Protein dephosphorylation group

Protein dephosphorylation group

  • Leader:  
    • Viktor Dombrádi,  Ph.D., D. Sc., Professor
  • Members:
    • Ilona Farkas  Ph.D., Associate professor
    • Andrea Farkas-Tanka technician 
    • Krisztina Szabó, Ph.D. student
    • Csilla Szundi, B.Sc., M.Sc. student
    • Bea Kerezsi, B.Sc. student
    • Patricia Szücs, B.Sc. student

Research Interest

Protein phosphorylation is an essential post-synthetic protein modification in eukaryotic organisms. The dynamic balance between protein kinases and protein phosphatases determines the actual phosphorylation state of target proteins and has a profound effect on cellular regulation and signaling. While the kinases belong to a single superfamily the phosphatases are more diverse according to their structures and catalytic mechanism. Our group concentrates on the kinases and first of all on the phosphatases that are specific for the Ser/Thr side chains.  We are studying the classical members of the phosphoprotein phosphatase enzyme family (like PPP1 and PP2A) as well as the more recently uncovered novel phosphatases (like PPY and PPZ). By the combination of biochemistry, molecular biology and genetics we are investigating the physiological functions of these enzymes in animals, plants and fungi.

1. Cloning, functional analysis and evolution of protein phosphatases in Drosophila

In Drosophila melanogaster we identified several new members of the phosphoprotein phosphatase (PPP) family, and cloned novel regulators of protein phosphatases. Most importantly with the aid of Drosophila mutants we demonstrated the essential role of protein phosphatase 1 (PP1) in the regulation of animal cell cycle.

Figure 1. Role of protein phosphatase 1in the regulation of cell cycle in Drosophila melanogaster. The mutation of the PP1-87B gene coding for the dominant form of the protein phosphatase 1 in the fruit flies resulted in the formation of collapsed spindle, condensed chromosomes and incomplete chromosome separation on the brain of third instar larvae.

Our recent investigation of the evolution of Ser/Thr specific protein phosphatase (the so called PPP enzyme family) revealed additional phosphatase genes in several Drosophila species. We demonstrated the dynamic changes in the gene numbers, localization and structure of PPP genes in the Drosophilidae, and proved that the novel PPP retrogenes are predominantly expressed in the males. The sex specific expression of the new phosphatase genes supports the “out of testis hypothesis” suggesting that the testis is the main stage for the expression and selection of the new genes produced by gene duplication.

Most recently, with our collaborators at the Institute of Genetics of the Hungarian Academy of Sciences we have identified a new regulatory subunit of PP1 that targets the enzyme to glycogen and influences glycogen metabolism. In addition, we revealed that CalpB, that codes for a calcium regulated protease, is involved in the border cell migration within the egg chambers of Drosophila females. Thus, our Drosophila studies have been instrumental in revealing fundamental functional and evolutionary aspects of protein modifying enzymes like protein phosphatases and proteases.

2. Cloning and functional analysis of plant protein phosphatases

In collaboration with the Institute of Plant Physiology of the Hungarian Academy of Sciences we cloned the catalytic subunit of protein phosphatase 1 (PP1) as well as the regulatory subunits of protein phosphatase 2A (PP2A) from the plant Medicago sativa. With the aid of endothall, a cell-permeable inhibitor of serine/threonine-specific protein phosphatases, we proved the involvement of PP2A in the regulation of the cell division cycle. More recently we have studied the role of the inhibitor proteins of PP2A (NRPs) in Arabidopsis thaliana, and we are still investigating the role of the PP2A B’’ subunit in the dephosphorylarion of the plant Rb homologs in Oryza sativa.

Figure 2. Role of protein phosphatase 2A in the regulation of the plant specific steps of cell cycle. Inhibition of PP2A by endothall results in abnormal preprophase band and phragmoplast formation in Medicago sativa cells.

3. Characterization of a fungus specific protein phosphatase

We cloned the genes and the corresponding cDNAs of the novel protein phosphatase Z (PPZ) from a number of fungal species (N. crassa, C. albicans, A. nidulans and A. fumigatus). The physiological functions of these fungus specific enzymes have been investigated by the complementation of known yeast mutants and by the direct disruption of the PPZ genes in Candida albicans and Aspergillus nidulans. Our results revealed that CaPPZ1 is important in the cell wall biosynthesis, osmotic stability as well as for the hyphal outgrowth and the morphological changes of the opportunistic pathogen C. albicans. In addition we identified a novel function for the PPZ phosphatases, namely the modulation of the oxidative stress response. We took part in the characterization of the unusual PPZ inhibitor termed Hal3 in S. pombe, and recently we introduced time-lapse video microscopy for the morphological analysis of C. albicans.

Figure 3. 3D model of the catalytic domain of C. albicans CaPpz1. Alpha helices are red, beta sheets are blue, and loops are yellow. Two essential metal ions in the catalytic centre are gray and the amino acid side chains involved in catalysis are in violet. Three amino acid residues that are affected by natural polymorphisms are highlighted.

