title: Dysregulation of a potassium channel, THIK-1, targeted by caspase-8 accelerates cell shrinkage.
abstract: Activation of caspases is crucial for the execution of apoptosis. Although the caspase cascade associated with activation of the initiator caspase-8 (CASP8) has been investigated in molecular and biochemical detail, the physiological role of CASP8 is not fully understood. Here, we identified a two-pore domain potassium channel, tandem-pore domain halothane-inhibited K+channel 1 (THIK-1), as a novel CASP8 substrate. The intracellular region of THIK-1 was cleaved by CASP8 in apoptotic cells. Overexpression of THIK-1, but not its mutant lacking the CASP8-target sequence in the intracellular portion, accelerated cell shrinkage in response to apoptotic stimuli. In contrast, knockdown of endogenous THIK-1 by RNA interference resulted in delayed shrinkage and potassium efflux. Furthermore, a truncated THIK-1 mutant lacking the intracellular region, which mimics the form cleaved by CASP8, led to a decrease of cell volume of cultured cells without apoptotic stimulation and excessively promoted irregular development of Xenopus embryos. Taken together, these results indicate that THIK-1 is involved in the acceleration of cell shrinkage. Thus, we have demonstrated a novel physiological role of CASP8: creating a cascade that advances the cell to the next stage in the apoptotic process.
authors: Department of Animal Development and Physiology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan. Electronic address: sakamaki.kazuhiro.7u@kyoto-u.ac.jp.
authors: Kazuhiro
authors: K
authors: Sakamaki
authors: Department of Physiology, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
authors: Takahiro M
authors: TM
authors: Ishii
authors: Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan.
authors: Toshiya
authors: T
authors: Sakata
authors: Research Institute for Electronic Science, Hokkaido University, Sapporo 001-0020, Japan.
authors: Kiwamu
authors: K
authors: Takemoto
authors: Department of Developmental Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan.
authors: Chiyo
authors: C
authors: Takagi
authors: Department of Physiology and Biophysics, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
authors: Ayako
authors: A
authors: Takeuchi
authors: CellFree Sciences Co., Ltd., Yokohama 230-0046, Japan.
authors: Ryo
authors: R
authors: Morishita
authors: Proteo-Science Center, Ehime University, Matsuyama 790-8577, Japan.
authors: Hirotaka
authors: H
authors: Takahashi
authors: Proteo-Science Center, Ehime University, Matsuyama 790-8577, Japan.
authors: Akira
authors: A
authors: Nozawa
authors: The Institute of Scientific and Industrial Research, Osaka University, Ibaraki 567-0047, Japan.
authors: Hajime
authors: H
authors: Shinoda
authors: Department of Animal Development and Physiology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan.
authors: Kumiko
authors: K
authors: Chiba
authors: Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan.
authors: Haruyo
authors: H
authors: Sugimoto
authors: Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan.
authors: Akiko
authors: A
authors: Saito
authors: Department of Electronic Science and Engineering, Graduate School of Engineering, Kyoto University, Kyoto 615-8530, Japan.
authors: Shuhei
authors: S
authors: Tamate
authors: Department of Zoology, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors: Yutaka
authors: Y
authors: Satou
authors: SCOTS, Tensei Suisan Co., Ltd., Karatsu 847-0193, Japan.
authors: Sang-Kee
authors: SK
authors: Jung
authors: Center for Innovation in Immunoregulative Technology and Therapeutics, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
authors: Satoshi
authors: S
authors: Matsuoka
authors: Center for Promotion of Excellence in Higher Education, Kyoto University, Kyoto 606-8501, Japan.
authors: Koji
authors: K
authors: Koyamada
authors: Proteo-Science Center, Ehime University, Matsuyama 790-8577, Japan.
authors: Tatsuya
authors: T
authors: Sawasaki
authors: Research Institute for Electronic Science, Hokkaido University, Sapporo 001-0020, Japan; The Institute of Scientific and Industrial Research, Osaka University, Ibaraki 567-0047, Japan.
authors: Takeharu
authors: T
authors: Nagai
authors: Department of Developmental Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan.
authors: Naoto
authors: N
authors: Ueno
mesh_terms: D000818:Animals; D017209:Apoptosis; D019556:COS Cells; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism*; D048429:Cell Size; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D061986:MCF-7 Cells; D009154:Mutation; D024683:Potassium Channels, Tandem Pore Domain / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D034622:RNA Interference; D015398:Signal Transduction; D013379:Substrate Specificity; D013997:Time Factors; D014162:Transfection; D014982:Xenopus laevis
chemical_list: C486603:KCNK13 protein, human; C486604:Kcnk13 protein, mouse; D024683:Potassium Channels, Tandem Pore Domain; C505530:CASP8 protein, human; D053181:Caspase 8
keywords: Apoptosis; Cell shrinkage; FRET; Field effect transistor; Patch clamp; Two-pore potassium channel