title: Phosphorylation of the dimeric cytoplasmic domain of the phytosulfokine receptor, PSKR1.
abstract: Phytosulfokines (PSKs) are plant peptide hormones that co-regulate plant growth, differentiation and defense responses. PSKs signal through a plasma membrane localized leucine-rich repeat receptor-like kinase (phytosulfokine receptor 1, PSKR1) that also contains a functional cytosolic guanylate cyclase with its cyclase catalytic center embedded within the kinase domain. To functionally characterize this novel type of overlapping dual catalytic function, we investigated the phosphorylation of PSKR1 in vitro Tandem mass spectrometry of the cytoplasmic domain of PSKR1 (PSKR1cd) revealed at least 11 phosphorylation sites (8 serines, 2 threonines and 1 tyrosine) within the PSKR1cd. Phosphomimetic mutations of three serine residues (Ser686, Ser696 and Ser698) in tandem at the juxta-membrane position resulted in enhanced kinase activity in the on-mutant that was suppressed in the off-mutant, but both mutations reduced guanylate cyclase activity. Both the on and off phosphomimetic mutations of the phosphotyrosine (Tyr888) residue in the activation loop suppressed kinase activity, while neither mutation affected guanylate cyclase activity. Size exclusion and analytical ultracentrifugation analysis of the PSKR1cd suggest that it is reversibly dimeric in solution, which was further confirmed by biflourescence complementation. Taken together, these data suggest that in this novel type of receptor domain architecture, specific phosphorylation and dimerization are possibly essential mechanisms for ligand-mediated catalysis and signaling.
authors.affiliation: Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia.
authors.forename: Victor
authors.initials: V
authors.lastname: Muleya
authors.affiliation: Division of Biological and Environmental Sciences and Engineering, 4700 King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Cambridge, U.K.
authors.forename: Claudius
authors.initials: C
authors.lastname: Marondedze
authors.affiliation: Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia.
authors.forename: Janet I
authors.initials: JI
authors.lastname: Wheeler
authors.affiliation: Division of Biological and Environmental Sciences and Engineering, 4700 King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
authors.forename: Ludivine
authors.initials: L
authors.lastname: Thomas
authors.affiliation: Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, 30 Flemington Rd, Parkville, VIC 3010, Australia.
authors.forename: Yee-Fong
authors.initials: YF
authors.lastname: Mok
authors.affiliation: Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, 30 Flemington Rd, Parkville, VIC 3010, Australia.
authors.forename: Michael D W
authors.initials: MD
authors.lastname: Griffin
authors.affiliation: Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia.
authors.forename: David T
authors.initials: DT
authors.lastname: Manallack
authors.affiliation: Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia.
authors.forename: Lusisizwe
authors.initials: L
authors.lastname: Kwezi
authors.affiliation: Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Cambridge, U.K.
authors.forename: Kathryn S
authors.initials: KS
authors.lastname: Lilley
authors.affiliation: Division of Biological and Environmental Sciences and Engineering, 4700 King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
authors.forename: Christoph
authors.initials: C
authors.lastname: Gehring
authors.affiliation: Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia.
authors.forename: Helen R
authors.initials: HR
authors.lastname: Irving
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002384:Catalysis; D002850:Chromatography, Gel; D003593:Cytoplasm / Q000378:metabolism*; D019281:Dimerization; D006162:Guanylate Cyclase / Q000378:metabolism; D008024:Ligands; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D053719:Tandem Mass Spectrometry
chemical_list: D029681:Arabidopsis Proteins; D008024:Ligands; C515018:PSKR1 protein, Arabidopsis; D011956:Receptors, Cell Surface; D010770:Phosphotransferases; D006162:Guanylate Cyclase
keywords: dimerization; dual-specificity kinase; guanylate cyclase; leucine-rich receptor-like kinase