Skip to main content
NCBI home page
Plant Signaling & Behavior logoLink to Plant Signaling & Behavior
. 2012 Sep 1;7(9):1197–1199. doi: 10.4161/psb.21305

Eat in or take away? How phosphatidylinositol 4-kinases feed the phospholipase C pathway with substrate

Elise Delage 1, Eric Ruelland 1, Alain Zachowski 1, Juliette Puyaubert 1,*
PMCID: PMC3489660  PMID: 22899063

Abstract

Phosphatidylinositol 4-kinases (PI4Ks) catalyze the first step in the synthesis of phosphoinositide pools hydrolysed by phosphoinositide-dependent phospholipase C (PI-PLC) and thus constitute a potential key regulation point of this pathway. Twelve putative PI4K isoforms, divided as type-II (AtPI4KIIγ1-8) and type-III PI4Ks (AtPI4KIIIα1-2 and AtPI4KIIIβ1-2), have been identified in Arabidopsis genome. By a combination of pharmalogical and genetic approaches we recently evidenced that AtPI4KIIIβ1 and AtPI4KIIIβ2 contribute to supply PI-PLC with substrate and that AtPI4KIIIα1 is probably also involved in this process. Given the current knowledge on PI-PLC and type-III PI4Ks localization in plant cells it raises the question whether type-III PI4Ks produce phosphatidylinositol 4-phosphate at the site of its consumption by the PI-PLC pathway. We therefore discuss the spatial organization of substrate supply to PI-PLC in plant cells with reference to recent data evidenced in mammalian cells.

Keywords: Arabidopsis, cold stress, phosphatidylinositol 4-kinase, phosphoinositides, phospholipase C

The phosphorylated derivatives of phosphatidylinositol (PI), namely phosphoinositides, participate in a plethora of fundamental cellular processes such as membrane trafficking, cytoskeleton remodelling and multiple signal tranduction pathways.1-3 By phosphorylating PI at D4 position of its inositol ring, phosphatidylinositol 4-kinases (PI4Ks) catalyze the first step in the synthesis of two major phosphoinositides: phosphatidylinositol 4-phosphate (PI4P) and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). PI4Ks thus constitute a potential key regulation point for signaling events involving these lipids. PI4Ks have been divided into type-II and type-III according to their size, substrate affinity and sensitivity to inhibitors.4,5 In Arabidopsis genome, eight putative type-II PI4Ks and four putative type-III PI4Ks have been identified. These latter are subdivided into PI4KIIIα (AtPI4KIIIα1 and 2) and PI4KIIIβ (AtPI4KIIIβ1 and 2).5 Although the number of isoforms differ between organisms, their existence as a multigenic family appears to be a common feature of PI4Ks among eukaryotic kingdoms, thus raising the question of why cells require more than one form of the enzyme to produce the same phosphoinositide species. Evidences have accumulated recently that the different isoforms synthesize discrete cellular pools, thus mediating mostly non-overlapping biological functions.4,6,7 Therefore a crucial step in deciphering the spatio-temporal regulation of a given signaling pathway is to identify which PI4K isoforms are involved in it. This question has received much attention in the context of phosphoinositide-dependent phospholipase C (PI-PLC) signaling in mammalian cells. PI-PLCs hydrolyse PI(4,5)P2 (and potentially PI4P)1 to produce second messengers, and the synthesis of PI4P by the unique mammalian PI4KIIIα has emerged as an important regulatory step of this pathway.8,9 On the other hand, PI4K roles in plant PI-PLC signaling have just started to be unraveled.

