Phosphorylation-elicited quaternary changes of GA binding protein in transcriptional activation.
Enrichment of nicotinic acetylcholine receptors (nAChR) on the tip of the subjunctional folds of the postsynaptic membrane is a central event in the development of the vertebrate neuromuscular junction. This is attained, in part, through a selective transcription in the subsynaptic nuclei, and it has recently been shown that the GA binding protein (GABP) plays an important role in this compartmentalized expression. The neural factor heregulin (HRG) activates nAChR transcription in cultured cells by stimulating a signaling cascade of protein kinases. Hence, it is speculated that GABP becomes activated by phosphorylation, but the mechanism has remained elusive. To fully understand the consequences of GABP phosphorylation, we examined the effect of heregulin-elicited GABP phosphorylation on cellular localization, DNA binding, transcription, and mobility. We demonstrate that HRG-elicited phosphorylation dramatically changes the transcriptional activity and mobility of GABP. While phosphorylation of GABPbeta seems to be dispensable for these changes, phosphorylation of GABPalpha is crucial. Using fluorescence resonance energy transfer, we furthermore showed that phosphorylation of threonine 280 in GABPalpha triggers reorganizations of the quaternary structure of GABP. Taken together, these results support a model in which phosphorylation-elicited structural changes of GABP enable engagement in certain interactions leading to transcriptional activation.
Laboratoire Récepteurs et Cognition, CNRS URA 2182, Institut Pasteur, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France.
Morten
M
Sunesen
Monique
M
Huchet-Dymanus
Morten O
MO
Christensen
Jean-Pierre
JP
Changeux
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D051268:GA-Binding Protein Transcription Factor; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D020890:Neuregulin-1 / Q000378:metabolism / Q000494:pharmacology; D009469:Neuromuscular Junction / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D011978:Receptors, Nicotinic / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D051268:GA-Binding Protein Transcription Factor; D020890:Neuregulin-1; D021122:Protein Subunits; D011978:Receptors, Nicotinic; D011994:Recombinant Proteins; D014157:Transcription Factors; D004247:DNA