G Protein Activation without a GEF in the Plant Kingdom

English version České info

Animal heterotrimeric G proteins are activated by guanine nucleotide exchange factors (GEF), typically seven transmembrane receptors that trigger GDP release and subsequent GTP binding. In contrast, the Arabidopsis thaliana G protein (AtGPA1) rapidly activates itself without a GEF and is instead regulated by a seven transmembrane Regulator of G protein Signaling (7TM-RGS) protein that promotes GTP hydrolysis to reset the inactive (GDP-bound) state. It is not known if this unusual activation is a major and constraining part of the evolutionary history of G signaling in eukaryotes. In particular, it is not known if this is an ancestral form or if this mechanism is maintained, and therefore constrained, within the plant kingdom. To determine if this mode of signal regulation is conserved throughout the plant kingdom, we analyzed available plant genomes for G protein signaling components, and we purified individually the plant components encoded in an informative set of plant genomes in order to determine their activation properties in vitro. While the subunits of the heterotrimeric G protein complex are encoded in vascular plant genomes, the 7TM-RGS genes were lost in all investigated grasses. Despite the absence of a Gα-inactivating protein in grasses, all vascular plant Gα proteins examined rapidly released GDP without a receptor and slowly hydrolyzed GTP, indicating that these Gα are self-activating. We showed further that a single amino acid substitution found naturally in grass Gα proteins reduced the Gα-RGS interaction, and this amino acid substitution occurred before the loss of the RGS gene in the grass lineage. Like grasses, non-vascular plants also appear to lack RGS proteins. However, unlike grasses, one representative non-vascular plant Gα showed rapid GTP hydrolysis, likely compensating for the loss of the RGS gene. Our findings, the loss of a regulatory gene and the retention of the “self-activating” trait, indicate the existence of divergent Gα regulatory mechanisms in the plant kingdom. In the grasses, purifying selection on the regulatory gene was lost after the physical decoupling of the RGS protein and its cognate Gα partner. More broadly these findings show extreme divergence in Gα activation and regulation that played a critical role in the evolution of G protein signaling pathways.

Vyšlo v časopise: G Protein Activation without a GEF in the Plant Kingdom. PLoS Genet 8(6): e32767. doi:10.1371/journal.pgen.1002756
Kategorie: Research Article
prolekare.web.journal.doi_sk: https://doi.org/10.1371/journal.pgen.1002756

Souhrn

Zdroje

1. GilmanAG 1987 G proteins: transducers of receptor-generated signals. Annu Rev Biochem 56 615 649

2. SprangSR 1997 G protein mechanisms: insights from structural analysis. Annu Rev Biochem 66 639 678

3. SiderovskiDPWillardFS 2005 The GAPs, GEFs, and GDIs of heterotrimeric G-protein alpha subunits. Int J Biol Sci 1 51 66

4. JohnstonCATaylorJPGaoYKimpleAJGrigstonJC 2007 GTPase acceleration as the rate-limiting step in Arabidopsis G protein-coupled sugar signaling. Proc Natl Acad Sci U S A 104 17317 17322

5. JonesJCDuffyJWMachiusMTempleBRDohlmanHG 2011 The crystal structure of a self-activating G protein alpha subunit reveals its distinct mechanism of signal initiation. Sci Signal 4 ra8

6. ChenJGJonesAM 2004 AtRGS1 function in Arabidopsis thaliana. Methods Enzymol 389 338 350

7. ChenJGWillardFSHuangJLiangJChasseSA 2003 A seven-transmembrane RGS protein that modulates plant cell proliferation. Science 301 1728 1731

8. ChenJGGaoYJonesAM 2006 Differential roles of Arabidopsis heterotrimeric G-protein subunits in modulating cell division in roots. Plant Physiol 141 887 897

9. RichardsTACavalier-SmithT 2005 Myosin domain evolution and the primary divergence of eukaryotes. Nature 436 1113 1118

10. RogerAJSimpsonAG 2009 Evolution: revisiting the root of the eukaryote tree. Curr Biol 19 R165 167

11. SeoHSChoiCHLeeSYChoMJBahkJD 1997 Biochemical characteristics of a rice (Oryza sativa L., IR36) G-protein alpha-subunit expressed in Escherichia coli. Biochem J 324 Pt 1 273 281

12. IwasakiYKatoTKaidohTIshikawaAAsahiT 1997 Characterization of the putative alpha subunit of a heterotrimeric G protein in rice. Plant Mol Biol 34 563 572

