Search

AbstractGlycosylphosphatidylinositol (GPI) anchors contain a unique α-D-glucosamine-(1→6)-myo-inositol [αGlcN(1,6)Ins] motif in their conserved core structure. To facilitate investigations of the functional roles of this structural motif, two GPI analogues containing unnatural βGlcN(1,6)Ins, instead of αGlcN(1,6)Ins, and an alkyne group at different positions of the GPI core were designed and synthesized. To this end, an orthogonally protected pseudopentasaccharide derivative of GPIs with the βGlcN(1,6)Ins motif was convergently constructed via [3 + 2] glycosylation and used as the common intermediate to prepare both GPI analogues by streamlined synthetic protocols. The pseudopentasaccharide intermediate and developed protocols can be widely applicable to access various GPI analogues with the βGlcN(1,6)Ins motif. The target GPI analogues contain an alkyne, which allows their further modification to introduce various molecular labels via click chemistry, making them useful probes for the study of GPI anchorage. The differences in reactivity and NMR behavior of the two GPI analogues, as well as the differences of these analogues from previously reported GPI derivatives of similar structure containing an αGlcN(1,6)Ins motif, suggest that the 2-O-phosphoethanolamine moiety on mannose-I and the linkage form of GlcN in GPIs can have a decisive impact on the structure, which is likely relevant to biology. [ABSTRACT FROM AUTHOR]

Glycosylphosphatidylinositols (GPIs) need to interact with other components in the cell membrane to transduce transmembrane signals. A bifunctional GPI probe was employed for photoaffinity‐based proximity labelling and identification of GPI‐interacting proteins in the cell membrane. This probe contained the entire core structure of GPIs and was functionalized with photoreactive diazirine and clickable alkyne to facilitate its crosslinking with proteins and attachment of an affinity tag. It was disclosed that this probe was more selective than our previously reported probe containing only a part structure of the GPI core for cell membrane incorporation and an improved probe for studying GPI‐cell membrane interaction. Eighty‐eight unique membrane proteins, many of which are related to GPIs/GPI‐anchored proteins, were identified utilizing this probe. The proteomics dataset is a valuable resource for further analyses and data mining to find new GPI‐related proteins and signalling pathways. A comparison of these results with those of our previous probe provided direct evidence for the profound impact of GPI glycan structure on its interaction with the cell membrane. [ABSTRACT FROM AUTHOR]

A new, bifunctional glycosylphosphatidylinositol (GPI) derivative containing the highly conserved core structure of all natural GPI anchors with a photoactivable diazirine in the lipid chain and clickable alkynes in the glycan was synthesized by a convergent [3+2] glycosylation strategy with late stage protecting group manipulation and regioselective phosphorylation. The challenges of this synthesis were due to the presence of several distinctive functional groups in the synthetic target, which complicated the protection tactics, in addition to the inherent difficulties associated with GPI synthesis. This bifunctional GPI derivative can cross‐react with molecules in proximity upon photoactivation and be subsequently labeled with other molecular tags via click reaction. Therefore, it should be a valuable probe for biological studies of GPIs, such as analysis of GPI‐interacting membrane proteins, and gaining insights into their functional mechanisms. [ABSTRACT FROM AUTHOR]

A diacyl phosphatidylinositol (PI) derivative with an azide linked to its inositol C4-position was effectively synthesized in 19 steps for the longest linear sequence and in a ca. 1% overall yield from 1,2-distearoyl-sn-glycerol and D-glucose. This compound was designed as a biosynthetic precursor of glycosylphosphatidylinositol (GPI) anchors. Its azide would enable further modification to introduce other molecular tags by a biocompatible click reaction. Therefore, it can be a useful probe for metabolic engineering of cell surface GPI anchors and GPI-anchored proteins. [ABSTRACT FROM AUTHOR]

Glycosylphosphatidylinositol (GPI) attachment to the C -terminus of proteins is a prevalent posttranslational modification in eukaryotic species, and GPIs help anchor proteins to the cell surface. GPI-anchored proteins (GPI-APs) play a key role in various biological events. However, GPI-APs are difficult to access and investigate. To tackle the problem, chemical and chemoenzymatic methods have been explored for the preparation of GPI-APs, as well as GPI probes that facilitate the study of GPIs on live cells. Substantial progress has also been made regarding GPI-AP biosynthesis, which is helpful for developing new synthetic methods for GPI-APs. This article reviews the recent advancements in the study of GPI-AP biosynthesis, GPI-AP synthesis, and GPI interaction with the cell membrane utilizing synthetic probes. [Display omitted] [ABSTRACT FROM AUTHOR]

