期刊
BIOCHEMICAL JOURNAL
卷 378, 期 -, 页码 1089-1094出版社
PORTLAND PRESS LTD
DOI: 10.1042/BJ20031654
关键词
copine dominant negative; I kappa B; nuclear factor-kappa B (NF-kappa B); ubiquitin C12 (UBC12)
The role of copines in regulating signalling from the TNF-alpha (tumour necrosis factor-alpha) receptor was probed by the expression of a copine dominant-negative construct in HEK293 (human embryonic kidney 293) cells. The construct was found to reduce activation of the transcription factor NF-kappaB (nuclear factor-kappaB) by TNF-alpha. The introduction of calcium into HEK293 cells either through the activation of muscarinic cholinergic receptors or through the application of the ionophore A23187 was found to enhance TNF-alpha-dependent activation of NF-kappaB. This effect of calcium was completely blocked by the copine dominant-negative construct. TNF-alpha was found to greatly enhance the expression of endogenous copine 1, and the responsiveness of the TNF-alpha signalling pathway to muscarinic stimulation increased in parallel with the increased copine I expression. The copine dominant-negative construct also inhibited the TNF-alpha-dependent degradation Of IkappaB, a regulator of NF-kappaB. All of the effects of the dominant-negative construct could be reversed by overexpression of full-length copine 1, suggesting that the construct acts specifically through competitive inhibition of copine. One of the identified targets of copine I is the NEDD8-conjugating enzyme UBC12 (ubiquitin C12), that promotes the degradation Of IkappaB through the ubiquitin ligase enzyme complex SCFbetaTrCp. Therefore the copine dominant-negative construct might inhibit TNF-a signalling by dysregulation or mislocalization of UBC12. Based on these results, a hypothesis is presented for possible roles of copines in regulating other signalling pathways in animals, plants and protozoa.
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