Characterization of glycosyl inositol phosphoryl ceramides from plants and fungi by mass spectrometry

Abstract

Although glycosyl inositol phosphoryl ceramides (GIPCs) represent the most abundant class of sphingolipids in plants, they still remain poorly characterized in terms of structure and biodiversity. More than 50 years after their discovery, little is known about their subcellular distribution and their exact roles in membrane structure and biological functions. This review is focused on extraction and characterization methods of GIPCs occurring in plants and fungi. Global methods for characterizing ceramide moieties of GIPCs revealed the structures of long-chain bases (LCBs) and fatty acids (FAs): LCBs are dominated by tri-hydroxylated molecules such as monounsaturated and saturated phytosphingosine (t18:1 and t18:0, respectively) in plants and mainly phytosphingosine (t18:0 and t20:0) in fungi; FA are generally 14-26 carbon atoms long in plants and 16-26 carbon atoms long in fungi, these chains being often hydroxylated in position 2. Mass spectrometry plays a pivotal role in the assessment of GIPC diversity and the characterization of their structures. Indeed, it allowed to determine that the core structure of GIPC polar heads in plants is Hex(R1)-HexA-IPC, with R1 being a hydroxyl, an amine, or a N-acetylamine group, whereas the core structure in fungi is Man-IPC. Notably, information gained from tandem mass spectrometry spectra was most useful to describe the huge variety of structures encountered in plants and fungi and reveal GIPCs with yet uncharacterized polar head structures, such as hexose-inositol phosphoceramide in Chondracanthus acicularis and (hexuronic acid)4-inositol phosphoceramide and hexose-(hexuronic acid)3-inositol phosphoceramide in Ulva lactuca.

Differential Effect of Plant Lipids on Membrane Organization

“…More recently, controversy has arisen because no phase separation for DOPC/bovine brain SM (7:3) occurs at 20°C (77,117). Our data show no ability of GIPC, the major plant sphingolipid (51), to order the phospholipid bilayer ( Fig. 3) and argue in favor of no extensive phase separation in the binary sphingolipid/phospholipid system.…”

“…GIPCs are the predominant class of sphingolipids in plant cell PM (51,79,80), these molecular lipid species are not commercially available. We thus recently used a purification procedure described by Carter and Koob (41) modified by Bure et al (55) on tobacco cell culture to obtain milligram amounts of GIPCs.…”

“…51). GIPCs from Arabidopsis and tobacco, analyzed by mass spectrometry, were composed primarily of ceramide with t18:0 and t18:1 and 2-hydroxylated very long chain fatty acids (50,51).…”

A comprehensive insight into the lipid composition of Myxococcus xanthus by UPLC-ESI-MS

“…In general, glycosylated Cers are important signaling molecules in multicellular organisms ( 49 ), but no specifi c functions for PI-Cers are known in lower eukaryotes, except that inhibition of AUR1 is lethal to S. cerevisiae ( 50 ) and that PI-Cer is at least indirectly associated with the pathogenicity of Cryptococcus neoformans ( 51 ). A possible signaling function of PI-Cers in myxobacterial fruiting body formation or sporulation remains to be investigated.…”

GIPC: Glycosyl Inositol Phospho Ceramides, the major sphingolipids on earth

“…Many saccharides can be added, forming glycolipids like GIPC series A: GlcR1-GlcAinositol-1-phosphoceramide or GIPC series B: Gal-GlcR1-GlcA-inositol-1-phosphoceramide (Gal, galactose, GlcR1, glucose with a hydroxyl group, an amine or an N-acetylamine for R1, and GlcA, glucuronic acid). 9 Additional saccharides were found to be linked to inositol, e.g., arabinose, galactose, mannose and fucose, forming different series according to the number of sugar moieties, 7,10,11,12,9,13 see Fig. 1 right.…”