Mannosylinositol phosphorylceramide is a major sphingolipid component and is required for proper localization of plasma-membrane proteins inSchizosaccharomyces pombe

Abstract

SummaryIn Saccharomyces cerevisiae, three classes of sphingolipids contain myo-inositol -inositol phosphorylceramide (IPC), mannosylinositol phosphorylceramide (MIPC) and mannosyldiinositol phosphorylceramide [M(IP) 2 C]. No fission yeast equivalent of Ipt1p, the inositolphosphotransferase that synthesizes M(IP) 2 C from MIPC, has been found in the Schizosaccharomyces pombe genome. Analysis of the sphingolipid composition of wild-type cells confirmed that MIPC is the terminal and most abundant complex sphingolipid in S. pombe. Three proteins (Sur1p, Csg2p and Csh1p) have been shown to be involved in the synthesis of MIPC from IPC in S. cerevisiae. The S. pombe genome has three genes (SPAC2F3.01, SPCC4F11.04c and SPAC17G8.11c) that are homologues of SUR1, termed imt1 + , imt2 + and imt3 + , respectively. To determine whether these genes function in MIPC synthesis in S. pombe, single and multiple gene disruptants were constructed. Single imt disruptants were found to be viable. MIPC was not detected and IPC levels were increased in the triple disruptant, indicating that the three SUR1 homologues are involved in the synthesis of MIPC. GFP-tagged Imt1p, Imt2p and Imt3p localized to Golgi apparatus membranes. The MIPC-deficient mutant exhibited pleiotropic phenotypes, including defects in cellular and vacuolar morphology, and in localization of ergosterols. MIPC seemed to be required for endocytosis of a plasmamembrane-localized amino acid transporter, because sorting of the transporter from the plasma membrane to the vacuole was severely impaired in the MIPC-deficient mutant grown under nitrogen-limiting conditions. These results suggest that MIPC has multiple functions not only in the maintenance of cell and vacuole morphology but also in vesicular trafficking in fission yeast.

Antifungal compound honokiol triggers oxidative stress responsive signalling pathway and modulates central carbon metabolism

“…Another interesting module is related to redox balance, lipid and glycan metabolism. It includes three glutathione S -transferase genes (Gst2, Gst3 and SPCC1281.07C) (Kim et al 2004), one NAD + /NADH kinase (SPCC24B10.02C), four mannosyltransferase (Imt1, Imt2, Imt3 and Omh1) (Nakase et al 2010), and one acyl-CoA-sterol acyltransferase (Are1). We also observed several modules which are related to signalling transduction.…”

Vsl1p cooperates with Fsv1p for vacuolar protein transport and homotypic fusion in Schizosaccharomyces pombe

“…cerevisiae VAM7 was amplified from genomic DNA by PCR and was introduced into pART1 harbouring the constitutively strong adh1 + promoter (McLeod et al, 1987), resulting in pART1-VAM7. pREP1-GFP-Fsv1, pREP41-GFPFsv1 and pAU-Gms1p-RFP were made as reported previously (Takegawa et al, 2003a;Nakase et al, 2010). To construct pART1-GFP-Vsl1 and pART1-GFP-Fsv1, gfp-vsl1 + and gfp-fsv1 + were amplified by PCR using pREP41-GFP-Vsl1 and pREP41-GFP-Vsl1, respectively, as templates and introduced into pART1.…”

“…4b). To further analyse the localization of Vsl1p, we co-expressed GFP-Vsl1p and RFP-fused Gms1p, which is a UDP-Gal transporter and is used as a Golgi marker protein (Tabuchi et al, 1997b;Nakase et al, 2010), and revealed that GFP-Vsl1p was not co-localized with Gms1p-RFP (Fig. 4c).…”

Expression of budding yeast IPT1 produces mannosyldiinositol phosphorylceramide in fission yeast and inhibits cell growth

“…We previously reported that no fission yeast genes equivalent to Ipt1p have been found in the Schizosaccharomyces (Schiz.) pombe genome (Nakase et al, 2010). Sacc.…”

“…Schiz. pombe cells deficient in MIPC have been found to exhibit pleiotropic phenotypes, including defects in cell morphology and endocytosis, and in localization of ergosterols and plasma membrane-associated transporters (Nakase et al, 2010).…”