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Arranged marriage in lipid signalling? The limited choices of PtdIns(4,5)P2 in finding the right partner

Authors

  • M. Heilmann,

    Corresponding author
    • Department of Cellular Biochemistry, Institute for Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany
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  • I. Heilmann

    1. Department of Cellular Biochemistry, Institute for Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany
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Correspondence

I. Heilmann, Department of Cellular Biochemistry, Institute for Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Str. 3, 06120 Halle (Saale), Germany.

E-mail: ingo.heilmann@biochemtech.uni-halle.de

Abstract

Inositol-containing phospholipids (phosphoinositides, PIs) control numerous cellular processes in eukaryotic cells. For plants, a key involvement of PIs has been demonstrated in the regulation of membrane trafficking, cytoskeletal dynamics and in processes mediating the adaptation to changing environmental conditions. Phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) mediates its cellular functions via binding to various alternative target proteins. Such downstream targets of PtdIns(4,5)P2 are characterised by the possession of specific lipid-binding domains, and binding of the PtdIns(4,5)P2 ligand exerts effects on their activity or localisation. The large number of potential alternative binding partners – and associated cellular processes – raises the question how alternative or even contrapuntal effects of PtdIns(4,5)P2 are orchestrated to enable cellular function. This article aims to provide an overview of recent insights and new views on how distinct functional pools of PtdIns(4,5)P2 are generated and maintained. The emerging picture suggests that PtdIns(4,5)P2 species containing different fatty acids influence the lateral mobility of the lipids in the membrane, possibly enabling specific interactions of PtdIns(4,5)P2 pools with certain downstream targets. PtdIns(4,5)P2 pools with certain functions might also be defined by protein–protein interactions of PI4P 5-kinases, which pass PtdIns(4,5)P2 only to certain downstream partners. Individually or in combination, PtdIns(4,5)P2 species and specific protein–protein interactions of PI4P 5-kinases might contribute to the channelling of PtdIns(4,5)P2 signals towards specific functional effects. The dynamic nature of PI-dependent signalling complexes with specific functions is an added challenge for future studies of plant PI signalling.

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