In our recent paper we provided new data about PI4K isoforms feeding PI-PLC pathway with substrate in Arabidopsis thaliana. PI-PLC is activated within the first minutes of a cold exposure.10 Using a pharmacological approach based on the differential sensitivity of type-II and type-III PI4Ks to adenosine and wortmannin, respectively,11-13 we showed that type-III PI4Ks are required for PI-PLC activity at 0°C in Arabidopsis suspension cells. In order to assess the contribution of the different type-III PI4Ks in the synthesis of phosphoinositide pools hydrolysed by PI-PLC, we studied T-DNA insertion plants of the various isoforms. However, we failed to isolate homozygous mutants for AtPI4KIIIα1, suggesting lethality or gametophytic sterility induced by the mutation. As to AtPI4KIIIα2, no corresponding EST are present in the databases and it is probably a pseudogene.5 We therefore focused our study on pi4kIIIβ mutants. Interestingly, PI-PLC activity at 0°C was reduced by 40% in a pi4kIIIβ1β2 double-mutant whereas it was not significantly lowered in either pi4kIIIβ1 or pi4kIIIβ2 simple-mutants. These results highlighted that both AtPI4KIIIβ1 and AtPI4KIIIβ2 can supply in substrate the PI-PLC pathway activated by low temperatures. Nevertheless, since 60% of the PI-PLC activity was still detected in pi4kIIIβ1β2, other PI4Ks must be involved in this process. Since most of the residual phosphatidylinositol kinase activity in pi4kIIIβ1β2 was wortmannin-sensitive and adenosine-insensitive, our results strongly suggest that AtPI4KIIIα1 also participates in feeding the PI-PLC pathway with substrate. Plants might therefore represent an original model differing from mammals since the three type-III PI4Ks expressed in Arabidopsis appear to act redundantly upstream of PI-PLC.

Such a redundancy was quite surprising given the data on type-III PI4K and PI-PLC subcellular localization in plants reported in the literature thus far. PI4P and PI(4,5)P2 are present at very low level in cells14-16 and it is generally admitted that sustained PI-PLC activation requires the continuous phosphorylation of PI by PI4K and PI4P 5-kinases.14,17 Given the fast timing of PI-PLC pathway activation in response to many stimuli, one would expect to find the upstream PI4K in close vicinity of the PI-PLC. Yet, as in mammalian cells, all PI-PLC activities and proteins examined so far in plant cells were found to be predominantly localized in the plasma membrane (PM).18-20 On the other hand, AtPI4KIIIα1 expressed in insect cells has been observed in perinuclear membranes which may correspond to the endoplasmic reticulum (ER).20 As to AtPI4KIIIβs they are recruited to the trans-Golgi network (TGN) in Arabidopsis root hair22 and may also localize at the plasma membrane,23 in the nucleus24 and/or in small cytoplasmic vesicles.24 The apparent capacity of PI-PLC to hydrolyse phosphoinositide pools originating from these three PI4Ks raises the intriguing question of how the substrate supply to the pathway is spatially organized.

A first hypothesis is that AtPI4KIIIα1, AtPI4KIIIβ1 and AtPI4KIIIβ2 can synthesize PI4P directly at the location where PI-PLC is active. Unlike AtPI4KIIIβs, no PM localization of AtPI4KIIIα1 has been observed hitherto. However its mammalian homolog is responsible for replenishing the phosphoinositide pools at the PM after PI-PLC activation while it is mostly found at the ER.8,25 It has been hypothesized that PI4P synthesis by the mammalian PI4KIIIα could occur at ER-PM contact zones and a similar explanation is conceivable in plant cells.14 Alternatively, type-III PI4Ks could be recruited to the PM upon stimulation. Indeed PI4Ks are soluble proteins and their recruitment to specific membrane compartment is likely to be a critical determinant for their various biological functions. A recent study in mammalian cells reported that the protein kinase WNK1 potentiates PI-PLC signaling by stimulating PI4KIIIα and evidences suggest that this stimulation may involve PI4KIIIα relocalization from cytosol to membranes.9 Another possibility is that PI4P pools synthesized in other subcellular compartments contribute to feed the PI-PLC pathway at the PM. The involvement of Golgi PI4P in the maintenance of PI(4,5)P2 pools at the PM during PI-PLC activation has been highlighted in mammalian cells.26 PI4P generated at the TGN by the Arabidopsis PI4KIIIβs could thus contribute to supply the PI-PLC pathway with substrate. In such a case, TGN PI4P should be transported to the PM through vesicular trafficking since no PI-transfer proteins transferring PI4P have been identified so far.

Further investigations to unravel the subcellular localization of both type-III PI4Ks and their respective PI4P pools in the context of PI-PLC supply in stimulated plant cells thus appear as a promissing way to better understand this major signaling pathway.

graphic file with name psb-7-1197-g1.jpg

Open in a new tab

Figure 1. Hypothetical models depicting the spatial organization of PI4P supply to the PI-PLC pathway in Arabidopsis cells. Model (1): Synthesis at the PM by AtPI4KIIIβs and at ER-PM contact zone by AtPI4KIIIα1. Model (2): Type-III PI4K relocalization to the PM upon stimulation. Model (3): Vesicular transport of PI4P synthesized at the TGN to the PM PM: Plasma Membrane; ER: Endoplasmic Reticulum; N: Nucleus, TGN: trans-Golgi Network