Currently we are studying the detailed mechanism of the inhibition of Candida albicans CaPpz1 catalytic domain by its own N-terminal regulatory domain and by some putative endogenous proteins of Candida. The aim of our work is to understand how intrinsically disordered segments of the regulatory domain and regulator proteins modulate enzyme activity. We have initiated a combined approach including proetomimics, phosphoproteomics and DNA chip based gene expression studies to reveal the consequences of the deletion of CaPPZ1 gene and the effects of different stress treatments on Candida albicans. Since the PPZ phosphatases are fungus specific and have important functions our data may provide sufficient information for the development of potential drugs against pathogenic fungi. In this project we are collaborating with several research groups at the Departments of the University of Debrecen, and at the Autonomous University of Barcelona.

Selected Publications

  • Axton, J.M., Dombrádi, V., Cohen, P.T.W., Glover, D.M.: One of the protein phosphatase 1 isoenzymes in Drosophila is essential for mitosis. Cell 63 33-46 (1990)
  • Mann, D.J., Dombrádi, V., Cohen, P.T.W.: Drosophila protein phosphatase V functionally complements a SIT4 mutant in Saccharomyces cerevisiae and its amino-terminal region can confer this complementation to a heterologous phosphatase catalytic domain. EMBO J. 12 4833-4842 (1993)
  • Szöőr, B., Fehér, Zs., Zeke, T., Gergely, P., Yatzkan, E., Yarden, O.,Dombrádi, V.: pzl-1 encodes a novel protein phosphatase-Z-like Ser/Thr protein phosphatase in Neurospora crassa. Biochim. Biophys. Acta, Protein Structure and Molecular Enzymology 1388, 260-266 (1998)
  • Ayaydin, F., Vissi, E., Mészáros, T., Miskolczi, P., Kovács I., Fehér, A., Dombrádi, V., Erdődi, F., Dudits, D.: Inhibition of serine /threonine-specific protein phosphatases causes premature activation of cdc2MsF kinase at G2/M transition and early mitotic microtubule organization in alfalfa. The Plant Journal. 23, 85-96 (2000)
  • Dombrádi, V., Krieglstein, J., Klumpp, S.: Regulating the regulators: Protein phosphorylation and protein phosphatases. EMBO Reports 3, 120-124 (2002)
  • Kókai, E., Tantos, Á., Vissi, E., Szöőr, B., Tompa, P., Gausz, J., Alphey, L., Friedrich, P., Dombrádi, V.: CG15031/PPYR1 is an intrinsically unstructured protein that interacts with protein phosphatase Y. Archives of Biochemistry and Biophsycs. 451, 59-67 (2006)
  • Farkas,I., Dombrádi, V., Miskei, M., Szabados, L., Koncz,Cs.: Arabidopsis PPP family of serine/threonine phosphatases. Trends Plant Sci. 12, 169-176 (2007)
  • Miskei M, Ádám C, Kovács L, Karányi Z, Dombrádi V.: Molecular evolution of phosphoprotein phosphatases in Drosophila. PLoS One. 6:e22218. (2011)
  • Bíró J, Farkas I, Domoki M, Ötvös K, Bottka S, Dombrádi V, Fehér A.: The histone phosphatase inhibitory property of plant nucleosome assembly protein-related proteins (NRPs). Plant Physiol Biochem. 52,162-168. (2012)
  • Kókai E, Páldy FS, Somogyi K, Chougele A, Pál M, Kerekes É, Friedrich P, Dombrádi V, Ádám G: CalpB modulates border cell migration in Drosophila egg chambers. BMC Developmental Biology 12 1-12 (2012)
  • Ádám C, Erdei É, Casado C, Kovács L, González A, Majoros L, Petrényi K, Bagossi P, Farkas I, Molnár M, Pócsi I, Arino J, Dombrádi V: Protein phosphatase CaPpz1 is involved in cation homeostasis, cell wall integrity and virulence of Candida albicans. Microbiology-SGM 1581258-1267. (2012)
  • Leiter É, González A, Erdei É, Casado C, Kovács L, Ádám Cs, Oláh J, Miskei M, Molnár M, Farkas I, Hamari Zs, Arino J, Pócsi I, Dombrádi V: Protein phosphatase Z modulates oxidative stress response in fungi. Fungal Genetics and Biology 49 708-716 (2012)
  • Molero C, Petrényi K, González A, Carmona M, Gelis S, Abrie JA, Strauss E, Ramos J, Dombradi V, Hidalgo E, Ariño J: The Schizosaccharomyces pombe fusion gene hal3 encodes three distinct activities. Molecular Microbiology 90:367-82. (2013)
  • Kerekes É, Kókai E, Páldy FS, Dombrádi V: Functional analysis of the glycogen binding subunit CG9238/Gbs-70E of protein phosphatase 1 in Drosophila melanogaster. Insect Biochemistry and Molecular Biology 49 70-79 (2014)
  • Nagy G, Hennig GW, Petrenyi K, Kovacs L, Pocsi I, Dombradi V, Banfalvi G: Time-lapse video microscopy and image analysis of adherence and growth patterns of Candida albicans strains. Appl. Microbiol. Biotechnol. 98 5185–5194 (2014)
  • Ábrahám E, Yu P, Farkas I, Darula Zs, Varga E, Lukács N, Ferhan A, Medzihradszky KF,• Dombrádi V, Dudits D, Horváth GV: The B″ regulatory subunit of protein phosphatase 2A mediates the dephosphorylation of rice retinoblastoma related protein 1. Plant Mol. Biol. 87:125–141 (2015)      

Frissítés dátuma: 2017.08.08.