title: Molecular identification of the dominant-negative, splicing isoform of the two-pore domain K(+) channel K(2P)5.1 in lymphoid cells and enhancement of its expression by splicing inhibition.
abstract: The two-pore domain background K(+) channel K2P5.1 is expected as a possible therapeutic target for autoimmune and inflammatory disorders and cancers because it plays an important role in maintaining the resting membrane potential and regulation of Ca(2+) signaling in T lymphocytes and cancer cells. However, the lack of selective K2P5.1 blockers has led to difficulties conducting experimental studies on this K(+) channel. We identified a novel splicing isoform of K2P5.1, K2P5.1B from the mammalian spleen, which lacked the N-terminus of full-length K2P5.1A. A co-immunoprecipitation assay using mice spleen lysates revealed an interaction between K2P5.1A and K2P5.1B in the cytoplasmic C-terminal domain. In a heterologous HEK293 expression system, K2P5.1B inhibited the trafficking of K2P5.1A to the plasma membrane. The alkaline pHe-induced hyperpolarizing response was significantly suppressed in K2P5.1B-transfected human leukemia K562 cells. Enhancement in cell proliferation by the overexpression of K2P5.1A in K562 was significantly prevented by the transfection of K2P5.1B. The spliceosome inhibitor pladienolide B significantly enhanced the relative expression of K2P5.1B in K562, resulting in decreases in the activity of K2P5.1A. K2P5.1B suppresses the function of the K2P5.1 K(+) channel in a dominant-negative manner, suggesting that the mRNA splicing mechanisms underlying the transcriptional regulation of K2P5.1B may be a new therapeutic strategy for autoimmune and inflammatory disorders and cancers.
authors.affiliation: Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan. Electronic address: ky10057@poppy.kyoto-phu.ac.jp.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Endo
authors.affiliation: Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan. Electronic address: ky10131@poppy.kyoto-phu.ac.jp.
authors.forename: Natsumi
authors.initials: N
authors.lastname: Kurokawa
authors.affiliation: Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan. Electronic address: kito@mb.kyoto-phu.ac.jp.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kito
authors.affiliation: Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan. Electronic address: ky09246@poppy.kyoto-phu.ac.jp.
authors.forename: Sawa
authors.initials: S
authors.lastname: Nakakura
authors.affiliation: Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan. Electronic address: fujii@mb.kyoto-phu.ac.jp.
authors.forename: Masanori
authors.initials: M
authors.lastname: Fujii
authors.affiliation: Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan. Electronic address: sohya@mb.kyoto-phu.ac.jp.
authors.forename: Susumu
authors.initials: S
authors.lastname: Ohya
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D057809:HEK293 Cells; D006801:Humans; D020014:K562 Cells; D051379:Mice; D008969:Molecular Sequence Data; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D015221:Potassium Channels
keywords: Alternative splicing; Clofilium tosylate (PubChem CID: 175533); Di-BA-C4 (PubChem CID: 6438341) WST-1 (150849-52-8) (PubChem CID: 6099081); FURA-2 (PubChem CID: 57054); Isoginkgetin (PubChem CID: 5318569); Lymphocyte; Membrane trafficking; Pladienolide B (PubChem CID: 52946850); Potassium channel; Propidium iodide (PubChem CID: 104981); Syber Green I (PubChem CID: 10436340); Thymidine (PubChem CID: 5789)