title: MaxiK channel interactome reveals its interaction with GABA transporter 3 and heat shock protein 60 in the mammalian brain.
abstract: Large conductance voltage and calcium-activated potassium (MaxiK) channels are activated by membrane depolarization and elevated cytosolic Ca(2+). In the brain, they localize to neurons and astrocytes, where they play roles such as resetting the membrane potential during an action potential, neurotransmitter release, and neurovascular coupling. MaxiK channels are known to associate with several modulatory proteins and accessory subunits, and each of these interactions can have distinct physiological consequences. To uncover new players in MaxiK channel brain physiology, we applied a directed proteomic approach and obtained MaxiK channel pore-forming α subunit brain interactome using specific antibodies. Controls included immunoprecipitations with rabbit immunoglobulin G (IgG) and with anti-MaxiK antibodies in wild type and MaxiK channel knockout mice (Kcnma1(-/-)), respectively. We have found known and unreported interactive partners that localize to the plasma membrane, extracellular space, cytosol and intracellular organelles including mitochondria, nucleus, endoplasmic reticulum and Golgi apparatus. Localization of MaxiK channel to mitochondria was further confirmed using purified brain mitochondria colabeled with MitoTracker. Independent proof of MaxiK channel interaction with previously unidentified partners is given for GABA transporter 3 (GAT3) and heat shock protein 60 (HSP60). In human embryonic kidney 293 cells containing SV40 T-antigen (HEK293T) cells, both GAT3 and HSP60 coimmunoprecipitated and colocalized with MaxiK channel; colabeling was observed mainly at the cell periphery with GAT3 and intracellularly with HSP60 with protein proximity indices of ∼ 0.6 and ∼ 0.4, respectively. In rat primary hippocampal neurons, colocalization index was identical for GAT3 (∼ 0.6) and slightly higher for HSP60 (∼ 0.5) association with MaxiK channel. The results of this study provide a complete interactome of MaxiK channel the mouse brain, further establish the localization of MaxiK channel in the mouse brain mitochondria and demonstrate the interaction of MaxiK channel with GAT3 and HSP60 in neurons. The interaction of MaxiK channel with GAT3 opens the possibility of a role of MaxiK channel in GABA homeostasis and signaling.
authors.affiliation: Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, USA; Department of Anesthesiology, University of California, Los Angeles, CA 90095, USA. Electronic address: harpreet.singh@drexelmed.edu.
authors.forename: H
authors.initials: H
authors.lastname: Singh
authors.affiliation: Department of Anesthesiology, University of California, Los Angeles, CA 90095, USA. Electronic address: mli@mednet.ucla.edu.
authors.forename: M
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Anesthesiology, University of California, Los Angeles, CA 90095, USA. Electronic address: halll@kenyon.edu.
authors.forename: L
authors.initials: L
authors.lastname: Hall
authors.affiliation: Department of Anesthesiology, University of California, Los Angeles, CA 90095, USA. Electronic address: scarlett.chen2009@gmail.com.
authors.forename: S
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, USA. Electronic address: ss3773@drexel.edu.
authors.forename: S
authors.initials: S
authors.lastname: Sukur
authors.affiliation: Department of Anesthesiology, University of California, Los Angeles, CA 90095, USA. Electronic address: ronglu@ucla.edu.
authors.forename: R
authors.initials: R
authors.lastname: Lu
authors.affiliation: Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA. Electronic address: annacaputo83@hotmail.it.
authors.forename: A
authors.initials: A
authors.lastname: Caputo
authors.affiliation: Department of Physiology, University of Maryland, Baltimore, MD 21201, USA. Electronic address: ameredith@som.umaryland.edu.
authors.forename: A L
authors.initials: AL
authors.lastname: Meredith
authors.affiliation: Department of Anesthesiology, University of California, Los Angeles, CA 90095, USA; Department of Physiology, University of California, Los Angeles, CA 90095, USA; Brain Research Institute, University of California, Los Angeles, CA 90095, USA. Electronic address: estefani@ucla.edu.
authors.forename: E
authors.initials: E
authors.lastname: Stefani
authors.affiliation: Department of Anesthesiology, University of California, Los Angeles, CA 90095, USA; Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095, USA; Brain Research Institute, University of California, Los Angeles, CA 90095, USA; Cardiovascular Research Laboratory, University of California, Los Angeles, CA 90095, USA. Electronic address: ltoro@g.ucla.edu.
authors.forename: L
authors.initials: L
authors.lastname: Toro
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D002478:Cells, Cultured; D018834:Chaperonin 60 / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000378:metabolism; D050485:GABA Plasma Membrane Transport Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000235:genetics*; D057809:HEK293 Cells; D006624:Hippocampus / Q000166:cytology / Q000648:ultrastructure; D006801:Humans; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism; D008958:Models, Molecular; D009474:Neurons / Q000378:metabolism; D040901:Proteomics; D014162:Transfection
chemical_list: D018834:Chaperonin 60; D050485:GABA Plasma Membrane Transport Proteins; D051036:Large-Conductance Calcium-Activated Potassium Channels; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2
keywords: BK(Ca); GABA transporter; HSP60; MaxiK interactome; mitochondria; proteomics