title: HIF-1α-mediated upregulation of TASK-2 K⁺ channels augments Ca²⁺ signaling in mouse B cells under hypoxia.
abstract: The general consensus is that immune cells are exposed to physiological hypoxia in vivo (PhyO2, 2-5% P(O2)). However, functional studies of B cells in hypoxic conditions are sparse. Recently, we reported the expression in mouse B cells of TASK-2, a member of pH-sensitive two-pore domain K(+) channels with background activity. In this study, we investigated the response of K(+) channels to sustained PhyO2 (sustained hypoxia [SH], 3% P(O2) for 24 h) in WEHI-231 mouse B cells. SH induced voltage-independent background K(+) conductance (SH-K(bg)) and hyperpolarized the membrane potential. The pH sensitivity and the single-channel conductance of SH-K(bg) were consistent with those of TASK-2. Immunoblotting assay results showed that SH significantly increased plasma membrane expressions of TASK-2. Conversely, SH failed to induce any current following small interfering (si)TASK-2 transfection. Similar hypoxic upregulation of TASK-2 was also observed in splenic primary B cells. Mechanistically, upregulation of TASK-2 by SH was prevented by si hypoxia-inducible factor-1α (HIF-1α) transfection or by YC-1, a pharmacological HIF-1α inhibitor. In addition, TASK-2 current was increased in WEHI-231 cells overexpressed with O2-resistant HIF-1α. Importantly, [Ca(2+)]c increment in response to BCR stimulation was significantly higher in SH-exposed B cells, which was abolished by high K(+)-induced depolarization or by siTASK-2 transfection. The data demonstrate that TASK-2 is upregulated under hypoxia via HIF-1α-dependent manner in B cells. This is functionally important in maintaining the negative membrane potential and providing electrical driving force to control Ca(2+) influx.
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Division of Natural Medical Sciences, College of Health Science, Chosun University, Gwangju 501-759, Republic of Korea;
authors.forename: Dong Hoon
authors.initials: DH
authors.lastname: Shin
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
authors.forename: Haiyue
authors.initials: H
authors.lastname: Lin
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
authors.forename: Haifeng
authors.initials: H
authors.lastname: Zheng
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
authors.forename: Kyung Su
authors.initials: KS
authors.lastname: Kim
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
authors.forename: Yang Sook
authors.initials: YS
authors.lastname: Chun
authors.affiliation: Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Department of Pharmacology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; and.
authors.forename: Jong Wan
authors.initials: JW
authors.lastname: Park
authors.affiliation: Channelopathy Research Center, Dongguk University College of Medicine, Goyang 410-773, Republic of Korea.
authors.forename: Joo Hyun
authors.initials: JH
authors.lastname: Nam
authors.affiliation: Channelopathy Research Center, Dongguk University College of Medicine, Goyang 410-773, Republic of Korea.
authors.forename: Woo Kyung
authors.initials: WK
authors.lastname: Kim
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
authors.forename: Yin Hua
authors.initials: YH
authors.lastname: Zhang
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; sjoonkim@snu.ac.kr.
authors.forename: Sung Joon
authors.initials: SJ
authors.lastname: Kim
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D015687:Cell Hypoxia; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D007191:Indazoles / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D010100:Oxygen / Q000494:pharmacology*; D024683:Potassium Channels, Tandem Pore Domain / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D061251:Primary Cell Culture; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism
chemical_list: C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007191:Indazoles; C498739:Kcnk5 protein, mouse; D024683:Potassium Channels, Tandem Pore Domain; D034741:RNA, Small Interfering; C090937:3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole; D010100:Oxygen; D002118:Calcium