title: Multilevel control of Arabidopsis 3-hydroxy-3-methylglutaryl coenzyme A reductase by protein phosphatase 2A.
abstract: Plants synthesize a myriad of isoprenoid products that are required both for essential constitutive processes and for adaptive responses to the environment. The enzyme 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) catalyzes a key regulatory step of the mevalonate pathway for isoprenoid biosynthesis and is modulated by many endogenous and external stimuli. In spite of that, no protein factor interacting with and regulating plant HMGR in vivo has been described so far. Here, we report the identification of two B'' regulatory subunits of protein phosphatase 2A (PP2A), designated B''α and B''β, that interact with HMGR1S and HMGR1L, the major isoforms of Arabidopsis thaliana HMGR. B''α and B''β are Ca²⁺ binding proteins of the EF-hand type. We show that HMGR transcript, protein, and activity levels are modulated by PP2A in Arabidopsis. When seedlings are transferred to salt-containing medium, B''α and PP2A mediate the decrease and subsequent increase of HMGR activity, which results from a steady rise of HMGR1-encoding transcript levels and an initial sharper reduction of HMGR protein level. In unchallenged plants, PP2A is a posttranslational negative regulator of HMGR activity with the participation of B''β. Our data indicate that PP2A exerts multilevel control on HMGR through the five-member B'' protein family during normal development and in response to a variety of stress conditions.
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Barcelona 08028, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Leivar
authors.forename: Meritxell
authors.initials: M
authors.lastname: Antolín-Llovera
authors.forename: Sergi
authors.initials: S
authors.lastname: Ferrero
authors.forename: Marta
authors.initials: M
authors.lastname: Closa
authors.forename: Montserrat
authors.initials: M
authors.lastname: Arró
authors.forename: Albert
authors.initials: A
authors.lastname: Ferrer
authors.forename: Albert
authors.initials: A
authors.lastname: Boronat
authors.forename: Narciso
authors.initials: N
authors.lastname: Campos
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D006903:Hydroxymethylglutaryl CoA Reductases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D011485:Protein Binding / Q000187:drug effects; D014176:Protein Biosynthesis / Q000187:drug effects; D054648:Protein Phosphatase 2 / Q000737:chemistry / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000201:enzymology; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological / Q000187:drug effects; D013997:Time Factors
chemical_list: D021122:Protein Subunits; D012333:RNA, Messenger; D012965:Sodium Chloride; D006903:Hydroxymethylglutaryl CoA Reductases; D054648:Protein Phosphatase 2; D002118:Calcium