Glycosylphosphatidylinositol-anchored cell-surface proteins from Arabidopsis

Sherrier, D. Janine; Prime, Tracy A.; Dupree, Paul

doi:10.1002/(sici)1522-2683(19990701)20:10<2027::aid-elps2027>3.0.co;2-a

Cited by 130 publications

(134 citation statements)

References 68 publications

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“…Vol. 58,2001 Multi-author Review Article cleaved in vitro and in vivo to release proteins, including AGPs, from the plasma membrane [33,34]. Thus, the model that emerges is that AGPs containing a GPI anchor are associated with the plasma membrane and are cleaved so as to release the AGP to and beyond the cell wall.…”

Section: Agp Expression In Plant Cellsmentioning

confidence: 99%

Arabinogalactan-proteins: structure, expression and function

Showalter

2001

CMLS, Cell. Mol. Life Sci.

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Abstract. Arabinogalactan-proteins (AGPs) are a family of extensively glycosylated hydroxyproline-rich glycoproteins that are thought to have important roles in various aspects of plant growth and development. After a brief introduction to AGPs highlighting the problems associated with defining and classifying this diverse family of glycoproteins, AGP structure is described in terms of the protein component (including data from molecular cloning), carbohydrate component, processing of AGPs (including recent data on glycosylphosphatidylinositol membrane anchors) and overall molecular shape. Next, the expression of AGPs is examined at several different levels, from the whole plant to the cellular levels, using a variety of experimental techniques and tools. Finally, AGP function is considered. Although the existing functional evidence is not incontrovertible, it does clearly droxyproline poor, lightly glycosylated and largely unreactive with Yariv reagent. It is worth remembering that it is human nature to group and classify things to facilitate their comprehension and discourse, whereas Mother Nature simply constructs biological entities, including AGPs, using material at hand with blatant, pedagogical disregard. Structure Protein moietyKnowledge of the protein moieties of AGPs has mostly come from purifying AGPs, deglycosylating them and analyzing their respective core proteins by amino acid analysis and, to a more limited extent, by sequence analysis ( fig. 2) [3 -10]. More recently, molecular cloning of several confirmed and putative AGP core proteins has CMLS, Cell. Mol. Life Sci. 58 (2001) 1399 -1417 1420-682X/01/101399-19 $ 1.50 + 0.20/0 © Birkhäuser Verlag, Basel, 2001 CMLS Cellular and Molecular Life Sciences point to roles for AGPs in vegetative, reproductive, and cellular growth and development as well as programmed cell death and social control. In addition and most likely inextricably linked to their functions, AGPs are presumably involved in molecular interactions and cellular signaling at the cell surface. Some likely scenarios are discussed in this context. AGPs also have functions of real or potential commercial value, most notably as emulsifiers in the food industry and as potential immunological regulators for human health. Several important questions remain to be answered with respect to AGPs. Clearly, elucidating the unequivocal functions of particular AGPs and relating these functions to their respective structures and modes of action remain as major challenges in the years ahead.

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Section: Agp Expression In Plant Cellsmentioning

confidence: 99%

Arabinogalactan-proteins: structure, expression and function

Showalter

2001

CMLS, Cell. Mol. Life Sci.

523

480

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“…Arabinogalactan (AG) proteins (AGPs), cell surface proteoglycans, are the best characterized class of such proteins (Youl et al, 1998; Oxley and Bacic, 1999;Sherrier et al, 1999; Svetek et al., 1999). Already, 12 classical AGPs, five AG peptides, and 17 fasciclin-like AGPs have been predicted to be GPI anchored in Arabidopsis (Gaspar et al, 2001).…”

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confidence: 94%

“…As part of this targeting mechanism, GAPs are thought to associate with lipid rafts (Muniz and Riezman, 2000;Ikonen, 2001), and there is evidence for rafting of GAPs in plants ( Peskan et al, 2000). Therefore, this class of proteins forms a potentially important group of molecules involved in plant cell surface generation and remodeling (Sherrier et al, 1999).GAPs have only relatively recently been discovered in plants. Arabinogalactan (AG) proteins (AGPs), cell surface proteoglycans, are the best characterized class of such proteins (Youl et al, 1998; Oxley and Bacic, 1999;Sherrier et al, 1999; Svetek et al., 1999).…”

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confidence: 99%

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Prediction of Glycosylphosphatidylinositol-Anchored Proteins in Arabidopsis. A Genomic Analysis

