title: SAP97 and cortactin remodeling in arrhythmogenic Purkinje cells.
abstract: Because structural remodeling of several proteins, including ion channels, may underlie the abnormal action potentials of Purkinje cells (PCs) that survive in the 48 hr infarcted zone of the canine heart (IZPCs), we sought to determine the subcellular structure and function of the KV1.5 (KCNA5) protein in single IZPCs. Clustering of the Kv1.5 subunit in axons is regulated by a synapse-associated protein, SAP97, and is linked to an actin-binding protein, cortactin, and an intercellular adhesion molecule, N-cadherin. To understand the functional remodeling of the Kv1.5 channel and its regulation in IZPCs, Kv1.5 currents in PCs were measured as the currents blocked by 10 µM RSD1379 using patch-clamp techniques. Immunocytochemistry and confocal imaging were used for both single and aggregated IZPCs vs normal PCs (NZPCs) to determine the relationship of Kv1.5 with SAP-97, cortactin and N-cadherin. In IZPCs, both the sarcolemma (SL) and intercalated disk (ID) Kv1.5 protein are abundant, and the amount of cytosolic Kv1.5 protein is greatly increased. SAP-97 is also increased at IDs and has notable cytosolic localization suggesting that SAP-97 may regulate the functional expression and stabilization of Kv1.5 channels in IZPCs. Cortactin, which is located with N-cadherin at IDs in NZPCs, remains at IDs but begins to dissociate from N-cadherin, often forming ring structures and colocalizing with Kv1.5 within IZPCs. At the same time, cortactin/Kv1.5 colocalization is increased at the ID, suggesting an ongoing active process of membrane trafficking of the channel protein. Finally, the Kv1.5 current, measured as the RSD1379-sensitive current, at +40 mV did not differ between NZPCs (0.81±0.24 pA/pF, n = 14) and IZPCs (0.83±0.21 pA/pF, n = 13, NS). In conclusion, the subcellular structural remodeling of Kv1.5, SAP97 and cortactin maintained and normalized the function of the Kv1.5 channel in Purkinje cells that survived myocardial infarction.
authors.affiliation: Department of Pharmacology, Center for Molecular Therapeutics, Columbia University, New York, New York, United States of America.
authors.forename: Wen
authors.initials: W
authors.lastname: Dun
authors.affiliation: The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States of America.
authors.forename: Patrick
authors.initials: P
authors.lastname: Wright
authors.affiliation: Department of Pharmacology, Center for Molecular Therapeutics, Columbia University, New York, New York, United States of America.
authors.forename: Peter
authors.initials: P
authors.lastname: Danilo
authors.affiliation: The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States of America; Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States of America; Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States of America.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Mohler
authors.affiliation: Department of Pharmacology, Center for Molecular Therapeutics, Columbia University, New York, New York, United States of America.
authors.forename: Penelope A
authors.initials: PA
authors.lastname: Boyden
mesh_terms: D000200:Action Potentials; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D051356:Cortactin / Q000378:metabolism*; D004285:Dogs; D051666:Kv1.5 Potassium Channel / Q000378:metabolism*; D008297:Male; D009203:Myocardial Infarction / Q000378:metabolism* / Q000473:pathology; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D011689:Purkinje Cells / Q000378:metabolism* / Q000473:pathology
chemical_list: D015820:Cadherins; D051356:Cortactin; D051666:Kv1.5 Potassium Channel