Identification of a neuregulin and protein-tyrosine phosphatase response element in the nicotinic acetylcholine receptor epsilon subunit gene: regulatory role of an Rts transcription factor.
At the neuromuscular synapse, innervation induces endplate-specific expression of adult-type nicotinic acetylcholine receptors by selective expression of their subunit-encoding genes (alpha2betaepsilondelta) in endplate-associated myonuclei. These genes are specifically regulated by protein-tyrosine phosphatase (PTPase) activity. In addition, neuregulin/acetylcholine-receptor-inducing activity, a nerve-derived factor that stimulates nicotinic acetylcholine receptor synthesis, induces adult-type specific epsilon subunit gene expression via activation of a Ras/mitogen-activated protein kinase pathway. However, the DNA regulatory elements and the binding proteins that mediate PTPase and neuregulin-dependent gene expression remain unknown. Herein we report that PTPase, neuregulin, and Ras-dependent regulation of the epsilon subunit gene map to a 15-bp promoter sequence. Interestingly, this same 15-bp sequence appears to be necessary for low epsilon subunit gene expression in extrajunctional regions of the muscle fiber. Site-directed mutagenesis of a putative Ets binding site located within this 15-bp sequence, reduced PTPase, neuregulin, and Ras-dependent regulation. Overexpression of the rat muscle Ets-2 transcription factor resulted in a sequence-specific induction of epsilon subunit promoter activity. Further, a dominant negative mutant of Ets-2 abolished neuregulin-dependent induction of epsilon subunit gene expression. Thus, these results indicate a crucial role for the 15-bp element in determining synapse-specific and neuregulin-mediated motor neuron control of epsilon subunit gene expression and suggest the participation of Ets transcription factor(s) in this control.
Sapru
M K
MK
Mental Health Research Institute and Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
Florance
S K
SK
Kirk
C
C
Goldman
D
D
D000818:Animals; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation; D006023:Glycoproteins / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*; D020880:Neuregulins; D011401:Promoter Regions, Genetic; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D050787:Proto-Oncogene Protein c-ets-2; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D011978:Receptors, Nicotinic / Q000235:genetics*; D012097:Repressor Proteins; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors; D014162:Transfection; D018631:ras Proteins / Q000502:physiology
D004268:DNA-Binding Proteins; C107465:ERF protein, human; C494071:Ets2 protein, rat; D006023:Glycoproteins; D020880:Neuregulins; D050787:Proto-Oncogene Protein c-ets-2; D011518:Proto-Oncogene Proteins; D011978:Receptors, Nicotinic; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D004247:DNA; D011505:Protein-Tyrosine Kinases; D017027:Protein Tyrosine Phosphatases; D018631:ras Proteins