et al. 2002

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Glycosylphosphatidylinositol (GPI) anchoring of proteins provides a potential mechanism for targeting to the plant plasma membrane and cell wall. However, relatively few such proteins have been identified. Here, we develop a procedure for database analysis to identify GPI-anchored proteins (GAP) based on their possession of common features. In a comprehensive search of the annotated Arabidopsis genome, we identified 167 novel putative GAP in addition to the 43 previously described candidates. Many of these 210 proteins show similarity to characterized cell surface proteins. The predicted GAP include homologs of ␤-1,3-glucanases (16), metallo-and aspartyl proteases (13), glycerophosphodiesterases (6), phytocyanins (25), multi-copper oxidases (2), extensins (6), plasma membrane receptors (19), and lipid-transfer-proteins (18). Classical arabinogalactan (AG) proteins (13), AG peptides (9), fasciclin-like proteins (20), COBRA and 10 homologs, and novel potential signaling peptides that we name GAPEPs (8) were also identified. A further 34 proteins of unknown function were predicted to be GPI anchored. A surprising finding was that over 40% of the proteins identified here have probable AG glycosylation modules, suggesting that AG glycosylation of cell surface proteins is widespread. This analysis shows that GPI anchoring is likely to be a major modification in plants that is used to target a specific subset of proteins to the cell surface for extracellular matrix remodeling and signaling.Conventional membrane proteins possess one or more transmembrane domains that traverse the hydrophobic lipid bilayer. A glycosylphosphatidylinositol (GPI) anchor is an alternative means of attaching a protein to the membrane (for review, see Udenfriend and Kodukula, 1995), and it is found in all eukaryotic organisms. The C terminus of a GPIanchored protein (GAP) is covalently attached via phosphoethanolamine and a conserved glycan to phosphatidylinositol or a ceramide (Kinoshita and Inoue, 2000). GAPs have many features that distinguish them from proteins with transmembrane domains. The anchor can be removed by the action of specific phospholipases (Griffith and Ryan, 1999), converting the protein into a water-soluble form. In many organisms, they are found specifically at the outer leaflet of the plasma membrane (PM). It is important that GPI anchoring can target proteins to the PM in a polarized or localized manner, for example to the apical membrane of polarized mammalian epithelial cells (Le Gall et al., 1995) or the axon of neurons (Brown et al., 2000). As part of this targeting mechanism, GAPs are thought to associate with lipid rafts (Muniz and Riezman, 2000;Ikonen, 2001), and there is evidence for rafting of GAPs in plants ( Peskan et al., 2000). Therefore, this class of proteins forms a potentially important group of molecules involved in plant cell surface generation and remodeling (Sherrier et al., 1999).GAPs have only relatively recently been discovered in plants. Arabinogalactan (AG) proteins (AGPs), cell surface proteo...

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“…Addition of the GPI anchor is performed in the endoplasmic reticulum and implies the cleavage of a hydrophobic C-terminal peptide and the subsequent linkage of a preassembled GPI anchor via an amide bond onto the last amino acid residue remaining after the cleavage, called the attachment or -site (Udenfriend and Kodukula, 1995). This posttranslational modification has been commonly associated with cell surface proteins in animal cells and yeast (Saccharomyces cerevisiae), but has been discovered only recently in plants (Youl et al, 1998;Oxley and Bacic, 1999;Sherrier et al, 1999;Svetek et al, 1999). In animals, the GPI anchor is frequently associated with polar protein sorting, and proteins containing this modification are found in microdomains at the cell surface (Simons and Ikonen, 1997;Friedrichson and Kurzchalia, 1998;Varma and Mayor, 1998).…”

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The COBRA Family of Putative GPI-Anchored Proteins in Arabidopsis. A New Fellowship in Expansion

et al. 2002

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Identification of regulatory molecules that determine the extent and direction of expansion is necessary to understand how cell morphogenesis is controlled in plants. We recently identified COB (COBRA) as a key regulator of the orientation of cell expansion in the root. Analysis of the Arabidopsis genome sequence indicated that COB belongs to a multigene family consisting of 12 members, all predicted to encode glycosylphosphatidylinositol-anchored proteins. All but two of the COBL (COB-like) genes are expressed in most organs examined, suggesting possible redundancy. Sequence comparisons, phylogenetic analyses, and exon-intron positions revealed that the COB family is composed of two main subgroups sharing a common architecture, one subgroup being characterized by an additional N-terminal domain. Identification of expressed sequence tags corresponding to potential orthologs in other plant species suggested that COB-related functions are required in all vascular plants. Together, these results indicate that COB family members are likely to be important new players at the plasma membrane-cell wall interface.Cell morphogenesis is heavily influenced and restricted by the presence of an extracellular network of carbohydrates and proteins, the cell wall. Far from being an inert and stable exoskeleton, the primary wall is a highly dynamic extracellular matrix characterized by plastic, elastic, and viscous physical properties. These properties are conferred by the nature of the different constituent polymers, a load-bearing cellulose/xyloglucan (hemicellulose) array, and a compression-resistant pectin gel (Roberts, 1994). The developmental regulation of cell wall dynamics required for cell expansion and cell shape modeling must be directed by proteins capable of organizing, loosening, and rearranging the different polysaccharide networks and incorporating newly synthesized material. More than 17% of Arabidopsis genes contain a signal peptide sequence and over 400 proteins are annotated as being localized in the cell wall (Arabidopsis Genome Initiative [AGI], 2000), suggesting the possibility that more than 1,000 genes are implicated in wall biogenesis and modification .Proteins localized to the cell wall, such as the Hyp-, Pro-, or Gly-rich proteins, arabinogalactan proteins, and expansins, were originally identified through assays for biochemical and/or biophysical activities. More recently, forward and reverse genetic approaches have led to the identification of new classes of cell wall modifiers such as cellulose synthases (Arioli et al., 1998; Fagard et al., 2000), endo-␤-1,4-glucanases (Nicol et al., 1998), and wall-associated kinases (Kohorn, 2001). By analyzing Arabidopsis mutants exhibiting abnormal cell expansion during root development (Benfey et al., 1993;Hauser et al., 1995), COBRA was identified as an essential player in the regulation of the orientation of cell expansion (Schindelman et al., 2001). Reduced levels of crystalline cellulose microfibrils in the mutant suggested a role for COBRA in cellulose de...

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Glycosylphosphatidylinositol-anchored cell-surface proteins from Arabidopsis

Cited by 130 publications

References 68 publications

Arabinogalactan-proteins: structure, expression and function

Arabinogalactan-proteins: structure, expression and function

Prediction of Glycosylphosphatidylinositol-Anchored Proteins in Arabidopsis. A Genomic Analysis

The COBRA Family of Putative GPI-Anchored Proteins in Arabidopsis. A New Fellowship in Expansion

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