Inositol phospholipids are critical regulators of membrane biology throughout eukaryotes. The general principle by which they perform these roles is conserved across species and involves binding of differentially phosphorylated inositol head groups to specific protein domains. This interaction serves to both recruit and regulate the activity of several different classes of protein which act on membrane surfaces. In mammalian cells, these phosphorylated inositol head groups are predominantly borne by a C38:4 diacylglycerol backbone. We show here that the inositol phospholipids of Dictyostelium are different, being highly enriched in an unusual C34:1e lipid backbone, 1‐hexadecyl‐2‐(11Z‐octadecenoyl)‐sn‐glycero‐3‐phospho‐(1'‐myo‐inositol), in which the sn‐1 position contains an ether‐linked C16:0 chain; they are thus plasmanylinositols. These plasmanylinositols respond acutely to stimulation of cells with chemoattractants, and their levels are regulated by PIPKs, PI3Ks and PTEN. In mammals and now in Dictyostelium, the hydrocarbon chains of inositol phospholipids are a highly selected subset of those available to other phospholipids, suggesting that different molecular selectors are at play in these organisms but serve a common, evolutionarily conserved purpose.
See also: GRV Hammond & T Balla (October 2014)
A new mass spectrometry technique reveals that inositol phospholipids in Dictyostelium are based on a novel backbone. These plasmanyl inositides are functionally identical to the canonical diacyl glycerol configurations found in mammalian cells.
Most inositol lipids in Dictyostelium are plasmanylinositols with a C16:0‐ether, C18:1‐acyl glycerol backbone.
Dictyostelium uses these unusually structured lipids as signalling molecules in an analogous fashion to their phosphatidylinositol counterparts in mammalian cells.
Other major phospholipid classes in Dictyostelium are comprised of a more heterogeneous collection of diacyl and acyl/ether species, suggesting evolutionary pressure to create a molecularly homogenous pool of plasmanylinositols in this organism.
The EMBO Journal (2014) 33: 2188–2200
- Received April 7, 2014.
- Revision received July 29, 2014.
- Accepted July 30, 2014.
- © 2014 The Authors