Modulation of Ionic Channel Function by Protein Phosphorylation
2007
Montal, Mauricio
Protein phosphorylation is considered a key event in synaptic physiology. The acetylcholine receptor (AChR), a prototype of ligand-gated ion channels, plays a central role in postsynaptic signal transduction. To examine the functional consequences of AChR phosphorylation, single-channel properties of purified Torpedo californica AChR reconstituted in planar lipid bilayers, were evaluated before and after phosphorylation by purified protein-serine and - tyrosine kinases, or dephosphorylation by recombinant protein tyrosine phosphatase. Single-channel conductance was not altered by changing the AChR serine or tyrosine phosphorylation state. In contrast, the AChR open-channel probability was markedly affected both by the extent of receptor phosphorylation in different subunits and by agonist concentration. Notably, the spontaneous open-channel probability of serine-phosphorylated AChRs is significantly higher than that of AChRs phosphorylated on tyrosine residues or of unphosphorylated AChRs. Channel activation by protein kinase A and protein kinase C is correlated with AChR phosphorylation and is abolished by alpha-bungarotoxin.... Protein phosphorylation/ion channels, RA1
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