Tyrosine phosphorylation of Kv1.2 modulates its interaction with the actin-binding protein cortactin.
Tyrosine phosphorylation evokes functional changes in a variety of ion channels. Modulation of the actin cytoskeleton also affects the function of some channels. Little is known about how these avenues of ion channel regulation may interact. We report that the potassium channel Kv1.2 associates with the actin-binding protein cortactin and that the binding is modulated by tyrosine phosphorylation. Immunocytochemical and biochemical analyses show that Kv1.2 and cortactin co-localize to the cortical actin cytoskeleton at the leading edges of the cell. Binding assays using purified recombinant proteins reveal a 19-amino acid span within the carboxyl terminus of Kv1.2 that is necessary for direct cortactin binding. Phosphorylation of specific tyrosines within the C terminus of Kv1.2 attenuates that binding. In HEK293 cells, activation of the M1 muscarinic acetylcholine receptor evokes tyrosine phosphorylation-dependent suppression of Kv1.2 ionic current. We show that M1 receptor activation also reduces the interaction of cortactin with Kv1.2 and that mutant Kv1.2 channels deficient for cortactin binding exhibit strongly attenuated ionic current. These results demonstrate a dynamic, phosphorylation-dependent interaction between Kv1.2 and the actin cytoskeleton-binding protein cortactin and suggest a role for that interaction in the regulation of Kv1.2 ionic current.
Hattan
David
D
Department of Pharmacology, University of Vermont College of Medicine, Burlington, Vermont 04505, USA.
Nesti
Edmund
E
Cachero
Teresa G
TG
Morielli
Anthony D
AD
D000199:Actins / Q000378:metabolism; D000818:Animals; D001923:Brain Chemistry; D002458:Cell Fractionation; D002460:Cell Line; D051356:Cortactin; D003599:Cytoskeleton / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D051663:Kv1.2 Potassium Channel; D008840:Microfilament Proteins / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D043643:Receptor, Muscarinic M1; D011976:Receptors, Muscarinic / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*; D014982:Xenopus laevis
D000199:Actins; C495868:CTTN protein, human; D051356:Cortactin; C495870:Cttn protein, rat; C496969:KCNA2 protein, human; C496972:Kcna2 protein, rat; D051663:Kv1.2 Potassium Channel; D008840:Microfilament Proteins; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D043643:Receptor, Muscarinic M1; D011976:Receptors, Muscarinic; D011993:Recombinant Fusion Proteins; D014443:Tyrosine