Reversible phosphorylation of the membrane-bound acetylcholine receptor.
We have found that the acetylcholine receptor (AChR) of Torpedo californica is phosphorylated and dephosphorylated in situ by a membrane-bound protein kinase and phosphatase [1]. There is increasing evidence that other neurotransmitters [2], light [3-6], polypeptide hormones [7], and growth factors [8-12] also may act by regulating the level of phosphorylation of membrane proteins. These observations suggest that membrane protein phosphorylation may be a general regulatory mechanism affecting the response of cells to exogenous metabolic and physical signals. To understand the role of membrane protein phosphorylation, we have chosen to study acetylcholine receptor-enriched membranes purified from the electric organ of T californica. This organ is an ideal model system for such studies since it is a rich source of the acetylcholine receptor. Membranes can be purified from the electric organ that are enriched in the AChR[13] and that show cholinergic agonist-dependent changes in cation flux [14]. Moreover, the AChR from T californica has been purified [15[, biochemically characterized [16], and used to generate specific antibodies [17]. Receptor, enriched membranes contain only a few other proteins that are closely associated with the receptor in the postsynaptic membrane. Such associated proteins may play a critical role in regulating the function of the AChR in the postsynaptic membrane. We have taken advantage of these conditions to study phosphorylation of the membrane-bound AChR in this well-defined, homogeneous system.
D000255:Adenosine Triphosphate; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004557:Electric Organ / Q000378:metabolism*; D005399:Fishes; D006160:Guanosine Triphosphate; D007700:Kinetics; D008970:Molecular Weight; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D054645:Protein Phosphatase 1; D011950:Receptors, Cholinergic / Q000378:metabolism*; D013379:Substrate Specificity
D011950:Receptors, Cholinergic; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1