed for NFkappaB-DNA binding activity and IkappaB protein levels.


RESULTS
The NFkappaB-DNA binding activity was induced by X-rays in a dose- and time-dependent manner in the absence of IkappaB protein degradation in astrocytes as well as in the human glioma cell line U-373MG. Whereas a protease inhibitor (calpain inhibitor 1) and a protein kinase C inhibitor (CGP-41251) did not affect X-ray-induced NFkappaB-DNA binding, treatment of astrocytes with the tyrosine kinase inhibitor (erbstatin) completely prevented the increase in NFkappaB activity after irradiation. Erbstatin also reduced the phosphorylation of IkappaBalpha after X-ray exposure.


CONCLUSIONS
These results indicate that, in contrast with the more frequently investigated activators of NFkappaB, radiation-induced activation of this transcription factor proceeds in the absence of IkappaBalpha degradation and requires tyrosine phosphorylation.
Raju
U
U
Department of Experimental Radiation Oncology-66, The University of Texas MD Anderson Cancer Center, Houston 77030, USA.
Gumin
G J
GJ
Noel
F
F
Tofilon
P J
PJ
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005910:Glioma / Q000378:metabolism / Q000473:pathology; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D020672:I-kappa B Proteins; D016328:NF-kappa B / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D052002:NF-kappa B p50 Subunit; D009842:Oligopeptides / Q000494:pharmacology; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D013997:Time Factors; D014157:Transcription Factors / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000528:radiation effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D006873:Hydroquinones; C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; C489548:NFKB1 protein, human; D009842:Oligopeptides; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; C047473:N-(3-N-(benzyloxycarbonyl)amino-1-carboxypropyl)leucyl-O-methyltyrosine N-methylamide; D004247:DNA; D020794:Receptor Protein-Tyrosine Kinases; C048212:erbstatin