title: Thioredoxin h regulates calcium dependent protein kinases in plasma membranes.
abstract: Thioredoxin (Trx) is a key player in redox homeostasis in various cells, modulating the functions of target proteins by catalyzing a thiol-disulfide exchange reaction. Target proteins of cytosolic Trx-h of higher plants were studied, particularly in the plasma membrane, because plant plasma membranes include various functionally important protein molecules such as transporters and signal receptors. Plasma membrane proteins from Arabidopsis thaliana cell cultures were screened using a resin Trx-h1 mutant-immobilized, and a total of 48 candidate proteins obtained. These included two calcium-sensing proteins: a phosphoinositide-specific phospholipase 2 (AtPLC2) and a calcium-dependent protein kinase 21 (AtCPK21). A redox-dependent change in AtCPK21 kinase activity was demonstrated in vitro. Oxidation of AtCPK21 resulted in a decrease in kinase activity to 19% of that of untreated AtCPK21, but Trx-h1 effectively restored the activity to 90%. An intramolecular disulfide bond (Cys97-Cys108) that is responsible for this redox modulation was then identified. In addition, endogenous AtCPK21 was shown to be oxidized in vivo when the culture cells were treated with H2 O2 . These results suggest that redox regulation of AtCPK21 by Trx-h in response to external stimuli is important for appropriate cellular responses. The relationship between the redox regulation system and Ca(2+) signaling pathways is discussed.
authors.affiliation: Division of Material Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, Japan. hnakanis@bio.phys.nagoya-u.ac.jp
authors.forename: Hanayo
authors.initials: H
authors.lastname: Ueoka-Nakanishi
authors.forename: Takashi
authors.initials: T
authors.lastname: Sazuka
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Nakanishi
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Maeshima
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Mori
authors.forename: Toru
authors.initials: T
authors.lastname: Hisabori
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D020013:Calcium Signaling; D002462:Cell Membrane / Q000201:enzymology*; D002478:Cells, Cultured; D003553:Cystine / Q000737:chemistry; D004229:Dithiothreitol / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008969:Molecular Sequence Data; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism; D019163:Reducing Agents / Q000737:chemistry; D054480:Thioredoxin h / Q000737:chemistry / Q000502:physiology*; D020798:Two-Hybrid System Techniques
chemical_list: C504905:ATTRX1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D016877:Oxidants; D019163:Reducing Agents; D054480:Thioredoxin h; D003553:Cystine; D006861:Hydrogen Peroxide; D011494:Protein Kinases; C583356:At4g04720 protein, Arabidopsis; D004229:Dithiothreitol
keywords: Arabidopsis thaliana; calcium signaling; plasma membrane; redox regulation; thioredoxin