The eag potassium channel binds and locally activates calcium/calmodulin-dependent protein kinase II.
Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) has been implicated in the regulation of neuronal excitability in many systems. Recent studies suggest that local regulation of membrane potential can have important computational consequences for neuronal function. In Drosophila, CaMKII regulates the eag potassium channel, but if and how this regulation was spatially restricted was unknown. Using coimmunoprecipitation from head extracts and in vitro binding assays, we show that CaMKII and Eag form a stable complex and that association with Eag activates CaMKII independently of CaM and autophosphorylation. Ca(2+)/CaM is necessary to initiate binding of CaMKII to Eag but not to sustain association because binding persists when CaM is removed. The Eag CaMKII-binding domain has homology to the CaMKII autoregulatory region, and the constitutively active CaMKII mutant, T287D, binds Eag Ca(2+)-independently in vitro and in vivo. These results favor a model in which the CaMKII-binding domain of Eag displaces the CaMKII autoinhibitory region. Displacement results in autophosphorylation-independent activation of CaMKII which persists even when Ca(2+) levels have gone down. Activity-dependent binding to this potassium channel substrate allows CaMKII to remain locally active even when Ca(2+) levels have dropped, providing a novel mechanism by which CaMKII can regulate excitability locally over long time scales.
Sun
Xiu Xia
XX
Department of Biology and Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02454-9110, USA.
Hodge
James J L
JJ
Zhou
Yi
Y
Nguyen
Maidung
M
Griffith
Leslie C
LC
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002147:Calmodulin / Q000737:chemistry; D002460:Cell Line; D004330:Drosophila; D029721:Drosophila Proteins; D004789:Enzyme Activation; D004926:Escherichia coli / Q000378:metabolism; D051638:Ether-A-Go-Go Potassium Channels; D017353:Gene Deletion; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry*; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D002147:Calmodulin; D029721:Drosophila Proteins; D051638:Ether-A-Go-Go Potassium Channels; D015221:Potassium Channels; D011993:Recombinant Fusion Proteins; C496883:eag protein, Drosophila; D005982:Glutathione Transferase; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium