title: AMP-activated protein kinase in BK-channel regulation and protection against hearing loss following acoustic overstimulation.
abstract: The energy-sensing AMP-activated serine/threonine protein kinase (AMPK) confers cell survival in part by stimulation of cellular energy production and limitation of cellular energy utilization. AMPK-sensitive functions further include activities of epithelial Na+ channel ENaC and voltage-gated K+ channel KCNE1/KCNQ1. AMPK is activated by an increased cytosolic Ca2+ concentration. The present study explored whether AMPK regulates the Ca2+-sensitive large conductance and voltage-gated potassium (BK) channel. cRNA encoding BK channel was injected into Xenopus oocytes with and without additional injection of wild-type AMPK (AMPKα1+AMPKβ1+AMPKγ1), constitutively active AMPKγR70Q, or inactive AMPKαK45R. BK-channel activity was determined utilizing the 2-electrode voltage-clamp. Moreover, BK-channel protein abundance in the cell membrane was determined by confocal immunomicroscopy. As BK channels are expressed in outer hair cells (OHC) of the inner ear and lack of BK channels increases noise vulnerability, OHC BK-channel expression was examined by immunohistochemistry and hearing function analyzed by auditory brain stem response measurements in AMPKα1-deficient mice (ampk-/-) and in wild-type mice (ampk+/+). As a result, coexpression of AMPK or AMPKγR70Q but not of AMPKαK45R significantly enhanced BK-channel-mediated currents and BK-channel protein abundance in the oocyte cell membrane. BK-channel expression in the inner ear was lower in ampk-/- mice than in ampk+/+ mice. The hearing thresholds prior to and immediately after an acoustic overexposure were similar in ampk-/- and ampk+/+ mice. However, the recovery from the acoustic trauma was significantly impaired in ampk-/- mice compared to ampk+/+ mice. In summary, AMPK is a potent regulator of BK channels. It may thus participate in the signaling cascades that protect the inner ear from damage following acoustic overstimulation.
authors: Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076 Tübingen, Germany.
authors: Michael
authors: M
authors: Föller
authors: Mirko
authors: M
authors: Jaumann
authors: Juliane
authors: J
authors: Dettling
authors: Ambrish
authors: A
authors: Saxena
authors: Tatsiana
authors: T
authors: Pakladok
authors: Carlos
authors: C
authors: Munoz
authors: Peter
authors: P
authors: Ruth
authors: Mentor
authors: M
authors: Sopjani
authors: Guiscard
authors: G
authors: Seebohm
authors: Lukas
authors: L
authors: Rüttiger
authors: Marlies
authors: M
authors: Knipper
authors: Florian
authors: F
authors: Lang
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D003051:Cochlea / Q000166:cytology / Q000378:metabolism; D005260:Female; D034381:Hearing Loss / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D009865:Oocytes / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014981:Xenopus
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D055372:AMP-Activated Protein Kinases