13. BishtNCJezJMPandeyS 2011 An elaborate heterotrimeric G-protein family from soybean expands the diversity of plant G-protein networks. New Phytol 190 35 48

14. ChakravortyDTrusovYZhangWAcharyaBRSheahanMB 2011 An atypical heterotrimeric G-protein gamma-subunit is involved in guard cell K(+) -channel regulation and morphological development in Arabidopsis thaliana. Plant J 67 840 851

15. TrusovYRookesJETilbrookKChakravortyDMasonMG 2007 Heterotrimeric G protein gamma subunits provide functional selectivity in Gbetagamma dimer signaling in Arabidopsis. Plant Cell 19 1235 1250

16. GookinTEKimJAssmannSM 2008 Whole proteome identification of plant candidate G-protein coupled receptors in Arabidopsis, rice, and poplar: computational prediction and in-vivo protein coupling. Genome Biol 9 R120

17. MoriyamaENStropePKOpiyoSOChenZJonesAM 2006 Mining the Arabidopsis thaliana genome for highly-divergent seven transmembrane receptors. Genome Biol 7 R96

18. MooreMJSoltisPSBellCDBurleighJGSoltisDE 2010 Phylogenetic analysis of 83 plastid genes further resolves the early diversification of eudicots. Proc Natl Acad Sci U S A 107 4623 4628

19. HigashijimaTFergusonKMSmigelMDGilmanAG 1987 The effect of GTP and Mg2+ on the GTPase activity and the fluorescent properties of Go. J Biol Chem 262 757 761

20. HigashijimaTFergusonKMSternweisPCRossEMSmigelMD 1987 The effect of activating ligands on the intrinsic fluorescence of guanine nucleotide-binding regulatory proteins. J Biol Chem 262 752 756

21. TesmerJJBermanDMGilmanAGSprangSR 1997 Structure of RGS4 bound to AlF4–activated G(i alpha1): stabilization of the transition state for GTP hydrolysis. Cell 89 251 261

22. SuzukiNTsumotoKHajicekNDaigoKTokitaR 2009 Activation of leukemia-associated RhoGEF by Galpha13 with significant conformational rearrangements in the interface. J Biol Chem 284 5000 5009

23. WillardFSKimpleRJSiderovskiDP 2004 Return of the GDI: the GoLoco motif in cell division. Annu Rev Biochem 73 925 951

24. TakasakiJSaitoTTaniguchiMKawasakiTMoritaniY 2004 A novel Galphaq/11-selective inhibitor. J Biol Chem 279 47438 47445

25. JonesJCTempleBRJonesAMDohlmanHG 2011 Functional reconstitution of an atypical G protein heterotrimer and regulator of G protein signaling protein (RGS1) from Arabidopsis thaliana. J Biol Chem 286 13143 13150

26. BaucomRSEstillJCChaparroCUpshawNJogiA 2009 Exceptional diversity, non-random distribution, and rapid evolution of retroelements in the B73 maize genome. PLoS Genet 5 e1000732

27. BennetzenJL 2005 Transposable elements, gene creation and genome rearrangement in flowering plants. Curr Opin Genet Dev 15 621 627

28. UllahHChenJGYoungJCImKHSussmanMR 2001 Modulation of cell proliferation by heterotrimeric G protein in Arabidopsis. Science 292 2066 2069

29. UllahHChenJGTempleBBoyesDCAlonsoJM 2003 The beta-subunit of the Arabidopsis G protein negatively regulates auxin-induced cell division and affects multiple developmental processes. Plant Cell 15 393 409

30. FujisawaYKatoTOhkiSIshikawaAKitanoH 1999 Suppression of the heterotrimeric G protein causes abnormal morphology, including dwarfism, in rice. Proc Natl Acad Sci U S A 96 7575 7580

31. BersteinGBlankJLJhonDYExtonJHRheeSG 1992 Phospholipase C-beta 1 is a GTPase-activating protein for Gq/11, its physiologic regulator. Cell 70 411 418

32. TamuraKPetersonDPetersonNStecherGNeiM 2011 MEGA5: Molecular evolutionary genetic analysis using maximum likelihood, evolutionary distance, and maximum parsimony methods. Mol Biol Evol 28 2731 2739

33. JonesDTTaylorWRThorntonJM 1992 The rapid generation of mutation data matrices from protein sequences. Comput Appl Biosci 8 275 282