Glycosylphosphatidylinositol (GPI) anchoring of proteins to the cell surface is important for various biological processes, but GPI-anchored proteins are difficult to study. An effective strategy was developed for the metabolic engineering of cell-surface GPIs and GPI-anchored proteins by using inositol derivatives carrying an azido group. The azide-labeled GPIs and GPI-anchored proteins were then tagged with biotin on live cells through a click reaction, which allows further elaboration with streptavidin-conjugated dyes or other molecules. The strategy can be used to label GPI-anchored proteins with various tags for biological studies. [ABSTRACT FROM AUTHOR]

Highlights: [•] Great progress has been made in revealing GPI and GPI-anchored protein biosynthesis. [•] Progress in GPI and GPI-anchored protein synthesis has made their access practical. [•] Synthetic GPIs and GPI-anchored proteins have facilitated the study of GPI biology. [ABSTRACT FROM AUTHOR]

Glycosylphosphatidylinositol (GPI) anchors are a group of complex glycolipids that attach extracellular proteins and glycoproteins to the eukaryotic cell outer membrane. To better understand GPI anchorage, it is necessary to have access to homogeneous, structurally defined, and functionalized GPIs and GPI analogs. In this regard, chemical synthesis is necessary, as GPI anchors are rather scarce and heterogeneous in natural sources. Three GPI analogs with phosphoglycerolipids linked to the pseudodisaccharide core and their fluorescein conjugates were prepared in this work as a small tool set useful for probing how the lipid composition and carbohydrate anomeric configuration may affect the properties of GPI anchors. [ABSTRACT FROM AUTHOR]

Green fluorescent protein and a glycosylphosphatidylinositol (GPI) anchor containing the common core structure and a lipid chain were synthesized and then coupled together in the promotion of bacterial sortase A (SrtA), which was the first example for the synthesis of a full-size GPI-anchored protein by SrtA, demonstrating that this can be a generally useful method for GPI-anchored protein synthesis. [ABSTRACT FROM AUTHOR]

In this article, the authors focus on a research published in the journal "Current Organic Synthesis" in 2013 related to the glycosylphosphatidylinositol (GPI) anchors and GPI-anchored glycopeptides, peptides and proteins.

Glycosylphosphatidylinositol (GPI) anchorage is one of the most common mechanisms to attach proteins to the plasma membrane of eukaryotic cells. GPI-anchored proteins (GPI-APs) play a critical role in many biological processes but are difficult to study. Here, a new method was developed for the effective and selective metabolic engineering and labeling of cell surface GPI-APs with an azide-modified phosphatidylinositol (PI) as the biosynthetic precursor of GPIs. It was demonstrated that this azido-PI derivative was taken up by HeLa cells and incorporated into the biosynthetic pathway of GPIs to present azide-labeled GPI-APs on the live cell surface. The azido group was used as a molecular handle to install other labels through a biocompatible click reaction to enable various biological studies, e.g., fluorescent imaging and protein pull-down, which can help explore the functions of GPI-APs and discover new GPI-APs. [Display omitted] • A new method for metabolic engineering of GPI-anchored proteins (GPI-APs). • Labeling GPI-APs on live cells with an azide to enable further functionalization. • Labeling GPI-APs on cells with fluorophores to enable fluorescence-based studies. • Labeling GPI-APs on cells with an affinity tag to facilitate proteomics analysis. [ABSTRACT FROM AUTHOR]

Analogs of the human CD52 and CD24 antigens carrying the common core structure of glycosylphosphatidylinositol (GPI) anchors and the intact polypeptide sequences of CD52 and CD24 were chemoenzymatically synthesized. CD52 and CD24 proteins were obtained by solid-phase peptide synthesis and then coupled to chemically synthesized GPI anchors under the influence of a bacterial enzyme, sortase A, to afford the target molecules in good yields. [ABSTRACT FROM AUTHOR]