The functions of steryl glycosides come to those who wait: Recent advances in plants, fungi, bacteria and animals

• Published in: Progress in lipid research Vol. 49; no. 3; pp. 262 - 288
• Main Authors: Grille, Sandra, Zaslawski, Anna, Thiele, Swantje, Plat, Jogchum, Warnecke, Dirk
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2010
• Subjects: Animals; Arabidopsis - metabolism; Arabidopsis thaliana; Bacteria - metabolism; Fungi - metabolism; Glycosides - biosynthesis; Glycosides - metabolism; Glycosyltransferases - genetics; Glycosyltransferases - metabolism; Helicobacter pylori; Humans; Pexophagy; Pichia pastoris; Sterol glycoside; Sterol glycosyltransferase; Sterols - chemistry; acyl-CoA; SGT; UGT superfamily; PS; ALS-PDC; αCPG; Pichia pastoris; T H2; Arabidopsis thaliana; TrPH-G; Sterol glycosyltransferase; SG; Helicobacter pylori; ASG; PH-G; POPC; αCG; OMPLA; PtdIns; GT1; Pexophagy; CL; MIPA; Aox; ATG proteins; PSM; APC; PGL; PE; αCAG; PIP; PG; PM; DRM; Sterol glycoside
• ISSN: 0163-7827; 1873-2194
• DOI: 10.1016/j.plipres.2010.02.001

The attachment of a sugar moiety to the 3-hydroxy group of a sterol drastically increases the size of the hydrophilic part of the lipid. It is obvious that the glycosylation of a considerable fraction of membrane-bound free sterols alters the biophysical properties of the membrane. However, the consequences of such changes in the proportions of free sterols and steryl glycosides on the biological functions of a membrane are still unclear. This is the main hurdle in understanding the biological functions of steryl glycosides on a molecular level. The recent cloning of sterol glycosyltransferase genes from plants, fungi and bacteria has enabled genetic approaches to analyze steryl glycoside functions. Down regulation of phytosteryl β-glycoside biosynthesis in Arabidopsis thaliana causes several dysfunctions in seed development. Ergosteryl β-glycoside depleted mutants of the yeast Pichia pastoris lose their ability to degrade their peroxisomes by an autophagic mechanism called micropexophagy. In the plant-pathogenic fungus Colletotrichum orbiculare the same defect impairs invasion of the cucumber host plants. Helicobacter pylori, a bacterium colonizing the human stomach, is unable to modulate the host’s immune response when the cholesteryl α-glycoside biosynthesis of the bacterium is mutated. These mutants with manipulated steryl glycoside metabolism will inspire further studies with cell biological, biophysical and other methods that will provide us with a mechanistic understanding of steryl glycoside functions.