Thematic review series: Lipid Posttranslational Modifications. GPI anchoring of protein in yeast and mammalian cells, or: how we learned to stop worrying and love glycophospholipids

Abstract

Glycosylphosphatidylinositol (GPI) anchoring of cell surface proteins is the most complex and metabolically expensive of the lipid posttranslational modifications described to date. The GPI anchor is synthesized via a membrane-bound multistep pathway in the endoplasmic reticulum (ER) requiring .20 gene products. The pathway is initiated on the cytoplasmic side of the ER and completed in the ER lumen, necessitating flipping of a glycolipid intermediate across the membrane. The completed GPI anchor is attached to proteins that have been translocated across the ER membrane and that display a GPI signal anchor sequence at the C terminus. GPI proteins transit the secretory pathway to the cell surface; in yeast, many become covalently attached to the cell wall. Genes encoding proteins involved in all but one of the predicted steps in the assembly of the GPI precursor glycolipid and its transfer to protein in mammals and yeast have now been identified. Most of these genes encode polytopic membrane proteins, some of which are organized in complexes. The steps in GPI assembly, and the enzymes that carry them out, are highly conserved. GPI biosynthesis is essential for viability in yeast and for embryonic development in mammals. In this review, we describe the biosynthesis of mammalian and yeast GPIs, their transfer to protein, and their subsequent processing.-Orlean, P., and A. K. Menon. GPI anchoring of protein in yeast and mammalian cells, or: how we learned to stop worrying and love glycophospholipids.

Diversity of aminopeptidases, derived from four lepidopteran gene duplications, and polycalins expressed in the midgut of Helicoverpa armigera: Identification of proteins binding the δ-endotoxin, Cry1Ac of Bacillus thuringiensis

“…On the other hand, contrary to our findings, the HaAPN4 orthologue, H. virescens AF378666 bound Cry1Ac independent of glycosylation (Banks et al, 2001). Finally, it is possible that GPI anchors are modified with GalNAc residues (Orlean and Menon, 2007) and it may be through this structure that the HaAPN4 protein binds Cry1Ac.…”

Profiling the expression pattern of GPI transamidase complex subunits in human cancer

“…Although GPI proteins are functionally diverse, most of them are predicted to serve as receptors, differentiation antigens or membranous enzymes. 1 Genes encoding GPI-anchored proteins specify two signal sequences in the primary translation product: an N-terminal signal sequence for ER targeting and a C-terminal sequence that directs the attachment of a GPI anchor. The crucial and the ultimate steps of cleaving the signal sequence and attaching the preassembled GPI anchor are catalyzed by GPI transamidase (GPIT), a multisubunit membrane-bound enzyme.…”

“…The crucial and the ultimate steps of cleaving the signal sequence and attaching the preassembled GPI anchor are catalyzed by GPI transamidase (GPIT), a multisubunit membrane-bound enzyme. 1 The GPIT complex consists of five proteins; in mammals and yeast these are PIG-K (or GPI8)/Gpi8p, GPAA1 (or GAA1)/Gaa1p, PIG-S/Gpi17p, PIG-T/ Gpi16p and PIG-U/Gab1p. 1 Gaa1p and Gpi8p were the first to be identified as proteins essential for GPI anchor attachment onto proteins, 2,3 and were subsequently shown to form a complex.…”

Lentiviral transfer of an inducible transgene expressing a soluble form of Gas1 causes glioma cell arrest, apoptosis and inhibits tumor growth

“…To obtain a secretable form of Gas1, we generated truncated forms of Gas1, lacking the GPI-link consensus sequence, so these forms of Gas1 will be secreted from the cells. 14,38,39 The autocrine and paracrine effects of Gas1 will significantly increase its therapeutic capacity, by allowing the diffusion and distribution of the therapeutic molecule away from producer cells. To reach this objective we generated lentivirus expressing a truncated form of Gas1 (Arg 315), and determined that infected cells release a soluble form of Gas1 that can induce cell arrest and apoptosis when transferred to independent cultures of C6 cells.…”