Glossary

Abbreviations:

ER

endoplasmic reticulum

PI

phosphatidylinositol

PI4Ks

phosphatidylinositol 4-kinases

PI4P

phosphatidylinositol 4-phosphate

PI(4,5)P2

phosphatidylinositol 4,5-bisphosphate

PI-PLC

phosphoinositide-dependent phospholipase C

PM

plasma membrane

TGN

trans-Golgi network

Delage E, Ruelland E, Guillas I, Zachowski A, Puyaubert J. Arabidopsis type-III phosphatidylinositol 4-kinases β1 and β2 are upstream of the phospholipase C pathway triggered by cold exposure. Plant Cell Physiol. 2012;53:565–76. doi: 10.1093/pcp/pcs011.

Footnotes

References

  • 1.Munnik T, Nielsen E. Green light for polyphosphoinositide signals in plants. Curr Opin Plant Biol. 2011;14:489–97. doi: 10.1016/j.pbi.2011.06.007. [DOI] [PubMed] [Google Scholar]
  • 2.Michell RH. Inositol derivatives: evolution and functions. Nat Rev Mol Cell Biol. 2008;9:151–61. doi: 10.1038/nrm2334. [DOI] [PubMed] [Google Scholar]
  • 3.Ischebeck T, Seiler S, Heilmann I. At the poles across kingdoms: phosphoinositides and polar tip growth. Protoplasma. 2010;240:13–31. doi: 10.1007/s00709-009-0093-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Balla A, Balla T. Phosphatidylinositol 4-kinases: old enzymes with emerging functions. Trends Cell Biol. 2006;16:351–61. doi: 10.1016/j.tcb.2006.05.003. [DOI] [PubMed] [Google Scholar]
  • 5.Mueller-Roeber B, Pical C. Inositol phospholipid metabolism in Arabidopsis. Characterized and putative isoforms of inositol phospholipid kinase and phosphoinositide-specific phospholipase C. Plant Physiol. 2002;130:22–46. doi: 10.1104/pp.004770. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 6.Audhya A, Foti M, Emr SD. Distinct roles for the yeast phosphatidylinositol 4-kinases, Stt4p and Pik1p, in secretion, cell growth, and organelle membrane dynamics. Mol Biol Cell. 2000;11:2673–89. doi: 10.1091/mbc.11.8.2673. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 7.Chu KME, Minogue S, Hsuan JJ, Waugh MG. Differential effects of the phosphatidylinositol 4-kinases, PI4KIIα and PI4KIIIβ, on Akt activation and apoptosis. Cell Death Dis. 2010;1:e106. doi: 10.1038/cddis.2010.84. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8.Balla A, Kim YJ, Varnai P, Szentpetery Z, Knight Z, Shokat KM, et al. Maintenance of hormone-sensitive phosphoinositide pools in the plasma membrane requires phosphatidylinositol 4-kinase IIIalpha. Mol Biol Cell. 2008;19:711–21. doi: 10.1091/mbc.E07-07-0713. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9.An S-W, Cha S-K, Yoon J, Chang S, Ross EM, Huang C-L. WNK1 promotes PIP₂ synthesis to coordinate growth factor and GPCR-Gq signaling. Curr Biol. 2011;21:1979–87. doi: 10.1016/j.cub.2011.11.002. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Ruelland E, Cantrel C, Gawer M, Kader JC, Zachowski A. Activation of phospholipases C and D is an early response to a cold exposure in Arabidopsis suspension cells. Plant Physiol. 2002;130:999–1007. doi: 10.1104/pp.006080. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 11.Balla A, Tuymetova G, Toth B, Szentpetery Z, Zhao X, Knight ZA, et al. Design of drug-resistant alleles of type-III phosphatidylinositol 4-kinases using mutagenesis and molecular modeling. Biochemistry. 2008;47:1599–607. doi: 10.1021/bi7017927. [DOI] [PubMed] [Google Scholar]
  • 12.Nakanishi S, Catt KJ, Balla T. A wortmannin-sensitive phosphatidylinositol 4-kinase that regulates hormone-sensitive pools of inositolphospholipids. Proc Natl Acad Sci U S A. 1995;92:5317–21. doi: 10.1073/pnas.92.12.5317. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 13.Krinke O, Ruelland E, Valentová O, Vergnolle C, Renou JP, Taconnat L, et al. Phosphatidylinositol 4-kinase activation is an early response to salicylic acid in Arabidopsis suspension cells. Plant Physiol. 2007;144:1347–59. doi: 10.1104/pp.107.100842. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14.Balla T, Szentpetery Z, Kim YJ. Phosphoinositide signaling: new tools and insights. Physiology (Bethesda) 2009;24:231–44. doi: 10.1152/physiol.00014.2009. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 15.Vermeer JE, Thole JM, Goedhart J, Nielsen E, Munnik T, Gadella TW., Jr. Imaging phosphatidylinositol 4-phosphate dynamics in living plant cells. Plant J. 2009;57:356–72. doi: 10.1111/j.1365-313X.2008.03679.x. [DOI] [PubMed] [Google Scholar]
  • 16.van Leeuwen W, Vermeer JEM, Gadella TWJ, Jr., Munnik T. Visualization of phosphatidylinositol 4,5-bisphosphate in the plasma membrane of suspension-cultured tobacco BY-2 cells and whole Arabidopsis seedlings. Plant J. 2007;52:1014–26. doi: 10.1111/j.1365-313X.2007.03292.x. [DOI] [PubMed] [Google Scholar]
  • 17.Rebecchi MJ, Pentyala SN. Structure, function, and control of phosphoinositide-specific phospholipase C. Physiol Rev. 2000;80:1291–335. doi: 10.1152/physrev.2000.80.4.1291. [DOI] [PubMed] [Google Scholar]
  • 18.Hunt L, Otterhag L, Lee JC, Lasheen T, Hunt J, Seki M, et al. Gene-specific expression and calcium activation of Arabidopsis thaliana phospholipase C isoforms. New Phytol. 2004;162:643–54. doi: 10.1111/j.1469-8137.2004.01069.x. [DOI] [PubMed] [Google Scholar]
  • 19.Zheng S-Z, Liu Y-L, Li B, Shang ZL, Zhou R-G, Sun D-Y. Phosphoinositide-specific phospholipase C9 is involved in the thermotolerance of Arabidopsis. Plant J. 2012;69:689–700. doi: 10.1111/j.1365-313X.2011.04823.x. [DOI] [PubMed] [Google Scholar]
  • 20.Bunney TD, Katan M. PLC regulation: emerging pictures for molecular mechanisms. Trends Biochem Sci. 2011;36:88–96. doi: 10.1016/j.tibs.2010.08.003. [DOI] [PubMed] [Google Scholar]
  • 21.Stevenson-Paulik J, Love J, Boss WF. Differential regulation of two Arabidopsis type III phosphatidylinositol 4-kinase isoforms. A regulatory role for the pleckstrin homology domain. Plant Physiol. 2003;132:1053–64. doi: 10.1104/pp.103.021758. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 22.Kang BH, Nielsen E, Preuss ML, Mastronarde D, Staehelin LA. Electron tomography of RabA4b- and PI-4Kβ1-labeled trans Golgi network compartments in Arabidopsis. Traffic. 2011;12:313–29. doi: 10.1111/j.1600-0854.2010.01146.x. [DOI] [PubMed] [Google Scholar]
  • 23.Lou Y, Ma H, Lin WH, Chu ZQ, Mueller-Roeber B, Xu ZH, et al. The highly charged region of plant beta-type phosphatidylinositol 4-kinase is involved in membrane targeting and phospholipid binding. Plant Mol Biol. 2006;60:729–46. doi: 10.1007/s11103-005-5548-x. [DOI] [PubMed] [Google Scholar]
  • 24.Koroleva OA, Tomlinson ML, Leader D, Shaw P, Doonan JH. High-throughput protein localization in Arabidopsis using Agrobacterium-mediated transient expression of GFP-ORF fusions. Plant J. 2005;41:162–74. doi: 10.1111/j.1365-313X.2004.02281.x. [DOI] [PubMed] [Google Scholar]
  • 25.Hammond GRV, Fischer MJ, Anderson KE, Holdich J, Koteci A, Balla T, et al. PI4P and PI(4,5)P2 are essential but independent lipid determinants of membrane identity. Science. 2012 doi: 10.1126/science.1222483. In press. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.Szentpetery Z, Várnai P, Balla T. Acute manipulation of Golgi phosphoinositides to assess their importance in cellular trafficking and signaling. Proc Natl Acad Sci U S A. 2010;107:8225–30. doi: 10.1073/pnas.1000157107. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Plant Signaling & Behavior are provided here courtesy of Taylor & Francis

RESOURCES